Neuro Outline Test 1

Test 1

Embryology

Charts for Development of the head and the neck:

Charts below list all the arches and pouches and important structures associated with them.

ARCH NERVE MUSCLES SKELETAL STRUCTURES LIGAMENTS First (mandibular)

Trigeminal (CN V) Muscles of mastication Mylohyoid and anterior belly of digastrics Tensor tympani Tensor veli palatine

Malleus Incus

Anterior ligament of malleus Sphenomandibular ligament

Second (hyoid) Facial (CN VII) Muscles of facial expression Stapedius Stylohyoid Posterior belly of digastrics

Stapes Styloid process Lesser cornu of hyoid bone Upper part of body of hyoid bone

Stylohyoid ligament

Third Glossopharyngeal (CN IX) Stylopharyngeus Greater cornu of hyoid bone Lower part of body of hyoid bone

Fourth and Sixth Superior laryngeal branch of vagus (CN X) Recurrent laryngeal branch of vagus (CN X)

Cricothyroid Levator veli palatine Constrictors of pharynx Intrinsic muscles of larynx Striated muscles of esophagus

Thyroid cartilage Cricoid cartilage Arytenoid cartilage Corniculate cartilage Cuneiform cartilage

PHARYNGEAL POUCHES

DERIVATIVES

First Formation of tubotympanic recessthe expanded distal part of recess contacts the

The cavity of the tubotympanic recess becomes the tympanic cavity and mastoid antrum

pharyngeal groove to later contribute to form the tympanic membrane (eardrum)

The connection of the tubotympanic recess with the pharynx gradually elongates to from the pharyngotympanic tube (auditory tube)

Second Obliterated as palatine tonsil develops Part of cavity of pouch remains as tonsillar sinus/fossa Endoderm proliferates and grows into the underlying mesenchyme..the central parts of these buds break down forming tonisllar

crypts At ~20wks, mesenchyme around crypts differentiates into lymphoid tissue, which soon organizes into the lymphatic nodules of

the palatine tonsil Third Expands and develops a solid, dorsal bulbar part and a hollow, elongate ventral part

It connection with the pharynx is reduced to a narrow duct that degenerates By The epithelium of the elongate ventral parts of the pouch proliferates, obliterating their cavities

wk, the epithelium of each dorsal bulbar part of pouch begins to differentiate into inferior parathyroid glands

Both come together to form the thymus The developing thymus and the parathyroid glands lose their connects with the pharynx Later, the parathyroid glands separate from the thymus and lie on the dorsal surface of the thyroid gland

Fourth Expands into dorsal bulbar and elongate ventral parts Its connection with pharynx is reduced to a narrow duct that degenerates By wk, each dorsal part develops into a superior parathyroid gland, which lies on the dorsal surface of the thyroid gland

Outline for development of the head and neck

I. Development of skull (consists of cranium and mandible) a. Condrocranium (neurocranium): early development.

i. Cranial base formed by endochondral ossification. Cartilage is converted into bone. BV and nerves are incased in the cartilage, which is transformed into bone. It contains sensory capsules for vision, olfaction, audition and postural balance.

ii. Cranial vault: develops by direct intramembranous ossification. Blastemic sheet of mesenchymal cells from the flat bones of the cranial vault and the face. Cells become osteoblasts, which make osteoids. Osteoids overtime make bone.

b. Viscerocranium-develops into the facial skeleton. There are 40 muscles of the face. II. Pharyngeal arches (brachial arches, Gill Bars)

a. Four basic elements i. Consists of a cartilaginous skeletal core, a hard substance. The core comes from the neural crest, except for arches IV and VI which are

formed from the lateral plate mesoderm.

ii. Striated skeletal muscle anlagen derived from paraxial mesoderm. iii. Innervations by cranial nerves iv. Blood vessels derived from external and internal carotid which branch from aortic arches

b. Brachial arches are covered externally with ectoderm (skin-stratified squamous keratinized epithelium) and internally with endoderm (mucosal surface).

c. There are 5 arches. The i. Arch I: Mandibular arch.

arch is rudimentary. On the outside, there are 5 clefts, clefts 2-5 obliterate. On the inside there are 5 pouches.

1. Has two processes: maxillary and mandibular. If something goes wrong with the fusion of the two processes, it can result in cleft lip and cleft palates.

2. Following structures develop from Arch I: a. Upper jaw, zygomatic bone and squamous part of the temporal bone from maxillary process b. Lower jaw from mandibular process. c. Muscles of mastication: temporalis, masseter, medial and lateral pterygoid muscles. d. Mylohyoid, anterior belly of digastrics, tensor tympani and tensor veli palatini muscles. e. Incus from the maxillary cartilage. f. Malleus from the mandibular cartilage (Meckels cartilage)

3. Innervated by CN Vtrigeminal nerve. a. Trigeminal nerve has three major branches

i. CN V 1:

ii. CN V Ophthalmic. sensory only

2:

iii. CN V Maxillary. sensory only

3:

ii. Arch II (Hyoid arch) Mandibular. sensory and motor

1. Following structures develop from Arch II. a. Muscles of facial expression: originate from different aspects of the skull. Insert into dermis of skin to pull skin around for

an expression. b. Reicherts cartilage (from neural crest origin) Gives rise to the ear bone Stapes c. Styloid process of the temporal bone: muscles attach to this bone. d. Stylohyoid ligament e. Lesser cornua and superior portion of the body of the hyoid bone. Hyoid is a small bone, but 10 muscles attach to it.

2. Innervated by CN VII: facial nerve. Has sensory and motor components. iii. Arch III

1. Following structures develop from Arch III a. Stylopharyngeus muscle in the neck b. Greater cornua and inferior portion of the body of the hyoid bone.

2. Innervated by CN IX: glossopharyngeal neve. Has sensory and motor components. iv. Arch IV and Arch VI (Arch V is rudimentary):

1. Following structures develop from Arch IV and VI:

a. Development of laynx. Larynx cartilages (thyroid, cuniform, corniculate, arytenoids and cricoids cartilages ) derive from mesenchyme of the IV pharyngeal arch

b. Epiglottis derives from cephalic part of the hypobranchial eminence or it may form by migration of mesenchyme into the area of the IV arch

c. Muscles from arch IV: Pharyngeal constrictor, levator veli palatine and cricothyroid muscles. These are innervated by the superior laryngeal branch of the Vagus nerve (CN X)

d. Intrinsic muscles of the larynx are derived from the paraxial mesoderm of the and

2. Innervated by CN X: Vagus nerve. Has sensory and motor components. Arch IV innervated by superior laryngeal branch and Arch VI innervated by recurrent (inferior) laryngeal branch.

occipital somites associated with arch VI. These muscles are innervated by recurrent laryngeal branch of the Vagus nerve

III. Development of the face a. Occurs between the and b. The five processes must fuse in consort

embryonic/fetal weeks.

i. Frontonasal process: prominence. 1. Nasal placodes (nasal discs, nasal plates) 2. Nasal pits develop during

ii. Lateral nasal processes (2) fuses with maxillary swelling to produce nasolabial fold. Depression in the depth of the fold is called nasolacrimal groove. Tears come out of here when someone cries hard. Further invagination of the cleft produces a tube like structure called nasolacrimal duct (maxilla)

week

iii. Medial nasal processes (2). Fusion of the two forms the septum of nose and the bridge of the nose. When the tips of the medial nasal process fuse, the intermaxillary process (premaxilla) develops and helps form the philtrum of the lip. The posterior extension of the intermaxillary process forms the primary palate. When the septum fuses with the hard palate, the nasal cavity is portioned into two chambers, which communicate posteriorly with the region of the oropharynx via passages called choanae.

iv. Maxillary processes (2) swellings. The secondary palate arises fom palatine shelves (processes of the maxilla). The medial part of the maxillay continues to assist in the development of hard palates. After completion of the fusion of both secondary palates, and subsequent endochondral ossification of the anterior part of the secondary palate, both the hard and soft palates form.

v. Mandibular processes (2) swellings: The lower lip develops by fusion of the distal extent of the mandibular swelling. The embryonic stomatodeum (mouth) is formed by rupture of the bucco/oropharyngeal membrane.

c. Clefts-located between the pharyngeal brachial arches. i. Cleft 1 develops the external acoustic meatus

ii. Clefts 2, 3 and 4 normally degenerate and are obliterated. Failure to do so can lead to development of brachial cysts or fistulas located anterior to the sternocleidomastoid muscle.

d. Pouches- invagination of the endodermal lining forms these. i. Pouch 1: Tubotympanic recess and tympanic cavity

ii. Pouch 2: palatine tonsils iii. Pouch 3: thymus gland, inferior parathyroid glands iv. Superior parathyroid glands

v. Ultimobranchial body parafollicular (C-cells) of the thyroid

Outline for Neuroembryology

I. Neurulation a. NS development is initiated in the fourth week of gestation (22-b. Nerve tissue is derived from surface ectoderms of the neuroepithelium (neuroectoderm)

day)

c. Neuroectoderm on the dorsal surface of the embryo produces the neural plate. d. The neuroectoderm of the neural plate forms a neural groove. e. On the outside of the neural plate are the neural crest cells (stem cells of the NS). These migrate and form many things, like the ganglia,

ordontablasts in teeth, chromaffin cells in the adrenal medulla. Formation of the ganglia is the most important function. Ganglia are a population of neurons that have the same cytoarchitechtonics and function.

i. From the neuroectoderm of the neural tube ii. All the sensory ganglia of spinal and cranial nerves.

iii. All autonomic motor ganglia throughout the body, i.e.,postganglionic motor neurons. iv. The chromaffin cells of the adrenal medulla v. Some of the cartilage and skeletal muscle of the head region.

f. The neural groove becomes the neural tube on the g. Neural tube forms the spinal cord and the cephalic portion of the tube develops into 3 primary brain vesicles

day. Occurs via fusion.

i. Proencephalon: forebrain. Undergoes transformation into two secondary vesicular structures 1. Telencephalon (end brain) cerebrum, CN I, lateral brain ventricles and basal ganglia. 2. Diencephalon (interbrain. Connects the telencephalon with the rest of the brain) thalamus, hypothalamus, optic chiasm and CN

II. ii. Mesencephalon: midbrain. Forms the tectum, CN III (oculomotor nuclear complex), CN IV (trochlear nucleus and nerve, red nucleus,

cerebral aqueduct, periaquiductal gray, substantia nigra and the locus ceruleus). Also has the cerebral peduncles that contain the corticospinal tracts.

iii. Rhombencephalon: hindbrain. 1. Metencephalon pons, cerebellum, cerebellar peduncles, nuclei associated with CN V thru CN VIII and some of the fourth

ventricle. 2. Myelencephalon medulla oblongata which contains the nuclei associated with CN VII (in part) thru CN XII) and remainder of

the fourth ventricle. The mesencephalon (midbrain), metencephalon (pons), and myelencephalon (medulla oblongata) form the brainstem.

