Epithelial Cells and Tissues

Question 1

What are tissues

Answer 1

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

Tissues are made up of cells, extracellular matrix and fluid

Question 2

What are the five main cell types

Answer 2

Connective tissue cells - fibroblasts, condrocytes, osteocytes

Contractile tissues - skeletal muscle, cardiac muscle, smooth muscle

Haematopoietic cells - blood cells, tissue-resident immune cells, cells of bone marrow

Neural cells - cells of the nervous system, neurones and glial cells

Epithelial cells - cells forming continours layers which surface and separate tissue compartments

Question 3

Tumours based on where they originate

Answer 3

Epithelial cells - carcinomas

Mesenchymal cells - sarcomas

Haematopoietic cancers - leukaemias or lymphomas

Neural cells - neuroblastomas or gliomas

Question 4

Epithelial Classification

Answer 4

Shape: squamous, cuboidal, columnar

Layering: single layer, multi-layer

Question 5

Single squamous epithelium

Answer 5

Found in the lung alveolar (air sac) epithelium

Mesothelium (lining major body cavities)

Endothelium lining blood vessels

Allow for exchange to happen

Question 6

Simple cuboidal epithelium

Answer 6

Linings found in ducts - those lining the kidney collecting ducts

Question 7

Simple columnar epithelium

Answer 7

Absorption and secretion of molecules

Enterocytes lining the gut involved in the take up of breakdown products of digestion

Question 8

Stratified squamous epithelium

Answer 8

Keratinizing: epithelial cells which produce keratin and become thicker in doing so. Lose their cellular organelles and nuclei, not visible under light microscopy

Non-keratinizing: Epithelial cells which do not undergo keratinisation, retain their nuclei and organelles (line mouth, oesophagus, anus, cervix and vagina)

Question 9

Keratinizing and non-keratinizing

Answer 9

Keratinizing epithelium can form thick layers that protect underlying tissues from various physical and chemical insults

Question 10

Pseudo-stratified epithelium

Answer 10

Surface cells have contact with basal lamina

e.g. airway epithelium, various ducts in the urinary and reproductive tracts

Question 11

What is the membrane between two adjacent cells

Answer 11

Lateral membrane

Question 12

What is required to give directionality of the epithelial cells

Answer 12

epithelial polarity

Question 13

Why can directionality only be achieved when transported is polarised

Answer 13

Only pumping on one aspect of the membrane

Question 14

Where do tight junction form

Answer 14

Involved in sealing the gap between cells

Apical membrane

Question 15

What is the adherens junction

Answer 15

Master junctions which controls the formation of the other junctions

Question 16

What is the desmosomes junction

Answer 16

Form mechanically tough junction between cells

Resist mechanical stress

Question 17

What does the gap junction do

Answer 17

Form pores between cells to allow cells to share material

Question 18

What are the key features of transporting epithelia

Answer 18

Plasma membranes contain high concentrations of ion transporters

Mitochondria concentrated towards basal lamina

Ion and water transport will have directionality

Question 19

What are the key features of absorptive epithelium

Answer 19

Carriers transporting nutrients

found in Absorptive intestinal cells (enterocytes) and kidney proximal tubule cells

Secretory cells are found among the absorptive cells of the intestinal villi

Question 20

Picture of the brush-border membrane

Answer 20

Question 21

What are the key features of the secretory epithelium

Answer 21

Two main types of secretion: exocrine (into a duct or lumen) and endocrine (into the bloodstream)

Question 22

Picture of the secretory epithelium of exocrine cells

Answer 22

Question 23

Picture of secretory epithelium of an endocrine cell

Answer 23

Question 24

What other ways you can classify an endothelial cell

Answer 24

Constitutive - secretory vesicles move directly to plasma membrane and release contents as they are formed

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

Question 25

What are examples of epithelial proliferation

Answer 25

Cells in intestinal crypts replacing cells lost from the tips of intestinal villi

Cells of the basal layer of stratified squamous epithelia dividing to replace cells lost from the surface

Question 26

Why does cancer chemotherpay cause gastro-intestinal distrubances

Answer 26

Inhibition of the proliferation of intestinal crypt cells which results in the loss of the finger like villi

Question 27

What happens during hyperproliferation

Answer 27

Increased cell number and thickening of cell layers in response to repeated or constant pressure

If increase in cell production is greater than cell loss from surface, cells will accumulate creating hard skin of corns

Question 28

What are diagrams of papilloma virus

Answer 28

They hijack the cellulary machinery of stratified squamous epithelia