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Molecular biology of the cell > 2.8 Epithelial cells and tissues > Flashcards

2.8 Epithelial cells and tissues Flashcards

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1
Q

What is a tissue

A

A group of cells whose type architecture and organisation are vital to its function
composed of cells, extra cellular matrix and fluid

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2
Q

What is an extracellular matrix

A

material formed by cells that are insoluble and extracellular
generally made of fibrillar protiens (elastin, fibrilin, collagens 1-3) that are in a hydrated ‘gel’ of proteoglycans
connective tissue is loosely organised, whereas bones and tendons are highly organised

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3
Q

What are the 5 main cell types

A

1) connective tissue
2) contractile tissue
3) haematopoetic cells
4) neural cells
5) epithelial cells

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4
Q

What are examples of connective tissue cells

A

fibroblasts (many tissues)
chondrocytes ( in cartilage )
osteocytes (in bones )

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5
Q

what are contractile tissues

A

cardiac muscles, skeletal muscle, smooth muscle

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6
Q

what are haematopoetic cells

A

blood cells
tissue resident immune cells
bone marrow cells

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7
Q

what constitutes neural cells

A

neurons and glial cells

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8
Q

what constitutes epithelial cells

A

-cells forming continuous layers

layers line surfaces and separate tissue compartments

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9
Q

What are epithelial cancers called

A

carcinomas

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10
Q

what are mesenchymal (connective tissue and muscle) cancers called

A

sarcomas

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11
Q

what are haematopoeitic cancers called

A

leukemias (if of bone marrow)

lymphomas (from lymphocytes )

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12
Q

what are neural cell cancers calls

A

neuroblastomas

gliomas

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13
Q

describe epithelial cells (3)

A
  • make organised and stable cell- cell junctions and form continous and cohesive layers
  • line internal and external body surfaces and tissue parts
  • cell-cell junctions are v important to maintaining epithelial layers
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14
Q

What are the 3 ways that epithelial cells can by classified by

A

squamous - ‘plate like’
columnar
cuboidal

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15
Q

What is single layered epithelium called

A

simple epithelium

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16
Q

what is multi layered epithelium called

A

stratified epithelium

17
Q

give 3 examples of squamous epithelial cells in the body

A

1) lining alveolus
2) lining internal cavities ( mesothelium )
3) endothelium lining blood vessels

18
Q

where are cuboidal epithelia often found

A

lining found in ducts (eg collecting ducts of kidney )

19
Q

Where are columnar cells found

A

surfaces involved in absorption or secretion

eg enterocytes lining guts

20
Q

What are the 2 types of stratified squamous epithelial cells found

A

1) keratinising

2) non keratinising

21
Q

What are keratinising stratified squamous epithelial cells and where are they found

A

squamous epithelial cells that produce keratin and so become thicker and die
They become thicker and more protective and stronger
They lose their nuclei and organelles
Not visible under a light microscope
eg epidermis (skin epithelium)

22
Q

What are no keratinising cells and where are they found

A

do not undergo keratinisation

found in epithelium of oesophagus, mouth, anus, cervix and vagina

23
Q

What is the point of keratinisation

A

form thick layers that protect underlying tissue from physical and chemical insults
(eg provides protection against cold, abrasion, solvents )

24
Q

What are pseudo stratified epithelia and where are they located

A

They look like they are stratified but on closer inspection the apical cells have contact with the basal lamina

25
Q

name the 4 cell-cell junctions from top to bottom

A

tight junction - seeling cells at apex like a belt
Adherens junction - ‘master junction ‘ that controls formation of all of the other junctions
desmosomes - spot junctions that form mechanically tough junctions between cells
gap junction - a channel forming junction forming pores between cells

26
Q

What are the characteristics of transporting epithelia

A
  • many mitochondria along the basal membrane
  • basal membrane has infoldings for active transport
  • apical membrane has ion channels for passive transport
27
Q

what are some characteristics of absorptive epithelia using examples

A

eg. enterocytes (absorptive intestinal cells ) and and kidney proximal tubule cells
intestinal epithelial cells have villi which have microvilli to increase SA (microvilli are plasma membrane projections of villi)
- secretory cells (goblet cells secreting mucus present)
- carriers transporting nutrients on microvillous brush border

28
Q

How are secretory epithelia often arranged

A

in tubules and glands

29
Q

What are the 2 main types of secretion and define them

A

exocrine - into a duct or lumen

endocrine - into the bloodstream

30
Q

Describe the arrangement of an exocrine secretory epithelium

A

1) it will be transporting AWAY from the basal membrane and capillary
2) its secretory vesicles and golgi apparatus will be at the apical part
3) nucleus and rough ER part will be at the basal part

31
Q

Describe the arrangement of an endocrine secretory epithelium

A

1) will be transporting into the blood stream
2) so will be pointing TOWARDS the basal membrane and capillary
3) secretory vesicles and golgi will be towards the basal membrane
4) nucleus and rough ER will be at the apical membrane

32
Q

What are the 2 ways in which you can classify secretory epithelial cells

A

stimulative - already has the secretory vesicles but only fuses with plasma membrane to release their contents ( fight and flight response meaning adrenaline is released from the adrenal medulla )
constitutive - as soon as secretory vesicles are formed, they fuse with the plasma membrane (hepatocytes making plasma proteins)

33
Q

How are intestinal absorptive cells replaced

A

by crypt stem cells to replace cells lost from the villius tip

34
Q

What can go wrong with the replacement mechanism for absorptive epithelia in the intestinal cells

A
  • intestinal crypt cells can be inhibited from proliferating by chemotherapy
  • leads to flattening of intestinal mucosa
  • loss of finger like villi projections
35
Q

What can produce hyperproliferation of the epidermis

A

papillomavirus

36
Q

Why does hyperproliferation of the epidermis happen

A

increased production of epithelial cells outnumbers the number lost

  • cells accumulate
  • increased thickening and hardening

Molecular biology of the cell (8 decks)

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