II. Spinal cord development a. Regions of the neural tube (embryonic cord)

i. Marginal zone: the outermost region of the wall of the neural tube. 1. Contains axons of spinal neurons projecting to higher centers via tracts and pathways. 2. Also contain descending axons from higher centers that regulate the function of the spinal cord neurons 3. These neurons are first apolar and then form bipolar neurons (which are in the retina, cochlea). These neurons fuse with the DRG.

ii. Mantle zone: lies peripheral to the ependymal layer. It forms the grey matter. 1. Neuroblasts and glioblasts transform into mature cell population in the mantle layer. 2. These neurons transmit axons to higher and lower levels of the CNS.

iii. Ependymal zone: surrounds the central canal of the neural tube. Cells: neuroblasts, glioblasts and ependymal cells develop in this zone. b. Development of the cells:

i. Neuroblasts transform into mature neurons. ii. Glioblasts become CNS glial cells (astrocytes and oliogodendrocytes)

iii. Microglia are derived from mesoderm and migrate into the embryonic CNS tissue via the blood supply. iv. Ependymal cells line the walls of the canal of the neural tube and the ventricles of the developing brain.

c. Neurons in the ventral gray matter occupy the basal plate, which becomes the ventral grey horns of the spinal cord. i. Axons from the neurons in the basal plate exit the cord and from the alpha motor neurons of the peripheral nerves. These are the LMN.

d. Motor components of cranial nerves are also derived from basal plate neurons i. The sulcus limitans is a depression in the lateral wall of neural canal and brain ventricles. It separates the alar plate neurons from basal

plate. e. The alar plate of grey matter are located doroslaterally and form the dorsal grey horns.

i. Alar plate neurons are sensory. They receive input from the cord and the brainstem via the cranial nerves. ii. Cranial nerves that possess sensory components synapse with neurons derived from the alar plate.

f. The motor and sensory neuron populations of the spinal cord and brainstem are organized in a longitudinal axial array. The neuron population continues rostrally into the brain stem.

III. Brain development

IV. Development disorders a. Spinal

i. Spinal bifida occulata ii. Spinal bifida cystic

1. Meningocele 2. Meningomyelocele 3. Myeloschisis 4. Anecephaly (meroanecephaly)

b. Brain disorders i. Meroanencephalyfailure to have brain form porperly

ii. Microencephaly-small brain, small head iii. Hydrocephalus-plug up cerebral aqueduct. Lateral ventral and

1. Aqueductal stenosis ventral

iv. Meningoencephalocele v. Meningohydroencepalocele

vi. Arnold - Chiari Malformation

ANATOMY

Outline for anatomy of the superficial face, triangles of the neck and cervical fascia

I. Anatomic region of the face and scalp a. Frontal regionforehead b. Orbital regioneye socket c. Infraorbital (malar) regioncheek d. Nasal regionnares (Nostrils) nose e. Oral regionlips, mouth f. Mental regionchin g. Parotid regionangle of jaw h. Auricular region ear i. Temporal region temple j. Occipital region

II. Facial innervations a. Trigeminal nerve (CN V): cutaneous innervations of the face and part of the scalp refer to sensory supply provided by one of the three divisions of

the trigeminal nerve: ophthalmic division (CN V1), maxillary division (CN V2) or mandibular division (CN V3). Dermatomes: area of skin innervated by the sensory component of a cranial nerve or spinal nerve.

i. Ophthalmic division: supplies eyeball (afferent limp-blink reflex), supraorbital region (forehead, frontal sinus pain) and the scalp. 1. Supraorbital and supratrochlear branches of CN V1 supply the scalp up to the vertex of the skull 2. External nasal branch of the nasociliary nerve supplies the bridge of the nose. 3. Lacrimal nerve supplies the lateral and superior region of the orbit.

ii. Maxillary division: supplies infraorbital region, including the lower eyelid, lateral nasal area and the upper lip 1. Infraorbital nerve with its lateral nasal and superior labial branches is primarily involved 2. Zygomatic branch of CN V2 supplies the zygomatic facial and zygomaticotemporal regions of the head.

iii. Mandibular division: sensory component supplies the skin of lower lip, the chin via the mental nerve (which is a continuation of inferior alveolar nerve) and temporal region of the scalp. The motor component supplies muscles of mastication.

b. Facial nerve:

i. banchiomotor components of facial nerve (SVE: special visceral efferent component. Innervates facial expression muscles that derived from brachial arch.

1. Pathway a. Origin: facial motor nucleus in the brainstem (pons). b. Exits brainstem at inferior pontine sulcus. Joins CN VIII and enters the internal acoustic meatus of the petrous temporal

bone. Travels in the facial canal of temporal bone. c. Exits the skull at the stylomastoid foramen. Divides within the parotid gland to supply the muscles of facial expression.

Nerve to the stapedius m. is given off while the nerve travels through the facial canal. Contraction of the stapedius m. dampens the oscillations of the stapes.

d. Dysfunction of the branchiomotor (SVE) component of CN VII can result in Bells palsy and hyperacusia. i. Bells palsy: ipsilateral hemifacial paralysis. Flattened nasolabial fold. Saliva dripping from the corner of the

mouth. Conjunctivitis (failure to close eyelid and reduced lacrimation). Structures affected: facial nucleus in the pons or the infranuclear lower motor neuron distribution. Due to inflammation, viral etiology or facial trauma.

2. Branches a. Temporal branch: Supplies the frontalis part of the occipitofrontalis m. b. Zygomatic branch: Supplies the orbicularis oculi and frontalis mm. c. Buccal branch: Supplies the orbicularis oris and other perioral mm. d. Marginal mandibular branch: Supplies the platysma and perioral mm. e. Cervical branch: Supplies the platysma m. f. Posterior auricular branch: Supplies the auricular mm. and occipitalis part of the occipitofrontalis m.

III. Muscles of facial expression: derived from brachial arch and is innervated by facial nerve (CN VII).

a. Occipitofrontalis muscle: Frontalis connected to occipital via aponeurotic sheath. Muscles get a dual nerve supply. Frontalis portion is indicator of neuropathy, like Bells palsy.

b. Orbicularis oculi muscle: closes the eyelid. Weakness causes eyes to dry and can contribute to conjunctivitis. c. Obicularis oris: surrounds the lips d. Zygomatic major and minor: creates the nasolabial fold (crease) which flattens in facial paralytic states like Bells palsy and stroke. e. Levator anguli oris muscle: elevates the angle of the oral cavity. if weak, will cause drooling of saliva from corner of mouth. f. Buccinator muscle: assists with mastrication. Classificed as facial expression muscle because it originates from the

brachial arch.

IV. Arterial supply a. External carotid: 8 major branches

i. Superior thyroid artery and superior laryngeal branch ii. Ascending pharyngeal artery

iii. Lingual artery iv. Facial artery

1. Ascending palatine br.--- 2. Tonsillar br.palatine tonsils. 3. Submental a. br.sublingual gland 4. Sup. and inf. labial aa. brs. Above and below lip 5. Angular br.comes up along lateral aspect of nose. 6. Anastomoses with the supratrochlear a. branch of the ophthalmic a. from internal carotid. If have issue w/internal carotid, can still

get flow from here. Anastomosis btwn external and internal carotid. v. Posterior auricular artery

vi. Maxillary artery: major terminal branch of external carotid. Supplies blood to a wide area via the zygomaticofacial artery; this branch supplies the superior and lateral orbital region and is derived from the orbital branch of the maxillary artery.

1. Inferior alveolar artery: sends a branch to the skin over the chin, known as the mental artery 2. Buccal branch: supplies the skin over the lateral cheek 3. Infraorbital artery: supplies the skin over the malar region of the face.

vii. Superior temporal artery: terminal branch of external carotid. 1. Transverse facial artery

b. Internal carotid artery i. Ophthalmic artery: supplies all the structure in the orbit.

1. Supraorbital artery 2. Supratrochlear artery

V. Venous return

a. Supraorbital vein b. Ophthalmic vein c. Infraorbital vein d. Deep facial vein e. Transverse facial vein

VI. Lymphatic drainage a. Forehead and temporal scalp region: parotid nodes superficial cervical nodes deep cervical nodes b. Nose and upper lip: submandibular nodes superficial cervical nodes deep cervical nodes c. Lower lip (central part): submental nodes superficial cervical nodes deep cervical nodes d. Lower lip (lateral part): submandibular nodes superficial cervical nodes deep cervical nodes e. Cheek: buccal (facial) nodes submandibular nodes superficial cervical nodes deep cervical nodes f. Posterior scalp: occipital nodes deep cervical nodes g. Posterior scalp: retroauricular (mastoid) nodes deep cervical nodes

VII. Anterior cervical triangles a. Boundaries

i. Anterior: midline plane ii. Superior: lower boarder of the mandible

iii. Posterior: anterior border of the sternocleidomastoid b. Submandibular Triangle -lower border of the mandible and the anterior and posterior bellies of the digatric mm. makes anterior and posterior

bellies. c. Carotid Triangle -Omohyoid m, (muscle from hyoid bone to scapula) sternocleidomastoid m., and the posterior belly of the digastric m. contains

carotid arteries d. Submental Triangle -Anterior bellies of the two digastrics muscles and the hyoid bone. Lymph node that takes lymph from tip of tongue and bring

it to node (which one?)

e. Muscular Triangle- Omohyoid m., sternocleidomastoid m. and the midline plane. VIII. Infrahyoid (strap) muscles

a. Sternothyroid b. Sternohyoid c. Thyrohyoid d. Omohyoid

Muscles Origin Insertion Innervation Action Omohyoid Inferior belly: upper border of

scapula medial to scapular notch Superior belly: intermediate tendon

Superior belly: lower border of hyoid lateral to sternohyoid insertion Inferior belly: intermediate tendon

Ansa cervicalis Depresses/stabilizes hyoid bone

Sternohyoid Posterior surfaces of manubrium and sternal end of clavicle

Lower border of hyoid bone, medial to omohyoid insertion

Ansa cervicalis Depresses/stabilizes hyoid bone

Sternothyroid Posterior surface of manubrium below sternohyoid origin

Oblique line of thyroid cartilage Ansa cervicalis Depresses/stabilizes thyroid cartilage

Thyrohyoid Oblique line of thyroid cartilage Lower border of hyoid bone Ansa cervicalis (via fibers running with hypoglossal nerve that leave XII distal to the superior limb of ansa)

Elevates larynx; Depresses/stabilizes hyoid bone

Sternocleidomastoid Sternal head: anterior surface of manubrium; Clavicular head: medial one-third of clavicle

Mastoid process and lateral aspect of superior nuchal line

Spinal accessory nerve (XI), with sensory supply from C2 & C3 (for proprioception)

Draws mastoid process down to same side; turns chin up toward opposite side

Table obtained from : ://anatomy.med.umich.edu/nervous_system/antneck_ans.

