Question

Give Five functions of the skin.

Answer 1

Hint: The skin is one of the major organs of the integumentary system of the human body made up of multiple layers of ectodermal tissue which guards the underlying muscles, bones, ligaments & internal organs. It has major functions like –
1. Thermoregulation
2. Protection
3. Cutaneous Sensation
4. Excretion & Absorption
5. Synthesis of Vitamin D
6. Act as blood reservoir

Complete answer:
The major functions of the skin described in following –
Thermoregulation: Thermoregulation is the homeostatic regulation (not hemostasis) of the body temperature. The skin contributes to thermoregulation in two ways –
1. By liberating sweat at its surface – In response to high environmental temperature or heat produced by exercise, sweat production from eccrine sweat glands increases, the evaporation of sweat from the skin helps to lower body temperature.
2. By adjusting the flow of blood in the dermis (dermis = layers of skin) – Blood vessels in the dermis of the skin dilate & consequently, more blood flows through the dermis, which increases the amount of heat loss from the body.
Protection: Keratin protects underlying tissues from microbes, abrasion, heat, chemicals etc. & tightly interlocked keratinocytes resist invasion by microbes. Lipids released by lamellar granules inhibit evaporation of water from the skin surface guarding against dehydration and swims.
Cutaneous sensation: There are sensations that arise in the skin, including tactile sensations – touch, pressure, vibration, tickling as well as thermal sensations like warmth & cold.
Excretion & Absorption: Removing water and heat from the body, sweat also is the vehicle for excretion of small amounts of salts, $CO_2$, ammonia, urea etc.
Certain amounts of lipid soluble materials like vitamin A, D, E & K, Oxygen etc are absorbed by skin.
Synthesis of vitamin D: Vit D synthesis requires activation of a precursor molecule in the skin by ultraviolet rays in sunlight.
Act as Blood reservoir: The dermis houses are an extensive network of blood vessels that carry 8-10% of total blood. So, skin acts as a blood reservoir.

Note:
The wound healing process is also mediated by the skin. This is a process of homeostasis i.e. the self-regulating process or maintaining stability of any organization in the human body.