Growth Adaptations

Question 1

Basic Principles of Growth Adaptations

Answer 1

Baseline: Organ is in homeostasis w/ physiologic stress placed on it

Increase, decrease or change in stress on the organ leads to growth adaptations.

Question 2

Hyperplasia vs. Hypertrophy

Answer 2

Both: Increased Stress → Increased Size

Hyperplasia: More cells
Hypertrophy: Bigger cells

Question 3

Mechanism of Hypertrophy

Answer 3

Make more cytoskeleton & organelles via:

Gene Activation
Protein Synthesis
Production of Organelles

Question 4

Mechanism of Hyperplasia

Answer 4

Production of new cells from stem cells

Question 5

Gravid Uterus: Hyperplasia or Hypertrophy?

Answer 5

Both!

Question 6

Permanent Tissues

Answer 6

No Stem Cells
Only Undergo Hypertrophy

3 Types:
Cardiac Myocytes
Skeletal Muscle
Nerve Tissue

Question 7

Pathologic Hyperplasia

Answer 7

Dysplasia, cancer

Example: Endometrial hyperplasia

Exception: BPH (does not have an increased risk of cancer)

Question 8

Atrophy

Answer 8

Decreased Stress → Decreased Size

Smaller Cells (Ubiquitination or Autophagy)

OR

Fewer Cells (Apoptosis)

Question 9

Ubiquitination

Answer 9

Ubiquitin marks IFs
Proteosome destroys ubiquitinated structures
Cytoskeleton reduces
Cell shrinks

Question 10

Autophagy

Answer 10

Vacuoles form

Vacuoles fuse w/ lysosomes

Question 11

Metaplasia

Answer 11

Stress Change → Stem Cell Reprogramming → Cell Type Change
Most common in surface epithelium
Metaplastic cells handle new stress better (eg Barrett’s)
Reversible via removal of driving stressor (eg GERD → Barrett’s, GERD resolution → Return to normal epithelium)
Can progress to dysplasia & cancer (except Apocrine Metaplasia)
Can be due to Vitamin A Deficiency
Mesenchymal tissues can undergo metaplasia too

Question 12

Barrett’s Esophagus Metaplasia

Answer 12

Normal esophagus:
Squamous epithelium
Sharp demarcation between esophagus (squamous) & stomach (columnar)

Reflux → Metaplasia of esophagus
Squamous → Columnar, nonciliated, mucinous
New cells handle acid better

Question 13

Apocrine Metaplasia

Answer 13

Does not increase risk for cancer
Fibrocystic breast changes can be involved in increased risk for breast cancer, but the Apocrine Metaplasia, itself, is not.

Question 14

Myositis Ossificans Metaplasia

Answer 14

Trauma → Skeletal Muscle Inflammation → Bone Formation in skeletal muscle

Seen as opacity in muscle or X-Ray

Question 15

Radiologic difference between Myositis Ossificans and an Osteosarcoma

Answer 15

Myositis Ossificans if:
Adjacent bone is normal
There is a separation between lesion and adjacent bone.

Question 16

3 Types of Epithelium

Answer 16

Squamous (Keratinizing or Not)
Columnar
Transitional (Almost exclusively seen in the context of urothelium)

Question 17

Mesenchymal Tissues

Answer 17

AKA Connective Tissues:

Bone
Blood Vessels
Cartilage
Fat

Question 18

Apocrine Tissue

Answer 18

Exocrine Tissue that behaves very specifically

Membrane buds off into lumen
Secreting cell loses cytoplasm with each secretion
Seen in breast tissue

Question 19

Vitamin A Deficiency Leads To:

Answer 19

Night Blindness (Nyctalopia)
Keratomalacia (Conjunctival Thickening)
Immune Deficiency (Cells stuck in blast phase)

Question 20

Malignant Cause of Vitamin A Deficiency

Answer 20

Acute Promyelocytic Leukemia

15:17 Translocation
Involves retinoic acid receptor
Too many cells trapped in blast phase
Can treat with ATRA

Question 21

Vitamin A - Uses

Answer 21

Maturation of immune cells beyond blast phase

Maintenance of specialized epithelium

Question 22

ATRA

Answer 22

All Trans-Retinoic Acid

Binds Retinoic Acid receptor
Allows immune cells to mature

Question 23

Dysplasia

Answer 23

Disordered Cellular Growth
Proliferation of precancerous cells
Arises from longstanding pathologic hyperplasia (eg endometrial) or metaplasia (eg Barrett’s)
Reversible with removal of inciting stress
Stress Persists → Carcinoma (Irreversible)

Question 24

Example of Dysplasia

Answer 24

CIN

CIN1 - LSIL: Mild dysplasia, basal 1/3 of cervix
CIN2 - HSIL: Moderate dysplasia, basal 2/3 of cervix
CIN3 - HSIL: Severe dysplasia, more than 2/3 of cervix

Question 25

Aplasia

Answer 25

Failure of cell production during embryogenesis

Example:
Unilateral renal agenesis

Question 26

Hypoplasia

Answer 26

Decrease in cell production during embryogenesis
Leads to small organs

Example:
Streak ovary in Turner Syndrome