Integument and Functions of Integument

What is Integument?

Integument also called skin, is the outer covering of the body. Integument consists of epidermis and dermis. These are closely related but differ greatly in their origin and nature. Integument contains many unicellular and multicellular skin glands.

The epidermis is modified into various structures in different organisms such as hairs, nails, scales, feathers, claws, hoofs, etc. The dermis is modified into dermal scales as present in many groups of vertebrates. Dermis also has the potential for bone formation.

Functions of Integument

The integument of skin performs various essential functions which are necessary for the survival and good life of species. Following are given its vital functions.

1. Protection

1. Integument as dermal armor protects animals from attacks. In the head region, it especially protects the brain and sensory organs from any mechanical injury.
2. Skin glands produce poisonous or disgusting and unpleasant substances to repel and avoid enemies.
3. Some glands keep the skin moist and the conjunctiva of the eye free from irritants.
4. Skin pigments provide protective coloration while in naked skin they absorb excess sun radiation.
5. The bristling coat of an angry mammal and disarranged feathers of a bird make them look angry and are used as a warning for others.
6. Nails, horns, claws, spines, barbs, etc. are beneficial in the struggle for survival.

2. Regulation of Temperature

1. In mammals and birds, skin plays a vital role in thermoregulation in different ways.
2. Feathers and fur coats insulate the body against heat and cold environments.
3. Sweat discharged from sweat glands of the skin makes the body cool by evaporation.
4. Dilation of blood vessels within the dermis increases heat loss by radiation. When heat conservation is required, vessels constrict.

3. Homeostasis

Homeostasis is the maintenance of the body’s internal condition irrespective of fluctuations in the external environment. It is the balance in the physical and chemical properties of the body. The skin helps by homeostasis in the following ways:

1. Dermal scales serve as storage places. Calcium and phosphate ions are stored there and can be used according to their requirement of usage.
2. Chloride secreting glands secrete excess chloride ions obtained from marine water.
3. The thick integument (stratum corneum) of many terrestrial vertebrates conserve water.

4. Exteroception

Nerve endings are present in the skin. When the skin comes in contact with some object the nerve endings are stimulated. Thus, they provide information about possible dangers such as pain from the heat.

5. Respiration

Many vertebrates such as aquatic amphibians use their skin for respiration. Urodeles obtain around ¾ oxygen from water by respiring through their skin. Some amphibians do not have lungs. They respire only from the skin.

6. Signal for Species

The pigmentation, color distribution, and scent from pheromones or scent glands often signal sex and identify other members of species. Pheromones also serve as alarms. For example, lions secrete pheromones to mark their region.

7. Locomotion

Adhesive pads and claws help in climbing such as in lizards. Feathers provide an airfoil (sheet of air) for aerial locomotion. Webbed feet of ducks and frogs help in swimming.

8. Excretion

In some aquatic amphibians, carbon dioxide – a respiratory waste is released from the body only through the skin. While small amounts of nitrogenous wastes are excreted by sweat glands.

9. Nourishment

Newborn mammals get nourishment from maternal mammary glands. In some teleosts, hatchlings are nourished by feeding on mucous secreted by the mother’s skin.

10. Synthesis of Vitamin D

Synthesis of vitamin D takes place in the skin of higher animals. For example, in humans.