S2) Integrating Cells into Tissues

Question 1

How are cells held together in a tissue?

Answer 1

• Cells are held together in a tissue through their attachment to each other (lateral domain)
• This involves tight junctions, desmosomes and gap junctions

Question 2

What is the basement membrane?

Answer 2

The basement membrane is the structural site for overlying cells and underlying connective tissue

Question 3

How do cells attach to the basement membrane?

Answer 3

- Hemidesmosomes – found in tissues subject to abrasion, such as skin, epithelium of oral cavity

- Focal adhesions – that anchor intracellular actin filaments to the basement membrane

Question 4

What are integrins?

Answer 4

Integrins are transmembrane proteins that function mechanically, by attaching the cell cytoskeleton to the extracellular matrix (ECM), and biochemically, by sensing whether adhesion has occurred.

Question 5

What are the two main functions of integrins?

Answer 5

• Attachment of the cell to the ECM
• Signal transduction from the ECM to the cell

Question 6

Outline the 3 forms of cell renewal in living body and where it occurs

Answer 6

• Static – CNS, cardiac and skeletal muscle cells
• Stable – fibroblasts, endothelium, smooth muscle cells
• Renewing – blood, skin epithelium, gut epithelium

Question 7

Why is cell renewal significant?

Answer 7

There is a relationship between cell renewal rate and the propensity to develop cancer

Question 8

Outline the endosymbiotic theory

Answer 8

• Ancestral eukaryotes lived symbiotically with prokaryotes
• These eukaryotes engulfed the prokaryotes which then evolved to become intracellular mitochondria
• The mitochondria share DNA, replication patterns, rRNA, RNA with prokaryotes

Question 9

What are the four basic tissue types?

Answer 9

• Epithelial
• Muscle
• Nerve
• Connective tissue

Question 10

What are the 6 specialised connective tissues?

Answer 10

• Cartilage
• Haemopoietic
• Lymphatic
• Adipose
• Bone
• Blood

Question 11

What is epithelium?

Answer 11

Epithelium: a tissue composed of cells that covers the exterior body surface and lines internal closed cavities and body tubes that communicate with the exterior

Question 12

Identify the 3 different types of apical domain of epithelial cells

Answer 12

• Microvilli
• Cilia
• Stereovilli

Question 13

What are microvilli?

Answer 13

Microvilli are cytoplasmic processes that extend from the cell surface e.g. intestine and kidney tubule

Question 14

What are cilia?

Answer 14

Cilia are motile cytoplasmic processes that can beat in synchrony e.g. tracheobronchial tree and the oviducts

Question 15

What are stereovilli?

Answer 15

Stereovilli are particularly long microvilli limited to epididymis and sensory hair cells of the ear

Question 16

What is necrosis?

Answer 16

Necrosis is a form of cell injury which results in the premature death of cells in living tissue by autolysis

Question 17

What is apoptosis?

Answer 17

Apoptosis is a naturally occurring programmed and targeted cause of cellular death

Question 18

Why is necrosis worse than apoptosis?

Answer 18

• Necrosis is always detrimental and can be fatal
• Necrosis does not follow the apoptotic signal transduction pathway
• Necrosis results in the loss of cell membrane integrity and an uncontrolled release of cell contents into the extracellular space

Question 19

Why do necrotic cells swell and burst?

Answer 19

Necrotic cells swell and burst because of failure of action of Na, K ATPase

Question 20

Define osmosis

Answer 20

Osmosis is the spontaneous net movement of solvent molecules through a semi-permeable membrane into a region of higher solute concentration until dynamic equilibrium is reached

Question 21

What is oncotic pressure?

Answer 21

Oncotic pressure is a form of osmotic pressure exerted by proteins (albumin) in a blood vessel’s plasma that usually tends to pull water into the circulatory system