Sweat Glands
Sweat glands are tube-like an coiled glands, located within the dermis, which produce a watery secretion. Millions of these glands are found in the dermis all over the body. Eccrine sweat glands are more common and are found mainly in the palms, soles and forehead. When the temperature of the body rises due to emotional stress, a hot environment or exercise, eccrine glands become activated. Evaporation of these secretions on the skins surface causes cooling. There are two separate typ eccrine and apocrine.
Eccrine
Eccrine sweat glands develop from down budding of the epidermis. The secretory portion is a coiled structure in the deep reticular dermis; the excretory duct spirals upwards to ope onto the skin surface. An estimated 2.5 million sweat ducts are present on the skin surface. They are universally distributed but are most profuse on t palms, soles, axillae and forehead where the glands are under both psychological and thermal control [those elsewhere being under therma control only). Eccrine sweat glands ar innervated by sympathetic (cholinergic) nerve fibres.
Apocrine
Also derived from the epidermis, apocrine sweat glands open into hair follicles and are larger than eccrine glands. They are most numerous around the axillae, perineum and areolae. Their sweat is generated by 'decapitation' secretion of the gland's cells and is odourless when produced; an odour develops after skin bacteria have acted upon it. Sweating is controlled by sympathetic (adrenergic) innervation. The apocrine glands represent a phylogenetic remnant of the mammalian sexual scent gland.
An unappreciated advantage of old age is reduced sweating and body odor.
Fewer number of sweat and apocrine glands coupled with lesser amount of
sweat secretion leads to an overall diminished discharge. Histologically
fewer glands in sections of unexposed skin and disarray and shrinkage of
the secretory coil sometimes with complete involution have been
observed. Testosterone production controls the oil-producing sebaceous glands
throughout life. A steady decline in sebum secretions of 23 percent per
decade in men and 32 percent in women has been observed.
However,
normally sebum production is also proportional to gland size. Studies have
proven that the sebaceous gland almost doubles in size in older skin and
hence ideally more sebum should be secreted in old than young skin.
After
menopause, sebaceous gland activity gradually decreases in the female,
while it remains unaltered in men until the seventh or eighth decade before
a decrease is seen.
Thus, low production of sebum causing skin dryness
and increased local over-production of melanin collectively makes the skin
more prone to insult with age.
There is a lower
ability to sweat in infants due to the low concentration of eccrine sweat
glands.