Epithelia

Question 1

4 basic types of tissues classification

Answer 1

Four Basic Types:

A. Epithelium (epithelial tissue)

B. Connective tissue

C. Muscle tissue

D. Nerve tissue

Question 2

Where are epithelia found?

Answer 2

in skin, internal cavities, lumen of bodies

Question 3

Main functions = PASSEF

Answer 3

protection, exchange, filtration, absorption, sensation, secretion

Question 4

Structure

Answer 4

Avascular. closely apposed to each other by:
- tight junctions (impermeability of cells, limit movement of substances)
- anchoring junctions (mechanical stability)
- channel forming junctions (fluid exchange.)
=CAT

Question 5

basement membrane =

Answer 5

basal lamina + reticular lamina (composed of type 3 collagen)

Question 6

epc’s are specialized for

Answer 6

absorption, secretion, or protection

Question 7

basal lamina thickness

Answer 7

40-120 nm thick

Question 8

basal lamina composed of:

Answer 8

strong flexible foundation.
meshwork formed by: 4 cans of lame intact pearls = perlecan, type 4 collagen, intactin, laminin.

also acts as a mechanical barrier + anchoring epc’s.
important in angiogenesis

Question 9

Epithelial tissue calssification can be based on:

Answer 9

1. Based on the number of cell layers
   - Simple
   - Stratified
2. Based on shape of surface cells
   - Squamous
   - Cuboidal
   - Columnar
3. Special categories
   - Pseudostratified epithelium
   - Transitional epithelium

Note: Specialisation of apical cell surface domain can be added
( eg. simple columnar ciliated epithelium)

Question 10

simple squamous function and location:

fried egg shaped

Answer 10

Function: Absorption, filtration, diffusion, barrier (CNS), exchange, lubrication

Location: Capillaries (endothelium), alveoli, abdominal & pleural cavities (mesothelium) and Bowman’s capsule (kidney)

Question 11

simple cuboidal fl:

round nucleus, centrally located.

Answer 11

Function: Absorption, secretion and transportation

Location: Glands and ducts, kidney tubules, surface of ovary (germinal epithelium), thyroid follicles

**triangular cells are still classifed as simple cuboidal.

**nuclei form rows or circles.

Question 12

stratified squamous (keratinized/non-keratinized) fl:

Answer 12

Function: Barrier and protection

Location: Skin, oral cavity, upper throat, oesophagus, vagina

keratinized: resists abrasion. looks like a highlighter brush border. darkly stained. can prevent sun damage and dehydration.

non-keratinized: eg inside cheeks. exposed to friction but not outer environment.

Question 13

Stratified Cuboidal fl:

**lumen is not always round

Answer 13

Function: Barrier and transport

Location: Sweat gland ducts, large ducts of exocrine glands, anorectal junction

Question 14

Pseudostratified Columnar

**appears to have many layers but only has one. ciliated apical surface. tall+thin, nuclei squashed together. have goblet cells

Answer 14

Function: Secretion, absorption and protection

Location: Upper Respiratory tract, trachea and bronchial tree, ductus deferens, efferent ductules of epididymis

**ciliated apical surface. tall+thin, nuclei squashed together. have goblet cells. all cells are connected to the basement membrane.

Question 15

Transitional Epithelium

**look like bubbles of soap stacked on top of each other.

Answer 15

Function: Barrier, distensible property
Location: Bladder, renal calyces, ureters, urethra

**number of layers and shapes of cells change depending on stretching of the organ.

allows for distension without damage.

Question 16

microvilli - surface specialization

**actin, cytoplasmic processes

Answer 16

Surface specialisation of GI tract
Cytoplasmic process containing a core of network of cytoskeletal proteins (actin filaments)
Massively increases surface area for absorption

Question 17

cilia - surface specialization

**microtubules

Answer 17

Surface specialisation of respiratory tract and fallopian tube

Cytoplasmic process containing microtubules (central and peripheral)

Transport secretions and foreign bodies

Transport cells on the surface (oviduct/fallopian tube)

found in cells which have to move fluids, to confer cell motility

Question 18

in keratinised squamous epithelium, there are desmosomes. what if desmosomes were not working?

Answer 18

it gives mechanical strength to tissues, found in tissues which experience high mechanical force.