Flashcards in Topics A12-15 - Atrophy, Hypertrophy, Hyperplasia, Metaplasia, Tissue Repair Deck (23)
Which cell types undergo hypertrophy but not hyperplasia when they are adapting to increased workload?
Permanent Cells: Skeletal and Cardiac Muscle
(Neurons also permanent but don't become hypertrophic)
Although the number of cells doesn't change, how might DNA and expression of proteins change in hypertrophy?
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
What are 3 circumstances that cause hypertrophy?
1. Increased mechanical trigger: need more mechanical force to do same job
2. Increased hormonal effects
3. Increased growth factors
What is the difference between concentric and eccentric cardiac hypertrophy?
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
What are 3 conditions that can cause left-sided concentric hypertrophy?
All increase resistance to left ventricle pumping
2. Aortic stenosis
3. Coarctatio Aortae: developmental disease that causes aortic arch lumen to become narrower, thus increasing resistance
What are 2 conditions that can cause left-sided eccentric hypertrophy?
Both cause volume overload
1. Mitral insufficiency
2. Aortic insufficiency
What is the "point of no-return" with left-sided concentric hypertrophy?
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
What might cause right-sided cardiac hypertrophy? (5 things listed)
Anything that increases resistance in the pulmonary circulation
3. Vascular disease (pulmonary embolism)
4. Vasculitis in pulmonary vessels
5. Deformity of chest: scoliosis, even obesity
What are two signs that often accompany right-sided hypertrophy?
1. Pulmonary sclerosis: atherosclerosis of pulmonary vessels
2. Nutmeg liver: backwards pressure overloads IVC and liver, causing hypoxia and "nutmeg" appearance
What two tissues undergo hyperplasia from hormonal changes?
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)
What type of hyperplasia may occur from exercising at high altitudes?
Which hyperplasia might occur from infection?
Bone marrow hyperplasia from high altitude exercise (need for more RBCs)
Lymph node hyperplasia in infection (lymphocyte proliferation)
What are some examples of chronic irritation causing hyperplasia? (3 listed)
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
How might the thyroid and parathyroid gland undergo hyperplasia?
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
What 2 cell types can undergo hyperplasia:
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.
6 Causes of Atrophy:
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)
Which pathway handles increased protein degradation, as seen in atrophy?
What does metaplasia mean?
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.
What is Barrett Esophagus?
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
How might metaplasia occur in the lung bronchi from smoking?
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
What is intestinal metaplasia when it occurs with H. pylori infection of the stomach?
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
What are 4 risk factors for developing dysplasia?
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
What are the 2 types of tissue repair?
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