THE SKELETAL SYSTEM: THE AXIAL SKELETON. Essential Question What is the main contribution the axial skeleton makes to homeostasis?

THE SKELETAL SYSTEM:THE AXIAL SKELETON

Essential Question

What is the main contribution the axial skeleton makes to homeostasis?

Divisions of the Skeleton

AXIAL SKELETON

Skull Cranium Face

Hyoid Auditory

Ossicles Vertebral

Column Thorax

APPENDICULAR SKELETON:

Pectoral Girdle Upper Limbs Pelvic Girdle Lower Limbs

Types of Bone

bones fall into 1 of 5 main types based on shape: Long Short Flat Irregular Sesamoid

Long Bones

longer than they are wide may be slightly curved (to absorb

stress of weight at more points along the bone i.e. Straight bones would fracture more easily)

Consist of: shaft & variable #s of ends compact bone in diaphysis and spongy

bone in epiphysis

Long Bones

Short Bones

somewhat cube-shaped nearly equal in length as width Consist of:

Spongy Bone except @ surface

Short Bones

Flat Bones

Composed of: 2 nearly parallel plates of compact

bone enclosing spongy bone inside Function:

give considerable protection place for muscle attachment

Flat Bones

Irregular Bones

complex shapes (do not fit in other categories)

vary in amt spongy bone

Sesamoid Bones

develop w/in certain tendons where there is considerable friction, tension, & physical stress

Function: protect tendon from excessive wear & tear

vary in # person to person but everyone has 2 patella which develop in quadriceps femoris tendon

Sesamoid Bone

Sutural Bones

classified by location (w/in a suture: a seam between 2 cranial bones)

not everyone has them

Bone Surface Markings

2 major types:1. depressions & openings

form joints or allow passage of vessels & nerves

2. processes projections or outgrowths that either

help form joints or serve as attachment points for ligaments & tendons

SKULL

Skull

22 bones in 2 categories:1. Cranium

8 bones that form cranial cavity

1. 1 frontal bone2. 2 parietal bones3. 2 temporal bones4. 1 occipital bone5. 1 sphenoid bone6. 1 ethmoid bone

Skull

2. Facial Bones14 bones that form the face

2 nasal bones 2 maxillae 1 mandible 2 zygomatic 2 lacrimal 2 palantine 2 inferior nasal conchae 1 vomer

Skull: Cavities

1. Cranial Cavity2. Nasal Cavity3. Orbits4. Paranasal Sinuses5. Middle & Inner Ear Cavities

Movable Joints of the Skull1. Mandible2. Auditory Ossicles

Functions of Cranial Bones1. protecting brain2. stabilizing position of brain,

vessels, & nerves through attachments to the meninges

3. outer surfaces provide large areas of attachment for muscles that move parts of the head & some for facial expression

Cranial Bones: Frontal Bone forms:

forehead upper part of eye socket most of anterior part of cranial floor in newborns: rt & lt which fuse

shortly after birth

Frontal Bone

Parietal Bones

form greater portion of sides & roof of cranial cavity

Temporal Bones

form inferior, lateral aspects of the cranium & part of the cranial floor

its zygomatic proceess forms the lateral half of the zygomatic arch

mandibular fossa: where condylar process of mandible forms TMJ (temporal mandibular joint)

Temporal Bones

Temporal Bones

external auditory meatus: ear canal mastoid: posterior & inferior to

external auditory meatus, contains “air cells” (mastoiditis: inflammation in air cells)

Temporal Bone: Petrous Portion

base of skull between sphenoid & occipital bones

houses middle & inner ear Carotid foramen & Jugular foramen

Temporal Bones

internal auditory meatus: passage of Cranial nerves VII (facial n.) and VIII (vestibulocochlear n.)

styloid process: point of attachment for muscles & ligaments of the tongue & neck

Temporal Bone: Internal Surface

Occipital Bone

forms back of head & most of base of skull

foramen magnum: large hole spinal cord passes thru,

occipital condyles: articulate with 1st cervical vertebra (atlas)

Occipital Bone

Sphenoid Bone

middle base of skull *articulates with all other cranial

bones shape resembles a bat

Sphenoid Bone

sella turcica: (Turkish saddle) the “seat” of the saddle is the hypophyseal fossa: where the pituitary gland sits

optic foramen: between body & lesser wings, cranial nerve II (optic n.) and opthlamic artery pass thru

Sphenoid Bone

Ethmoid Bone

“like a sieve” midline of anterior part of cranial

floor, anterior to sphenoid, posterior to nasal bones

cribiforme plate: forms roof of nasal cavity, the holes of the sieve where olfactory nerves pass from roof of nasal cavity to brain

crista galla: triangular process which serves as pt of attachment for meninges of brain

Ethmoid Bone

Ethmoid Bone

perpendicular plate: forms superior portion of nasal cavity

superior & middle nasal conchae: (or turbinate) increase vascular & mucous membrane surface area in nasal cavities: aids in sense of smell, warms, filters & moistens air being inhaled. Filters because the turbinates cause air to swirl as a result inhaled particles strike & become trapped in mucus

Ethmoid Bone

“Sometimes when you study anatomy, you start seeing others differently.”

