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Physiology

Behrouz Mahmoudi

Epithelial Tissue

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Tissue: group of cells that are similar in structure and function

Histology: study of tissues

Types of Tissues:1. Epithelium (covering)2. Connective (support)3. Muscle (movement)4. Nervous (control)

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Preparing tissues for microscopy

• Specimen is fixed (preserved)• Cut into thin sections (slices)• Stained with colored dyes

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Epithelial Tissue• “epithe” = laid on, covering• Structure:

1. Covering and lining epithelium2. Glandular epithelium

• Function:– Protection– Absorption– Filtration– Secretion

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Special Properties1. Polarity

– Apical surface = exposed free surface or edge (some with microvilli, cilia)

– Basal surface = lower, attached surface2. Specialized contacts

– Fits close together to form continuous sheets

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Special Properties

3. Supported by connective tissue– Rests on basement membrane

4. No blood supply (avascular)– Rely on diffusion and underlying connective

tissue for food/O2

5. Regeneration – Replace lost cells

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Classification• Two names = (# cell layers) + (shape of cells)• Cell Layers: simple or stratified• Shapes: squamous, cuboidal, or columnar

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Simple Epithelium

Absorption, secretion, filtration Very thin

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Simple Epithelium

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Simple Epithelium Simple squamous

Filtration, rapid diffusion Capillary walls, air sacs in lungs, kidney

filtration Serous membranes: slick layer lining ventral

body cavity and its organs

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Simple Epithelium Simple cuboidal

Secretion & absorption Lines ducts of glands (salivary), kidney

tubules, ovary surface

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Simple Epithelium• Simple columnar

– Absorption and secretion– Lines digestive tract– Microvilli, cilia– Mucous membranes:

lubricating mucus

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Simple Epithelium• Pseudostratified columnar

– Rests on basement membrane – false impression (pseudo) of being multi-layered

– Secretes or absorbs– Respiratory tract – cilia propels mucus from

lungs

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Stratified Epithelium

• 2+ layers, more durable• Main function = protect

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Stratified Epithelium• Stratified squamous

– Withstand abuse, friction– Esophagus, mouth, outer portion of skin

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Stratified Epithelium• Stratified cuboidal

– Usually 2 layers– Mainly in ducts of large glands (sweat,

mammary, salivary)

Sweat Gland Esophageal Gland

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Stratified Epithelium• Stratified columnar

– Thick, waterproof layer– Pharynx, male urethra, lining ducts

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Transitional Epithelium• Able to change shape (cuboidal

squamous)• Lining of hollow urinary organs (bladder,

ureter, urethra)• Stretches when filled with urine

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Glandular Epithelium• Gland: make and secrete a particular product• 2 Types:

– Endocrine gland: produce hormones secreted into tissue fluid or bloodstream

– Exocrine gland: secrete products into ducts onto body surfaces or body cavities• Eg. mucous, sweat, oil, saliva, bile

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Exocrine Glands

Unicellular• Mucus cells or goblet

cells

Multicellular• Duct structure