Epithelia cells and tissues

Question 1

What is a tissue?

Answer 1

a group or groups of cells whose type, organisation and architecture are integral to its function

Question 2

What is a tissue made up of?

Answer 2

extracellular matrix and fluid

Question 3

What are the 5 main cell types?

Answer 3

Connective tissue cells
Contractile tissues
Haematopoietic cells
Neural cells
Epithelial cells

Question 4

What are connective tissue cells?

Answer 4

fibroblasts (many tissues), chondrocytes (cartilage), osteocytes (bone)

Question 5

What are contractile tissue cells?

Answer 5

skeletal muscle, cardiac muscle, smooth muscle

Question 6

What are Haematopoietic cells?

Answer 6

blood cells, tissue-resident immune cells, and the cells of the bone marrow from which they are derived

Question 7

What are neural cells?

Answer 7

cells of the nervous system having two main types; neurones (carry electrical signals) and glial cells (support cells)

Question 8

What are epithelial cells?

Answer 8

cells forming continuous layers, these layers line surfaces and separate tissue compartments and have a variety of other functions

Question 9

What are carcinomas?

Answer 9

epithelial cancers

Question 10

What are sarcomas?

Answer 10

mesenchymal (connective tissue and muscle) cancers

Question 11

What are lymphomas?

or leukemias?

Answer 11

haematopoietic cancers

Question 12

What are neuroblastomas or gliomas?

Answer 12

neural cell cancers

Question 13

What is the function of epithelial cells?

Answer 13

transport, absorption, secretion, protection

Question 14

What is key to the formation and maintenance of epithelial layers?

Answer 14

cell-cell junctions

Question 15

how are epithelial cells classified?

Answer 15

their shape

their layering

Question 16

how are epithelial cells classified by their shape?

Answer 16

squamous (flattened plate-shape)
cuboidal
columnar

Question 17

how are epithelial cells classified by their layering?

Answer 17

single layer = simple epithelium

multi-layered = stratified epithelium

Question 18

Where is the single squamous epithelium found?

Answer 18

lung alveolar (air sac) epithelium, mesothelium (lining major body cavities), endothelium lining blood vessels and other blood spaces). 
THIN

Question 19

Where is the simple cuboidal epithelium found?

Answer 19

in ducts

e.g. those lining the kidney collecting ducts

Question 20

Where is the simple columnar epithelium found?

Answer 20

typical of surfaces involved in absorption and secretion of molecules
-enterocytes(lining the gut)

Question 21

What are the 2 main types of stratified squamous epithelium?

Answer 21

Keratinizing

Non-keratinizing

Question 22

What is keratinizing Stratified squamous epithelium?

(loose organelles and nuclei) not visible under light microscopy

Answer 22

Epithelial cells which produce keratin and in doing so die becoming thicker, stronger, protective structures

Question 23

Where is keratinizing stratified squamous epithelium found?

Answer 23

epidermis (skin epithelium)

Question 24

What is non-keratinizing Stratified squamous epithelium?

Answer 24

Epithelial cells which do not undergo keratinisation. They retain their nuclei and organelles

Question 25

Where is non-keratinizing stratified squamous epithelium found?

Answer 25

epithelium lining the mouth, oesophagus, anus, cervix and vagina

Question 26

What is pseudo-stratified epithelium?

Answer 26

appears to be multi-layered | -- On close examination, the surface cells have contact with the basal lamina

Question 27

Where is pseudo-stratified epithelium found?

Answer 27

. airway (trachea and bronchi) epithelium, various ducts in the urinary and reproductive tracts

Question 28

Why is epithelial polarity required?

Answer 28

to give the directionality needed for epithelial function

Question 29

What are transporting epithelia?

Answer 29

transport ions and fluids across epithelial layers

Question 30

What is polarised in the transporting epithelia?

Answer 30

pumps and channels active Na+/ K+ exchanger only pumping in one aspect of plasma membrane?