IX. Posterior cervical triangle a. Boundaries

i. Anterior border of the trapezius m. (posteriorly) ii. Posterior border of the Sternocleidomastoid m. (anteriorly)

iii. Clavicle (inferiorly) b. Occipital Triangle: Trapezius, sternocleidomastoid and omohyoid mm (inferior belly). c. Subclavian (Supraclavicular) Triangle -Omohyoid, sternocleidomastoid mm, and the clavicle. Above clavicle. Fell subclavian vessel

Diagram obtained from: ://images.google.com/imgres?imgurl=http://iris3.med.tufts.edu/headneck/Triangles/triangle4.jpg&imgrefurl=http://iris3.med.tufts.edu/headneck/Triangles/Anterior%2520Triangle%2520of%2520the%2520Neck.htm&usg=__8eLcO82RwELMGeNf9FefKaI0IIs=&h=329&w=360&sz=25&hl=en&start=2&sig2=9sM6-zcIdHRt_IwWybOF3A&um=1&tbnid=1I0BtM_toBy7yM:&tbnh=111&tbnw=121&prev=/images%3Fq%3Danterior%2Bcervical%2Btriangles%2Bof%2Bthe%2Bneck%26hl%3Den%26rls%3Dcom.microsoft:en-us:IE-SearchBox%26rlz%3D1I7ADFA_en%26sa%3DN%26um%3D1&ei=

X. Cervical fascial layers a. Investing layer b. Prevertebral fasciaassociates w/bony spine. c. Infrahyoid fascia d. Pretracheal fascia e. Carotid sheathcarotid artery (internal jugular vein and vagus nerve are wrapped in this) f. Alar fascialinks one carotid sheath to other. g. Buccopharyngeal fasciafascia that is found on the outer aspect of buccinator msucle

Outline for boundaries of the temporal fossa, parotid region and TMJ

I. Temporal fossa a. Boundaries

i. Superior: superior temporal line of the skull ii. Anterior: frontal process of the zygomatic bone and zygomatic process of frontal bone

iii. Inferior and lateral: zygomatic arch of the skull iv. Floor: frontal, sphenoid, parietal and temporal bones

b. Contents of the temporal fossa i. Temporal fascia:

1. Extent: from the superior temporal line of the skull continuing inferiorly to envelope the external surface of the temporalis muscle. It terminates by attaching to the zygomatic arch.

2. Clinical relevance: the temporal fascia may help to contain the spread of infections by confinement to the region of the temporal fossa.

ii. Temporalis muscle: muscle of mastication 1. Origin: from the floor of the temporal fossa and temporal fascia. 2. Insertion: the coronoid process and the anterior border of the ramus of the mandible. 3. Nerve supply: deep temporal nerves from the anterior division of CN V3. 4. Action: elevates and retracts the mandible.

iii. Nerves 1. Motor:

a. Temporal branches of CN VII (facial nerve) to frontalis portion of occipitofrontalis and auricular muscles. b. Deep temporal nerve temporalis muscle

2. Sensory a. Auriculotemporal nerve from the posterior division of CN

i. Causes severe headaches associated with temporal arteritis, a severe disease. The eyeball is supplied by the ophthalmic artery, but inflammation in the superficial temporal artery can occur concurrently in the ophthalmic artery because of common vascular origin. If temporal arteritis is left untreated, it can lead to blindness. Affects patients over 60 and those who have elevated sedimentation rates. Treat with steroidsprednisone.

b. Zygomaticotemporal nerve from CN c. Greater occipital n. (dorsal ramus, C 2)

d. Lesser occipital n. (ventral ramus, C 2 - C 3) iv. Arteries

1. Superficial temporal artery: major terminal branch of external carotid. Main supply to scalp. 2. Deep temporal arteries from the maxillary artery. Supplies the temporalis muscle.

v. Anastomoses 1. Anterior: supraorbital artery (branch of ophthalmic) joins with superficial temporal artery.

2. Posterior: posterior auricular artery (branch of external carotid) joins the superficial temporal artery. vi. Lymph drainage

1. Anterior Drainage : lymph drains to parotid nodes superficial cervical nodes deep cervical nodes 2. Posterior Drainage: lymph drains to mastoid (retroauricular nodes) superficial cervical nodes deep cervical nodes

II. Parotid region a. Boundaries

i. Anterior: Ramus and angle of the mandible, masseter and medial pterygoid mm. ii. Posterior: External acoustic meatus of the temporal bone and sternocleidomastoid m.

iii. Medial: Posterior belly of the digastric m., stylohyoid m., and the sphenomandibular ligament b. Contents

i. Parotid facia 1. Great auricular nerve terminals 2. Stylomandibular ligament

ii. Parotid gland 1. Superficial portion 2. Retromandibular portion

iii. Anterior auricular/parotid nodes iv. Parotid duct

1. Crosses masseter muscles 2. Accompanies transverse facial nerve 3. Pierces buccinators muscle 4. Enters mucosa of the vestibule of the mouth lateral and superior to the second molar of the maxilla.

v. External carotid artery vi. Superficial temporal artery

vii. Transverse facial artery and vein viii. Posterior auricular nervestylomastoid branch

ix. Maxillary artery x. Retomandibular vein

xi. Great auricular n. xii. Facial n.

xiii. Auriculotemporal n. (CN

xiv. Postganlionic parasympathetics of CN IX from the otic ganglion utilize the auriculotemporal n. to reach the parotid gland. posterior div.)

xv. Postganlionic sympathetics from the superior cervical ganglion course through the parotid gland with the carotid vessels. III. Temporomandibular joint (TMJ)

a. Compound synovial joint. It possesses an intervening articular disc which divides the synovial cavity into superior and inferior compartments. b. Classified as a condylar joint, but it is truly an ellipsoid joint capable of producing a pivotial hinge type sliding and gliding action c. Establishes articulation between the condyle of the mandible, the mandibular fossa and the articular tubercle of the temporal bone.

d. Stabilized by i. Articular (fibrous) capsule

ii. Articular disc iii. Lateral ligament iv. Sphenomandibular ligament v. Stylomandibular ligament

e. Muscles acting on the TMJ: muscles of mastication i. Temporalis muscle: elevates and retracts mandible (closes the jaw)

ii. Lateral pterygoid muscle: protrudes and depresses the mandible (opens the jaw) iii. Medial pterygoid muscle: elevates and protrudes the manbile (closes the jaw) iv. Masseter muscles: elevates, protrudes and retracts the mandible (closes the jaw)

f. Innervations: i. Auriculotemporal nerveprimary supply

ii. Branches from the mesenteric nerve: derived from the anterior and posterior division of the mandibular division of the trigeminal nerve. iii. Facial nerve branches cross the joint

g. Blood supply: i. Superficial temporal artery

ii. Branches of the maxillary artery. iii. Parotid lymph nodes

Outline for Scalp, skull and cranial vault

I. Scalp a. Layers of the scalp

i. Skin: stratified squamous keratinized ii. Connective tissue: collagen

iii. Aponeurosis (galea aponeuroticaconnects the muscles that make the occipitofrontalis (epicranius) iv. Loose connective tissue layer v. Periosteum of cranial bones

b. Arterial supply i. External carotid branches

1. Superficial temporal artery 2. Posterior auricular artery 3. Occipital artery

ii. Internal carotid ophthalmic artery 1. Supratrochlear artery 2. Supraorbital artery 3. Zygomaticotemporal artery

c. Venous return i. External jugular vein

ii. Emissary veins drain the diploe (marrow) of flat bones of the skull. Superficial drainage iii. Dipole is also drained by diploic veins to the venous dural sinuses. Deep drainage.

II. Skull a. Components

i. Cranium 1. Neurocranium: skeleton surrounding the brain 2. Viscerocanium: skeleton of the face 3. Calvaria: skull cap-the flat bones of the skull 4. Cranial base: inferior aspect of the skull

ii. Mandible (jaw bones) b. Bones: 22 bones of the adult skull

i. Unpaired (6) 1. Mandible

a. Condyle

b. Coronoid process c. Mental process (protuberance) d. Mental foramen e. Mandibular foramen f. Lingula

2. Vomer: flat bone. Medial nasal septum 3. Frontal

a. Squamma (flat) b. Supraorbital margin and foramen c. Glabella --importance in strokes, reflex testing is hyperactive. It is between the supraorbital arches. d. Fontal sinuses

4. Ethmoid a. Crista galli b. Cribriform plate: sieve like plate (olfactory bulbs) c. Perpendicular plate: helps form nasal septum d. Orbital plate: delicate e. Superior and middle nasal concha

5. Sphenoid a. Greater and lesser wings b. Sella turcica: contains pituitary gland (hypoglosseal foss) c. Pterygoid process: pterygoid muscles originate here d. Optic foramen (canal): allows passage of optic nerve and ophthalmic artery e. Superior orbital fissure: CN 3, 4, 6, 5, 1, superior ophthalmic vein f. Foramen rotundum: maxillary nerve palatine fossa g. Foramen ovale: mandibular division of trigeminal h. Foramen spinosum: middle meningeal artery

6. Occipital a. Foramen magnum b. Hypoglossal canal: anterior potion of basal portion of occipital bone c. Occipital condyles d. External occipital protuberance e. Superior nuchal line f. Inferior nuchal line

ii. Paired (8) 1. Palatine 2. Inferior nasal concha 3. Maxilla

a. Anterior nasal spine b. Tuberosity c. Infraorbital foramen

4. Zygomatic a. Temporal process (zygomatic arch) b. Frontal process: articulates with frontal bone c. Maxillary process: articulates with the maxillary bone d. Zygomaticofacial foramen: zygomaticofacial nerve, artery and vein

