GENERAL HISTOLOGY
DR SAMINA SHAHEENASSISTANT PROFESSOR OF ANATOMY
KEMU
BASIC TISSUES
Epithelium
Connective tissue
Muscular tissue
Nervous tissue
Organs divided into:
Parenchyma –cells
Stroma –supporting tissue
SIMPLE SQUAMOUS EPITHELIUM
Composed of very thin flat
irregular shaped cell that form
a continuous surface
Also called pavement
epithelium
Found in:
Lining of blood & lymph vessels
Alveoli of lungs
Parietal layer of Bowman’s
capsule
Loop of Henle in kidney
SIMPLE CUBOIDAL EPITHELIUM
Cells appear cube or box like
Nucleus is rounded & placed in
centre of cell
cells rest on basement
membrane
Present in:
Follicles of thyroid gland
Distal convoluted tubules of kidney
FUNCTION
Absorption
excretion
SIMPLE COLUMNAR NON CILIATED EPITHELUIUM
Composed of tall columnar cells
Rests on basement membrane
Nucleus in elongated & lies in basal half of cell
Apical surface of cells may have microvilli which give apperance of brush border
Found in: Lining of GIT FUNCTIONS: Absorption Excretion
SIMPLE COLUMNAR CILIATED EPITHELIUM
CILIA present on surface of
simple columnar epithelium
Present in:
Small intrapulmonary bronchi
Simple columnar non-ciliated
cells may be present between
ciliated cells
Example :
Uterine tube
Efferent ductules of testis
PSEUDOSTRATIEIED EPITHELIUM
NON-CILIATED
Variant of simple columnar
epithelium
Tall & short cells are present
All cells rest on basement
membrane
Nuclei disposed at different
levels
Present in;
Parts of male urethra
PSEUDOSTRATIEIED EPITHELIUM
CILIATED
This epithelium
may be ciliate
with goblet cells
Example:
Trachea
Larger bronchi
STRATIFIED EPITHELIASTRATIFIED SQUAMOUS NON
KERATINIZEXEPITHELIUM Multi-layered Basal layer low columnar or high
cuboidal This layer divides Subsequent layers polygonal Surface layers flattened Underlying connective tissue
raised into ridges Examples : Oesophagus Anal canal Cervix Vagina
STRATIFIED SQUAMOUS KERATINIZED EPITHELIUM
Features same as
non-keratinized
epithelium except
Surface layer
composed of non-
nucleated cells
They acquire
protein keratin
Example :
Skin
TRANSITIONAL EPITHELIUM
IN RELAXED STATE Is 4-5 cell layer thick Basal layer is cuboidal Intermediate layer is
polyhedral surface layer is cuboidal
with binucleate cells
IN STRETCHED STATE Is 2-3 cell thick Surface layer is
squamous Example : urinary tract
STRATIFIED CUBOIDAL
Consists of two
layers of cuboidal
cells
Cells of superficial
layer are smaller
Examples :
Ducts of salivary
glands
Ducts of sweat
glands
STRATIFIED COLUMNAR EPITHELIUM Basal layer consists of low columnar or cuboidal cells
Surface layer is of tall columnar cells
Examples :
Conjunctiva
Parts of male urethra
ENDOTHELIUM Lines all blood & lymph channels
MESOTHELIUM Lining of pleura, pericardium & peritoneum
CONNECTIVE TISSUE
Characterized by the presence of relatively few cells & abundant
intercellular substance
FUNCTIONS
STRUCTURE
Cells
Fibres
Ground substance
Develops from MESENCHYME
CELLS OF CONNECTIVE TISSUE
Fibroblasts
Mast cells
Plasma cells
Macrophages (histiocytes)
Leukocytes
Adipocytes
MESENCHYMAL CELLS
FIBROBLASTS
MACROPHAGES
PLASMA CELLS
MAST CELLS
ADIPOCYTES
FIBERS OF CONNECTIVE TISSUE
Collagen
Elastic
Reticular
COLLAGEN FIBERS
ELASTIC FIBERS
RETICULAR FIBRES
GROUND SUBSTANCE
Glycosaminoglycans (mucopolysaccharides)
Proteoglycans
Multiadhesive glycoproteins
TYPES OF CONNECTIVE TISSUE
Embryonic connective tissue Mesenchyme Mucous
Adult connective tissue Connective tissue proper
Loose Dense
Irregular Regular
Specialized Reticular Adipose
Bone Cartilage
LOOSE CONNECTIVE TISSUE & DENSE IRREGULAR CONNECTIVE
TISSUE
DENSE REGULAR CONNECTIVE TISSUE
RETICULAR TISSUE
EMBRYONIC CONNECTIVE TISSUE
MESENCHYME MUCOUS
CARTILAGE
Cells (chondrocytes)
Extra-cellular matrix
Fibrils
Ground substance
Proterglycan
Glycosaminoglycanp (mucopolysaccharide)
TYPES OF CARTILAGE
Hyaline
Elastic
Fiibrocartilage
HYALINE CARTILAGE
ELASTIC CARTILAGE
FIBROCARTILAGE
BONE
Cells Osteocytes Osteoblasts Osteoclasts
Bone matrix Organic
Collagen type 1 Ground substance
Proteoglycans Glycoproteins
