L2 Other Forms Of Epithelium

Question 1

What are the specialized forms of covering of epithelium

Answer 1

1-germinal epithelium, cells that differentiate in to sperms or ovum and is present in seminiferous tubules of testis in male and ovaries in female
2-sensory epithelium, cells that have a sensory nerve supply and function as sensory receptors such as taste buds,hair cells of ear and retina of eye

Question 2

What is epithelial cell polarity

Answer 2

Most epithelial cells demonstrate structural changes in one or more of its cell membranes that represent cell adaptation to perform a special function.
Cell membranes with special structure have a polarity which means its directed towards a certain surface in relation to function

Question 3

What are the types of polarity

Answer 3

1-apical domain
   ~microvilli
    ~stereocilia
    ~cilia
2-basolateral domain
   ~basal enfoldings
    ~hemidesmosomes
     ~basal lamina
3-glandular epithelium

Question 4

Describe the apical domain

Answer 4

Region of epithelial cells facing the lumen
Function: transport of ions molecules and water
Its rich in ion channels, carrier proteins and H+ atpases, glycoproteins, hydrolytic enzymes and aquaporins

Question 5

What are the structural modifications of the apical domain

Answer 5

Microvilli with associated glycocalyx
Sterocilia
Cilia and flagella in sperms

Question 6

Describe microvilli

Answer 6

Small finger like cytoplasmic projections covered by the cell membrane emanating from the free surface of the cell in to the lumen
Inc surface area of upper cell membrane involved in high rate of absorption
Contain bundle of microfilaments in core to maintain rigidity
Represent striated border of intestinal absorptive cells and brush border of kidney proximal tubule cells

Question 7

Describe stereocilia

Answer 7

Long microvilli found only in epididymis and on sensory hair cells of the inner ear
Non motile
Usually rigid due to core of actin filaments
In epididymis usually inc surface area and in hair cells function in signal generation

Question 8

Describe cilia

Answer 8

Long motile apical cells processes that have regular rhythmic bending movement
Core of cilium contains a complex of regularly arranged microtubules called the axoneme
Each of the 9 doublets is composed of A and B
Dyein is MT associated protein

Question 9

What is the axoneme composed of

Answer 9

Constant number of longitudinal microtubules arranged in a consistent 9+2

Question 10

What does dynein do

Answer 10

Active in flagella and has atpase activity to release energy and radiates from subunit A of one doublet towards subunit B of neighboring doublet

Question 11

What is kartagener’s syndrome

Answer 11

Results from hereditary defects in ciliary dynein that would normally provide energy for ciliary bending
Person is susceptible to lung infections
And males are sterile

Question 12

What is the basolateral domain

Answer 12

Subdivided in to 2 regions:
Lateral plasma membrane and basal plasma membrane
Each region possesses its own junctional specializations and receptors for hormones and neurotransmitters
Rich in Na+ and K+ Toase and ion channels

Question 13

What are the basal domain specializations

Answer 13

1)basal enfoldings
2)hemidesmosomes
3)basal lamina
These are the features that mark the basal surface of the epithelia

Question 14

Describe basal enfoldings

Answer 14

Basal surface of some epithelia especially those involved in ion transport possesses multiple finger like enfoldings of basal plasma membranes that inc surface areas of plasmalemma and partition the mitochondria rich basal cytoplasm

Question 15

Describe hemidesmosomes

Answer 15

They resemble half desmosomes and serve to attach to basal cell membrane to the basal lamina

Question 16

How do hemidesmosomes attach

Answer 16

Kertain tonofilaments insert in to plaques
Cytoplasmic aspects of transmembrane linker proteins(integrins) are attached to plaque whereas their extra cellular moieties bind to laminin and type 4 collagen of the basal lamina

Question 17

Describe the basal lamina

Answer 17

Located at the plane of junction between epithelium and underlying CT
Formed if adhesive glycoproteins as lamnin and collagen type 4

Question 18

What is metaplasia

Answer 18

Transformation of one type of epithelium in to another with loss of function
Ex: pseduostratfied columnar epithelium undergo metaplasia in heavy smokers in to squamous

Question 19

What is glandular epithelium

Answer 19

Type of epithelium found in diff types of glands
Glands are either exocrine(duct)
Or endocrine(ductless)