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  The Mammalian skin, Biology tutorial

Introduction:

In humans, the whole surface of the body is covered by the skin which has sparse growth of hair. The skin is around 1 to 2 mm thick. The skin of palm of the hand and soles of the feet are around 6 mm thick. The mammalian skin comprises of an outer layer (that is, epidermis) and an inner layer (that is, dermis). The skin, being an external covering of the body surface, needs constant care to ward off microorganisms that can penetrate it to cause the infection.

Structure of the Mammalian skin:

The skin is build up of two layers, an external epidermis and an inner dermis. The dermis is much thicker than the epidermis. The epidermis comprises of three layers: (a) the outer most cornified layer or stratum corneum, (b) the middle granular layer or stratum granulosum and (c) an innermost pigmented Malphighian layer or stratum Malpighi.

The Malpighian layer (that is, the innermost layer) has vigorously dividing cells that generate new epidermal cells. The Malpighian layer includes the pigment melanin for skin color; it defends the skin from ultra-violet rays penetration. The layer as well includes keratin (that is, protein) which imparts stiffness and flexibility to skin.

The granular layer (that is, the middle layer) as well comprise of living cells which are constantly pushed upwards from the Malpighian layer. In this procedure they become flattened, accumulate keratin and finally die.

The cornified layer (that is, the outermost or surface layer) comprises of dead cells impregnated with keratin. The layer is a tough water-proof layer which protects the skin from damage and infection. The cells of cornified layer are always being worn-out and substituted by cells from the layer beneath.

The dermis includes blood vessels, muscles, lymphatic vessels, fat cells, nerves & hair follicles, and glands like sweat and sebaceous glands. Hair comprises of the hair shafts and hair root. Hair follicles in the dermis are related with erector muscle or pili. The sebaceous gland generates an oily substance termed as sebum, for keeping the hair water-proof.

The Sweat glands are coiled tubes fixed in the dermis. Each and every gland is enclosed by blood capillaries; thus waste products like water, urea and salts are absorbed and excreted via the pore. The skin thus, acts as an excretory organ. The subcutaneous (that is, fatty) layer is beneath the dermis. It comprises fat cells, it stores food and it acts as the insulating layer which stops the loss of heat from the body.

Functions of the Skin:

The major functions of the skin comprise:

1) Protection: The dead cells of the cornified layer (that is, the outer layer of skin surface) defend the body from infectious substances Melanin (body pigment) protects the body from the ultra-violet radiation.

2) Sensitivity: There are many nerve endings and touch receptors (that is, Meissner's corpuscles) on the skin which are sensitive to touch, heat, cold, pressure and pain; as such, the skin is a sense organ.

3) Temperature regulation:

  • Fur or hair on the skin surface entraps warm air close to the body surface for the rationale of preserving body heat.
  • On hot days, the sweat glands formed sweat. The evaporation of the sweat reasons cooling.
  • On hot days, the blood vessels of the skin widen, a procedure that lets more heat loss from the body. While on cold days, blood vessels narrow to preserve heat loss.
  • The fat stored in the subcutaneous layer stops loss of heat from the body that is, acts as an insulator.

4) Excretion: Water and salts are expelled through the sweat glands of the skin.

5) Production of Vitamin D:  Ultra-violet radiation assists in transforming fat derivatives in the skin to vitamin-D.

6) The mammary glands (that is, breasts) are transformations of the sebaceous glands of the skin. They aid to generate milk for feeding the young ones.

7) Nails, claws-scales and horns are modified outgrowth of the cornified layer of the skin. They serve up for protection of the internal organs and also weapons of offence and defense.

Care of the Skin:

The skin of humans is in direct contact with the surroundings and gets dirty simply. Thus, we must take proper care of it by examining the given:

1) Bathe by using soap to take away natural oils, sweat and dirt from skin. This will prevent jamming of the sweat pores, decrease stale unpleasant smells and limit bacterial action on the skin.

2) After bathing, dry the body by using a clean towel.

3) The feet should be washed on a regular basis. Cut the nails of toe on a regular basis. Wear hygienic stockings to absorb sweat from clefts of toes. The sweat in toes promotes the growth of fungi and bacteria resulting 'athlete's foot'. Wear proper shoes out doors to prevent hook-worms and tetanus infection.

4) Cuts, sores and wounds on the skin must be cleaned by antiseptics and covered.

5) Check skin diseases like scabies, eczema, ringworm and other fungal and parasitic infestations and infections to the medical doctor.

6) Keep your skin moist with proper lotion or cream throughout harmattan wind or dry seasons to look after the skin from cracking. Don't use bleaching creams. Bleached skin affects a person to skin infection and cancer.

7) Don't expose the skin to needless ultraviolet radiation from the sun, more particularly the albinos. Direct sunlight might cause skin bums (that is, sunburns).

8) Take special cleanliness of the given body parts:

  • The hair and scalp
  • Armpits and groins
  • Eyes, ear and nose
  • Hands and fingernails
  • Feet and toe nails
  • Teeth

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