5. Nasal 6. Lacrimal

a. Lacrimal fossa 7. Temporal

a. Zygomatic process (zygomatic arch b. Mastoid process: sternoclidomastoid process attaches here c. External acoustic meatus d. Internal acoustic meatus: labarithin/internal auditory from basilary artery e. Styloid process: stylomandibular and hyoid ligament. 3 muscles: tongue, hyoid and pharynx f. Stylomastoid foramen g. Mandibular fossa: accepts condyle of mandible h. Carotid canal i. Jugular foramen

8. Parietal: interior of bone is concave a. Parietal eminence (rounded portion) b. Parietal foramen: emissary veins

iii. Ear ossicles 1. Malleus 2. Incus 3. Stapes

c. Sutures linking the cranial bones i. Coronal: between the frontal and parietal bones

ii. Sagittal: between the parietal bones iii. Squamosal: between the temporal and parietal bones iv. Lambdoidal: between parietal and occipital bones v. Occipitomastoid: between the occipital and temporal bones. At the base of the skull. This is where eccomatic hemorrhages occur. CN 9-11

and the beginning of the internal jugular veins.

d. Cranial cavities

i. Fossae: depressions 1. Anterior cranial fossa 2. Middle cranial fossa 3. Posterior cranial fossa

ii. Orbits: contain the eyeball and extraocular eye muscle iii. Middle and inner ear structures in the temporal bone contain the ear ossicles and neuroreceptor organs. iv. Nasal cavity - contain the chonchae, and olfactory epithelium v. Paranasal sinuses - frontal, sphenoid, ethmoid, maxillary sinuses

vi. Oral cavity - hard and soft palate, teeth and tongue e. Foramina, canals and fissures

i. Supraorbital notch (foramen): supraorbital nerve ii. Infraorbital foramen: distal extent of maxillary from trigeminal nerve (infraorbital nerve)

iii. Mental foramen: distal extent of inferior alveolar nerve (mental nerve) iv. Superior orbital fissure: superior orbital nerve v. Inferior orbital fissure: inferior orbital (maxillary division)

vi. Infraorbital canal: ophthalmic artery vii. Optic foramen (canal): optic nerve

viii. Ostium of the maxillary sinus f. Skull passage

i. Incisive foramen (fossa, canal): between palatine shelves of maxilla and pre-maxilla ii. Greater and lesser palatine foramina: posterior laterally on hard palate, passage of nerves and arteries from pteryigalpalatine fossa.

iii. Foramen ovale iv. Foramen spinosum

v. Carotid canal vi. Stylomastoid foramen: major blood supply to brain (vertebral-posterior vertebral and back of brain and internal carotid-pareital). Canal is

in the temporal bone. vii. Juglar foramen: branchiomotor component of facial nerve

viii. Hypoglossal foramen (canal) ix. Foramen magnum x. Cribriform plate of the ethmoid bone

xi. Optic canal xii. Superior orbital fissure

xiii. Foramen rotundum xiv. Foramen ovale xv. Foramen spinosum

xvi. Internal acoustic meatus xvii. Jugular foramen

Outline for the infratemporal fossa

I. Boundaries a. Anterior: infratemporal portion and tuberosity of the maxilla b. Superior (roof): infratemporal parts of the greater wing of the sphenoid bone and the temporal bone c. Posterior: mandible and styloid process of temporal bone d. Medial posterior: styloid process of the temporal bone e. Medial anterior: lateral pterygoid plate of the sphenoid bone f. Floor: open

II. Muscles of mastication in the infratemporal fossa a. Lateral pterygoid muscle

i. Origin: lateral pterygoid plate of the sphenoid ii. Insertion: articular disk of TMJ (capsule of TMJ) and neck of mandibular condyle

iii. Action: protrudes and depresses the mandible (opens jaw) b. Medial pterygoid muscle

i. Origin; scaphoid (pterygoid) fossa, and pyramidal process of palatine bone ii. Insertion: inner aspect of the mandible at its angle

iii. Action: elevates and protrudes the mandible (closes jaw) III. Arteries

a. Maxillary artery (mandibular, i. Deep auricular aa.

portion)

ii. Anterior tympanic aa. : supplies part of the tympanic membrane iii. Middle meningeal a. iv. Accessory meningeal a. v. Inferior alveolar a.: mylohyoid a. (muscles on the floor of the mouth)

b. Maxillary artery (pterygoid, i. Deep temporal artery (anterior and posterior)

portion)

ii. Arterial branches to masseter and pterygoid iii. Buccal artery

c. Maxillary artery (pterygopalatine, i. Posterior superior alveolar a.

portion)

ii. Middle superior alveolar a. iii. Infraorbital a. iv. Greater (descending) palatine a.

v. Pharyngeal br. vi. A. of pterygoid canal

vii. Sphenopalatine a.: principal blood supply to nasal cavity

IV. Veins

a. Deep facial vein b. Pterygoid plexus of vein c. Maxillary vein

V. Nerves a. Mandibular nerve (CN V3)

i. Anterior division 1. N. to medial and lateral pterygoid mm. 2. N. to tensor veli palatini m. 3. N. to tensor tympani m. 4. Deep temporal nn. 5. Buccal n. (sensory)

ii. Posterior divison 1. Inferior alveolar n.

2. Mylohyoid n. (motor) 3. Recurrent meningeal n. (nervus spinosum): hangover 4. Lingual nerve

a. Chorda tympani nerve of CN VII is carried to the tongue and submandibular ganglion by the lingual nerve 5. Auriculotemporal nerve: headaches

iii. Chorda tympani n. (CN VII) iv. Postganglionic parasympathetics from otic ganglion (CN IX) v. Postganglionic sympathetics from the superior cervical ganglion via the deep petrosal nerves.

Outline for the spinal cord anatomy

I. Blood supply to the cord a. Cervical cord: anterior spinal artery

1. Spinal branches from the vertebral artery Spinal segmental branches (radicular artery which constitute an intrinsic supply to the cord) 2. Ascending cervical artery 3. External carotid branches 4. Deep cervical artery

b. Thoracic cord: 1. Upper segments (T1 T4) are vulnerable to infarction. Only a few segmental branches from the thoracic aorta supplies the cord in this

region. c. Lumbosacral cord:

1. Vulnerable to infarction 2. Artery of Adamkieqicz (Great radicular artery)

i. Sole supply to the lumbar enlargement ii. Sometimes involves following repair of aortic aneurysms iii. Redicula: a spinal nerve root

d. Venous return 1. Anterior and posterior spinal veins drain the spinal cord 2. Anterior and posterior internal vertebral plexus of veins are located in the epidural space. They drain to the intervertebral vein. 3. Intervertebral vein

i. Joins the anterior and posterior external vertebral plexus of veins and basivertebral veins that penetrate the body of the vertebra. ii. Drain to the azygous, hemiazygous vein or deep vein of the neck region.

II. Major tracts found in the funiculus a. Sensory tracts: cross over and terminate at the thalamus. Relay information to the sensory areas of the cerebral cortex. Cerebral lesions result in

contralateral defects.

1. Spinothalamic tract i. Pathway for pain and temperature ii. Enters spinal cord and crosses to the opposite half immediately (within one or two spinal cord vertebral segments) iii. Ascends to thalamus on the opposite side and then moves on to the cerebral cortex. iv. Lesion to tract: loss of pain and temperature sensation contralaterally below the level of lesion.

2. Fasciculus gracilis and fasiculus posterior column i. Pathways for proprioception, stereognosis and perception of vibration (conscious) ii. Remains on the same side of the spinal cord and crosses over at the junction between the spinal cord and the brain stem. iii. The synaptic area prior to crossing over is called the nucleus cuneatus (conveys info from the upper part of the body fasiculus

cuneatus) and nucleus gracilis (conveys proprioceptive info from lower part of the body fasiculus gracillis) iv. Lesion of the posterior column results in decrease in conscious proprioception and sterognosis ipsilaterally below the level of the

lesion. 3. Pathway for light touch

i. Partly remains uncrossed until it reaches the level of the brain stem ii. Partly crosses over at the lower level iii. Light touch spared in unilateral spinal cord lesion because there is an alternative route.

b. Sensory tract: connects with the cerebellum (unconscious organ) 1. Spinocerebellar pathway

i. Unconscious pathway for walking and performing complex tasks subconsciously without having to think which joint to flex/extend

ii. Remains ipsilateral because one side of the cerebellum connects with the same side of the body iii. Lesion to the cerebellum produces ipsilateral malfunction. iv. Cerebellum has three penduncles: superior (midbrain), middle (pons), and inferior (medulla). v. Spinocerebellar enters the cerebellum via the superior and inferior peduncles

c. Motor tract: extends from the motor area of the cerebral cortex 1. Corticospinal tract: extends from the motor area of the cerebral cortex down through the brain stem, crossing over the same level as the

medial lemniscus (junction between brain stem and spinal cord). i. Synapses in the anterior horn (motor gray matter) just prior to leaving the cord. ii. Motor neurons above the synapse (which connect the cerebral cortex and anterior horn) are the UPPER MOTOR NEURONS

(UMN). iii. Motor neuron beyond this level (peripheral nerve neurons) are the LOWER MOTOR NEURONS (LMN)

UMN LMN Spastic paralysis Flaccid paralysis No significant muscle atrophy Significant atrophy Fasciculations and fibrillations are not present

Fasciculations and fibrillations present

Hyperreflexia Hyporeflexia Babinski reflex may be present Babinski reflex not present

d. White matter contains: Ascending pathways: relay sensory information to the brain and Descending pathways: relay motor instructions down from

the brain 1. Dorsal columns (funiculus)

i. Median sulfus: seperates the right and left dorsal funiculi. ii. Intermediate sulcus: present only in segments above T6. Separates the dorsal columnsfasiculus gracilis from fasciculus cuneatus iii. Proprioception, epicritic, two point discriminative touch and vibratory sensation are carried by dorsal column pathways (DCML)

of the posterior funiculus. iv. DCML tracts

a. Ascending tracts of the spinal cord: i. Fasiculus Cuneatus: C1 to T6

ii. Fasiculus Gracilis: T6 to L5 2. Lateral columns (funiculus)

i. Sensory (anterior and posterior spinocellebellar tract, lateral spinothalmic) and motor (lateral corticospinal tract) pathways 3. Anterior columns (funiculus)

i. Motor pathways primarily (anterior corticospinal, anterior reticulospinal, lateral vestibulospinal, tectospinal trancts). Sensory (anterior spinothalmic tract)

III. Rexed Lamina & spinal gray matter nuclear groups a. Spinothalamic tract: Lamina I -V contain neurons in the dorsal grey horn that receive primarily sensory input from primary order sensory neurons

for pain, temperature and touch sensations. b. Autonomic nervous system: Lamina VI-VII: contains neurons of the intermediate grey-locus of preganglionic autonomic neurons

(intermediolateral cell column-IMLCC which is in the spinal cord sections between T1L2.

c. Nucleus dorsalis (clarks nucleus): origin of the dorsal spinocerebellar tract. Lamina VII (C8-L3). IV. Clinical considerations

a. Anacephaly: failure of neural tube to close at the cranial end. Maldevelopment of the brain. Incompatible with life b. Spina bifida: failure of neural tube to close at the caudal end. Maldevelopment of the vertebrate.

