7 - Epithelia Flashcards

1
Q

Two broad types of epithelia (divided by function)

A

1) Surface epithelia (line surfaces and lumena)

2) Glandular epithelia (involved in secretion)

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2
Q

How are glandular epithelia formed?

A

Invaginations of secreting cells

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

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

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4
Q
Characteristics of epithelial cells
1)
2)
3)
4)
A
1)  Exhibit polarity: apical,
lateral and basal
domains
2) Connected by cell
junctions
3) Supported by a
basement membrane
4) Avascular
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5
Q

Examples of simple squamous epithelium

A

Mesothelium, endothelium, lining of alveoli, glomeruli

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6
Q

Examples of simple cuboidal epithelium

A

Thyroid follicles, renal tubules

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7
Q

Examples of simple columnar epithelium

A

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

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8
Q

Difference between stratified and simple epithelia

A

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

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9
Q

What are pseudostratified epithelial cells?

A

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

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10
Q

Examples of pseudostratified columnar epithelial cells

A

Respiratory tract (ciliated)

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11
Q

Examples of stratified squamous epithelial cells

A

Keratinising: skin

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

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12
Q

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

A

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

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13
Q

Where does surface epithelium get nutrients?

A

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

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14
Q

Brush border

A

When there are lots of microvili on an epithelial layer.

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15
Q

Length of microvili

A

0.5 - 1μm in length

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16
Q

How much can microvili increase surface area by?

A

A factor of 20

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17
Q

Length of cilia

A

2 - 10 μm long

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18
Q

Can cilia move?

A

Yes. Have a core of microtubules

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19
Q

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

A

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

20
Q

Tight junctions
1)
2)
3)

A

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

21
Q

Difference in desmosome and hemidesmosome function

A

1) Desmosome (cell-cell)

2) Hemidesmosome (cell-basement membrane)

22
Q

Components of a desmosome
1)
2)

A

1) Cadherens link two cells

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

23
Q

Function of desmosomes and adherens junctions

A

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

24
Q

Gap junction function

A

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

25
Q

Components of a gap junction

A

Connexin proteins form pores

26
Q

Components of a hemidesmosome
1)
2)

A

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)

27
Q

CAM function

A

Cell adhesion molecules

Link with CAMs on other cells to join together, communicate

28
Q

Four types of CAMs

A

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

29
Q

Basement membrane

A

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

30
Q

What produces basement membrane?

A

Mainly produced by the cells being supported

31
Q

Components of basement membrane

A

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

32
Q

Function of laminins and fibronectin in basement membrane

A

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

33
Q

Function of collagen VII and reticulin in basement membrane

A

Link basement membrane to underlying tissue

34
Q

Mucosa

A

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

35
Q

Serosa

A

Surface mesothelium and underlying supportive connective tissue

36
Q

Examples of serosa

A

Lines pericardial, pleural, peritoneal cavities and tunica vaginalis

37
Q

Two types of glandular epithelium

A

1) Exocrine - secrete into ducts

2) Endocrine - secrete into blood

38
Q
Types of glandular epithelial cell shapes
1)
2)
3)
4)
5)
6)
7)
A

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

39
Q

Example of simple coiled tubular glandular epithelial cell

A

Sweat gland

40
Q

Example of simple tubular glandular epithelial cell

A

Within colon

41
Q

Example of a simple branched tubular glandular epithelial cell

A

In stomach

42
Q

Two types of secretions from glandular epithelial cells

A

1) Serous secretion (proteins in water medium)

2) Mucosal secretion (glycoproteins in water medium)

43
Q

Goblet cells

A

Mucus secreting cells full of membrane-bound mucous

droplets

44
Q

Goblet cell appearance in H&E

A

1) Mucous membranes non-staining

2) Nucleus, organelles displaced basally

45
Q
Acini
1)
2)
3)
4)
A

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