7 - Epithelia

Question 1

Two broad types of epithelia (divided by function)

Answer 1

1) Surface epithelia (line surfaces and lumena)

2) Glandular epithelia (involved in secretion)

Question 2

How are glandular epithelia formed?

Answer 2

Invaginations of secreting cells

Question 3

Epithelial cell functions
1)
2)
3)
4)
5)

Answer 3

1) Protection
2) Barrier, selective diffusion
3) Absorption
4) Secretion
5) Receptors e.g. smell, taste

Question 4

Characteristics of epithelial cells
1)
2)
3)
4)

Answer 4

1)  Exhibit polarity: apical,
lateral and basal
domains
2) Connected by cell
junctions
3) Supported by a
basement membrane
4) Avascular

Question 5

Examples of simple squamous epithelium

Answer 5

Mesothelium, endothelium, lining of alveoli, glomeruli

Question 6

Examples of simple cuboidal epithelium

Answer 6

Thyroid follicles, renal tubules

Question 7

Examples of simple columnar epithelium

Answer 7

1) Non-ciliated e.g. stomach, small and large intestines,
gallbladder and bile ducts, endocervix
2) Ciliated: Fallopian tubes, bronchioles

Question 8

Difference between stratified and simple epithelia

Answer 8

Simple epithelial cells all have contact with basement membrane.
Stratified epithelial cell basal layer only has contact with basement membrane

Question 9

What are pseudostratified epithelial cells?

Answer 9

Epithelial cells that have nuclei in different places, and can appear stratified, but all all cells have contact with basement membrane

Question 10

Examples of pseudostratified columnar epithelial cells

Answer 10

Respiratory tract (ciliated)

Question 11

Examples of stratified squamous epithelial cells

Answer 11

Keratinising: skin

Non-keratinising: Oral cavity, oesophagus, anal cavity, vagina

Question 12

Example of stratified epithelium where one cell type lies over a different cell type

Answer 12

Breast, sweat glands, salivary glands: Surface columnar layer overlying myoepithelial layer

Question 13

Where does surface epithelium get nutrients?

Answer 13

From diffusion of blood vessels underlying basement membrane. Epithelial layers are avascular

Question 14

Brush border

Answer 14

When there are lots of microvili on an epithelial layer.

Question 15

Length of microvili

Answer 15

0.5 - 1μm in length

Question 16

How much can microvili increase surface area by?

Answer 16

A factor of 20

Question 17

Length of cilia

Answer 17

2 - 10 μm long

Question 18

Can cilia move?

Answer 18

Yes. Have a core of microtubules

Question 19

Types of intercellular junctions in epithelia
1)
2)
3)

Answer 19

1) Tight junctions
2) Adherens junctions
3) Gap junctions

Question 20

Tight junctions
1)
2)
3)

Answer 20

1) Located at apical junction between epithelial cells
2) Link cells, limit what can pass between them
3) Made of occludin proteins

Question 21

Difference in desmosome and hemidesmosome function

Answer 21

1) Desmosome (cell-cell)

2) Hemidesmosome (cell-basement membrane)

Question 22

Components of a desmosome
1)
2)

Answer 22

1) Cadherens link two cells

2) Within cells, catenins link cadherens to intermediate filament cytoskeleton (catenins make up ‘plaque’)

Question 23

Function of desmosomes and adherens junctions

Answer 23

Link the cytoskeletons of two cells (desmosomes - intermediate filaments, adherens junctions - actin)

Question 24

Gap junction function

Answer 24

Allow continuous cytoplasm between linked cells (EG: for transfer of depolarisation between cardiac muscle cells)

Question 25

Components of a gap junction

Answer 25

Connexin proteins form pores

Question 26

Components of a hemidesmosome 1) 2)

Answer 26

1) Integrin proteins project from cell and anchor to basement membrane 2) Plaque within cell links integrins with intermediate filaments of cytoskeleton (link to laminins in basement membrane)

Question 27

CAM function

Answer 27

Cell adhesion molecules | Link with CAMs on other cells to join together, communicate

Question 28

Four types of CAMs

Answer 28

1) Cadherins: component of adherens junctions 2) Integrins: interact between actin and extracellular matrix molecules 3) Selectins: mediate white blood cell-endothelial cell interactions 4) Immunoglobulin superfamily: mediate homotypic cell-cell adhesions e.g. ICAM, CCAM, PECAM

Question 29

Basement membrane

Answer 29

Interface between support tissues and parenchymal cells e.g. epithelia

Question 30

What produces basement membrane?

Answer 30

Mainly produced by the cells being supported

Question 31

Components of basement membrane

Answer 31

Extracellular matrix: predominantly collagen IV, heparan sulphate and structural glycoproteins: laminins, fibronectin. Underlying collagen VII and reticulin

Question 32

Function of laminins and fibronectin in basement membrane

Answer 32

Laminins and fibronectin are involved in linking integrins of epithelial cells to extracellular matrix

Question 33

Function of collagen VII and reticulin in basement membrane

Answer 33

Link basement membrane to underlying tissue

Question 34

Mucosa

Answer 34

Lines body passages that communicate with the exterior – Surface epithelium with underlying supportive tissue, maybe with underlying smooth muscle (muscularis mucosae) – Associated glands that secrete mucus or other secretions onto the epithelium

Question 35

Serosa

Answer 35

Surface mesothelium and underlying supportive connective tissue

Question 36

Examples of serosa

Answer 36

Lines pericardial, pleural, peritoneal cavities and tunica vaginalis

Question 37

Two types of glandular epithelium

Answer 37

1) Exocrine - secrete into ducts | 2) Endocrine - secrete into blood

Question 38

``` Types of glandular epithelial cell shapes 1) 2) 3) 4) 5) 6) 7) ```

Answer 38

1) Simple tubular 2) Simple coiled tubular 3) Simple branched tubular 4) Simple acinar tubular 5) Compound acinar 6) Compound tubular 7) Compound tubuloacinar

Question 39

Example of simple coiled tubular glandular epithelial cell

Answer 39

Sweat gland

Question 40

Example of simple tubular glandular epithelial cell

Answer 40

Within colon

Question 41

Example of a simple branched tubular glandular epithelial cell

Answer 41

In stomach

Question 42

Two types of secretions from glandular epithelial cells

Answer 42

1) Serous secretion (proteins in water medium) | 2) Mucosal secretion (glycoproteins in water medium)

Question 43

Goblet cells

Answer 43

Mucus secreting cells full of membrane-bound mucous | droplets

Question 44

Goblet cell appearance in H&E

Answer 44

1) Mucous membranes non-staining | 2) Nucleus, organelles displaced basally

Question 45

``` Acini 1) 2) 3) 4) ```

Answer 45

1) Serous cells can form a secretory unit called an acinus 2) Secrete into common, narrow lumen 3) Secretion carried away by a duct 4) Basophilic at base, acidophilic at apex