1. Meningocele: protrusion of the membranes of the brain or spinal cord through a defect in the cranium or spinal cord. 2. Meningomyelocele: protrusion of the spinal cord and its membrane through a defect in the vertebral column.

V. Spinal cord: gray matter a. Gray matter contains: Neuronal cell bodies and synapses b. Anterior gray horn: Cell bodies of lower motor neurons c. Dorsal gray horn: Axons of the sensory neurons d. Dorsal root ganglion: Cell bodies of sensory neurons

Outline for CSF

I. Blood supply to the Choroid Plexus a. Lateral ventricles

i. Anterior choroidal arteries (branches of the internal carotid arteries) ii. Posterior lateral choroidal arteries (branches of posterior cerebral arteries)

b. Third ventricle i. Posterior medial choroidal arteries (branches of posterior cerebral arteries)

c. Fourth ventricle i. Branches of posterior inferior cerebellar arteries

ii. Branches of anterior inferior cerebellar arteries (choroid plexus extends through lateral foramina) II. The flow of CSF starting with the Lateral ventricles and ending with the superior sagittal sinus

a. CSF flows from the two lateral ventricles (located in the telencephalon) through the two interventricular foramaina into the single midline third ventricle (located in the diencephalon).

b. Through the single midline of the cerebral aqueducts, this passes through the mesencephalon. c. Into the single midline fourth ventricle (located in the metencephalon and myelencephalon). The central canal is continuous with the d. Passes outside the brain via three openings in the fourth ventricle: central canal, foramen of Luschka (lateral) and foramen of Magendie (medial)

ventricle.

e. Once outside the brain, it enters into the subarachnoid space and exits into the superior sagittal sinus via specialized structures in the sinus wall called arachnoid villi.

f. An obstruction at any point along the pathway will lead to dilation of the lateral ventricles (hydrocephalus). Hydrocephalus is caused by increased levels of CSF or blockage of CSF flow. It results in an enlargement of ventricles, damage to neural tissue and alters the cranium, especially in infants.

III. Volume of CSF, and rate of production a. CSF contains fewer cells than blood plasma b. Total CSF volume is 120-150 ml c. CSF production rate is 450-500 ml/day. Turnover CSF 3-4 times a day. d. CSF provides buoyancy

Outline for Meninges

I. Membranes of the meninges a. Dura mater (outer layer): composed of fibroblasts and dense collage. Contains blood vessels, nerves and mast cells.

i. Layers 1. Periosteal: large fibroblasts not elongated. Ends at the foramen magnum (not in the spinal cord). Adherent to the sutures of the

skull. 2. Meningeal: surrounds the brain and spinal cord. Has flat and spindly fibroblasts. 3. Dural border cells: innermost layer. Continuous with the arachnoid. Lacks collage and elastic fibers. There are gap junctions and

desmosomes between the cells. Layer is split by subdural hemorrhage. ii. Anterior cranial fossa

1. Blood supply a. Cavernous portion of the internal carotid artery b. Ethmoidal arteries of the ophthalmic artery c. Branches of the ascending pharyngeal artery

2. Nerve supply a. Trigeminal nerve

i. Ethmoidal nerve (ophthalmic division CN V1) ii. Branches of maxillary (CN V2), and mandibular (CN V3)

iii. Middle cranial fossa

1. Blood supply a. Middle meningeal artery (maxillary artery) b. Accessory meningeal artery (maxillary artery) c. Branches from lacrimal artery (ophthalmic artery)

2. Nerve supply a. Trigeminal nerve

i. Branches of maxillary (CN V2) ii. Branches of mandibular (CN V3)

iv. Posterior cranial fossa 1. Blood supply

a. Branches of the ascending pharyngeal arteries b. Branches of the occipital arteries c. Branches of the vertebral arteries

2. Nerve supply a. Sensory from C1-C3 dorsal roots

v. Spinal cord: dura mater of the spinal cord forms the coccygeal ligament (filum terminale externum) 1. Blood supply

a. Meningeal branches of vertebral, intercostals and lumbosacral arteries b. These enter the spinal canal via the intervertebral foramina

2. Nerve supply a. Tentorium cerebella: tentorial nerve, branch of ophthalmic division of CN V (forms a tent between the occipital bone) b. Autonomic nerves (sympathetic innervations of blood vessels) via superior cervical ganglion. c. Spinal cord: recurrent meningeal nerves.

vi. Dural infoldings and sinuses: regions where the meningeal dura separates from the periosteal dura from infoldings including the falx cerebri.

1. Venous sinuses: lined by endothelium. Large veins of brain drain into the sinuses and these veins may be torn by trauma to the head causing subarachnoid or subdural hemorrhages.

a. Superior sagittal sinus: superior falx cerebri b. Inferior sagittal sinus: inferior falx cerebri c. Straight sinus: between superior and inferior sagittal sinuses at confluence of sinuses d. Occipital sinus: inferior to confluence of sinuses e. Transverse sinus: laterally from confluence of sinuses f. Sigmoid sinus: continuation of transverse sinuses and extends as internal jugular vein as it passes exits the jugular

foramen. g. Great cerebral vein of Galen extends to straight sinus to receive blood from the internal cerebral veins. h. Cavernous sinus: can receive blood from ophthalmic veins and receives blood from olfractory vein. i. Anterior and posterior intercavernous sinuses

j. Superior petrosal sinus (to sigmoid sinus) k. Inferior petrosal sinus (to sigmoid sinus)

2. Folds from the meningeal dura mater a. Falx cerebri extends from crista galli to internal occipital protuberance and separates cerebral hemispheres. b. Tentorium cerebelli forms roof over posterior cranial fossa and separates the occipital lobes from the cerebellum. c. Falx cerebelli extends from tentorium and separates cerebellar hemispheres. d. Diaphragma sella forms roof over pituitary fossa.

b. Arachnoid (middle layer): i. Avascular and thin

ii. Continuous with the dura. iii. Forms a barrier between dural blood and CSF (in the subaracnoid space)

1. Forms a wall of the subaracnoid space between the pia and arachnoid which is filled with cerebrospinal fluid (CSF). 2. Cisterns are expanded areas of subarachnoid space.

iv. Arachnnoid villi: 1. Protrusions of arachnoid that extend into the superior sagittal sinus to drain CSF from the subarachnoid space. 2. Known as Pacchionian bodies when large and calcified. 3. These villi are capped by arachnoid cap cells. 4. CSF passes through cells into sinus. 5. This structure is a barrier to passage of blood into subarachnoid space.

v. Arachnoid trabeculae 1. Crosses the subarachnpid space and attaches to the pia mater to form the leptomeninges 2. Consists of flattened fibroblasts attached to collagen fibrils to create strength to arachnoid.

vi. Arachnoid barrier cells 1. Continuous with dural border cells. 2. Joined together by tight junctions. 3. Form a barrier between the subarachnoid space and vessels of the dura mater.

c. Pia mater (innermost layer) i. Follows all convolutions of the brain

ii. Leptomeninges (pia mater and arachnoid) iii. Perivascular space iv. Vascularized v. Forms the denticulate ligaments and filum terminale internum

vi. The pia mater consists of flattened cells of neural crest origin and is separated from the brain by astrocyte processes (glial limitansformed by processes of astrycytes)

vii. Pia mater and arachnoid form a cuff around blood vessels that penetrate the brain creating Virchow-Robin spaces (perivascular spaces). II. Meningiomas

a. Thought to be of arachnoid origin.

b. Slow growing and benign, atypical or malignant. c. Originate at arachnoid villi or where nerves or blood vessels penetrate the dura mater. d. These tumors do not invade the brain or spinal cord parenchyma. e. Dysfunction of meningiomas is due to mass effects on the surrounding brain. f. Treatment for this tumor is usually by surgical excision, although some meningiomas can be treated by radiotherapy. g. Most common sites of meningiomas.

i. Parasagittal and falx (29%) ii. Convexity (15%)

iii. Sella (13%) iv. Sphenoid ridge (12%) v. Olfactory groove (10%)

III. Meningeal hemorrhages a. Epidural (extradural) hemorrhage

i. Usually trauma induced. ii. Middle and accessory meningeal arteries are involved.

iii. Following trauma, blood separates the periosteal dura from skull (epidural hematoma). b. Subdural hemorrhage

i. Usually trauma induced. ii. This trauma can tear bridging veins.

iii. Following injury, blood dissects along dural border cells. c. Subarachnoid hemorrhage

i. Most often caused by cerebral aneurysms (85%). ii. Other causes include damage to arteries, disorders of spinal cord blood vessels, and bleeding from tumors.

iii. The average survival rate is 50%. IV. Meningitis

a. An inflammation of the meninges, termed arachnoiditis and leptomeningitis. b. Meningitis may be caused by infection of bacterial or viral origin. c. The most common bacterial agents are Streptococcus pneumoniae and Neisseria meningitidis. d. Over 70% of cases are caused by these bacteria. e. Symptoms:

i. Alternating chills and fever, ii. Headache,

iii. Increased temperature, iv. CSF becomes cloudy and contains increased white blood cells and proteins as revealed by a spinal tap.

f. Viral meningitis (aseptic) i. Usually seen in individuals younger than 25 years of age caused by echovirus (Enterovirus), poliomyelitis and coxsackievirus which are

responsible for 80% of these cases.

ii. Symptoms 1. Fever headaches, and confusion. 2. More seriously, symptoms include seizures, rigidity and cranial nerve palsies. 3. After 1-2 weeks, the symptoms moderate, and the patient usually recovers without permanent problems.

