Epithelium vocab

Question 1

Functions of epithelia

Answer 1

1. protect underlying tissues
2. provide selective barrier between a lumen and underlying tissue
3. synthesize substances like hormones, saliva for secretion
4. transport substances by endo- and exocytosis

Question 2

Characteristics of epithelia

Answer 2

1. composed of continuous sheets of cells
2. have specialized cell junctions
3. are polarized
4. are avascular

Question 3

squamous

Answer 3

long, flat, much wider than tall

Question 4

cuboidal

Answer 4

roughly even width and height

Question 5

columnar

Answer 5

taller than wide

Question 6

simple

Answer 6

one layer of cells only

Question 7

stratified

Answer 7

have more than one layer of cells- one contacting basement membrane, one on free surface, maybe some layers in between

Question 8

pseudostratified

Answer 8

appear stratified but are not; all cells contact basement membrane but not all reach apical surface; nuclei found at two levels

Question 9

goblet cells

Answer 9

unicellular exocrine glands that secrete mucus onto a free surface; found in simple or pseudostratified epithelia

Question 10

endothelium

Answer 10

simple squamous epithelium that lines the heart and all blood and lymphatic vessels

Question 11

mesothelium

Answer 11

simple squamous epithelium that lines pleural and peritoneal cavities

Question 12

metaplasia

Answer 12

chronic irritation in epithelia is prolonged so normal epithelia replaced by stratified squamous epithelia- very resistant to stress; reversible change

Question 13

functions of basement membrane

Answer 13

1. separate and bind epithelium and connective tissues
2. form a selective sieve-like barrier to regulate which molecules and cells cross interface between tissues
3. establish polarity of epithelium
4. guide repair

Question 14

Lamina rara

Answer 14

clear layer that lies directly adjacent to basal surface of epithelia

Question 15

lamina densa

Answer 15

darkly stained layer that lies immediately beneath lamina rara; together they form the basal lamina

Question 16

lamina reticularis

Answer 16

secreted by cells in the adjacent connective tissue; third component of basement membrane

Question 17

Alport syndrome

Answer 17

inherited disorder of Type IV collagen that affects kidney, eye, cochlea of ear; most common in males; gene mutation prevents proper production of type IV collagen network

Question 18

lateral interdigitations

Answer 18

sites where the membranes of adjacent cells do not form a straight line to from the base to the apex- fit together like puzzle pieces

Question 19

occluding junctions

Answer 19

seal cells together and form a barrier to regulate what crosses the epithelium; prevent passage of molecules via paracellular pathway

Question 20

anchoring/ adhering junctions

Answer 20

hold epithelia together by attaching cells and their cytoskeletons to each other or to the extracellular matrix; incl adhesion belts and spot desmosomes

Question 21

communicating/ gap junctions

Answer 21

allow cells to communicate with each other by chemical or electrical signals

Question 22

tight junctions

Answer 22

only in epithelia; closest to apex; form barrier between epithelium’s free surface and connective tissue ex to prevent microbes from entering bloodstream; maintain the apical and lateral cell membranes by preventing diffusion of integral membrane proteins from one surface to the other

Question 23

apical modifications

Answer 23

microvilli, sterocilia, cilia on an epithelial cell

Question 24

basal lamina

Answer 24

lamina rara+ lamina densa

Question 25

basement membrane

Answer 25

basal lamina+ lamina reticularis

Question 26

paracellular pathway

Answer 26

the space between two epithelial cells through which solutes can pass

Question 27

Steps in epithelial repair

Answer 27

a. Epithelial cells are depolarized b. Cells become repolarized along lateral axis c. Epithelial cells divide by mitosis d. When cells from opposite sides of the wound meet, they make a new basement membrane, reestablish polarity, and restore the epithelium

Question 28

adhesion belts

Answer 28

just below tight junction; hold epithelial cells in a continuous sheet by forming a complete ring around the apex of the cell

Question 29

cadherins

Answer 29

transmembrane proteins in adhesion belts that connect to actin cytoskeleton; external portion of proteins have 5 domains interact in a calcium-dependent manner to bind with identidal proteins on adjacent cells cell. adhesion is disrupted if calcium concentration is low

Question 30

terminal web

Answer 30

network of cytoskeletal proteins that extends across apical cytoplasm and provides an attachment point for the basal bodies of cilia and for the actin filaments in microvilli and stereocilia

Question 31

spot desmosomes

Answer 31

type of anchoring junction; composed of dense protein plaques; keratin filaments extend away from plaques to link different spot desmosomes and to absorb and dissipate mechanical stress

Question 32

gap junctions

Answer 32

communicating junctions formed between cytoplasm of two cells by a connexon of six intermembrane protein connexins; allow small molecules to pass through; can open and close

Question 33

microvilli

Answer 33

extensions of cell membrane on apical surface; contain actin filaments

Question 34

stereocilia

Answer 34

long like cilia; contain actin filaments like microvilli; function to increase surface area

Question 35

cilia

Answer 35

extensions of apical membrane specialized for movement; contain microtubules

Question 36

hemidesmosomes

Answer 36

anchoring junctions that anchor basal surfaces of epithelial cells to basal lamina with plaque of integrin proteins

Question 37

basal infoldings

Answer 37

increase surface area on basal surface for ion transport; active transport so surrounded by many mitochondria

Question 38

merocrine

Answer 38

exocrine glands that release product by exocytosis; can be constitutive or regulated

Question 39

apocrine

Answer 39

exocrine glands that accumulate secretory products in apex then a portion of the apex pinches off and is released (ex mammary glands)

Question 40

holocrine

Answer 40

exocrine glands that secrete the entire cell along with its content (sebaceous glands only)