Topics A12-15 - Atrophy, Hypertrophy, Hyperplasia, Metaplasia, Tissue Repair

Question 1

Which cell types undergo hypertrophy but not hyperplasia when they are adapting to increased workload?

Answer 1

Permanent Cells: Skeletal and Cardiac Muscle

Neurons also permanent but don’t become hypertrophic

Question 2

Although the number of cells doesn’t change, how might DNA and expression of proteins change in hypertrophy?

Answer 2

DNA might undergo polyploidity (2N -> 4N -> 8N, etc)

Proteins may change from adult to fetal forms, as in alpha myosin heavy chain changing to fetal (beta) form that produces slower, more energetically economical contraction

Question 3

What are 3 circumstances that cause hypertrophy?

Answer 3

1. Increased mechanical trigger: need more mechanical force to do same job
2. Increased hormonal effects
3. Increased growth factors

Question 4

What is the difference between concentric and eccentric cardiac hypertrophy?

Answer 4

Concentric: the heart is pumping against too much pressure, and so the wall thickens but the chamber size is the same

Eccentric: there is volume overload, and so you have hypertrophy with a dilated lumen

Question 5

What are 3 conditions that can cause left-sided concentric hypertrophy?

Answer 5

All increase resistance to left ventricle pumping

1. Hypertension
2. Aortic stenosis
3. Coarctatio Aortae: developmental disease that causes aortic arch lumen to become narrower, thus increasing resistance

Question 6

What are 2 conditions that can cause left-sided eccentric hypertrophy?

Answer 6

Both cause volume overload

1. Mitral insufficiency
2. Aortic insufficiency

Question 7

What is the “point of no-return” with left-sided concentric hypertrophy?

Answer 7

Terminal dilation:
Heart uses Frank-Starling mechanism and has to stretch (dilate) to use more force, and then it cannot compensate anymore. So, in autopsy, dilation doesn’t necessarily mean it’s eccentric hypertrophy - have to see if there was mitral/ aortic insufficiency too

Question 8

What might cause right-sided cardiac hypertrophy? (5 things listed)

Answer 8

Anything that increases resistance in the pulmonary circulation

1. Emphysema
2. Pneumoconiosis
3. Vascular disease (pulmonary embolism)
4. Vasculitis in pulmonary vessels
5. Deformity of chest: scoliosis, even obesity

Question 9

What are two signs that often accompany right-sided hypertrophy?

Answer 9

1. Pulmonary sclerosis: atherosclerosis of pulmonary vessels

2. Nutmeg liver: backwards pressure overloads IVC and liver, causing hypoxia and “nutmeg” appearance

Question 10

What two tissues undergo hyperplasia from hormonal changes?

Answer 10

1. Endometrium: estrogen makes it build up. If there is pathological increase of estrogen or loss of progesterone, endometrium continues to proliferate and may bleed irregularly, and also have an increased risk for cancer
2. Prostate: hyperplasia from increased E2 with less testosterone as men age. This is benign and NOT related to cancer. (Also note that book say BPH is from increased sensitivity to dihydrotestosterone, different than what Matolcsy said)

Question 11

What type of hyperplasia may occur from exercising at high altitudes?

Which hyperplasia might occur from infection?

Answer 11

Bone marrow hyperplasia from high altitude exercise (need for more RBCs)

Lymph node hyperplasia in infection (lymphocyte proliferation)

Question 12

What are some examples of chronic irritation causing hyperplasia? (3 listed)

Answer 12

1. Cystitis/ UTI: mucous membrane proliferates to protect better
2. Bronchial mucous gland hyperplasia in smokers
3. Regenerative nodules in cirrhosis of liver, may be seen in alcoholics

Question 13

How might the thyroid and parathyroid gland undergo hyperplasia?

Answer 13

Thyroid gland from lack of iodine or Grave’s disease causing the glands to work harder to increase thyroid hormone

Parathyroid via hypocalcemia to secrete more PH and bring calcium levels up

Question 14

What 2 cell types can undergo hyperplasia:

Answer 14

1. Labile cells (stem cells)
2. Non-permanent Stable cells (resting cells) - hepatocytes, astrocytes, smooth muscle cells. Divide infrequently but will replicate under stimulation. May undergo both hyperplasia and hypertrophy.

Question 15

6 Causes of Atrophy:

Answer 15

1. Reduced function (i.e. wearing a cast)
2. Loss of Innervation (i.e. paralyzed legs)
3. Loss of Endocrine Stimulation
4. Oxygen/nutrition deficit (i.e. atherosclerosis)
5. Persistent Injury (i.e. H. pylori -> chronic atrophied gastritis, or pressure atrophy with hydronephrosis after kidney stone)
6. Aging (i.e. brown atrophy of heart with lipofuscin)

Question 16

Which pathway handles increased protein degradation, as seen in atrophy?

Answer 16

Ubiquitin-proteasome pathway

Question 17

What does metaplasia mean?

And dysplasia?

Answer 17

Metaplasia: changing from one cell type to another type (actually through reprogramming of stem cells rather than ones that have already differentiated). Changes are reversible.

Dysplasia: disordered growth, losing polarity, polymorphism, chromatin decondenses, and cells lose differentiation, i.e. have more undifferentiated stem cells that have lost their polarity. Bad sign for cancer risk.

Question 18

What is Barrett Esophagus?

Answer 18

An example of metaplasia where acid reflux into the esophagus causes the squamous cells of the esophagus to become replaced by columnar cells with mucous-secreting goblet cells that handle the acid better

Barrett esophagus has an increased risk of distal esophageal adenocarcinoma

Question 19

How might metaplasia occur in the lung bronchi from smoking?

Answer 19

Lung bronchi have respiratory epithelium (pseudostrat columnar ciliated). Toxins in smoke may cause those cells to be replaced by squamous epithelium which is more resistant to injury

Question 20

What is intestinal metaplasia when it occurs with H. pylori infection of the stomach?

Answer 20

An increase in goblet and Paneth cells in the stomach, which are normally characteristic for the intestines

Has an increased risk of gastric cancer in the pylorus or antrum

Question 21

What are 4 risk factors for developing dysplasia?

Answer 21

1. Hyperplasia or metaplasia
2. Infection (e.g. HPV 16 or 18 cause squamous dysplasia of cervix)
3. Chemicals: irritants of cigarette smoke cause squamous metaplasia to become dysplasia
4. UV light

Question 22

What are the 2 types of tissue repair?

Answer 22

1. Regeneration: return to normal state, requires only slight damage with intact framework (like in a papercut). Human embryos and some animals can fully regenerate tissue without scars
2. Scar formation: framework is damaged and so you have to grow new connective tissue that lacks the previous tissue’s function

Question 23

Will put more cards on tissue repair later, for now it’s really boring and I don’t want to go over it.

Answer 23

OK