Anatomy-The Epithelium

Question 1

What is the epithelium ?
(3)
How is it categorised ?
(3)

Answer 1

Tissue which covers and lines other tissues and it’s classified according to :
1-the number of cell layers
2-shape of cells
3-surface specialisation

Question 2

Name some characteristics of covering epithelium ?

5

Answer 2

1-closely apposed -continuous barrier
2-almost no intercellular substances
3-polarised ( apical and basal part)
4-epithelia can be supported by basement membrane
5-AVASCULAR - no blood supply ( relies on diffusion from underlying connective tissue)

Question 3

what are the types of lining epithelium and what do they mean ?
(7)
give summary of some …

Answer 3

1-simple squamous ( 1 layer , 1 flat nucleus )
2-simple cuboidal (1 layer , 1 cuboidal cell with rounded and centrally located nucleus )
3-simple columnar (1 Layer of columnar cells, nucleus elongated , most commonly found in GI tracts= goblet cells, associated with absorption and secretion )
4–pseudostratified columnar ciliated epithelium ( appears to have several layers due to squished nuclei but acc has one layer , most commonly found in trachea and bronchi =cilia)
5-stratified squamous keratinising ( many layers , flat nuclei and produce skin = epidermis of skin )
6-stratified squamous , non-keratinising ( variety line wet surfaces lining of mouth, vagina etc)
7- transitional epithelium exclusive to urinary /ureter bladder = adapted to withstand stretch . It appears in a. variable state , either relaxed or stretched , layers are present .

Question 4

what’s a gland ? (2)

Answer 4

specialised secretory epithelium which can be divided into two broad categories : exocrine and endocrine.

Question 5

How are glands classified ? (3)
remember you should be able to apply this !
- what features are used to classify them ?

Answer 5

1-Ducts can be : simple or compound(branched)
2-secretory shape: Acinar (hollow berry ) or Tubular ( test tube shape )
3-secretion: mucous(shows up pale pink ) , serous (shows up dark pink) , seroumucous gland .

Question 6

what’s a holocrine gland ? (1)

Answer 6

Disscharges whole cell and becomes hollow ( sebaceous

gland)

Question 7

what is a merocrine /eccrine gland ? (1)

Answer 7

exocytosis via vesicles = most common = sweat gland s

Question 8

what’s a apocrine gland ? (1)

apo–>top

Answer 8

discharge of unbroken , membrane bound vesicles !, top of the cell is released = found in places u get BO rich in protein !

Question 9

What is the basement membrane ?
why is it useful ?
(4)

Answer 9

1-thin extracellular layer which consist of basal lamina, lamina Lucida and reticular lamina = just above the dermis)
2- helps to tell cell what is up and down ( polarity ) because the basement is at the bottom!
3-scaffolding template
4-separates epithelial cells from connective tissue and can control the movement of ions and exchange of molecules

Question 10

what are the different types of cell junctions and what do (8)
DATG

Answer 10

1-Tight Junction (TJs) - water tight PREVENTS transport between cells.
2-Adherens Junction - Zonula Adherens = Anchors cells into place using Actin filaments
3-Desmosomes- in areas of stress also an anchoring junction which used intermediate filaments . Water and ions can flow through the gaps .
4-Gap junctions = tunnels for transport ! ( think of spreading an AP , in cardiac muscle and nerve cells)