Epithelial architecture and renewal

Question 1

describe desmosomes

Answer 1

cell-cell via intermediate filaments, mechanical strength, spot welds, uses cadherins for desmosome-desmosome adhesion between cells (Ca dependent)

Question 2

describe cadherins

Answer 2

proteins that keep epithelial cells joined

Question 3

describe epithelial tissue

Answer 3

cytoskeleton of cells is linked from cell to cell by anchoring junctions;
little extracellular matrix which consists of basal lamina

Question 4

describe the cell matrix

Answer 4

attach epithelial cells to connective tissue

Question 5

describe connective tissue

Answer 5

extracellular matrix is plentiful and cells are interspersed in it

Question 6

how is mechanical stress handled in epithelial tissue?

Answer 6

mechanical stresses are transmitted from cell to cell by cytoskeletal filaments anchored to cell-matrix and cell-cell adhesion sites

Question 7

describe the occluding junction

Answer 7

it is near the apical end of the gap between cells. it is a tight junction between the cells that keeps foreign bodies from entering the space

Question 8

describe cell-cell anchoring junctions

Answer 8

adheren junctions connects actin filament bundle each cell;

desmosome connects intermediate filaments in one cell to those in the next cell

Question 9

describe channel forming junctions

Answer 9

gap junctions are what allows the passage of water-soluble molecules from cell to cell

Question 10

What is a hemidesmosome?

Answer 10

it anchors intermediate filaments in a cell to the extracellular matrix

Question 11

what cell-matrix anchoring junctions are there?

Answer 11

actin-linked anchors and hemidesmosomes

Question 12

describe desmosomal cadherins

Answer 12

(desmoglein, desmocollin) homophilic, intermediate filaments

Question 13

Ig family members

Answer 13

(N-CAM, ICAM) both hetero and homo, neuronal and immune synapses

Question 14

Selectins

Answer 14

(blood cells and endothelial cells) hetero, actin

Question 15

integrins

Answer 15

hetero, actin, focal adhesions or hemidesmosomes

Question 16

transmembrane proteoglycans

Answer 16

syndecans, hetero, actin

Regulate signalling molecules

Question 17

what are the tight junction proteins?

Answer 17

claudin and occludin

Question 18

Describe connexins

Answer 18

aqueous channel proteins cell-cell, coupling cells metabolically and electrically;
can be closed if need be cell is damaged to isolate damage

Question 19

what proteins are in cadherens

Answer 19

desmoglein and desmocollin

Question 20

What tissues need desmosomes?

Answer 20

any that undergo high mechanical stress

Question 21

describe intermediate filaments

Answer 21

strongest, keratins

Question 22

describe microtubules

Answer 22

slinky, centrioles and mitotic spindle, Tau

Question 23

Describe Actin

Answer 23

cell locomotion, Arp, beads

Question 24

What do fibroblasts do?

Answer 24

secrete ECM contents

Question 25

what composes a blood vessel?

Answer 25

endothelial cells (polarized)

Question 26

What do dendritic cells do?

Answer 26

with macrophages they are defenders against microbes and pathogens;
in skin

Question 27

which cells provide adaptive immune responses?

Answer 27

lymphocytes

Question 28

Which cell is the most abundant in the skin?

Answer 28

keratinocytes

Question 29

what cells are in connective tissue?

Answer 29

macrophage, fibroblast, mast, endothelial, lymphocyte (loose tissue)
firbroblast (dense tissue)

Question 30

What cells are the source of any tissue cells?

Answer 30

basal stem cells

Question 31

What is the timeline for cells in epithelium?

Answer 31

basal cells divide; 1stay1move up the layer; gene expression changes as it moves from layer to layer (desmosomal and keratin proteins at each layer, but phenotypically different than apex); lose nucleus and other organelles; apoptosis; every 30 days complete cycle

Question 32

what are the layers of the epidermis?

Answer 32

stratified (karatinized squames), granular (waterproof, divides metabolically active from dead cells), prickle, basal layer, lamina, connective tissue

Question 33

What is found in clusters of cells near the basal lamina and bulge of hair follicles?

Answer 33

beta1 subunit of integrin

Question 34

What are adult stem cells?

Answer 34

stem cells that are tissue specific (partially differentiated)

Question 35

Describe hedgehog pathway in epithelium

Answer 35

overactivation-division after separation from basal lamina

underactivation-loss of sebaceous glands

Question 36

Describe Wnt signaling in epithelium growth factor

Answer 36

Wnt binds to frizzle
Dsh inhibits GSK3beta (apc)
B-catenin

No Wnt: b-cat degraded unless flooded by release from anchor proteins

Question 37

What is the function of cadherin-mediated adhesion?

Answer 37

it provides highly selective recognition, enables similar cells to stick together and stay segregated (sorting out)

Question 38

describe the E to N cadherin switch

Answer 38

in early development the cadherin switch facilitates the formation of the neural crest and other cell types