These sweat glands are mainly of two types. The first are the 'eccrine' glands, which are
distributed almost all over the body, though their density varies from region to region.
These eccrine glands usually secrete clear, odourless sweat. We humans utilise these
eccrine sweat glands as a primary form of cooling in response to temperature rise, in
order to maintain the body temperature within the normal range.
The second type sweat glands are the “apocrine” glands that are larger and
are mostly limited to the axilla
(armpits) and perianal areas. The apocrine sweat glands have a different
secretion mechanism, and secrete thicker sweat that is foul smelling. Although apocrine
glands contribute little to cooling in humans, they are the only effective sweat glands
in hoofed animals such as cattle, horse, donkey, camel etc.
There is a third variety of sweat glands that cannot be classified as either apocrine or
eccrine. These glands have characteristics of both and are termed “apoeccrine”
glands. These too are found in the armpits and perianal region and are presumed to have
developed from the eccrine glands at puberty. These comprise up to 50% of all sweat
glands in the armpits. Apoeccrine glands secrete more sweat than both eccrine and
apocrine glands, thus playing a large role in axillary sweating. Like eccrine glands,
they continuously secrete a thin, watery sweat.