Inorganic Hydroxyapatite Ca Po4, magnesium, bicarbonate, citrate, sodium & potassium
TYPES OF BONE(GROSS OBSERVATION)
TYPES OF BONE(MICROSCOPIC EXAMINATION)
PRIMARY/IMMATURE BONE SECONDARY/ MATURE
MUSCLE
Skeletal muscle
Smooth muscle
Cardiac muscle
ORGANIAZATION OF SKELETAL MUSCLE
Endomysium – muscle fiber
Perimysium – fascile
Epimysium – entire muscle
ORGANIZATION OF SKELETAL MUSCLE
SKELETAL MUSCLE
CARDIAC MUSCLE
CARDIAC MUSCLE
SMOOTH MUSCLE
SMOOTH MUSCLE
COMPARISON BETWEEN THE THREE TYPES OF MUSCLES
NERVE TISSUE & NERVOUS SYSTEM
Central nervous system Brain & spinal cord
Peripheral nervous system Spinal, cranial & peripheral nerves ganglia
Nerve cells (neuron) Glial cell (supporting cells)
STRUCTURE OF NEURON
Cell body
Axon
dendrite
GLIAL CELLS
CNS
Oligodendrocytes
Ependymal cells
Astrocytes
Microglial cells
PNS
Neurolemmocytes
(Schwann cells)
Saltellite cells
PERIPHERAL NERVOUS SYSTEMCOMPONENTS OF PNS• Nerves• Ganglia• Nerve endings.CONNECTIVE TISSUE COMPONENTS OF A
PERIPHERAL NERVE:• Endoneurium: constitues the loose c.t
associated with individual nerve fiber. It merges with an external lamina of IV collagen ,laminin and other proteins produced by schwann cells. Other cells are fibroblasts and mast cells.
• Perineurium is a specialized c.tissue surrounding a nerve fascicle. It serves as a metabolically active diffusion barrier that contribute to the formation of blood –nerve barrier. It may be one or two cell thick depending on the nerve diameter .It is formed by layers of flattened epithelial cells. The cells of each layer of the perineurium are joined at their edges by tight junctions
• Epineurium consists of dense irregular c .tissue that surround and binds nerve fascicles into a common bundle. Blood vessels that supply the nerve travel in epineurium.
GANGLIA• It is an ovoid structures
contain neuronal cell bodies and glial cells supported by c.tissue.
• Serves as relay stations to transmit nerve impulses.
Types of ganglia:• Sensory ganglia: They
receive afferent impulses that go to the CNS. They are associated with cranial nerves called cranial ganglia, and the dorsal root of spinal nerves called spinal ganglia
continued….• Connective tissue capsule which is continuous
with the epineurium of nerve on which ganglion is situated Ganglion cells are neurons of pseudounipolar type. Each neuron gives rise to a single process which makes several irregular turns around the cell body and bifurcate in a T- shaped manner. One branch acts as dendrite and pass in a spinal or cranial nerve to periphery and terminate at a receptor and other branch act as functional axon and passes to CNS. Size of nerve cell body varies. Small cell bodies give rise to unmyelinated processes, large perikarya give origin to myelinated processes. Nerve cell bodies are arranged as groups in peripheral zone of ganglion and surrounded by a single layer of low cuboidal cells called satellite cells. The central zone is devoid of nerve cell bodies and contain nerve fibers.
AUTONOMIC GANGLIA• They are associated with
sympathetic and parasympathetic division of autonomic nervous system.
• Arranged as small bulbous dilatations in autonomic nerves.
• Located in certain organs especially in the wall of GIT called intrameural ganglia.
• Covered by less well developed c. tissue capsule.
• Multipolar neuron which are evenly distributed.
• Covered by a layer of satellite cells.
• Parasympathetic ganglia lacks distinct capsule, perikarya and associated satellite cells form a loosely organized plexus within the surrounding c .tissue.
STRUCTURE OF THE CEREBRAL CORTEX The cerebral cortex forms a
complete covering of the cerebral hemisphere. It is composed of gray matter and contains approx. 10 million neurons. The gray matter contains nerve cells, neuroglia and blood vessels. The following types of nerve cells are present in the cerebral cortex: Pyramidal cells Nonpyramidal cells
PYRAMIDAL CELLS
Contains a large vesicular nucleus
Abundant nissl granules One main dendrite arises from
the apex and ends in the most superficial layer of the cortex.
