Skin

Vital, diverse, complex, extensive_thsese adjectives describe the body's largest thinnest, and one of its most important organs, the skin. It forms a self-repairing and protective boundary between the internal and environment of the body and an often hostile external world. The skin surface is as large as the body itself. The elastic covering is thinnest on the lips and eyelids and thickest on the palms and soles.

Skin Structure

The skin forms the external covering of the body. It consists of two major layers of completely different types of tissues. These layers are ;
I) Epidermis: The superficial layer is known as the epidermis.
ii) Dermis: An underlying layer of fatty tissue separates the skin from the muscle of the body wall beneath.
 

Epidermis

The outer layers of the epidermis are the body frontier to the outside world protecting the living tissue within from the ravages of the environment.
It contains four types of cells;
  • Keratinocytes
  • Melanocytes
  • Langerhans Cells
  • Merkel Cells
It is customary to recognize the four layers of the epidermis. From the outside these are;
  1. Layers of the Epidermis
The Horny layer....................Stratum Corneum.
The Granular layer................Stratum Granulosum.
The Prickle Cell....................Stratum Spinosum.
The Basal layer.....................Stratum Germinativum OR Basal.
Thick layer............................Stratum Lucidum (Only in the skin of palms & soles).

Dermis

The dermis or Conium is sometimes known as the True Skin. The dermis is a sheet of connective tissue that supports the epidermis and binds it to the hypodermis. It is composed of;
i) Papillary: A thin layer
ii) Reticular: A thicker layer

The dermis is a lot thicker than the epidermis and surpasses 4 mm on the soles and palms. It is thinnest on the eyelids, where the thumb is, and the dermis is on the surface of the body. An Andover the appendages are generally thinner than on the dorsal surface. The mechanical strength of the skin is in the dermis.

Structure of the dermis:

The main basic structure of the dermis is a dense network of crisis - crossing protein fibers embedded in a mass of firm jelly. The fibers are of two kinds;
  • Collagen fibers
  • Elastic fibers

Functions of Skin

The skin is a huge component of the body. This elastic defensive awning is thinnest on the lips and eyelids and thickest on the palms and soles.
Following are the functions of the skin:
Heat regulation: The skin modulates body temperature by sweating, which is the construction of moisture by the sweat glands. The evaporation of this moisture facilitates the body to cool itself.
Absorption: The epidermis layer of the skin keeps an acid mantle layer which controls the number of substances entering through the skin that impact the body to a minor degree.
Secretion: The sebaceous gland excretes oil to lubricate and maintain the health of the skin.
Protection: Taf cells provide insulation and protection against trauma to the infernal organs. The skin also keeps itself from the hazardous effects of light and acts as a barrier against the attack of bacteria.
Excretion: Perspiration is the procedure through which the sweat glands excrete waste materials.
Sensation: Nerve ending in the skin allows us to feel heat cold touch pleasure pressure and pain.
Production of Vitamin D: The skin produces vitamin D in the presence of sunlight.
Immunity: Specialized cells that attach to and destroy pathogenic microorganisms are found in the skin and play an important role in immunity.
The social effect of skin: By its colors, texture, and odor, transmit social and sexual signals to others.

Homeostasis of Body Temperature

In spite of sizable alterations in environmental temperatures, humans keep up a remarkably constant core body temperature. The functioning of the skin in the homeostasis of body temperature is critical to survival.
To maintain an even temperature, the body should balance the quantity of heat it generates with the amount it loses. This means that if extra heat is generated in the body, this same quantity of heat should be lost from it.

Heat production

Heat is produced by one means-metabolism of foods. Because the muscles and glands (specifically the liver) are the majority of active tissues. They convey more metabolisms and consequently generate more heat than any of the other tissues. So the main determinant of how much heat the body generates is the quantity of muscular work it does. During exercise and shivering, for example, metabolism and heat production increment remarkably. But during sleep, when a very minor muscular task is being done, metabolism and heat production diminishes.

Heat Loss

As already stated, one mechanism the body uses to maintain relative Constance of internal temperature is to regulate the amount of heat loss. Some 80% or more of this transfer of heat occurs through the skin; the remainder takes place in mucous membranes. If heat must be conserved to maintain a constant body temperature, dermal blood vessels constrict (vasoconstriction), keeping most of the warm blood circulating deeper in temperature, dermal blood vessels widen (vasodilation), increasing the skins' supply of warm blood from deeper tissues. Heat transferred from the warm blood to the epidermis can then be lost to the external environment through the physical processes of;
  • Evaporation
  • Radiation
  • Conduction
  • Convection

Homeostatic Regulation Of Heat Loss

The operation of the skins' blood vessels and sweat glands should be coordinated carefully and should take into account moment-by-moment rise and fall in body temperature. Such as most homeostatic mechanisms, heat loss by the skin is managed by a negative-feedback loop. Temperature receptors in a part of the brain, known as the hypothalamus, capture the changes in the body's interior temperature.