Growth Adaptations

Question 1

An organ is in homeostasis with the physiologic stress placed on it, therefor an increase in stress leads to an _________ in organ size

Answer 1

INCREASE

Question 2

How does an organ increase in size?

Answer 2

Hyperplasia and Hypertrophy

Question 3

Mechanism of Hyperplasia

Answer 3

Stem cell differentiation

Question 4

Mechanism of Hypertrophy

Answer 4

1) Gene activation
2) Protein Synthesis
3) Production of organelles (i.e. mitochondria)

Question 5

What are the permanent tissues in the body (the tissues that can only increase in size via hypertrophy not stem cell differentiation)?

Answer 5

1) Cardiac myocytes
2) Nerves
3) Skeletal muscle

Question 6

Pathologic hyperplasia can progress to dysplasia and eventually cancer. Give an example and an exception.

Answer 6

Example: Endometrial hyperplasia can progress to endometrial cancer.
Exception: Benign Prostatic Hyperplasia (BPH) does not increase the risk for prostate cancer

Question 7

An organ is in homeostasis with the physiologic stress placed on it, therefor a decrease in stress leads to a _________ in organ size

Answer 7

DECREASE

Question 8

How does an organ decrease in cell number?

Answer 8

Apoptosis

Question 9

How does an organ decrease in cell size? Include two mechanisms

Answer 9

1) Ubiquitin-proteosome degradation –> Intermediate filaments of the cytoskeleton are “tagged” with ubiquitin and destroyed by proteosomes
2) Autophagy of cellular components –> Generate auto-magic vacuoles where organelles and other cellular components enter, and are later fused with lysosomes whose hydrolytic enzymes breakdown cellular components.

Question 10

A change in stress on an organ leads to a _____ in cell type that can better handle the new stress (Metaplasia). Metaplasia is theoretically reversible if you remove the driving stress on the cell.

Answer 10

CHANGE

Question 11

Mechanism of metaplasia

Answer 11

Reprogramming of stem cells in the area of the stress

Question 12

Metaplasia can progress to dysplasia and cancer. Give an example and an exception

Answer 12

Example: Barrett Esophagus
Exception: Apocrine metaplasia (benign cystic breast disorder that does not increase your risk for breast cancer)

Question 13

What vitamin deficiency results in metaplasia?

Answer 13

Vitamin A Deficiency. Vitamin A is required to maintain differentiation of specialized epithelial surfaces

Question 14

Describe the effect of vitamin A deficiency on the conjunctiva of the eye?

Answer 14

Vitamin A is required for the maintenance of the differentiation of the cells of the conjunctiva and without it the conjunctiva undergoes metaplasia from thin squamous to stratified keratinizing squamous epithelium. This change is called KERATOMALACIA.

Question 15

• Dysplasia =
• Cause
• Theoretically, dysplasia is reversible but if stress persists it can result in cancer which is irreversible.

Answer 15

• Disordered cellular growth and proliferation of precancerous cells
• Cause: Longstanding pathologic hyperplasia or metaplasia.

Question 16

Aplasia =

Answer 16

Failure in cell production during embryogenesis

Ex. Unilateral renal genesis

Question 17

Hypoplasia =

Answer 17

Decrease in cell production during embryogenesis resulting in a relatively small organ
Ex. Streak ovary in Turner syndrome