Cell adaptation, injury, and death

• a lot of cell division is normal

• your bone marrow divides a lot every day; you make about 10 pounds of WBCs every year

• in retrospect, leukemia is a very rare disease, afflicting 1 in 5000 children. this is very low considering how much division occurs in bone marrow

• similarly, you redo your epidermis every two weeks—when you vacuum, you are vacuuming up your dead skin cells

• you shed 70 pounds of GI epithelium a year

• the female breast is an example of something that goes from milligrams of epithelial cells to grams of epithelial cells during puberty; in pregnancy, this goes up even more and undergoes differentiation

• after pregnancy and after nursing has stopped, breast tissue involutes and those cells go away

• so there are normal cycles of proliferation, differentiation, and regression

Differentiation

• there is a lot of differentiation in a developing fetus, for example

• a female breast starts with ducts only and develops lobules at puberty

• a male breast starts with ducts only and never develops lobules, not even in gynecomastia

Category: Medical Subject Notes , Pathology Notes