Outline for the Orbit:

I. Eyelids: palpebral structures a. Obicularis oculi: contraction of this muscle causes eyelids to close. Blinking squeezes the lacrimal sac. The fluid is then pushed into the

nasolacramal duct into the nasal cavity. b. Levator palpebrae superioris: has a skeletal and smooth muscle component. If the superior cervical ganglion is damaged, the lid would fall because

of the smooth muscle component of the muscle. c. Orbital septum: insertion site for muscles d. Tarsal plates: superior and inferior tarsi e. Tarsal glands (meiobian glands): infection chalazion. Found in the posterior aspect of the eyelid. f. Eyelashes (cilia) and sebaceous glands: can get infected g. Palpebral conjunctiva: the part of the conjunctiva that is associated with the posterior surface of the eyelid.

II. Lacrimal apparatus a. Lacrimal gland drains into the inferior nasal cochlear. b. Pilica semilunaris: folds c. Lacrimal lake: located in the lower lid. d. Lacrimal caruncle: elevation at the medial angle of the eye e. Superior and inferior lacrimal papilla and punctum: located along the margin of the upper and lower lids. In the center of the papilla is the lacramal

pumptum, which is hole that is the beginning of the canaliculi which lead into the lacrimal sac f. Lacrimal sac occupies the lacrimal fossa on the lacrimal bone. g. Nasolacrimal duct: tears accumulate here and the inferior nasal meatus.

III. Bones of the orbit

a. Frontal b. Zygomatic c. Maxilla d. Lacrimal e. Palatine f. Sphenoid g. Ethmoid

IV. Foramina of the orbit a. Orbital canal: optic nerve and ophthalmic artery (supplies the eyeball, retina, lacrimal glands, and sinus of the ethmoid. b. Superior orbial fissue: superior ophthalmic vein, CN III, IV, VI and CN V1. c. Inferior orbital fissue: inferior ophthalmic vein and zygomatic branches of CN V2 d. Supraorbital (notch) fissure: supraorbital artery and nerve. e. Anterior ethmoid foramen: anterior ethmoid artery and nerve f. Posterior ethomoid foramen: posterior ethmoid artery and nerve g. Zygomaticoorbital foramen: zygomatic nerve which forms the zygomaticotermporal and zygomaticofascial nerves. Branches of the maxillary

division. Infraorbital artery and nerve. V. Muscles of the orbit

a. Rectus muscles: all of these originate from the common tendonous ring at the apex of the orbit i. Medial rectus: adduction or medial rotation of the eye

ii. Lateral rectus: abduction or lateral rotation of the eye iii. Superior rectus: intortion (slightrotation around x axis). Elevation of eyeball. Medially rotates eyeball iv. Inferior rectus: extorts (slights) medially rotates, depresses the eyeball

b. Oblique muscles: c. Inferior oblique: laterally rotates (abducts), elevates eyeball. (up and out) d. Superior oblique: intorts, depresses, laterally rotates eyeball. e. Levator palpebrea superioris: elevates eyelids, f. Orbicularis oculi: closes the eyelids.

VI. Nerves of the orbit

a. Optic nerve (CN II) b. Ophthalmic division of CN V1

i. Frontal n.seen in the pariorbital. Continues as the: 1. Supratrochlear n. 2. Supraorbital n.

ii. Nasociliary n.reflex testing, touching globe of eyeball. Afferent component is carried t the 1. Infratrochlear n. continues to the orbital opening anteriorly 2. Anterior ethmoidal n.

iii. Lacrimal n.: sensory nerve. Continues through the orbit comes out in superior lateral..and is a sensory nerrve. c. Oculomotor nerve (CN III)

i. Superior division => lev.pal.sup., sup.rec. mm. if you have a person that truly has a third nerve problem, (diabetes, anurism pinching the nerve), instead of being able to constrict pupil, the pupil dialates on the side of the impingement because the parasympathic is still intact from the cervical ganglion.

ii. Inferior division => med.rec., inf.rec., inf.obl. mm. d. Paraympathetic nn. - postganglionics from ciliary ganglion. Controls constriction. e. Trochlear n. (CN IV): sup.obl.m. Found in the superiormedial part of the orbittrochlear fovea. f. Abducens n. (CN VI): lat. rec.mpure abductor. g. Sympathetic nn. - postganglionics from sup.

i. cervical ganglion h. Paraympathetics CN VII postganglionics from pterygopalatine ganglion..goes to lacrimal gland.

VII. Blood vessels

a. Arteries i. Ophthalmic artery: most important. Gives off posterior cilliary arteries that cover the optic sheath of the eye (called the lamina proposa). If

this is infracted, one can go blind. ii. Anastomosis: between the branches of the ophthalmic and the external carotid. Facial artery comes up as the angular artery. Establishes

anastomosis with the supratrochlear and supraorbital (from the ophthalmic artery) b. Veins

i. Superior orbital vein drains into the venous sinus ii. Inferior ophthalmic vein goes down to the canal and into the pterygoid plexus.

Outline for Spinal cord physiology

I. Motor units a. Consists of an alpha motor neuron, its axons and all the muscle fibers it innervates.

i. Small motor units: recruited first ii. Large motor units: recruited second iii. Connecting a fast motor neuron to a slow muscle changes the muscle to a fast muscle (or vice versa) Cross innervation

b. Motor neurons determine if the muscle is a slow twitch or a fast twitch. i. Slow twitch: red, high oxidative capacity and endurance fibers ii. Fast twitch: white, glycolytic, explosive power, fatigable fibers

c. Destruction of alpha motor units i. Weakness or paralysis flaccid (LMN) ii. Muscle denervation syndrome

i. Atrophy of muscle decrease in the number of muscle fibers. ii. Spontaneous contractions in muscles

1. Fasciculation: contraction of the entire bundle. Seen by the eye 2. Fibrillation: single muscle contraction that can be detected by an EMG

d. EMG

i. Normal EMG: 2 alpha motor neurons controlling 5 individual fibers. Combined/integrated EMG from 5 action potentials.

ii. Myopathic EMG: 3 of the 5 fibers die, so there is a less volume of individual fibers. Integrated EMG is less than A because there are less spontaneous individual action potentials.

iii. Neuropathic EMG: only 1 neuron survived and it innervates the 7 muscle fibers. The EMG is larger because there are 7 individual action potentials.

iv. In a resting condition, one can still see some noise on the EMG due to normal fasiculations and fibrillations, except in myopathic diseases (no noise in EMG during resting conditions). Use an EMG to determine if its a neuropathic disease or a myopathic disease. If no EMG noise during resting state, its a myopathic disease. Can also take a blood sample and test for levels of lactate dehydrogenase and creatine kinase leaving the skeletal muscles; in myopathic disease, the levels of this enzyme is higher.

II. Spinal cord organization a. Sensory input

i. Skin afferents: touch or vibration dorsal column via the fasiculus gracilis and cuneate thalamus somatosensory cortex. ii. Proprioceptors (come form the muscles)

1. Spindle (Ia and II): I a senses changes in length and rate of the change in length. II senses a change in strength. 2. Golgi tendon organ (Ib): senses a change in tension and strength of the skeletal muscle during contraction.

e. Motor neurons i. Alpha: controls regular skeletal muscle contraction ii. Gamma: smaller and innervates the spindles. Has no direct effect on the skeletal muscle. Contracts the spindle to change the tension and the

length which causes an intrinsic stretch of type 1a and 2 fibers. External stretch occurs by stretching an actual skeletal muscle fiber. f. Interneurons: more in number than alpha and gamma combined. Involved in inhibition of alpha motor neurons and sensory integration. g. Summary of proprioceptors: outside there are extrafusal fibers (the regular skeletal muscle fibers which are innervated by alpha motor neurons) and

inside are the intrafusal fibers (which are innervated by gamma motor neurons). The muscle spindle is on the inside, which is where type Ia and type II fibers are located. When muscle is stretched, these fibers are loaded. Type Ib fiber innervates the Golgi tendon organ.

III. Stretch (myotatic) reflex a. Pathway

i. Hit the tendon stretch muscle load stimulates the type Ia and II fibers sends signal to afferent traffic sensor neurons in the DRG sends signal to stimulate alpha motor neurons leads to muscle contraction.

ii. Ia directly innervates the alpha motor neuron and causes contraction of the muscle. At the same time, through the interneuron, there is inhibition of the alpha motor neuron for the flexor muscles. Recriporacal innervations: activation of agonist and inhibition of antagonist.

IV. Inverse myotatic reflex a. Occurs when there is too much muscle tension that has developed and sensed by type Ib. b. The Golgi tension organ sends a signal via the Ib fibers through the inhibitory interneuron to inhibit alpha motor neurons of the agonist. c. Inhibitory interneuron simultaneously excites the alpha motor neuron of the antagonist.

V. Flexion (withdrawal) reflex a. Regulated by the nociceptors (pain and temperature). A painful stimulus causes withdrawal reflex. b. Ipsilateral: The excitatory interneuron activates the alpha motor neurons that supply the flexor muscles, thus causing a flexor contraction. The

reciprocal inhibitory interneuron inhibits alpha motor neurons that supply the anagonist extensor muscles. c. Contralateral: commissural interneuron cross over and synapse at the alpha motor neurons to activate the extensors and inhibit the flexors for

stabilization. VI. Superficial reflexes

a. Plantar flexion reflex: response to scratching the surface of the foot. Babinski sign dorsiflexion of the toe. This reflex is present in upper motor neuron damage.

b. Abdominal reflex: stroking skin below umbilicus produces contraction of abdominal muscles. This reflex is absent in upper motor neuron damage.

VII. Upper and lower motor neurons a. Upper motor neuron: corticospinal tract. Upper motor neuron lesion causes contralateral affects to be seen b. Lower motor neuron lesion causes ipsilateral affects to be seen.