Four or more branching dendrite pass outward from the base of the perikaryon.
Axon emerges from the center of the base and runs into the underlying white matter.
Classified into small, medium and large varieties.
Nonpyramidal cells Stellate/granule cells: small polygonal
perikaryon; each cell gives off a number of small dendrites passing in various direction and a short axon which ramifies close to the cell body; most of the extrinsic inputs to the cerebral cortex terminate on the dendrites of the stellate cells.
Horizontal cells of cajal: small, fusiformed, horizontally oriented; found in the most superficial cortical layer; has many short dendrites and a long axon which runs parallel to the surface of the cortex making contact with the dendrites of the pyramidal cells.
CONTINUED Martinotti cells: small, multipolar cells found in the
deeper layers of the cerebral cortex; has a short dendrite but the long axon ascends towards the cortical surface to end in a more superficial layer.
Fusiform cells. They have long axis vertical to the surface and concentrated mainly in the deeper cortical layers.Dendrites arise from each pole of the cell body and ascend toward the surface of the surface of the cortex and branch in the superfical layers. The axon arises from the inferior pole of cell body and enter the white matter as a projection ,association or commissural fiber.
LAYERS OF THE CEREBRAL CORTEX Molecular or Plexiform Layer:
composed chiefly of cell processes (of the cells lying in the deeper layers). Some horizontal cells are also present.
External Granular Layer: contains large number of small pyramidal cells and numerous closely packed stellate cells.
Pyramidal Cell Layer: also known as external pyramidal layer and is composed mainly of large pyramidal cells. some granule cells are also present.
Internal Granular Layer: consists of closely packed stellate cells. There is a high concentration of horizontally arranged nerve fibers known as outer band of Baillarger.
Ganglionic Layer: also known as internal pyramidal layer contains large pyramidal cells. Scattered among the pyramidal cells are stellate and martinotti cells. This layer also contains a large number of nerve fibers which forms the inner band of Baillarger.
Multiform Layer: composed of neurons of many shapes. Also contains pyramidal cells, stellate cells and martinotti cells.Many nerve fibers are also present that are entering or are leaving the underlying white matter.
All areas of cerebral cortex do not possess six layers.
They are called as heterotypical as compared to majority which are homotypical and possess six layers.
Two heterotypical areas are the granular type and the agranular type.
In the granular type layer 2 and 4 are well developed and layer 3 and 5 are poorly developed. It is found in postcentral gyrus.
In agranular type layer 2 and 4 are absent, pyramidal cells in layer 3 and 5 are densely packed and are very large . It is found in precentral gyrus. These areas are associated with motor functions.
CEREBELLUM Cerebellum is
composed of an outer covering of gray matter called cortex and inner white matter. Embedded in the white matter of each hemisphere are three masses of gray matter forming intracerebellar nuclei.
STRUCTURE OF CEREBELLIUM The cerebellar cortex on section shows
three layers from within outwards. Molecular layer: This layer contains
two types of neurons, the outer stellate cells and inner basket cells. These neurons are scattered among dendritic arborizations and numerous thin axons that run parallel to the long axis of the folia. Neuroglial cells are found between these structures.
The Stellate cells have small star- shaped perikarya.Each cell has many short thin dendrites and a fini unmyelinated axon.The dendrites ramify near the cell body,while the axon extends tranversely to make synapses with the dendrites of Purkinje cells.
The Basket cells have small perikarya which give rise to numerous branching dendrites that ascends towards the surface. The unmyelinated axons of the basket cell runs horizontally,along its course it gives off many descending branches which form basket like terminal arborization around the bodies of the Purkinje cells.
PURKINJE CELL LAYER The Purkinje cells are large Golgi type l
neurons they are flask shaped and are arranged in a single layer. In a plane transverse to the folium ,the dendrites pass into the molecular layer, where they undergo profuse branching. The primary and secondary branches are smooth and subsequent branches are covered by short thick dendritic spines.Spine form synaptic contacts with the parallel fibers derived from the granule cell axons.
At the base of thePurkinje cells, the axons arises and passes through the granular layer to enter the white matter. On entering the white matter, the axons acquires a myelin sheath, and it terminates by synapsing with cells of one of the intracerebellar nuclei .Collateral branches make synaptic contact with the dendrites of basket and stellate cells of the granular layer in the same area or in distal folia. A few Purkinje cell axons pass directly to end in the vestibular nuclei of the brainstem.
GRANULAR LAYER
Small granule cells with dark staining nucleous with very little cytoplasm.
