Lecture 1 Epithelium

Question 1

Functions of epithelium

Answer 1

Functions as a selective barrier
Covers body surfaces, lines cavities, forms glands
Embryonic derivatives of ectoderm, mesoderm and endoderm
Absorption, excretion, lubrication, secretory

Question 2

Organ consists of

Answer 2

Epithelial
Connective
Muscular
Nervous tissue

Question 3

Domains of a polarized epithelium

Answer 3

Apical domain

Basateral domain

Question 4

Polarity

Answer 4

The structure, composition and function of the apical surface membrane differ from those of the basolateral surfaces. Polarity is established by the presence of tight junctions that act as fences to separate these two regions. Internal organelles are disposed asymmetrically in the cell. Tight junctions regulate the paracellular pathway because they prevent back flux of transported material and keep basolateral and apical membrane components separate.

Question 5

Cystic fibrosis channels

Answer 5

Pumps in the basolateral surface and channels in the apical surface providing a driving force for Na by producing electrical polarization of the epithelium. NaCl moves across and water follows. In cystic fibrosis, apical Cl channels do not open, thickening the mucous layer covering the epithelial

Question 6

What provides epithelial with nutrients and oxygen?

Answer 6

Since epithelia are avascular, interstitial tissue fluids of connective tissue provide oxygen and nutrients

Question 7

Basement membrane

Answer 7

The sum of basal laminate and reticular laminate–both part of the extracellular matrix
Separates the epithelial cells from the connective tissue, acellular

Question 8

Embryonic origins of epithelia

Answer 8

Epidermis of the skin- ectoderm
The linings of digestive, respiratory and lower urogenital systems- endoderm
Lining of internal cavities mesoderm

Question 9

Lamina lucida

Answer 9

Contains adhesive glycoproteins (integrins)
Electron Lucent layer between basal lamina and basal cell membrane
Could be an artifact of fixation

Question 10

Lamina densa

Answer 10

Type IV collagen

Question 11

Reticular lamina

Answer 11

Type III collagen
More deeply placed
Reticular fibers

Question 12

The basal lamina

Answer 12

Predominantly type IV collagen associated with laminin, proteoglycans, fibronectin, secreted by epithelial cells

Question 13

Integrins

Answer 13

Adhesive proteins that traverse the lamina lucida and link the basal lamina to anchor proteins on The cytoplasmic side of epithelial cell at hemidesmosomes and focal adhesions

Question 14

Classification of epithelia

Answer 14

Simple
Stratified

Columnar
Cuboidal
Squamous

Question 15

True cilia

Answer 15

Normally arranged in orderly rows, have a regular synchronous movement
200 mm thick and 5-10 mm long

Can move fluid and particles along the epithelial surface
9+2 pattern of microtubules
Movement requires ATP
Dynein is motor protein
Found on epithelial cells in respiratory system (trachea, bronchi) and tails of motile sperm cells (flagella)

Question 16

Microvilli

Answer 16

Increase surface area of cell for absorption (small intestine, kidney tubule)
Contain a core of actin filaments
Terminal web: where’s Microvilli interact with a network of horizontal actin filaments
Villin anchors actin filaments in the tip

Question 17

Terminal web

Answer 17

Where microvilli interact with a network of horizontal actin filaments

Question 18

Stereocilia

Answer 18

Unusually long microvilli
Actin filaments core
   Epididymis 
   Proximal part of ductus deferens(absorption)
   Sensory cells of inner ear

Interconnected by cytoplasmic bridges

Question 19

Glands

Answer 19

Mucous
Serous

Endocrine
Exocrine

Unicellular (goblet cell)
Multicellular