Lecture 5: Microstructure of Tissues: Epithelial Tissue

Question 1

4 major types of tissue in the body

Answer 1

1. epithelial (support) 2. muscle (contraction; smooth & cardiac) 3. connective (support) 4. nervous (conduction & reception)

Question 2

Derivation of epithelial tissues

Answer 2

All 3 germ layers, which is unique epidermis - ectoderm living of GI & respiratory tract - endoderm endothelium & mesothelium - mesoderm

Question 3

derivation of connective tissue

Answer 3

mesoderm

Question 4

derivation of muscle tissue

Answer 4

mesoderm

Question 5

derivation of nervous tissue

Answer 5

ectoderm

Question 6

2 major types of epithelial tissue

Answer 6

1. membranous epithelia - sheetlike tissues that cover and line surfaces, cavities, and rogans 2. glandular epithelia - perform secretory functions

Question 7

functions of epithelial tissue

Answer 7

1. protection and containment (skin) 2. absorption (intestines) 3. secretion (glands) 4. sensation (neuroepithelium) 5. contractility (myoepithelium)

Question 8

characteristics of epithelial tissue

Answer 8

1. 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

Question 9

structural components of epithelial cell

Answer 9

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

Question 10

simple epithelial tissue

Answer 10

one layer of cells on surface/facing lumen site of absorption, diffusion, secretion cilia and microvilli

Question 11

types of simple epithelial tissue

Answer 11

1. simple squamous epithelium 2. simple cuboidal epithelium 3. simple columnar epithelium 4. pseudostratified ciliated columnar epithelium 5. simple columnar ciliated epithelium

Question 12

stratified epithelial tissue

Answer 12

two or more layers of cells has protective function shape and structure of surface cells classify them (i.e. uppermost cells)

Question 13

types of stratified epithelial tissue

Answer 13

1. stratified squamous epithelium 2. stratified squamous keratinized epithelium 3. stratified cuboidal epithelium 4. transitional epithelium

Question 14

simple squamous epithelium

Answer 14

shape: flat, like fish scales fxn: diffucion of fluids and gases location: lungs, blood & lymphatic vessels, cavities (pleural, peritoneal, & pericardial)

Question 15

simple cuboidal epithelium

Answer 15

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

Question 16

simple columnar epithelium

Answer 16

shape: cells taller than cuboidal cells; elliptical, basally located nucleus fxn: absorption location: intestines

Question 17

simple columnar ciliated epithelium

Answer 17

shape: columnar cells w/ cilia at apical surface fxn: propel ovum over cell surface, –> uterus location: oviduct

Question 18

pseudostratified columnar ciliated epithelium

Answer 18

shape: ciliated, columnar cells w/ nuclei at different positions fxn: propel mucus & entrapped particles location: trachea

Question 19

stratified squamous epithelium

Answer 19

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

Question 20

stratified squamous keratinized epithelium

Answer 20

shape: many layers of squamous cells, with surface layer of keratin fxn: withstand chronic abrasion location: epidermis

Question 21

layers of stratified squamous keratinized epithelium

Answer 21

1. stratum corneum, contains keratin (most apical) 2. s. lucidum 3. s. granulosum 4. s. spinosum 5. s. basale

Question 22

stratified cuboidal epithelium

Answer 22

shape: 1-2 layers of cuboidal cells fxn: provide thicker lining location: larger excretory ducts fo exocrine glands, e.g. salivary glands, parotid gland

Question 23

transitional epithelium

Answer 23

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

Question 24

glandular epithelia

Answer 24

formed during embryonic development by invagination of epithelial surfaces into underlying connective tissue below epithelial cells proliferate into underlying connective tissue

Question 25

2 types of glandular epithelia

Answer 25

1. exocrine glands 2. endocrine glands

Question 26

characteristics of exocrine glands

Answer 26

gland formed still maintains contact with surface epithelium discards contents via duct, directly to epithelial surface has lower, secretory portion

Question 27

modes of exocrine secretion

Answer 27

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

Question 28

examples of exocrine glands

Answer 28

1. serous glands - composed of cuboidal cells 2. mucous glands - cuboidal tissue; produces mucous i.e. goblet cell - i.e. in small intestine

Question 29

mucigen

Answer 29

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

Question 30

goblet cells

Answer 30

1. 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

Question 31

endocrine secretion

Answer 31

whereby secretory products are released into connective tissue, and then to blood vessels therefore must reside close to blood vessels release via basal surface

Question 32

merocrine secretion

Answer 32

most common form of exocrine secretion no loss of membrane ie goblet cells

Question 33

apocrine secretion

Answer 33

exocrine secretion secretory products are put in vesicles made of membrane ie mammary gland

Question 34

holocrine secretion

Answer 34

exocrine secretion whole cell breaks for discharge of products ie sebaceous gland of skin