2.8 Epithelial cells and tissues

Question 1

What is a tissue

Answer 1

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

Question 2

What is an extracellular matrix

Answer 2

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

Question 3

What are the 5 main cell types

Answer 3

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

Question 4

What are examples of connective tissue cells

Answer 4

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

Question 5

what are contractile tissues

Answer 5

cardiac muscles, skeletal muscle, smooth muscle

Question 6

what are haematopoetic cells

Answer 6

blood cells
tissue resident immune cells
bone marrow cells

Question 7

what constitutes neural cells

Answer 7

neurons and glial cells

Question 8

what constitutes epithelial cells

Answer 8

-cells forming continuous layers

layers line surfaces and separate tissue compartments

Question 9

What are epithelial cancers called

Answer 9

carcinomas

Question 10

what are mesenchymal (connective tissue and muscle) cancers called

Answer 10

sarcomas

Question 11

what are haematopoeitic cancers called

Answer 11

leukemias (if of bone marrow)

lymphomas (from lymphocytes )

Question 12

what are neural cell cancers calls

Answer 12

neuroblastomas

gliomas

Question 13

describe epithelial cells (3)

Answer 13

• 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

Question 14

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

Answer 14

squamous - ‘plate like’
columnar
cuboidal

Question 15

What is single layered epithelium called

Answer 15

simple epithelium

Question 16

what is multi layered epithelium called

Answer 16

stratified epithelium

Question 17

give 3 examples of squamous epithelial cells in the body

Answer 17

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

Question 18

where are cuboidal epithelia often found

Answer 18

lining found in ducts (eg collecting ducts of kidney )

Question 19

Where are columnar cells found

Answer 19

surfaces involved in absorption or secretion

eg enterocytes lining guts

Question 20

What are the 2 types of stratified squamous epithelial cells found

Answer 20

1) keratinising

2) non keratinising

Question 21

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

Answer 21

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)

Question 22

What are no keratinising cells and where are they found

Answer 22

do not undergo keratinisation

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

Question 23

What is the point of keratinisation

Answer 23

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

Question 24

What are pseudo stratified epithelia and where are they located

Answer 24

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

Question 25

name the 4 cell-cell junctions from top to bottom

Answer 25

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

Question 26

What are the characteristics of transporting epithelia

Answer 26

- many mitochondria along the basal membrane - basal membrane has infoldings for active transport - apical membrane has ion channels for passive transport

Question 27

what are some characteristics of absorptive epithelia using examples

Answer 27

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

Question 28

How are secretory epithelia often arranged

Answer 28

in tubules and glands

Question 29

What are the 2 main types of secretion and define them

Answer 29

exocrine - into a duct or lumen | endocrine - into the bloodstream

Question 30

Describe the arrangement of an exocrine secretory epithelium

Answer 30

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

Question 31

Describe the arrangement of an endocrine secretory epithelium

Answer 31

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

Question 32

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

Answer 32

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)

Question 33

How are intestinal absorptive cells replaced

Answer 33

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

Question 34

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

Answer 34

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

Question 35

What can produce hyperproliferation of the epidermis

Answer 35

papillomavirus

Question 36

Why does hyperproliferation of the epidermis happen

Answer 36

increased production of epithelial cells outnumbers the number lost - cells accumulate - increased thickening and hardening