Also present in this layer are Golgi type II cells with vesicular nucleous and abundant cytoplasm
Clear spaces called glomeruli are present in this layerEach granule cell give rise to four to five short
dendrites .The unmyelinated axon of agranule cell ascend to the molecular layer where it bifurcate into two branches and called parallel fibers .Thesefibers make synapses with dendrites of purkinje cells. .
AFFERENT FIBERS OF CEREBELLUM Climbing fibers .They originate from inferior
olivery nucleus of m.oblongata.Asthey enter in cerebllum they run in white matter and then synapse with dendrites of purkinje cell in molecular layer.
Mossy fibers .They originates in spinal cord and terminate in glomeruli of cerebellar cortex where they synapse with dendrites of granule cells and axons of golgi type11 cells
CEREBELLUM
CEREBELLUM
SENSORY NERVE ENDINGS OR RECEPTORS• Morphologically divided into:• Non –encapsulated or free nerve endings• Encapsulated nerve endings• Free nerve endings• Afferent fibers are myelinated or unmyelinated• Specialized to respond to sensation of pain,
temperature or light touch.• In epidermis of skin they form disc like endings
with modified epithelial cells called Merkel corpuscle.
• Function as mechanoreceptors, detecting mechanical displacement of skin.
ENCAPSULATED NERVE ENDINGSTactile corpuscles of meissner:• Located in non hairy skin especially finger
tips, palm and soles, lips and nipples.• Oval bodies covered by c.t capsule
continuous with epineurim of nerve supplying the corpuscle which contain multilayered flattened cells.
• Myelinated nerve fibers supply each corpuscle.
• They are concerned with perception of touch sensation.
RUFFINIS ENDINGS
Fusiform struture 1-2mmin length and present in skin in joint capsule.
Consist of thin c.tissue capsule containing a fluid filled space.
A single myelinated nerve supply it .
Function as mechanoreceptor.
END BULB OF KRAUSE
They are spherical bodies covered by a c.tissue capsule and contain a central cavity.
A myelinated nerve supply it. Concerned with perception of cold
sensation Present in skin.
MUSCLE SPINDLES• Present in skeletal
muscle.• Fusiform structure,0.5-
5mm in length.• Consist of intrafusal
fibers and covered by a capsule.
• Supplied by both afferent and efferent fibers.
• Concerned with regulation of reflex muscle tone.
TENDON ORGANS OF GOLGI
Located in tendons close to muscle tendon junction.
Consist of small bundle of collagen fibers covered by a c.tissue capsule.
A large myelinated nerve enter the organ.
They respond to an increase in muscle tension.
NERVE FIBERS
PERIPHERAL NERVE
Endoneurium
Perineurium
epineurium
CIRCULATORY SYSTEM
Heart
Arteries
capillaries
Veins
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Blood Vessel Tunics Tunica Intima, or Tunica Interna
innermost layer composed of:
an endothelium (simple squamous epithelium) subendothelial layer (areolar CT)
Tunica Media middle layer of the vessel wall composed of:
circularly arranged smooth muscle cells Sympathetic innervation:
Increase: vasoconstriction (narrowing of the blood vessel lumen)
Decrease: vasodilation (widening of the blood vessel lumen)
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Blood Vessel TunicsTunica Externa, or Tunica Adventitia
outermost layer composed of:
areolar connective tissue that contains elastic and collagen fibers helps anchor the vessel to other tissues Term adventitia is used to specify outer layer in blood
vessels that are buried in CT Vasa vasorum : blood vessels that supply large blood
vessels In the externa
Arteries vs Veins: Media largest in arteries, externa largest in veins Lumen is smallest in arteries Artery wall have more elastic and collagen fibers
Capillaries: only the Interna
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Arteries In the systemic circulation, carry
oxygenated blood to the body tissues. Pulmonary arteries carry deoxygenated
blood to the lungs. Three basic types of arteries:
elastic arteries, muscular arteries, and arterioles
as an artery’s diameter decreases corresponding decrease in the amount of elastic fibers relative increase in the amount of smooth muscle
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Capillaries Contain only the tunica intima, but this layer
consists of a basement membrane and endothelium only.
Allow gas and nutrient exchange between the blood and the body tissues to occur rapidly.
Smallest blood vessels, connect arterioles to venules.
Are called the functional units of the cardiovascular system.
A group of capillaries (10–100) functions together
and forms a capillary bed.
STRUCTURE OF BLOOD VESSELS
Endothelium Smooth muscle Connective
tissue Collagen fibers Elastic fibres
Tunica intima Tunica media Tunica
adventitia
ARTERIES
Elastic artery
Muscular aryery
Arterioles
Capillaries
ELASTIC ARTERY
MUSCULAR ARTERY
ARTERIOLE
CAPILLARIES
STRUCTURE OF VEINS
VEINS
Venules
Medium sized veins
Large sized veins
SMALL VEIN
MEDIUM SIZED VEIN
LARGE VEIN
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