Epithelial Tissues Good fences make good neighbors Epithelial

Epithelial Tissues Good fences make good neighbors

Epithelial Tissues § Cover ALL body surfaces, line organs, are major tissues of glands § 1 side is exposed to open space, underside is attached to connective tissue by a thin, non-cellular basement membrane § Lack blood vessels, fed by diffusion from well vascularized connective tissues

More Epithelial Characteristics § Reproduce rapidly § Tightly packed § Good barriers: Skin, lining of mouth § Involved in secretion, absorption, excretion, sensory reception

Simple Squamous Epithelium § 1 layer, thin, flattened § Broad, thin nucleus § Things pass through these easily: diffusion, filtration § Easily damaged § Found in: Alveoli, capillary walls, blood, lymph vessel lining, body cavity lining

Simple Squamous Epithelium

Simple Cuboidal Epithelium § 1 layer, cube shaped cells § Central, spherical nucleus § Covers ovaries, kidney tubules, glandular ducts (salivary, thyroid, pancreas, liver) § Secretion (in glands) § Absorption (kidneys)

Simple Cuboidal Epithelium

Simple Columnar Epithelium § Elongated, 1 layer § Nuclei located near basement membrane on about the same level § Line uterus, most organs of digestive tract § Thick, protective of underlying structures § Secretes digestive fluids, absorbs nutrients § Can have microvilli § Can have goblet cells embedded, secrete mucus onto surface

Simple Columnar Epithelium

Pseudostratified Columnar Epithelium § Appear layered, but not: Nuclei stacked at different levels § Often found with cilia, goblet cells scattered throughout § Lines respiratory, reproductive systems

Pseudostratified Columnar Epithelium

Stratified Squamous Epithelium § Thick, composed of several layers § Cell division at deeper layers, older cells get pushed up/out § In epidermis, lines mouth, throat, vagina, anus § In epidermis, keratin (a tough protein) causes old cells to harden and die, forming a protective layer. § Keritinization causes cells to become tough, dry § This keeps water in, chemicals, microbes out

Stratified Squamous Epithelium

Stratified Cuboidal Epithelium § Have 2 -3 layers which line a lumen § Line larger ducts like in mammary glands, sweat glands, salivary glands, pancreas § Also found lining ovarian follicles, seminiferous tubules

Stratified Cuboidal Epithelium

Stratified Columnar Epithelium § Layers of cells § Superficial (shallow) cells are elongated, deeper cells (basal layers) are cuboidal § Found in male urethra, vas deferens, parts of pharynx

Stratified Columnar Epithelium

Stratified Columnar Epithelium vs Stratified Cuboidal Epithelium

Transitional Epithelium § Changes in response to tension: stretchy § Inner lining of bladder, lining of urinary passages § Several layers of cuboidal cells § Flatten when stretched, cuboidal when relaxed § Keeps urine in

Transitional Epithelium

Glandular Epithelium § Specialized to make and secrete a product § Found mostly within cuboidal and columnar epithelia § Exocrine glands secrete into ducts. § Merocrine glands: watery, protein-rich secretions § Serous Cells: secretions are watery, enzyme filled (serous fluid): found in glands in body cavities § Mucous cells: secrete thick mucous containing mucin, a glycoprotein: In digestive, respiratory systems § Holocrine Glands: cell bursts during secretion § Apocrine glands: cell loses some cytoplasm during secretion § Endocrine glands secrete into blood

Glandular Epithelium