Epithelial cells

Question 1

What types of cells are haemopoietic cells?(3)

Answer 1

Blood cell
Tissue-resident immune cells
Cells derived from bone marrow.

Question 2

What are neural cells?

Answer 2

Cells that constitute the nervous system: Neurones (transmit electrical signals), and glial cells (provides neurone support and insulation - Schwann cell).

Question 3

What are contractile tissues?

Answer 3

Skeletal muscle, cardiac muscle, smooth muscle.- Tissue with the ability to contract.

Question 4

What are connective tissue cells?

Answer 4

Fibroblasts (many tissues), chondrocytes (cartilage), osteocytes (bones)- Connects, bind and supports tissue cells.

Question 5

What are epithelial cells?

Answer 5

Cells forming continuous layers, layers line surfaces and separate tissues compartments- variety of alternative function- Secretion, selective absorption, protection, transcellular transport and sensing.

Question 6

What are squamous epithelial cells?

Answer 6

Flattened, plate shape, abundant cytoplasm and small round circular nucleus.

Question 7

What are columnar cells?

Answer 7

Arranged in columns; approximately 3000 microvilli per cell (maximises surface area for absorption). Simple columnar epithelial cells secrete molecules- enterocytes assist in molecular degradation in gut.

Question 8

What are cuboidal cells?

Answer 8

Cuboidal: Cube-like (lines nephrons, ovaries and ducts)- main function is secretion.

Question 9

What are stratified epithelium?

Answer 9

Multiple layers of cells

Question 10

What are pseudo-stratified epithelium?

Answer 10

T​his epithelium appears to be multi-layered, but on close examination, the surface cells have contact with the basal lamina. e.g. airway (trachea and bronchi) epithelium, various ducts in the urinary and reproductive tracts.

Question 11

What is epithelial cell polarity?

Answer 11

Membrane is organised into discrete domains through formation of junctions, distinct polarity has apical membrane at the luminal surface and a basolateral domain (basal surface is in contact with the extracellular matrix)

Question 12

What is a lateral membrane?

Answer 12

Membrane is situated between two surfaces, membranes of adjacent membrane appose each other

Question 13

Why is polarity important?

Answer 13

Important for secretion of fluid, and solute transport

Directional flow and ion/cotransporter proteins

Question 14

What are tight junctions?

Answer 14

Belt around apical lateral membrane (membranes of two adjacent cells accumulate together to form a barrier). Membranes are attached by strands of transmembrane proteins (claudins and occludins). Binding action prevents molecules from passing in between the cells- helps to maintain diffusion gradients

Question 15

What are adherens?

Answer 15

Initiation and stabilisation of cell-cell adhesion, regulation of the actin cytoskeleton, intracellular signalling, and transcriptional regulation. Junction holds adjacent epithelial cells together.

Question 16

What proteins comprise adherens?

Answer 16

Cadherins bound to calcium ions

Question 17

What are desmosomes?

Answer 17

Cell-cell anchoring junctions- provide mechanical stability as a result of strong cellular adhesives.

Question 18

What are gap-junctions and what do they allow for?

Answer 18

Allows various molecules and ions to pass between cells. Composed of two connexons (hemichannels) that align across the intercellular space. Hemichannels composed of complex of six connexin proteins (transmembrane domains). Gap junctions allow for electrical communication between cells, and passage of second messengers.

Question 19

What is exocrine secretion?

Answer 19

Exocrine secretion is the secretion of molecules within the duct or lumen

Question 20

What is endocrine secretion?

Answer 20

Secretion directly into the blood

Question 21

Which membrane do exocrine cells release secretions through?

Answer 21

Apical membrane

Question 22

Which membrane do endocrine cells releases secretions into?

Answer 22

Basal membrane

Question 23

What is constitutive secretion?

Answer 23

Secretary vesicles as they formed move directly to the plasma membrane, releasing their contents immediately

Question 24

What is stimulated secretion?

Answer 24

Stored in cytoplasm within secretory vesicles, fusing with membrane upon stimulation

Question 25

Which cells are produced within the small intestine?

Answer 25

Stem cells are present within the crypt of Lieberkuhn , replacing cells lost from the villus tip

Question 26

How does hyperproliferation occur?

Answer 26

Cell production > cell loss, cells accumulate into a thick layer known as corns

Question 27

What conditions cause hyper proliferation?

Answer 27

Frequent abrasions and pressure

Question 28

Which virus causes hyper proliferation?

Answer 28

The papilloma virus, controls stratified squamous epithelium

Question 29

What characterises a keratinising cell?

Answer 29

Epithelial cells which produce keratin and in doing so die, becoming thicker, stronger, protective structures (e.g. epidermis (skin epithelium). Such cells lose their cellular organelles and nuclei, not visible under light microscopy.

Question 30

How can you determine the direction a cell will secrete its substances towards?

Answer 30

Location of secretory vesicles, golgi apparatus, mitochondria

Question 31

How do stratified epithelial cells replace lost surface cells?

Answer 31

By dividing and migrating towards the apical membrane and replacing the lost cells.

Question 32

What can be a consequence of epithelial hyperproliferation?

Answer 32

Adenoma formation - Benign tumour