Skin Appendages

The skin Appendages
Source: Mayo Clinic

Skin Appendages

Skin appendages are the structures attached to the skin. Skin appendages present exclusively in certain areas of the skin while they are absent in another. According to the site, the function of these appendages may differ. The skin appendages include:

Hair Follicles

Hair follicles are present nearly in all parts of the skin except for small part of skin that include the palm of hand, the sole of foot. Woman's body has also hair everywhere however, they aren't obvious. Other areas of the skin such as the scalp, the beard and moustache area in men, the armpits and the groin have much more larger number of hair follicles, and known as the hairy areas.

Hair follicles are composed of three parts. The part deep in the skin is called the hair papilla, and it is responsible for the growth and maintenance of the whole hair. And, the second part, or the hair matrix, is located just under the surface of the skin. Then, the last part, which is seen over the skin, is called the hair shaft.

Sebaceous or Oil Glands

Sebaceous glands are present in the whole skin except for the palm of hand and sole of foot. In other words, sebaceous glands are present wherever hair follicles are present. Each sebaceous gland has a secretory part which produces an oily secretion, known as sebum, and a duct. Sebum is formed of lipids, and it helps lubricate the hair shaft making it supple and prevents the cracking of the skin exposed to either hot or cold climates.

Sweat Glands

There are two types of sweat glands in the skin, eccrine glands and apocrine glands.

Eccrine sweat glands are present in everywhere in the skin except for labia minora in women, and glans penis in men. They secrete the sweat that plays great role in body heat production, excretion of toxins and protection against infection (due to presence of lactic acid in it).

Apocrine sweat glands are present exclusively in certain areas of the body including the armpits, the groin, eyelids and the breast. They are sensitive to sex hormones and androgens. At puberty, they become active and begin to secrete odorless oily fluid which becomes odory by the action of normal floral bacteria giving these areas their characteristic odour.

Nails

Nails are present exclusively at the tips of fingers and toes. They are formed of three parts. The nail plate, which is the hard transparent part of the nail, is that we cut regularly. The second part is the nail bed, which is the part of skin under the nail plate that appears red due to the numerous blood capillaries in it. And, the nail fold, or the third part, is the part of skin around the nail plate. Nails grow very slowly. They grow by the rate of 0.1 millimeter everyday in hands, and the process is much slower in feet.