Integrated Guidance Programme of General Studies for IAS
(Pre) – 2013
Subject – General Science
Chapter : The Integumentary System
Integumentary System
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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.
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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”.
Skin and Homeostasis
Skin functions in homeostasis include protection, regulation of body
temperature, sensory reception, water balance, synthesis of vitamins and
hormones, and absorption of materials. The skin’s primary functions are to serve
as a barrier to the entry of microbes and viruses, and to prevent water and
extracellular fluid loss.
Skin and Sensory Reception
Sensory receptors in the skin include those for pain, pressure (touch), and
temperature. Deeper within the skin are Meissner’s corpuscles, which are
especially common in the tips of the fingers and lips, and are very sensitive to
touch. Pacinian corpuscles respond to pressure. Temperature receptors: more cold
ones than hot ones.
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