specialised tissues

Question 1

what do epithelial cells require to function to ensure they are directional

Answer 1

polarity

Question 2

what is key to having polarity

Answer 2

plasma membrane

Question 3

what domains do junctions separate the epithelial membrane into

Answer 3

apical (open) and basolateral (matrix)

Question 4

what allow directional flow and where are they located

Answer 4

polarised transporters restricted to specific parts of membrane

Question 5

what do tight junctions do

Answer 5

seal paracellular pathway so any passage must be via cell, controlling passage

Question 6

what is the fence function

Answer 6

maintains apical-basolateral polarity

Question 7

epithelial specialisation: absorption - examples

Answer 7

nephron, small intestine, enterocytes

Question 8

epithelial specialisation: absorption - requirements

Answer 8

absorptive, fluid transporting, selectively permeable, enterocytes possess striated brush border to increase SA

Question 9

epithelial specialisation: absorption - direction of transport

Answer 9

apical membrane to basal lamina → capillary

Question 10

epithelial specialisation: absorption - apical plasma membrane

Answer 10

many ion and water channels for passive transport

Question 11

epithelial specialisation: absorption - basal lamina

Answer 11

mitochondria and membrane transporters for active transport (e.g. Na+/glucose coupling) at basal membrane infoldings (increase SA)

Question 12

epithelial specialisation: secretion - examples

Answer 12

pancreas, goblet cells

Question 13

epithelial specialisation: secretion - exocrine direction of transport

Answer 13

capillary → basal lamina to apical membrane

Question 14

epithelial specialisation: secretion - exocrine

Answer 14

apical membrane leads to duct; secretory granules near apical membrane and RER and nucleus in basal cytoplasm

Question 15

epithelial specialisation: secretion - endocrine direction of transport

Answer 15

apical membrane to basal lamina → capillary

Question 16

epithelial specialisation: secretion - endocrine

Answer 16

secretory granules in basal cytoplasm; RER and nucleus near apical membrane; organised into glands (tubular and alveolar with varying complexities)

Question 17

epithelial specialisation: protective - examples

Answer 17

skin epidermis (dry), lining of oesophagus (wet)

Question 18

epithelial specialisation: protective - function

Answer 18

barrier to environment and mechanical damage

Question 19

epithelial specialisation: protective - epidermal damage

Answer 19

defects cytokerains or cell-to-cell junctions leading to blistering diseases

Question 20

cell turnover: how tissue architecture is maintained

Answer 20

balance between proliferation and apoptosis

Question 21

why do turnover times vary

Answer 21

due to function

Question 22

how are intestinal absorptive villi replaced

Answer 22

cell renewal by stem cells in mid-region of intestinal crypts → cells lost from villus top → new cells move up from crypt to replace

Question 23

how is proliferation reduced

Answer 23

chemotherapy prevents stem cell production

Question 24

how is proliferation increased

Answer 24

benign tumour formation with malignancy risk

Question 25

what affects turnover

Answer 25

infectious agents and mechanical pressure

Question 26

tight junction: type of junction

Answer 26

Zonulae (belt)

Question 27

tight junction: location

Answer 27

many points where adjacent membranes form very close contacts

Question 28

tight junction: function

Answer 28

seal paracellular pathways and segregate membranes (establishing polarity)

Question 29

define kiss points

Answer 29

linear array that hook up with membrane proteins on adjacent cells

Question 30

adhesion belt: type of junction

Answer 30

Zonulae (belt)

Question 31

adhesion belt: location

Answer 31

basal to apical tight junction

Question 32

adhesion belt: component

Answer 32

cadherin (transmembrane adhesion molecule which associated with actin)

Question 33

adhesion belt: function

Answer 33

first to form and controls assembly of other junctions ("master junction")

Question 34

desmosome junction: type of junction

Answer 34

Maculae (spot)

Question 35

desmosome junction: location

Answer 35

dotted between lateral membrane; abundant in epidermis

Question 36

desmosome junction: component

Answer 36

cadherin-like molecules for adhesion which link to intermediate filaments (cytokeratin in epithelium)

Question 37

gap junction: type of junction

Answer 37

Maculae (spot)

Question 38

gap junction: structure

Answer 38

cluster of pores continuous with adjacent pores

Question 39

gap junction: function

Answer 39

passage of ions and small molecules between cells

Question 40

diagram of epithelial tissue

Answer 40

diagram from tissues 1