Skin and Body Membranes. Body Membranes. Function of body membranes Cover body surfaces Line body cavities Form protective sheets around organs. Classification of Body Membranes. Epithelial membranes Cutaneous membranes Mucous membranes Serous membranes Connective tissue membranes
Skin and Body Membranes
Table 4.1 (1 of 2)
Table 4.1 (2 of 2)
Vernix caseosa: A white cheesy substance that covers and protects the skin of the fetus and is still all over the skin of a baby at birth. Vernix caseosa is composed of sebum (the oil of the skin) and cells that have sloughed off the fetus' skin.
"Vernix" is the Latin word for "varnish." The vernix varnishes the baby. "Caseosa" is "cheese" in Latin.
As we get older, the pigment cells in our hair follicles gradually die. When there are fewer pigment cells in a hair follicle, that strand of hair will no longer contain as much melanin and will become a more transparent color — like gray, silver, or white — as it grows. As people continue to get older, fewer pigment cells will be around to produce melanin. Eventually, the hair will look completely gray.
People can get gray hair at any age. Some people go gray at a young age — as early as when they are in high school or college — whereas others may be in their 30s or 40s before they see that first gray hair. How early we get gray hair is determined by our genes. This means that most of us will start having gray hairs around the same age that our parents or grandparents first did.
Gray hair is more noticeable in people with darker hair because it stands out, but people with naturally lighter hair are just as likely to go gray. From the time a person notices a few gray hairs, it may take more than 10 years for all of that person's hair to turn gray.
Some people think that a big shock or trauma can turn a person's hair white or gray overnight, but scientists don't really believe that this happens. Just in case, try not to freak out your parents too much. You don't want to be blamed for any of their gray hairs