73254007 Epithelial Tissue

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Elwathiq Khalid IbrahimUniversity of Kassala

Department of AnatomyDecember 2010


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Histology:

the study of tissues.

Tissues: groups of cells with similar structureand functions.


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Epithelial Tissue Connective Tissue

Muscle Tissue

Nervous Tissue


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Epithelium Coverings Linings of

surfaces

Connective Support

Bone, ligaments,fat

Muscle Movement

Nervous Control Brain, nerves,

spinal cord


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http://www.nucleusinc.com/


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Form continuous sheets Apical Surface

All epithelial cells have a top surface that bordersan open space known as a lumen

Basement Membrane Underside of all epithelial cells which anchors them

to connective tissue

Avascularity (a = without) Lacks blood vessels

Nourished by connective tissue Regenerate & repair quickly


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Figure 4.1


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Tight junctions Desmosomes

Gap junctions


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Human Anatomy, Larry M. Frolich,Ph.D.


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Protection Skin protects from sunlight & bacteria &physical damage.

bsorption Lining of small intestine, absorbingnutrients into blood

Filtration Lining of Kidney tubules filtering

wastes from blood plasma Secretion

Different glands produce hormones,digestive enzymes and mucus


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Human Anatomy, Larry M. Frolich,Ph.D.


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Structure Single Layer of flattened cells

Function Diffusion, and filtration

Not effective protection single layer of cells. Location

Walls of capillaries, air sacs in lungs Form serous membranes in body cavity


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Figure 4.3a


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Structure Single layer of cube shaped cells

Function

Secretion and transportation inglands Location Glands and ducts (pancreas &salivary), kidney tubules, coversovaries


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Figure 4.3b


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Structure Elongated layer of cells with nuclei at

same level Function

Absorption, Protection & Secretion

When open to body cavities calledmucous membranes Special Features

Microvilli, bumpy extension of apicalsurface, increase surface area andabsorption rate.

Goblet cells, single cell glands, produceprotective mucus.

Location Linings of entire digestive tract


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Figure 4.3c


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microvilli

capillarieslacteal

secretorycell

absorptive cell

intestinalgland

artery

vein

lymphaticvessel


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Structure Irregularly shaped cells with nuclei at

different levels appear stratified, butarent.

All cells reach basement membrane Function

Absorption and Secretion

Goblet cells produce mucus

Cilia (larger than microvilli) sweep mucus

Location Respiratory Linings & Reproductive tract


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Figure 4.3d


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Cili

a

Basement

Membrane


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Contain two or more layers of cells Regenerate from below

Major role is protection

Are named according to the shape of cells atapical(superficial) layer


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Structure Many layers (usually cubodial/columnar at

bottom and squamous at top)

Function Protection Keratin(protein) is accumulated in older

cells near the surface waterproofs andtoughens skin.

Location Skin (keratinized), mouth & throat (non-

keratinized)


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Figure 4.3e


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Multiple, mostly double rows of columnarcells . Rare!!

Location sweat glands and male urethra

Function barrier , conduit (thus ducts)


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Structure Many layers Very specialized cells at base are

cuboidal or columnar, at surface will vary.

Change between stratified & simple astissue is stretched out.

Function Allows stretching (change size)

Location Urinary bladder, ureters & urethra


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Figure 4.3h


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Epithelial cells specialized to producesecretion.

All glands are of composed of

epithelium. Molecules to be secreted may bestored in membrane bound secretory

granules (vesicles)


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A) Presence or absence of ducts: Exocrine ducted

Endocrine - ductless

B) Uni- or multicellularC) Mode of secretion

D) Secretion products


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GL NDUL R EPITHELIUM

Small intestine with villiMucin stain showing goblet cells

Colon with NO villiMucin stain showing goblet cells


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(How the glands product is released) Merocrine

Just released by exocytosis withoutaltering the gland at all.

Ex: Sweat glands and salivary glands Holocrine

The gland ruptures and releases secretionand dead cells as well.

Sebaceous (oil glands on the face) onlyexample


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73254007 Epithelial Tissue

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