Session 2 - Cells into Tissues

Question 1

How are cells held together in a tissue?

Answer 1

They attach side by side to each other (attached by their lateral domains)

Question 2

What are the 3 types of cell junctions?

Answer 2

Tight junctions, desmosomes and gap junctions

Question 3

What is a tight junction?

Answer 3

Where adjacent cells are tightly attached, forming a seal which prevents molecules passing between cells. The plasmalemma of adjacent cells fuse together.

Question 4

What is a desmosome?

Answer 4

A structure which attaches 2 adjacent cells. Consists of proteins that link the cells. The proteins and intermediate filaments in the cells firmly keep the junction together.

Question 5

Why are desmosomes found between epithelia cells in the skin?

Answer 5

Desmosomes strengthen connections between cells, preventing stretching and twisting. AS skin cells are under a lot of stress the desmosome helps keep them together.

Question 6

What are Gap Junctions?

Answer 6

They allow cell communication by having proteins (connexons) forming Channels between cells which allow the movement of ions and molecules.

Question 7

Where and how do cells attach to the basement membrane?

Answer 7

They attach by their basal domain via hemidesmosomes and focal adhesions

Question 8

What are the 2 methods of cell death?

Answer 8

Apoptosis and Necrosis

Question 9

What causes necrosis?

Answer 9

Physical disruption e.g. Injury, toxins or nutrient deprivation

Question 10

What happens in necrosis?

Answer 10

There is an increase in osmotic pressure so the organelles swell,the chromatin clumps and the cells eventually bursts.

Question 11

Why does necrosis induce tissue damage and inflammation?

Answer 11

When the cell bursts cytotoxic cellular components spill out

Question 12

What is apoptosis?

Answer 12

Programmed cell death via molecular signals

Question 13

How does apoptosis occur?

Answer 13

Deactivating the bcl-2 protein on the mitochondrial matrix initiates apoptosis through enzyme reactions. Enzymes digest shot solid components and the DNA fragments. Cell shrinks into vesicles which are taken up by phagocytes.

Question 14

What are the 3 specialised types of apical domain?

Answer 14

Microvilli, sterovilli and cilia

Question 15

What are sterovilli?

Answer 15

Long microvilli found on cells at the epididymis and sensory hair cells in the ear

Question 16

What are cells with no surface called?

Answer 16

Epitheloid cells

Question 17

What are the 6 types of cell communication?

Answer 17

Direct contact (gap junctions), autocrine, paraffins, endocrine, synaptic and neurocrine

Question 18

What is autocrine communication?

Answer 18

Where a cell secretes substances which bind to receptors on the same cell (positive feedback)

Question 19

What is paracrine communication?

Answer 19

Where cells secrete substances which attach to receptors on neighbouring cells

Question 20

What is endocrine communication?

Answer 20

Where cells secrete hormones directly into the blood

Question 21

What are integrins?

Answer 21

Transmembrane proteins which attach the cell to the basement membrane (mechanical function) and allows for the transduction of signals from the extracellular matrix to the cell ( biochemical function).

Question 22

What are the functions of integrins?

Answer 22

Mechanical, biochemical, used in cell migration and immune patrolling

Question 23

What are focal adhesions?

Answer 23

Where intercellular actin filaments are anchored to the basement membrane. They play a prominent role in cell movement such as migration of epithelial cells in wound repair

Question 24

What are hemidesmosomes?

Answer 24

Strong connection between the basement membrane and the basal domain of a cell, held together by integrin proteins.

Question 25

In which tissues would you find hemidesmosomes?

Answer 25

In the skin and epithelium of the oral cavity (tissue that is subject to abrasion).