Variable LMN UMN Weakness Flaccid paralysis Spastic paralysis Deep tendon reflex Decreased No change or hyper reactive Babinskis sign Absent Present Atrophy Significant If present it is due to disuse Fasciculation/Fibrillations Present absent

VIII. Spinal shock a. Transacation of the cord leads to immediate depression of somatic & visceral reflexes below the injury.

i. Flaccid paralysis, loss of sensation with retention of urine and feces. h. Some reflexes return but not sensation

i. Spastic paralysis, hyperactive reflexes, loss of superficial eflexes, appearance of infantile reflexes (Babinski) and novel reflexes (mass reflex)

IX. Clinical signs & symptoms of some spinal cord lesions a. ipsilateral lower motor neuron paralysis in segment of lesion (ventral horn) b. ipsilateral upper motor neuron paralysis below lesion (corticospinal tract) c. ipsilateral loss of ALL sensation in segment of lesion (dorsal horn) d. ipsilateral loss of conscious proprioception, fine touch below lesion (dorsal columns) e. contralateral loss of pain and temperature sense below lesion (spinothalamic tract)

HISTOLOGY

Outline for histology of the eye

I. Layers of the eye a. External layer (fibrous Tunic)

i. Cornea 1. Anterior 1/2. Nonvascular

of the eye

3. Colorless and clear. Transparent due to unique fiber arrangement and continual pumping out of interstitial fluid. 4. Five layers

a. Corneal epithelium: nonkeratinized stratified squamous 5-6 cells thick, contiguous with the bulbar conjunctival epithelium. Responsible for maintaining the transparency of the cornea because it is capable of transporting sodium ions to their apical surface. This keeps the stroma in a dehydrated state.

b. Bowmans membrane: contains collage fibrils, no cells c. Stroma: layers of collage, rich in chondroitin sulfate and few cells d. Descements membrane: homogenous structure of fine collagen fibrils e. Corneal endothelium: simple squamous epithelium. Responsible for maintaining the transparency of the cornea because

it is capable of transporting sodium ions to their apical surface. This keeps the stroma in a dehydrated state. ii. Limbus (corneolscleral junction)

1. Transition between the transparent cornea and white sclera 2. Highly vascularized 3. Contains stromal layer, irregular endothelium-lined channels, and trabecular meshwork, merge to form the canal of Schlemm

which drains aqueous humor from the anterior chamber of the eye. iii. Sclera

1. Posterior 5/2. Maintains the size and shape of the eye.

of the external layer of the eye.

3. External surface appears grayish/white 4. Optic nerve exits posteriorly at the lamina cribrosa, where the sclera is reduced to a fenestrated membrane 5. Anteriorly it is covered by the bulbar conjunctiva 6. Posterioly it is covered by bulbar sheath called Tenons capsule. 7. Site of attachment of the rectus and oblique muscles 8. Demarcated from the choroid by the sparchoroidal lamina (thin layer of loose connective tissue rich in melanocytes)

b. Middle layer or Vascular Tunic i. Choroid

1. Highly vascularized coat 2. Loose connective tissue rich in fibroblasts, macrophages, lymphocytes, mast cells, plasma cells, melanocytes and elastic fibers

between blood vessels. 3. Inner layer is called the choriocapillary layer rich in small blood vessels and has an important function in the nutrition of the

retina. Composed of fenestrated capillaries 4. The choriocapillary layer of the choroid is separated from the retina by a thin amorphous hyaline membrane called Bruchs

membrane. ii. Ciliary bodies

1. An anterior expansion of the choroid that lies at the inner surface of the anterior portion of the sclera. 2. Contains the ciliary muscle which controls the curvature of the lens by exerting tension via the zonules. 3. Ciliary processes are ridgelike extensions of the ciliary body from which the zonules emerge. 4. Cells from the ciliary process actively transport certain constituents of plasma into the posterior chamber as aqueous humor. 5. Aqueous humor flows from posterior chamber, over the lens to the anterior chamber and drains at the trabecular meshwork

iii. Iris 1. Extends from the angle of the anterior chamber partially covering the lens, leaving a round opening in the center called the pupil.

2. Anterior surface: spongy stroma (facing the anterior chamber) containing fibroblasts, collagen fibers and varying amounts of melanocytes.

3. Melanocytes function to keep stray light from interfering with image formation and in the stroma of the iris is responsible for the color of the eye.

4. Posterior surface: basal surface of the posterior cells attach loosely to the lens, anterior layer of the cells comprise the muscular elements and make up the dilator muscle, controlled by the sympathetic nervous system.

5. Smooth muscle bundles disposed in concentric with the papillary margin from the sphincter muscle which is parasympathetically controlled.

iv. Lens 1. Lens capsule: basement membrane, 10 20 microns thick, consisting mainly of collagen type IV, glycoproteins and heparan

sulfate proteoglycan 2. Subcapsular epithelium

a. Single layer of cuboidal epithelium b. Present on anterior surface c. At the equator, begin to elongate into fiber cells

3. Lens fiber cells a. Elongated, highly differentiated cells derived from epithelial cells b. Lose their nuclei and organelles c. At maturation, 7-10 microns in length and contains primarily crystallins as proteins

c. Internal layer or Photoreceptive Tunic

i. Retina 1. Retina comprises the inner layer and consists of a posterior portion which is photosensitive; the anterior portion, which is not

photosensitive, constitutes the ciliary body and the posterior part of the iris. 2. The ora serrata is the point of demarcation for the anterior and posterior portion of the retina. 3. The layers of the retina:

a. Pigment epithelium columnar cells with a basal nucleus that serves a variety of functions in the retina, including transport of nutrients from the choroidal blood vessels to the outer layers of the retina, removal of waste products from the sensory retina, phagocytosis of shed photoreceptor disks, synthesis of basal lamina of Bruchs membrane and is essential for the synthesis of the photopigment, rhodopsin because it converts trans-retinol into retinal.

b. Photoreceptor layer layer of outer segments of rods and cones c. Outer limiting membrane functional complexes between Muller cells and the receptor cells d. Outer nuclear layer cell bodies and nuclei of photoreceptors e. Outer plexiform layer synapses between photoreceptors and bipolar cells f. Inner nuclear layer layer of various nuclei, including Muller cells, and bipolar cells, also horizontal and amicrine cells g. Inner plexiform layer synaptic region between bipolar and ganglion cells h. Ganglion cell layer ganglion cells whose fibers form the optic nerve fiber layer i. Nerve fiber layer axons (nerve fibers) of the ganglion cells j. Inner limiting membrane formed as the basal lamina of Muller cell processes

II. Refractile media of the eye a. Cornea b. Anterior and posterior chambers-contain aqueous humor c. Lens d. Vitreous space-contains vitreous humor

Outline for Central nervous system histology

I. Parts i. Brain (cerebrum, cerebellum, brain stem) No CT in the CNS.

ii. Spinal cord II. Nervous tissue

i. Location: distributed throughout body as an integrated communications network ii. Function: to detect, analyze, integrate and transmit info generated by sensory stimuli and chemical or mechanical changes. Also to organize and

coordinate functions of the body III. General function of neurons

i. Respond to stimuli by altering electrical potential differences across membrane, which can spread along the membrane to generate an action potential (nerve impulse).

ii. Can be excitable or irritable. IV. Classification of neurons

i. Bipolar neurons: have an axon and dendrite. Found in the retina, olfactory epithelium and acuostic ganglia.

ii. Multipolar neurons: have an axon and two or more dendrites. Found throughout the NS and autonomic ganglia. iii. Pseudounipolar neurons: have single process which divides into two branches creating a T shaped structure. Found in the cranial and spinal ganglia. iv. Afferent neurons: transmit signals from the periphery t o the CNS. v. Efferent neurons: transmit signals from the CNS to the periphery.

vi. Interneurons: transmit signals within the area of the perikaryon (cell body, soma). These link neurons via synapses. vii. Projection neurons: transmit signals to distant targets.

V. General structure of neurons i. Perikaryon (neuron cell body):

a. Trophic center of the cell. It can also receive stimuli. b. Ranges from 5-150 micrometers in diameter. c. Contains nucleus and cytpoplasm. No processes. d. Receives nerve endings which transmit excitatory or inhibitory stimuli from other neurons. e. Nucleus is usually large and contains euchromatin. Also has a prominent nucleolus (cats eye). f. RER is highly developed and well organized. The RER and free ribosomes appear basophilic (stain dark purple), called Nissl bodies. g. Chromatolysis: reduction in the number of Nissl bodies due to injury to the neuron. The Nissl bodies dissolve. h. Golgi complex found only in perikaryon. i. Mitochondria abundant in the axon terminals because energy is required for transport.

j. Neurofilaments are intermediate filaments with a diameter of 10 nm. These are found in the neuronal perikaryon and processes. These form neurofibrils when tissue is stained with heavy metals, visible by light microscopy.

k. Contain 24 nm diameter microtubules that can be associated with microfilaments. Primary function is transport and mitosis. These help transport material from cytoplasm to into the axon or dendrites.

l. Lipofuscin: appears light brown; accumulates with age in the cell bodies (age pigment). Lysomes break down RER and leave behind lipofucin (brown vesicles). These are found in phagocyte cells.

m. Melanin granules: appear dark brown or black. Fount in perikarya of some neurons, particularly in substantia nigra of the midbrain. These protect nucleus from UV light.

ii. Dendrites:

a. Extend as processes from the perikarya. b. Elongated processes that receive stimuli from the environment. Takes information from the external environment back to the cell body. c. Increase receptive capacity of the neuron. The more dendrites, the more receptive the neuron is. d. Nissl bodies (RER and free ribsomes) are found in the dendrites, but not the golgi. e. Neurofilaments and microtubules are aligned along the long axis of the dendrites. f. Dendritic microtubules aid in transport of macromolecules to the distal regions g. Dendritic spines (small protusions) receive synaptic contacts. These are found all over the surface of the dendrites. In the Purkinje neuron,

there may be one million spines. iii. Axons:

a. Single process which generates or conducts a nerve impulse to other cells. b. May or may not be myelinated. Myelinated axons conduct AP faster because of salutatory conduction (jump from one node to another)

c. Plasma membrane of the axon is called axolemma and cytoplasm is called axoplasm. The PM and cytoplasm of the axon is different than that of the neuron perikarya.

d. Axon hillock is a conical elevation from which the axon originates from the perikaryon. Has no RER or free ribosomes in the axon. e. Microtubules and neurofilaments arrange in bundles. f. Initial segment: part of the axon between the hillock and the point at which it becomes myelinated. The membrane of the initial segment

has the lowest threshold of excitability. It is a site of nerve impulse initiation. Have synapses here. g. Synapse can occur between one axon and a dendrite (axodendritic), perikaryon (axosomatic) or other axon (axoaxonal). It can also be

between two dendrites (dendrodendritic)

