Page 44 - 84 human physiolofy part-1

Chapter 3

into the inner layer. They are distributed over almost the entire surface of the body in humans and
many other species, but are lacking in some marine and fur-bearing species. The sweat glands are
controlled by sympathetic cholinergic nerves which are controlled by a center in the hypothalamus. The
hypothalamus senses core temperature directly, and also has input from temperature receptors in the
skin and modifies the sweat output, along with other thermoregulatory processes.

Human eccrine sweat is composed chiefly of water with various salts and organic compounds in
solution. It contains minute amounts of fatty materials, urea, and other wastes. The concentration of
sodium varies from 35–65 mmol/l and is lower in people acclimatised to a hot environment. The sweat
of other species generally differ in composition.

Apocrine

Apocrine glands occur during the early to mid puberty ages approximately around the age of 15
and release more than normal amounts of sweat for approximately a month and subsequently regulate
and release normal amounts of sweat after a certain period of time. Apocrine sweat glands produce
sweat that contains fatty materials. These glands are mainly present in the armpits and around the
genital area and their activity is the main cause of sweat odor, due to the bacteria that break down the
organic compounds in the sweat from these glands. Emotional stress increases the production of sweat
from the apocrine glands, or more precisely: the sweat already present in the tubule is squeezed out.
Apocrine sweat glands essentially serve as scent glands.

In some areas of the body, these sweat glands are modified to produce wholly different secretions,
however, including the cerumen ("wax") of the outer ear. Other glands, such as Mammary glands, are
greatly enlarged and modified to produce milk.

44 | Human Physiology