Lecture 2: Epithelia

Question 1

Where are epithelial cells found

Answer 1

lining of hollow organs, cavities and ducts

Question 2

Different types of cell junctions

Answer 2

Tight, Adherens, Gap, Desmosomes, Hemidesmosomes

Question 3

Functions of Epithelial tissue

Answer 3

selective barrier - limiting the transfer of substances into the body
secretory surface - releases products onto free surfaces
protection - resists abrasion from the environment

Question 4

What is the apical surface

Answer 4

the outside world of the cell

Question 5

What is the lateral surface

Answer 5

the vertical surface of a cross section

Question 6

What is the basal surface

Answer 6

the surface attached to the base membrane

Question 7

What are microfilaments

Answer 7

proteins made from actin, beneath cell membrane and cytoplasm

Question 8

Functions of microfilaments

Answer 8

Strength, alter cell shape, tie cells together, muscle contraction, link membrane to cytoplasm

Question 9

What are intermediate filaments

Answer 9

predominant protein is keratin

Question 10

Function of intermediate filaments

Answer 10

Strength, movement of materials through the cytoplasm

Question 11

Where are tight junctions located

Answer 11

within the intercellular space of a cell membrane, joining cytoskeletons of adjacent cells

Question 12

What are the key binding proteins in a tight junction

Answer 12

Claudins and occludins

Question 13

Function of tight junctions

Answer 13

Keeps the junction electrically tight, so ions and proteins cannot move between the cells - keeps cell polarity (prevents migration of proteins between basal and apical). Specific environment within the cell

Question 14

Describe the adherens junction

Answer 14

Sits below tight junction at the apex of the cell, has an intracellular gap - closer to the basal membrane. Has a layer of proteins to join actin to cadherins

Question 15

Role of key protein cadherins

Answer 15

Spanning the gap, bind to actin to join the cytoskeleton to the skeleton of the membrane and adjacent cell

Question 16

Role of key protein catenins

Answer 16

Joins the cadherins to the microfilament actins

Question 17

Function of the Adherens junction

Answer 17

Key for cell stability, distributes tension forces around the cell to prevent cell seperation

Question 18

Describe a desmosome junction

Answer 18

Dome like structure with intercellular gap between the cell membranes on the lateral wall

Question 19

Key protein in a desmosome

Answer 19

Cadherin, the spanning protein

Question 20

Function of a desmosome

Answer 20

links cell surface to keratin (intermediate filament), creates structural integrity spanning from one desmosome to the other. Winds into keratin instead of locking into the actin. Binds muscle cells to prevent them pulling apart

Question 21

Where do the cell junctions bind

Answer 21

Into the cytoskeleton

Question 22

Composition of Gap Junctions

Answer 22

has connexIn protein molecules, 6 form a connexOn which can connect and open to form a hemichannel. Gap Junction = 2 hemichannels

Question 23

Function of Gap Junctions

Answer 23

hemichannel allows small molecules to pass between cells, key for communication and for contraction in the heart

Question 24

Where is the hemidesmosome located

Answer 24

It is a basal junction, on the basement membrane

Question 25

Function of the hemidesmosome

Answer 25

Linking of basal intermediate filament keratin to the basement membrane, connect epithelia to the membrane, locks cell down so it does not slide into the basement membrane

Question 26

Role of Integrin in the hemidesmosome

Answer 26

Linker protein (glycoprotein), spanning basement membrane to the inner part of cell. Binds to laminin in the membrane and keratin in the cytoplasm

Question 27

Two parts of the basement membrane

Answer 27

epithelia overlay the Basal Lamina and the retticular lamina. Found between the epithelium and connective tissues

Question 28

Composition of the basal lamina

Answer 28

Under the basal surface, secreted by the epithelial cells

Question 29

Composition of the reticular lamina

Answer 29

produced by the cells in the underlying connective tissue - the fibroblasts. Has no blood vessels. needs to allow the passage of nutrients through the basal lamina

Question 30

Exchange of nutrients in the epithelia

Answer 30

No blood vessels (avascular), exchange of nutrient takes place by diffusion

Question 31

Functions of the basement membrane

Answer 31

provides a surface for the migration of epithelial cells during wound healing, supports overlying epithelium, acts as a physical barrier to invasion, filtration of substances in the kidney

Question 32

Types of epithelial tissue

Answer 32

Covering and lining and glandular

Question 33

Description of covering and lining epithelia

Answer 33

outer covering of skin and internal organs, inner lining of blood vessels and body cavities

Question 34

Description of glandular proteins

Answer 34

the secretory portion of glands

Question 35

Function of endocrine glandular epithelia

Answer 35

secretion of hormones and precursors into the interstitial fluid, then blood

Question 36

Function of exocrine epithelia

Answer 36

secrete into passages/ducts and exterior surfaces