VI. Glial cells: cytoplasm of the glial cells stains the same as surrounding tissue. Only the nuclei is seen in a stain. These cells are very small.

i. Astrocytes:

a. Largest and most abundant glial cell. Large nuclei which stains light.

b. Star shaped or satellite cells that has many processes which terminate at blood vessels, nodes of Ranvier and the neuron cell bodies. Function in ion transport; have K channels. Play a role in maintaining the ion concentration at the nodes of Ranvier.

c. Protoplasmic astrocytes found in gray matter. These cover non-synaptic neuronal surfaces. Have a clearer cytoplasm than fibrous astrocytes.

d. Fibrous astrocytes: found in white matter. Can also be found in gray matter. Have a higher level of intermediate filament proteins, glial fibrillary acidic proteins (GFAP) than protoplasmic. These proteins are used in immunocytochemistry to detect astrocytes in the brain. Take an antibody which binds t the epitopes of the molecule. Another antibody which has a fluorescent molecule binds to the primary antibody. It fluoresces when hit with light.

e. If the brain is damaged, astrocytes hypertrophy to fill up the empty space and prevent regeneration. It forms a scar or a plaque. Cells also play a role in fluid transport by their investment of blood vessels.

ii. Oligodendryocytes

a. Nuclei are round and smaller. Stain more dense than astrocyte nuclei b. Abundant in the corpus callosum because this region is highly myelinated. c. Oligodendrocytes become enlarged during myelination. In white matter, these cells are reduced in diameter. d. Satellite-support cells. Sends processes that wrap around the axon to myelinate it. e. Detected in the brain by immunocytochemistry for the presence of myelin (myelin basic protein-MBP and myelin associated glycoprotein

proteinMAG) iii. Ependymal cell

a. Cubodial or squamous cells that line the ventricles of the brain and the central canal of the spinal cord. The ependymal cells and the

underlying capillaries form the choroid plexus which produces the CSF. CSF is located in the central canal. Cells are covered in CSF. b. Have cilia in order to move the CSF down. c. Have long processes which extend into neural tissue. Can also be flattened epithelial cell shaped. Tanycytes: long process bearing cells.

These are most prevalent at the floor of the third ventricle. iv. Microglia

a. Small, dense and elongated. Nuclei contains highly condensed chromatin and are small, bean shaped b. Found in white and gray matter c. Primary phagocytic cells. Arise from bone marrow stem cells. Contribute to formation of brain microphages. d. Have short extensions and are thorn like (spiny appearance) e. Lipofusin accumulates in these cells because the cells cant recycle the breakdown product anymore.

Outline for CNS II histology

I. Myelination of the CNS

a. Nerve fibers i. Nerver fibers: axons which are surrounded by specialized membrane processes (myelin) produced by oligodendryocytes (myelinates 3-50

axons) within the CNS or by Schwann cells (myelinates 1 axon) within the PNS. ii. Larger diameter axons are usually myelinated, while smaller axons are not. The larger the axon, the more wraps of myelin and the faster

the velocity of the action potential is. Dendrities are rarely myelinated. iii. Myelinated region is called internode and the non-myelinated region is called Node of Ranvier (where the AP occurs). Adjacent to the

Nodes of Ranvier are the terminal loops of myelin, a region called the paranode. Paranodal region is not compacted to allow myelin proteins to be replenished when the proteins turn over.

iv. Unmyelinated axons have no Nodes of Ranvier; thus have a slower velocity AP. Unmyelinated axons are surrounded randomly by processes of neurons, astrocytes and oligodendrocytes.

b. Components

i. In the CNS, it is composed of complex multi-lamellar sheath wrapped around axons to facilitate in axonal conduction (salutatory conduction).

ii. There are tight junctions in the PM layers of myelin which serve an adhesive function maintaining the compaction of myelin. These are also important in proliferation and migration of progenitor cells which are destined to become oligodendrocytes.

iii. 30% is protein, 70% is lipid. 1. Protolipid protein (PLP): found in the IPL of compact myelin. 2. Myelin basic protein (MBP): found in the MDL. 3. Myelin associated glycoprotein (MAG): less than 1% of myelin protein. Role not understood, but it may be important in

remyelination during nerve regeneration and inhibit neurite outgrowth by neurons. 4. Enzyme 2, 3 cyclic neucleotide 3 phosphodiesterase (CNPase) makes up 2% of CNS myelin protein. Not restricted to nervous

tissue and function not determined. c. Process

i. Axon becomes enclosed by the process of the oligodendrocyte. The process envelopes the axon and its lips come together to form the mesaxon. Pocess wraps around the axon in a spiral fashion, one wrap inside the next.

ii. Compaction: as wraps increase, the cytoplasmic face of the PM of each side of the process becomes positioned close together to form the major dense line (MDL). MDL formation is essential. If MDL doesnt form or lacks myelin basic protein (MBP), myeline will become loosely wrapped around the axon. Find tight junctions here. MDL is the darker line.

iii. Areas of normal myelin (loops, incisures) which are not compacted allow for transport of newly synthezied myelin components from the oligodendrocytes to the myelin proper.

iv. Outer face of the PM of the processes are in close apposition and form the intraperiod line (IPL) d. Multiple sclerosis

i. Autoimmune disease that leads to nerve fibers becoming devoid of myelin. Myelin is stripped from the axons by the macrophages. MS patients have antibodies to myelin proteins within their CSF.

ii. MS plaque: spaces created by the loss of myelin is taken up by astrocytic processes (astrocytic hyperplasia or hypertrophy). The plaque stains immunocytochemicallly for glial fibrillary acidic protein (GFAP)

II. Synapses a. Allow individual nerve cells to connect with one another. Occurs on neuronal cell processes or bodies. b. Axon expanded and contains vesicles containing neurotransmitters. c. NTs are released into the synaptic cleft, an extracellular space between the pre and post synaptic neurons. The synaptic cleft is occupied by

proteins and mucopolysaccharides. d. Its function is to limit transmitter diffusion, transport NTs and formation of receptor sites. e. Postsynaptic membrane may be a dendrite, perikaryon, axon or muscle/gland cells. f. NTs released from the vesicle can bind to pre or post synaptic membrane. It can inhibit or enhance activity. g. Vesicles that hold Ach are usually clear and lead to excitatory transmission. Vesicles that hold norepi are dense staining.

III. Spinal cord

a. Gray matter

i. Composed of primarily perikarya, unmyelinated axons, protoplasmic astrocytes, satellite oligodendrocytes and microglia. ii. Located in the center H.

iii. Gray matter of ventral bars forms the anterior horn which contains large motor neurons whose axons form the ventral roots of the spinal nerves.

iv. Gray matter of the dorsal horns receives sensory fibers from neurons in the spinal ganglia dorsal roots. v. Horns: continuous columns which extend up and down the spinal cord.

b. White matter i. Composed of primarily myelinated axons, fibrous astrocytes, oligodendrocytes and microglia.

ii. Located in the periphery. c. Central canal

i. Remnant of the lumen of embryonic neural tubes which are lined by ependymal cells that have cilia, and microvilla. These extend up and down the spinal cord.

IV. Cerebellum

a. Outer layer is made of gray matter and the central core is made of white matter b. 3 layers of the cerebellar cortex

i. Outer molecular layer: receives the dendrites of the Purkinje neurons ii. Central Purkinje cells (molecular layer): Purkinje neurons

iii. Inner granule layer: receives axon of Purkinje neuron. c. Purkinje neurons receive both excitatory and inhibitory impulses which arrive from the motor areas of the cerebral cortex. These neurons are flask

like cells and axons are myelinated. d. Function: modulates and organizes the motor impulses to coordinate movement of muscle groups.

V. Cerebrum

a. Layers

i. Outer layer of gray matter: cell bodies of neurons ii. Cortex: has glia and neurons which are pyramidal, stellate and spindle in shape. These cells are arranged in 6 layers.

1. Molecular layer: outer most layer. Has nerve fibers, processes and some neurons. Light staining because it has only few neurons 2. External granular layer: granule neurons (round neurons) and glial cells. Small layer. 3. External pyramidal layer: large pyramidal and granule neurons and glial cells. 4. Inner granular layer: granule neurons and some glial cells. 5. Internal pyramidal layer: medium sized pyramidal neurons and some glial cells. 6. Multiform layer (innermost) glial cells and neurons of various shape.

iii. Core of white matter: receives myelinated axons. b. Function: sensory information is integrated, voluntary motor responses are initiated and coordinated. Cerebrum coordinates complex processes

such as language, learning and memorization.

Outline for Peripheral nervous system Histology

I. Components a. Ganglia b. Nerves c. Nerve endings and organs of special sense

II. Nerve fibers a. Axons surrounded by sheaths of cells of ectodermal origin (Schwann cells)

b. Unmyelinated axons are enveloped by clefts of Schwann cells, but these axons have no Nodes of Ranvier. c. Collagen is visible, unlike in CNS. CNS also has no basal lamina. d. Arranged in bundles to form nerves.

III. Layers surrounding the nerve fibers

a. Epineurium: external fibrous coat that surrounds the peripheral nerve. Fills the space between nerve fiber bundles consisting of collagen,

fibroplasts and blood vessels. Surrounds neurofasicles. Provides structural suppor and elasticity to the nerve. b. Perineurium: surrounds each nerve bundle (fascicle). Consists of flattened epithelial like cells. Cells are joined by tight junctions which protect the

nerve fiber from toxic macromolecules. c. Schwann cells wrap each nerve fiber d. Endoneurium: connective tissue layer consisting of reticular cells and collagen fibers. Surrounds the Schwann cells.

IV. Myelination

a. Components i. Schwann cells are the myelinating cells in the PNS. These have mitotic activity, unlike oligodendrocytes. These cells only myelinate 1

axon. These cells are immediately adjacent to axon. ii. Neurilemma: each nerve fiber in the PNS is covered by thin cytoplasmic sheath of Schwann cells. Neurilemma is the outermost

cytoplasmic layer of a Schwann cell that surrounds an axon. Overlies the endoneurium. iii. Group of unmyelinated fibers (small diameter axons) are surrounded by one Schwann cell at one point. iv. Nodes of Ranvier seen between consecutive Schwann cells. v. 30% protein,