Facial Bones

shape of face changes dramatically during 1st 2 yrs of life: brain & cranial bones expand 1st set of teeth erupt paranasal sinuses enlarge growth of face stops ~16 years old

Facial Bones

14 facial bones:1. 2 nasal bones2. 2 maxillae3. 2 zygomatic bones4. 1 mandible5. 2 lacrimal bones6. 2 palatine bones 7. 2 inferior nasal conchae8. 1 vomer

Nasal Bones

form part of the bridge of the nose (rest is cartilage)

Maxillae

= upper jaws *articulate with every bone in face

except the mandible form part of floor of orbits, parts of

nasal cavity, & most of the hard palate (bony roof of mouth)

each one has large maxillary sinus alveolar process is small arch that

contains the alveolar sockets for upper set of teeth

Maxillae

Cleft Palate & Cleft Lip

10-12 wks gestation the palatine processes of maxillae typically join

not doing so cleft palate +/- cleft lip speech & swallowing can be affected many ear infections reparative surgery recommended 1st

few wks of life / surgery needs to be completed by 12 – 18 mos b/4 speech: speech therapy & orthodontic care frequently necessary

Zygomatic Bones

“cheekbones”: the temporal process of the zygomatic bone articulates with the zygomatic process of the temporal bone

also part of floor of orbit

Lacrimal Bones

thin, about the size of pinky fingernail (smallest bones of face)

part of medial wall of each orbit each contain lacrimal fossa that

houses lacrimal sac: gathers tears nasal cavity

Palatine Bones

L-shaped pair of bones that form the posterior portion of the hard palate & part of floors of nasal cavity & orbit

Inferior Nasal Conchae

inferior to the middle nasal conchae of the ethmoid bone forming part of lateral wall of nasal cavity

same function as superior & middle conchae: swirling inhaled air to deposit particulates but not involved in sense of smell

Vomer

Δ shaped bone on the floor of nasal cavity forming inferior portion of nasal septum

Mandible

largest & strongest facial bone (lower jaw)

alveolar processes hold lower teeth sockets

mental foramen: dentist numb mental nerve

Sutures

an immovable joint in an adult found only between skull bones & holds most skull bones together

name generally reflects bones they unite

Sutures

1. Coronal Suture unites frontal bone to both parietal

bones Sagittal Suture

unites rt & lt parietial bones

1. Lambdoid Suture unites 2 parietal bones to occipital

bone

2. Squamous Sutures unites parietal bones to temporal

bones

Sutures

Newborn Skull

fontanels: “soft spots” present between cranial bones made of unossified mesenchyme eventually replaced by mature bone function: provide some flexibility to

fetal head allowing skull to change shape as it passes thru birth canal

Newborn Skull

Newborn Skull

Hyoid Bone

“U-shaped “ *does not articulate with any other

bone in skeleton suspended by ligaments from

styloid process of temporal bone in anterior neck between mandible

& larynx Function: supports tongue *frequently fractured during

strangulation

Hyoid Bone

Vertebral Column

aka spine, backbone 2/5 of person’s height 26 in adult (starts as 33, some fuse

to form sacrum & coccyx) 7 cervical 12 thoracic 5 lumbar 1 sacrum 1 coccyx

Vertebral Column

Fetus has anteriorly concave curve

3 mos old when holds head cervical curve develops

lumbar curve develops as infant sits up, stands, walks

Intervertebral Discs

between bodies of consecutive vertebra under compression they flatten &

broaden harden, less elastic w/aging & narrow

loss of height annulus fibrosus: outer fibrous ring nucleus pulposus: inner soft, highly

elastic

Intervertebral Discs

Parts of a Vertebra

Body thicker, anterior portion, weight bearing

portion Vertebral Foramina

contains spinal cord, adipose, areolar CT, blood vessels

Spinous Process 1 of 7 processes, posterior, palpable on

back of body

Transverse Processes: on each side, extending laterally

Vertebrae: 1st & 2nd Cervical Atlas

ring-shaped articulates with

condyles of occipital bone

allows you to nod head “yes”

Axis 2nd cervical v. allows you to

shake head “no”

Typical Cervical Vertebrae

C-3 to C7 smaller than

other v. except coccyx but vertebral foramen largest

all cervical v. have extra foramen: 2 transverse foramen for vertebral a., v., & n.

Typical Thoracic Vertebrae T-1 to T-12 larger &

stronger than cervical v.

distinguishing feature: articulate with ribs (facets on transverse processes of T-1 to T-10

Typical Lumbar Vertebrae

L-1 to L-5 largest &

strongest of the vertebrae

processes are short & thick

Sacrum

triangular bone formed by union of S-1 to S-5

fusion begins ~16, complete by age 30

female: shorter, wider, more curved S-2 to S-3

Coccyx

small triangle formed by

fusion of 4 coccygeal v. (Co-1 to Co-4), start between 20 & 30

females points inferiorly; males it points anteriorly

Thorax

refers to entire chest skeletal part of thorax is thoracic

cage Sternum Ribs

Sternum

aka “breastbone” flat bone in center of anterior

thorax 3 bones that fuse by age 25

Sternum

1. Manubrium superior portion suprasternal notch clavicular notches articulates with

costal cartilage of 1st & 2nd rib

sternal angle: where it articulates with body

Sternum

2. Body middle &

largest portion articulates with

costal cartilage of 2nd thru 10 ribs

Sternum

3. Xiphoid Process

cartilagenous in infancy

not completely ossified until ~age 40

avoid it during CPR

Ribs 12 pairs increase in length 1st thru 7th then

decrease in length to 12th 1st thru 7th ribs (true ribs) have

direct anterior attachment to sternum by strip of hyaline cartilage which contribute to elasticity of thoracic cage

8th thru 10th ribs attach to each other & then to cartilages of 7th rib

11th & 12th ribs: floating ribs

Ribs

Ribs

all 12 attach posteriorly to vertebrae

Parts of a Rib1. Head2. Neck3. Tubercle 4. Body 5. Costal Angle

Abnormal Curvatures of Spine Scoliosis lateral bending usually in

thoracic region

Abnormal Curvature of Spine

Kyphosis exaggeration of

the thoracic curve

seen in TB of spine, congenital malformation, elderly