The skin completely covers the body and is continious with the membrane lining the body orifices. It protects the underlying structures from injury and from invasion by microbes.
Below are some functions of the skin 👇
PROTECTION
The skin is one of the main protective organs of the body. It protects the deeper and more delicate organs and acts as the main barrier against invasion of microbes and other harmful agents. Due to the presence of the sensory nerve endings in the skin the body react by reflex action to unpleasant or painful stimuli, protecting it from further injury.
FORMATION OF VIATAMIN D3
There is a fatty substance, 7-dehydrochloresterol, in the skin and ultraviolet light from the sun convert it to vitamin D. This circulate in the blood and is use, with calcium and phosphorus, in the formation and maintenance of bone. Any vitaminsD in excess of any requirements is stored in the liver.
REGULATION OF BODY TEMPERATURE
Human beings are warm-blooded animals and the body temperature is maintained at an average of 36.8cent... in health, variotions are usually limited to 0.5cent... And 0.75cent..., although it may be found that the temperature in the evening is a little higher than in the morning. This is the optimum temperature for the many chemical processes in the body. If the temperature is raised the metabolic rate is increased and if it is lowered the rate of metabolism is reduced. To ensure this constant temperature a fine balance is maintained between heat production in the body and heat lost to the environment.
HEAT PRODUCTION
Some of the energy released in the cells when carbohydrates, fats and deaminated amino acids are metabolized is in the form of heat. Because of this the most active organs involved are:
The muscles. Contraction of voluntary muscles produces a large amount of heat and the more strenuous the muscular exercise the greater the heat produced. Sheavering involves muscle contraction and produces heat when they is the risk of body temperature falling below normal.
The liver.is very chemically active, and heat is produce as a by product.
The digestive organs produces heat by the contraction of the muscle of the alimentary tract and by the chemical reactuons involve in digestion.
HEAT LOSS
Most of the heat loss from the body occurs through the skin. Small amount are loss in expired air, urine and feaces. Only the heat loss through the skin can be regulated to maintain a constant body temperature. They is no control over heat loss by other routes. Heat loss through the skin is affected by the difference between body and environmental temperature. The amount of the body surface exposed to the air and the type of cloth worn. Air is a poor conductor of heat and when layers of it are trapped in clothing and between the skin and clothing they acts as effective insulators against excessive heat loss. Control is achived mainly by hypothalamic and skin thermorecptors.
CONTROL OF BODY TEMPERATURE
NERVOUS CONTROL
The temperature regulating center in the hypothalamus is responsive to the temperature of circulating blood. This center affects body temperature through antonomic nerve stimulation of the sweat glands.
The vasomotor center is the mudulla oblongata controls theb caliber of the small arteries and arterioles, and they control the amount of blood which circulate in the capillaries in the dermis. When the skin of the cappilaries are dilated the extra blood near the surface increases heat loss by radiation, conduction and convection. Arteriolar constriction conserves heat.
ACTIVITY OF THE SWEAT GLANDS
If the temperature of the body is increased by 0.25cent.. to 0.5centigrade the sweat glands are stimulated to secret sweat, which is conveyed to the surface of the body by duct. The body is cooled by loss of the heat used to evaporate the water in sweat. When sweat droplet can be seen on the skin the rate of production is exceeding the rate of evaporation. This is most likely to happen the the environmental air is humid and the temperature high.
Loss of heat from the body by evaporation also occurs by insensible water loss. In this case heat is being contineously lost by evaporation, even dough the sweat glands are not active. Water diffuses upwards from the deeper layer of the skin to the surface of the body and evaporates into air. The individual is unaware of this process.
EFFECT OF VASODILATION
The amount of heat lost from the body depends to a great extents on the amount of blood in the vessels in the dermis. As the heat production increases the arterioles become dilated and more blood pours into the cappilary network in the skin. In addition to increasing the amount of sweat produced the temperature of the skin is raised and there is an increase in the amount of heat loss by radiation, conduction and convection.
In radiation the exposed part of the body radiates heat away from the body.
In conduction the cloth in contact with the skin take up heat.
In convection the the air passing over the exposed part of the body is heated and rises, cool air replaces it and convection currents are set up. Heat is also loss from the cloth by convection.
If the external environmental temperature is low or if head production is decreased, vasoconstriction occurs, stimulated by sympathetic nerves. This decreases the blood flow near the body surface, conserving heat.
HYPOTHERMIA
At a rectal temperature below 32centigrade, compensatory mechanism to restore body temperature usually fail, e.g., shivering is replaced by muscle rigidity and cramps, vasoconstriction fails and blood pressure and heart rate are raised. Death usually occurs when the temperature falls below 25centigrade.