Epithelial Tissue Morphology

Question 1

epithelia functions

Answer 1

trans-epithelial transport,

secretion and synthesis and absorption,

protection,

generation of movement over apical surface (thanks to cilia)

Question 2

how are epithelia classified?

Answer 2

dependent on their shape and number of layers

Question 3

different types of shape

Answer 3

cuboidal, flat and columnar

transitional- capacity to change shape

Question 4

different types of layers

Answer 4

simple epithelia- one layer

stratified epithelia- many layers

pseudostratified- appear as if many layers however only one

Question 5

another name for transitional epithelium

Answer 5

uroepithelium

Question 6

how else can epithelia be classified and give the classes?

Answer 6

dependent on function

absorptive, mechanical and secretory

Question 7

two different types of surface specialisations + functions

Answer 7

cilia- movement of particles

microvilli- increase surface area for absorption

Question 8

simple squamous location

Answer 8

blood vessels, loops of Henle

Question 9

simple cuboidal location

Answer 9

kidney

Question 10

simple columnar location

Answer 10

alimentary tract (nucleus is at the base of all cells)

Question 11

stratified squamous location

Answer 11

skin

Question 12

stratified squamous structure + function

Answer 12

many flat layers, that begin more cuboidal and become more squamous nearer the surface

differentiator cell found at the top

protect against abrasion and infection

Question 13

rarest epithelia + location

Answer 13

stratified cuboidal

sweat glands and ducts

Question 14

pseudostratified columnar cells location + structure

Answer 14

respiratory epithelium

nucleus appears in different places, cillia on surface

Question 15

location of transitional epithelium + function

Answer 15

urinary tract (bladder)

capacity to alter their width, able to distend or contract the bladder

Question 16

cilia structure + function

Answer 16

microtubulin core

move back and forwards to repel mucus out of the respiratory tract, dyenin

Question 17

microvilli structure + function

Answer 17

microfilament actin core

increase SA of small intestine for absorption, forming a brush border

Question 18

what separates epithelia from connective tissue?

Answer 18

basement membrane

Question 19

what is the basement membrane?

Answer 19

a thin, fibrous, non cellular matrix that separates the lining of an internal or external body surface from the underlying connective tissue

Question 20

structure of basement lamina

Answer 20

composed of three layers

lamina lucida- layer closest to the epithelia (not electron dense)

lamina densa (electron dense)- contains perlecan (heparan rich GAG)

lamina reticularis- also associated with reticular fibres of the underlying connective tissue

contains collagen VII anchoring fibrils and fibrillin microfibrils

Question 21

basement membrane function

Answer 21

anchors the epithelium down to loose connective tissue (dermis/lamina propria)

acts as a mechanical barrier, preventing the infiltration of malignant cells

cell differentiation

differentiates between apical and basolateral domains

Question 22

key feature of epithelia

Answer 22

polarity of cells

Question 23

two different domains

Answer 23

apical- external surface

basolateral- internal surface

Question 24

what does the basolateral domain consist of?

Answer 24

cell unctions

Question 25

5 main types of cell junctions

Answer 25

tight- occluding junctions

adhesive

gap

desmosomes and hemidesmosomes

Question 26

gap junctions structure + function

Answer 26

formed of connexins

allow chemical and electrical signals to diffuse through cells rapidly, forming syncytiums

Question 27

tight-occludng junctions structure + function

Answer 27

zona occludens, a band formed near the apical region of the cell

formed of occludins and other adhesion molecules

prevent intercellular transport

Question 28

explain adhesive junctions

Answer 28

bind cells together, forming the zonula adherens

cadherin proteins linked to actin cytoskeleton

Question 29

desmosome location

Answer 29

localised spot like adjesions on the lateral sides of plasma membranes

Question 30

desmosome structure

Answer 30

desmosome intermediate filament complexes

a network of cadherin proteins, linker proteins and keratin intermediate filaments

desmogleins and desmocollins

Question 31

desmosome function

Answer 31

strong cell to cell adhesions that are found in tissues that experience intense mechanical stress, such as cardiac muscle, bladder tissue

Question 32

hemidesmosome location + function

Answer 32

attach basal epithelial cells to lamina lucida (basement membrane)

Question 33

hemidesmosome structure

Answer 33

integrin and plectin membrane spanning components

no cadherin

bind to keratin intermediate filaments in the cytoskeleton

Question 34

two types of movement through epithelia defined

Answer 34

transcellular - through the cells

paracellular- between the cells

Question 35

what determines which transport will be favoured?

Answer 35

type and number of junctional complexes

Question 36

two types of epithelia

Answer 36

leaky, tight

Question 37

disorder of the junctional complexes

Answer 37

pemphigus

Question 38

explain pemphigus

Answer 38

antibodies produced against adherens and desmogleins in the skin

no desmosomes

cells become unglued from each other, resulting in blisters and sores