Sample Material of Our Online Coaching Programme

Subject: General Science

Topic: The Integumentary System

INTRODUCTION

The integumentary system (From Latin integumentum, from integere ‘to cover’; from in- + tegere ‘to cover’ is the organ system that protects the body from damage, comprising the skin and its appendages (including hair, scales, feathers, and nails). The integumentary system has a variety of functions; it may serve to waterproof, cushion, and protect the deeper tissues, excrete wastes, and regulate temperature, and is the attachment site for sensory receptors to detect pain, sensation, pressure, and temperature. In humans the integumentary system also provides vitamin D synthesis.

The skin is the largest organ in the body: 12-15% of body weight, with a surface area of 1-2 meters. Skin is continuous with, but structurally distinct from mucous membranes that line the mouth, anus, urethra, and vagina. Two distinct layers occur in the skin: the dermis and epidermis. The basic cell type of the epidermis is the keratinocyte, which contain keratin, a fibrous protein. Basal cells are the innermost layer of the epidermis. Melanocytes produce the pigment melanin, and are also in the inner layer of the epidermis. The dermis is a connective tissue layer under the epidermis, and contains nerve endings, sensory receptors, capillaries, and elastic fibers.

The integumentary system has multiple roles in homeostasis, including protection, temperature regulation, sensory reception, biochemical synthesis, and absorption. All body systems work in an interconnected manner to maintain the internal conditions essential to the function of the body.

GLANDS

Hair follicles are lined with cells that synthesize the proteins that form hair. A sebaceous gland (that secretes the oily coating of the hair shaft), capillary bed, nerve ending, and small muscle are associated with each hair follicle. If the sebaceous glands becomes plugged and infected, it becomes a skin blemish (or pimple). The sweat glands open to the surface through the skin pores. Eccrine glands are a type of sweat gland linked to the sympathetic nervous system; they occur all over the body. Apocrine glands are the other type of sweat gland, and are larger and occur in the armpits and groin areas; these produce a solution that bacteria act upon to produce “body odor”.

HAIR AND NAILS

Hair, scales, feathers, claws, horns, and nails are animal structures derived from skin. The hair shaft extends above the skin surface, the hair root extends from the surface to the base or hair bulb. Genetics controls several features of hair: baldness, color, texture. Nails consist of highly keratinized, modified epidermal cells. The nail arises from the nail bed, which is thickened to form a lunula (or little moon). Cells forming the nail bed are linked together to form the nail.