LECTURE 1 epithelial tissue Flashcards
functions of epithelial tissue (4)
protection, secretion (release molecules to surface), absorption (taking molecules into tissue), ion transport
characteristics of epithelium (7)
cellularity, specialized contacts, polarity, supported by connective tissue, avascular, innervated, highly regenerative
classification of epithelium: layers of cells (3)
simple, stratified, pseudostratified
classification of epithelium: shape of cells (3)
squamous, cuboidal, columnar
endothelium
(special epithelium) simple squamous epithelium that lines vessels (lymphatic and blood vessels, chambers of heart)
mesothelium
(special epithelium) simple squamous epithelium that forms the lining of body cavities (thoracic, abdominal, pleura, pericardium, peritoneum)
microvilli
(feature of apical surface) finger-like extensions of the plasma membrane of apical epithelial cell that increases surface area for absorption (in small intestine)
cilia
(feature of apical surface) whip-like, motile extension of plasma membrane that moves mucus (etc.) over epithelial surface one way (in respiratory tubes)
features of apical surface (2)
microvilli, cilia
cellularity (characteristic of epithelium)
many cells packed close together, small amount of extracellualr material around them
specialized contacts (characteristic of epithelium)
cells are joined by varying types of cell junctions (can be proteins, can change permiability)
polarity (characteristic of epithelium)
apical vs. basal surfaces differ (two distinct ends/surfaces), apical is free and unattached and next to lumen, basal is attatched to connective tissue - supported by CT because that’s where it gets nutrients from blood (since epithelium is avascular)
highly regenerative (characteristic of epithelium)
mitosis frequently and rapidly, epithelial cell lifespan usually two days
classification of epithelium
based on number of layers and cell shape
layers of epithelium
simple (one layer), stratified (multiple layers, characterized by shape of apical layer), pseudostratified (looks like multiple layers but only one, cells of different height that all touch basal surface)
shapes of epithelial cells
squamous (wider than tall, distance between apical and basal), cuboidal (even height to width, not perfect cube), columnar (taller than wide)
structure of epithelium
forms sheets of cells that cover a surface or line a cavity
simple squamous found in
lungs, blood vessels, ventral body cavity
simple cuboidal found in
kidney tubules, glands
simple columnar found in
stomach, intestines
pseudostratified columnar found in
respiratory passages (ciliated version)
stratified squamous found in
epidermis, mouth, vagina, esophagus
features of lateral surface
contour of cells (looks wavy as it fits together), cell junctions
desmosome
(lateral cell junction) proteins hold cells together to maintain integrity
tight junction
(lateral cell junction) plasma membrane of adjacent cells fuse, nothing passes
gap junction
(lateral cell junction) proteins allow small molecules to pass through
features of basal surface
basement membrane
basement membrane
(feature of basal surface) sheet between epithelium and connective tissue layers, attaches epithelium to connective tissue
basal lamina
(basement membrane) thin, non-cellular, supportive sheet made of proteins, superficial layer of basement membrane, acts as a selective filter, assists epithelial cell regeneration by moving new cells
reticular fiber layer
(basement membrane) deeper, supportive layer
glands
epithelial cells that make and secrete a product, products are water-based and usually contain proteins
gland classification
unicellular vs. multicellular, exocrine vs. endocrine
exocrine glands
secrete substance onto body surface or into body cavity, produce a variety of types of products, activity is local, have ducts, unicellular or multicellular, ex: goblet cells, salivary, mammary, pancreas, liver
endocrine glands
secrete product into blood stream, either stored in secretory cells or in follicle surrounded by secretory cells, always produce hormones, no ducts, unicellular or multicellular, activity is widespread, ex: pancreas, adrenal, pituitary, thyroid
