Definitions

• hypertrophy means increase in size

• hyperplasia means increase in cell number

• this can be confusing because a common disease that aging men get is prostatic hypertrophy

• example of cellular hyperplasia

  • prostatic hypertrophy (an increase in the size of the organ) is caused by hyperplasia (increase in the number of prostate cells)

• pure examples of cellular hypertrophy (of which, he implied, there are only two)

  • if you take steroids, you get hypertrophy of muscle due to hypertrophy of muscle cells

  • adipose tissue gets bigger because the cells get bigger because more fat is stored in each adipocyte. when you gain weight, adipocytes get bigger, and when you lose weight, adipocytes get smaller

• more examples: if we all move to Cusco, we will get hyperplasia of bone marrow that will lead to increased production of RBCs that will ultimately help us get enough oxygen. this is mediated by cytokines

• if you take erythropoietin, hematocrit is increased via hyperplasia of bone marrow

• lymph nodes get big because of hyperplasia—immune cells proliferate. they also trap cells, which is neither hyperplasia or hypertrophy

• cellular hyperplasia: the prostate gets bigger under the influence of androgens; the breast gets bigger under the influence of estrogens

• involution, e.g. a female breast post pregnancy: hyperplastic glandular cells undergo apoptosis and lobules shrink back down. cells are gobbled up by macrophages

Hypertrophic ventricle

• increase in size of muscle cells leads to thickening of heart chamber walls

• oxygen can’t diffuse as easily as the walls get bigger; this ischemia eventually leads to irreversible fibrosis

• so don’t let your patients have high blood pressure…there are many good medications to treat it

Normal-sized vs. pregnant uterus

• look at the difference between the distance between nuclei. a large uterus is due to hypertrophy of uterine smooth muscle cells, a fact we conclude because the nuclei are so much farther apart

• this also involutes after delivery

Epithelium

• normal ciliated columnar epithelial cells are depicted (normally found in cervix, lung)

• due to a variety of injuries, these cells may undergo metaplasia, meaning that they change to a different differentiated form; hyperplasia can also occur

• density of nuclei increases as hyperplasia proceeds, and indeed the nuclear-to-cytoplasmic ratio has increased as hyperplasia progresses

• so the normal epithelium which has cilia and makes mucus turns into an epithelium which is pretty much just dividing

• eventually these cells look flat, like epidermis; this is squamous metaplasia

• so now this is both hyperplasia and metaplasia at the same time

• the most common cause of squamous metaplasia and hyperplasia is cigarette smoking

• then, you notice that the cells don’t flatten off at the top anymore like squamous cells should. all the nuclei look the same, and this is called dysplasia

• meta- refers to a change, dys- means something’s wrong with it

• then you see carcinoma in situ. this is a malignant proliferation that hasn’t invaded through the basement membrane

• this happens to cigarette smokers over the course of years

Brains and atrophy

• normal brain has thinner sulci and thicker gyri than the atrophied brain

Category: Medical Subject Notes , Pathology Notes