Skin is very important to us. It is the body's outer covering and forms the largest organ of the integumentary system. The human skin and the skin of other mammals are similar, and the pigskin is very similar to human skin.
In this lesson, we will learn about the structure and functions of human skin. So, let's get started!
The skin has approximately 7 layers of ectodermal tissue that guard the underlying ligaments, muscles, bones, and internal organs. Most of the human skin is covered by hair follicles. Based on the presence or absence of hair follicles, the skin can be grouped into two general types - glabrous skin (hairless) and hairy skin.
The below illustration shows skin with three layers: epidermis, dermis, and subcutis, showing a hair follicle, gland, and sebaceous gland.
Since the skin interfaces with the environment, it plays a crucial immunity role by giving protection to the body against pathogens and excessive loss of water. Some of the other functions of the skin include; temperature regulation, synthesis of vitamin D, protection of the folates of vitamin B, sensation, and insulation. Scar tissue is formed in severely damaged skin in an attempt to heal. The scar tissue is normally depigmented and discolored.
Skin pigmentation differs among populations in humans, and the type of skin can range from oily to non-oily and from dry to non-dry.
The skin has mesodermal cells, pigmentation, like melanin provided by melanocytes, that absorb some potentially harmful ultraviolet radiation in sunlight. The skin also contains DNA repair enzymes which help in reversing UV damage. People that lack these enzymes have a higher rate of suffering from skin cancer. The pigmentation of the human skin differs greatly among populations. This has led to people being classified on the basis of the color of their skin.
The second-largest organ in the human body is the skin. The small intestine is about 15 to 20 times larger than the skin. The average size of the skin for an adult is between 1.5 to 2.0 square meters. The skin is made up of three primary layers; the hypodermis, the dermis, and the epidermis.
This is the outermost layer of the skin. It forms the protective, waterproof wrap over the surface of the body which also acts as a barrier to infection. This layer is made up of epithelium with a basal lamina underlying. The epidermis has no blood vessels. The major type of cells that make up this layer are the Langerhans cells, melanocytes, Merkel cells, and keratinocytes. This layer can be subdivided further into; strata (the outermost layer), granulosum, spinosum, basale and lucidum (only at the bottom of the feet and the palms of the hands).
This layer is found just beneath the epidermis. It is made up of connective tissue and cushions the body from strain and stress. A basement membrane tightly connects the dermis to the epidermis. This layer also harbors numerous nerve endings providing a sense of heat and touch. It also contains the sweat glands, hair follicles, sebaceous glands, blood vessels, apocrine glands, and lymphatic vessels. Blood vessels found in the dermis provide nourishment as well as waste removal from the cells. There is a structural division of the dermis into two, the papillary region (a superficial layer adjacent to the epidermis) and the reticular region (a deep thicker area).
This tissue is also known as hypodermis tissue. It is not part of the skin and it is found just below the dermis. Its main function is to attach the skin to the bones and muscles that underlie it. It also supplies the skin with nerves and blood vessels. It is made up of elastin, adipose tissue, and loose connective tissue. Fat acts as an insulator.
At least 5 different pigments determine the color of the skin. They are;
The skin is an organ of protection. The primary function of the skin is to act as a barrier. The skin provides protection from mechanical impacts and pressure, variations in temperature, microorganisms, radiation, and chemicals. The skin acts as a water-resistant barrier so essential nutrients are not washed out of the body.
The skin is an organ of regulation. The skin regulates several aspects of physiology, including body temperature via sweat and hair, and changes in peripheral circulation and fluid balance via sweat. It also acts as a reservoir for the synthesis of Vitamin D.
The skin is an organ of sensation. The skin contains an extensive network of nerve cells that detect and relay changes in the environment. There are separate receptors for heat, cold, touch, and pain.
