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EPITHELIAL TISSUE

EPITHELIAL TISSUE. Types of Epithelial Tissue. Membranous : covering or lining of body and parts; Lines cavities, vessels, respiratory, digestive and urinary/ reproductive systems Glandular : grouped in spinal cord, specialized follicles in the endocrine and exocrine glands. Functions.

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EPITHELIAL TISSUE

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  1. EPITHELIAL TISSUE

  2. Types of Epithelial Tissue • Membranous: covering or lining of body and parts; Lines cavities, vessels, respiratory, digestive and urinary/ reproductive systems • Glandular: grouped in spinal cord, specialized follicles in the endocrine and exocrine glands

  3. Functions • Protection: protection of body from chemical and mechanical injury; from bacteria and other microorganisms • Sensory: skin, nose, eyes, ears • Secretion: hormones, digestive juices, mucus, sweat • Absorption: nutrients from the gut, respiratory gases in the lungs • Excretion: kidney tubules for excretion of urine

  4. Epithelial Info • Attaches to connective tissue with the BASEMENT LAYER • Contains no blood vessels; AVASCULAR • Oxygen and nutrients come from capillaries in the basement layer

  5. Membranous Epithelium • Classified based on cell shape • 4 types: • Squamous: flat and platelike • Cuboidal: cube shaped • Columnar: higher than they are wide • Pseudostratified Columnar: one layer of oddly shaped columnar cells, some cells do not reach the surface but all touch the basement layer

  6. Membranous Epithelium • Can also be classified based on layers of cells • Simple Epithelium: single layer • Stratified Epithelium: cells are layered on one another • Transitional Epithelium: different cell shapes layered in a sheet

  7. Simple Squamous Epithelium • One layer of flat, scale-like cells • Easy for substances to diffuse or filter across • Found commonly in Aveoli in lungs, lining of blood vessels and lymphatic vessels • Endothelium: blood and lymphatic vessel lining • Mesothelium: surfaces of the pleura, pericardiaum, periteneum

  8. Simple Cuboidal Epithelium • One layer of cuboidal cells • Found in glands and ducts and tubules of some organs (kidney)

  9. Simple Columnar Epithelium • Single layer of tall cells • Surface of mucous membranes that line: stomach, intestines, uterus, uterine tubes, parts of respiratory system, goblet cells • Contains MICROVILLI: increases surface area of intestinal mucosa

  10. Pseudostratified Columnar • Found in air passages and in certain segments of the male reproductive systems • Why is it PSEUDOSTRATIFIED?

  11. Stratified Squamous • Keratinized Epithelium • Multiple layers of typical flattened squamous cells at the outer surface of the epithelial sheet • Presence of keratin helps with the protective qualities of the epithelium

  12. Stratified Squamous • Non-Keratinized Epithelium • Found lining the vagina, mouth and esophagus • Free surface is moist, does not contain keratin • Serves a protective function

  13. Stratified Cubiodal • Two or more rows of cubiodal cells are arranged over the basement layer • Located in the sweat gland ducts, pharynx, over the epiglottis (covers the larynx)

  14. Stratified Columnar • Only most superficial cells are truly columnar • Located in the male urethra and mucousal layer near the anus

  15. Stratified Transitional • Found in areas that are subjected to stress and tension changes • Wall of the urinary bladder

  16. Glandular Epithelium • Specialized for secretion • Can function singly as unicellular glands or function in clusters, cords or follicles as multicellular glands • All glands are either ENDOCRINE or EXOCRINE • Exocrine: discharge secretion into ducts; ex. Salivary glands • Endocrine: ductless, discharge hormones into blood or tissue; ex. Pituitary, thyroid and adrenal glands

  17. Multicellular Exocrine Glands • See table 5-5 for diagrams and descriptions • APOCRINE GLANDS: collect their products near the tip of the cell and release into a duct by pinching off the end; Ex. Mammary Glands • HOLOCRINE GLANDS: collect secretions inside the cell and then rupture to release; Ex. Sebaceous glands • MEROCRINE GLANDS: discharge secretions directly through the cell membrane; Ex. Salivary glands

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