Atrophy

Question 1

Atrophy

Answer 1

Condition where the decrease in the size of normally developed cells, tissues, or organs occurs

• decrease in cell number OR cell size
• is an adaptation to an altered cell environment
• can be physiologic or pathologic

Question 2

What are the 2 ways an organ can shrink?

Answer 2

• cell deletion (apoptosis)

- cell shrinkage

Question 3

Cell deletion

Answer 3

Most specialized cells are removed first (gland cells before ducts), leaving stroma –> fibrotic appearance

Question 4

Cell shrinkage

Answer 4

Each cell must trim down excess

• flesh and bones of cells are proteins
• organelles of atrophied cells are reduced, mitochondria are smaller, lack secretory granules

Question 5

What must occur for a cell to shrink?

Answer 5

Proteolysis

• autophagy
• ubiquitin/proteasome pathways

Question 6

Autophagy

Answer 6

Survival mechanism during ischemia or a response to hormones

• cells consume damaged organelles and recycle proteins/carbs
• protective mechanism to avoid cell death

Question 7

Autophagy mechanism

Answer 7

Autophagosome is produced –> contains dysfunctional organelles –> residual bodies –> may be retained (lipofuscin)

Question 8

What are the 3 types of protein removal systems?

Answer 8

• ubiquitin proteasome
• chaperone mediated autophagy
• macroautophagy

Question 9

Ubiquitin proteasome pathway

Answer 9

Anything that needs to go is tagged with ubiquitin and the proteasome is the “trash can”
- usually for small protein

Question 10

Chaperone mediated autophagy

Answer 10

Lysosomal digestion for larger proteins

Question 11

Macroautophagy

Answer 11

Taking cellular material and putting it in a lysosome for ingestion
- ULK1 complex that makes isolation membrane out of the golgi system

Question 12

What are the 10 possible etiologies for atrophy?

Answer 12

• decreased function
• physiologic
• cachexia
• impaired bloodflow
• pressure
• duct occlusion
• hormones
• age
• denervation
• inflammation/toxins

Question 13

Decreased use/function

Answer 13

Inactivity or limited movement –> promotes protein catabolism (as does muscle trauma)

Question 14

Physiologic

Answer 14

Programmed cell death of certain tissues

• thymus
• involution of uterus and mammary glands after parturition and lactation

Question 15

Cachexia

Answer 15

Starvation, chronic infections, cancer, uremia, burns, sepsis, fasting

Question 16

Diffuse muscle wasting

Answer 16

Catabolism via the ubiquitin-proteasome pathway

Question 17

Serous atrophy of fat

Answer 17

Utilization

Question 18

Moderate caloric restriction, can ______ lifespan

Answer 18

Increase

• occurs in: mammals, spiders, paramecia, dwarf flies
• undernutrition, NOT malnutrition!

Question 19

Impaired bloodflow

Answer 19

Chronic ischemia –> prolonged partial inadequacy of blood

Question 20

Pressure

Answer 20

Growing tumors cause local pressure –> due to reduced bloodflow

• constant local pressure stimulates osteoclasts –> bone loss
• meningioma, retina from glaucoma

Question 21

Duct occlusion

Answer 21

• exocrine glands: pancreas, salivary glands lose secretory cells by apoptosis
• kidney: occlusion of ureter leads to hydronephrosis

Question 22

Hormones/endocrine

Answer 22

• natural sexual cycles: ovary and testis
• iatrogenic supply of hormone –> the best way to atrophy an endocrine gland is to supply it with its own hormone
• could induce atrophy with corticosteroids

Question 23

Age

Answer 23

Reproductive organs –> muscles –> bone –> nervous system

Question 24

Denervation

Answer 24

• motor nerve: marked effects on skeletal muscle
• sensory nerve (humans): skin atrophies, nails become brittle
• sympathetic: metabolic effects on arteries, salivary gland atrophy, perirenal fat metaplasia (brown fat)

Question 25

Inflammation

Answer 25

Cytokines cause atrophy in organs

- rhinitis, intestinal viruses (villus atrophy)