Lecture 5: Microstructure of Tissues: Epithelial Tissue Flashcards
4 major types of tissue in the body
- epithelial (support) 2. muscle (contraction; smooth & cardiac) 3. connective (support) 4. nervous (conduction & reception)
Derivation of epithelial tissues
All 3 germ layers, which is unique epidermis - ectoderm living of GI & respiratory tract - endoderm endothelium & mesothelium - mesoderm
derivation of connective tissue
mesoderm
derivation of muscle tissue
mesoderm
derivation of nervous tissue
ectoderm
2 major types of epithelial tissue
- membranous epithelia - sheetlike tissues that cover and line surfaces, cavities, and rogans 2. glandular epithelia - perform secretory functions
functions of epithelial tissue
- protection and containment (skin) 2. absorption (intestines) 3. secretion (glands) 4. sensation (neuroepithelium) 5. contractility (myoepithelium)
characteristics of epithelial tissue
- cells are closely bound to each other by cell junctions that form sheets 2. supported by basement membrane (aka basal lumen) which separates them from underlying support tissue 3. not penetrated by blood vessels (avascular) 4. are polar
structural components of epithelial cell
apical surface - microvilli, regulation of nutrient uptake/secretion/protection lateral plasma membrane - cell contact & adhesion; contains zonula occludens, zonula adherens, desmosomes, gap junctions basal lateral membrane - signal reception & transduction basal membrane - cell-substratum contact; basement membrane receptors
simple epithelial tissue
one layer of cells on surface/facing lumen site of absorption, diffusion, secretion cilia and microvilli
types of simple epithelial tissue
- simple squamous epithelium 2. simple cuboidal epithelium 3. simple columnar epithelium 4. pseudostratified ciliated columnar epithelium 5. simple columnar ciliated epithelium
stratified epithelial tissue
two or more layers of cells has protective function shape and structure of surface cells classify them (i.e. uppermost cells)
types of stratified epithelial tissue
- stratified squamous epithelium 2. stratified squamous keratinized epithelium 3. stratified cuboidal epithelium 4. transitional epithelium
simple squamous epithelium
shape: flat, like fish scales fxn: diffucion of fluids and gases location: lungs, blood & lymphatic vessels, cavities (pleural, peritoneal, & pericardial)
simple cuboidal epithelium
shape: cells are as tall as they are wide; round, centrally located nucleus fxn: excretion, secretion, absorption location: ducts of kidney, thyroid glands, salivary glands
simple columnar epithelium
shape: cells taller than cuboidal cells; elliptical, basally located nucleus fxn: absorption location: intestines
simple columnar ciliated epithelium
shape: columnar cells w/ cilia at apical surface fxn: propel ovum over cell surface, –> uterus location: oviduct
pseudostratified columnar ciliated epithelium
shape: ciliated, columnar cells w/ nuclei at different positions fxn: propel mucus & entrapped particles location: trachea
stratified squamous epithelium
shape: many layers of cells; first is flattened, squamous fxn: handle chronic abrasion location: oral cavity, esophagus, cervix, vagina, lumen cells differentiate from basal to apical side and become progressively more squamous in shape so top is most flattened and bottom is most cuboidal shape
stratified squamous keratinized epithelium
shape: many layers of squamous cells, with surface layer of keratin fxn: withstand chronic abrasion location: epidermis
layers of stratified squamous keratinized epithelium
- stratum corneum, contains keratin (most apical) 2. s. lucidum 3. s. granulosum 4. s. spinosum 5. s. basale
stratified cuboidal epithelium
shape: 1-2 layers of cuboidal cells fxn: provide thicker lining location: larger excretory ducts fo exocrine glands, e.g. salivary glands, parotid gland
transitional epithelium
shape: many layers of cells; surface layer is round, large, pillow shaped fxn: handle toxicity or urine & accomodate stretch location: urinary tract (bladder) can be binucleated cells 6 layers of cells in urinary bladder flatten out when bladder is full
glandular epithelia
formed during embryonic development by invagination of epithelial surfaces into underlying connective tissue below epithelial cells proliferate into underlying connective tissue
2 types of glandular epithelia
- exocrine glands 2. endocrine glands
characteristics of exocrine glands
gland formed still maintains contact with surface epithelium discards contents via duct, directly to epithelial surface has lower, secretory portion
modes of exocrine secretion
occurs from apical surface 1. merocrine: most; most common, no loss of membrane, i.e. goblet cells 2. apocrine: put secretory products in vesicles made of membrane; i.e. mammary gland 3. holocrine: whole cell breaks for discharge of products; i.e. sebaceous gland of skin
examples of exocrine glands
- serous glands - composed of cuboidal cells 2. mucous glands - cuboidal tissue; produces mucous i.e. goblet cell - i.e. in small intestine
mucigen
protein component synthesized in rough ER, secreted to golgi secreted at a steady basal rate, but irritation will make goblet cell dump all its mucigen onto the surface
goblet cells
- provide coat in upper GI tract 2. provide lubrication in lower GI tract 3. prevent drying, helps humidify inspired air and acts as sticky surface to trap dust/microorganisms in respiratory tract, so they don’t reach the lungs functions by merocrine secretion contain mucigen
endocrine secretion
whereby secretory products are released into connective tissue, and then to blood vessels therefore must reside close to blood vessels release via basal surface
merocrine secretion
most common form of exocrine secretion no loss of membrane ie goblet cells
apocrine secretion
exocrine secretion secretory products are put in vesicles made of membrane ie mammary gland
holocrine secretion
exocrine secretion whole cell breaks for discharge of products ie sebaceous gland of skin
