Epithelial Tissue Epithelial Tissue Tissues - Introduction · a group of similar cells specialized to carry on a particular function · tissue = cells + extracellular matrix nonliving portion of a tissue that supports cells · 4 types epithelial - protection, secretion, absorption connective - support soft body parts and bind structures together muscle - movement nervous - conducts impulses used to help control and coordinate body activities Epithelial Tissues Characteristics Epithelial Classifications · free surface open to the outside or an open · classified based on shape and # of cell layers internal space (apical surface) · shape · basement membrane anchors epithelium to squamous - thin, flat cells underlying connective tissue cuboidal - cube-shaped cells columnar - tall, elongated cells · lack blood vessels · number · readily divide (ex. skin healing) simple - single layer · tightly packed with little extracellular space stratified - 2 or more layers Epithelial Locations Simple Squamous Epithelium · a single layer of thin, flattened cells · cover body surfaces, cover and line internal organs, and compose glands looks like a fried egg · easily damaged skin cells, cells that line the stomach and small intestine, inside your mouth · common at sites of filtration, diffusion, osmosis; cover surfaces · air sacs of the lungs, walls of capillaries, linings cheek cells of blood and lymph vessels intestines skin Epithelial Tissue Simple Cuboidal Epithelium Simple Columnar Epithelium · single layer of cube-shaped cells · single layer of cells that are longer than they are wide centrally located nucleus nucleus located near basement membrane · secretion and absorption · ciliated or nonciliated · surface of ovaries, linings of kidney tubules, and · some have microvilli linings of ducts of certain glands · goblet cells = secrete mucus · absorption, secretion, protection · linings of uterus, stomach and intestine Pseudostratified Columnar Stratified Squamous Epithelium Epithelium · many layers of flattened cells · appear stratified because nuclei are at 2 or more · named based on appearance of top layer of cells levels · protection NOT stratified because all cells touch basement mem. · outer layers of skin, linings of oral cavity, throat, · ciliated vagina, and anal canal · goblet cells (secrete mucus) · protection, secretion, movement of mucus · linings of respiratory system Stratified Cuboidal Epithelium Stratified Columnar Epithelium · 2 or 3 layers of cuboidal cells · protection and secretion · protection · vas deferens, part of the male urethra, parts of · linings of larger ducts or mammary glands the pharynx (throat) sweat glands, salivary glands, and pancreas Epithelial Tissue transitional Epithelium Glandular Epithelium · can stretch · cells that are specialized to produce and · distensibility (stretching), protection secrete substances into ducts or into body fluids · inner lining of urinary bladder and linings of the · gland = 1 or more cuboidal or columnar cells ureters and part of urethra · secretion · salivary glands, sweat glands, endocrine glands Exocrine vs. Endocrine Exocrine Glands · exocrine = secrete substances into ducts that · merocrine = release watery, open onto surfaces protein-rich fluid by exocytosis skin or linings of digestive tract salivary glands, sweat glands · endocrine = secrete substances into · apocrine = lose small portions tissue fluid or blood of their cell body during hormones secretion mammary glands, ear wax · holocrine = entire cell lyses exocrine (breaks apart) during endocrine secretion sebaceous glands of the skin Serous vs. Mucous · serous = typically watery with lots of enzymes lubrication · mucous = mucus digestive and respiratory systems protection.