Question 31

What is required for secretion from transporting epithelia?

Answer 31

polarity | most epithelia secrete in one direction only

Question 32

What are the 4 main cell-cell junctions in epithelia?

Answer 32

tight junction adherens junction desmosomes gap junction

Question 33

Where are the tight junctions?

Answer 33

form a belt usually around the apical lateral membrane

Question 34

What is the role of tight junctions?

Answer 34

sealing gaps between cells

Question 35

What is the role of adherens junctions?

Answer 35

controls the formation of all others

Question 36

What are desmosomes?

Answer 36

form mechanically tough junctions between cells

Question 37

What is the role of desmosomes?

Answer 37

important in tissues required to resist mechanical stresses

Question 38

What is a gap junction?

Answer 38

channel forming junction

Question 39

What is the role of the gap junction?

Answer 39

form pores between cells and allows cells to exchange and share materials

Question 40

What are mitochondria typically associated with?

Answer 40

extensive basal membrane infoldings, providing energy for active transport across the abundant membranes The infoldings increase the amount of basal membrane that can pump ions and water

Question 41

How is the small intestine surface area increased?

Answer 41

it is long, and also by the interior surface of the wall of the small intestine being folded into numerous finger-like processes that point into the interior: the villi (covered with intestinal epithelial cells)

Question 42

What are microvilli?

Answer 42

plasma membrane projections of the villi

Question 43

Where are carriers transporting nutrients typically found on the microvillus?

Answer 43

brush-border membranes, e.g. absorptive intestinal cells (enterocytes) and kidney proximal tubule cells

Question 44

What are the 2 main types of secretion?

Answer 44

exocrine (into a duct or lumen) and endocrine (into the bloodstream)

Question 45

Where do endocrine cells secrete their contents?

Answer 45

into the basal aspect -- secretory vesicles are positioned so that when their contents are released, they have close access to the blood circulation

Question 46

What are the 2 classes of endothelial cells (by the way they secrete)?

Answer 46

constitutive | stimulated

Question 47

What are constitutive endothelial cells?

Answer 47

secretory vesicles, as they are formed, move directly to the plasma membrane and release their contents

Question 48

example of constitutive endothelial cells?

Answer 48

production of plasma proteins by hepatocytes (constitutive endocrine secretion).

Question 49

What are Stimulated endothelial cells?

Answer 49

secretory vesicles are stored in the cytoplasm and only fuse with the plasma membrane to release their contents

Question 50

example of Stimulated endothelial cells?

Answer 50

release of adrenaline from cells of the adrenal medulla after a fight-or-flight stimulus (stimulated endocrine secretion); when stomach contents enter the duodenum, pancreatic acinar cells are stimulated to release their digestive enzymes into ducts (stimulated exocrine secretion)

Question 51

When calls migrate up the villus epithelium, new cells are made by what?

Answer 51

crypt stem cells

Question 52

What happens when the proliferation of intestinal crypt cells are inhibited? eg. cancer chemotherapy

Answer 52

results in loss of the finger-like intestinal villi and flattening of the intestinal mucosa. This is responsible for many of the gastro-intestinal disturbances that are side-effects

Question 53

how are keratinising squamous epithelial cells formed?

Answer 53

new cells being formed in the basal layer which migrate up while undergoing a programme of differentiation that eventually leads to them flattening out and keratinising

Question 54

What does hypoproliferation of epithelial cells result in?

Answer 54

increased cell numbers and a thickening of cell layers | - in response to repeated or constant pressure

Question 55

What happens if the cell production is greater than the cells lost from the surface?

Answer 55

cells will accumulate creating an increased thick hard layer

Question 56

What does papilloma virus do?

Answer 56

induces hyperproliferation -- by hijacking the cellular machinery of stratified squamous epithelia and inducing increased cell proliferation, which results in a surface growth, e.g. a wart