Post on 20-Feb-2017
Anatomy & Physiology Of Integumentary
System
By:Mr. M. Shivananda Reddy
Structure Of Skin
• The integumentary system is the largest body organ and is composed of the skin, hair, nails, and glands.
• The skin is further divided into three layers: a) Epidermis b) Dermis And c) Subcutaneous tissue
Epidermis• The epidermis, the thin avascular superficial layer of
the skin, is made up of an outer dead cornified portion that serves as a protective barrier and a deeper, living portion that folds into the dermis.
• Together these layers measure 0.05 to 0.1 mm in thickness.
• The epidermis regenerates with new cells every 28 days.
Layers of Epidermis:Layers (from deep to superficial):
• Stratum basale or germinatum – single row of cells attached to dermis; youngest cells
• Stratum spinosum – Made up of bundles of protein resist tension
• Stratum granulosum – layers of flattened keratinocytes producing keratin.
• Stratum lucidum layer that is present only on palms and soles
• Stratum corneum – horny cornified superficial layer
Layers of epidermis:
Cells of Epidermis:• The two major types of epidermal cells are
melanocytes (5%) and keratinocytes (90%).• Melanocytes are contained in the deep,
basal layer (stratum germinativum) of the epidermis.
• They contain melanin, a pigment that gives color to the skin and hair and protects the body from damaging ultraviolet (UV) sunlight.
• Sunlight and hormones stimulate the melanosome (within the melanocyte) to increase the production of melanin.
• The wide range of skin color is caused by the amount of melanin produced; more melanin results in darker skin color.
• Keratinocytes are synthesized from epidermal cells in the basal layer.
• As they mature (keratinize), they move to the surface, where they flatten and die to form the outer skin layer (stratum corneum).
• Keratinocytes produce a fibrous protein, keratin, which is vital to the skin’s protective barrier function.
Dermis
• The dermis is the connective tissue below the epidermis.
• Dermal thickness varies from 1 to 4 mm. The dermis is very vascular.
• The dermis is divided into two layers, an upper thin papillary layer and a deeper, thicker reticular layer.
• The papillary layer is folded into ridges which extend into the upper epidermal layer.
• These exposed surface ridges form congenital patterns called fingerprints and footprints.
Subcutaneous Tissue.
• The subcutaneous tissue lies below the dermis and is not part of the skin.
• The subcutaneous tissue is often discussed with the skin because it attaches the skin to underlying tissues such as muscle and bone.
• The subcutaneous tissue contains loose connective tissue and fat cells that provide insulation.
• This layer also stores lipids, regulates temperature, and provides shock absorption.
Skin Appendages
Appendages of the skin include:• Hair• Nails• Glands (Sebaceous, Apocrine, And
Eccrine).
Hair• Grows on most of the body except for the lips,
the palms of the hands, and the soles of the feet • The color of the hair is a result of heredity and is
determined by the type and amount of melanin in the hair shaft.
• Hair grows approximately 1 cm per month. • On average 100 hairs are lost each day.• When lost hair is not replaced, baldness results.
Parts of Nail:
Nails:• Nails grow from the matrix. • The nail matrix is located at the proximal area of
the nail plate. • The matrix is commonly called the lunula, which
is the white crescent-shaped area visible through the nail plate.
• The nail bed that is under the nail matrix and nail plate is normally pink and contains blood vessels.
• Fingernails grow at a rate of 0.7 to 0.84 mm per week, with toenail growth 30% to 50% slower.
Glands:• Two major types of glands are associated with the
skin: Sebaceous and Sweat (apocrine and eccrine) glands.
• The sebaceous glands secrete sebum, which is emptied into the hair follicles.
• Sebum prevents the skin and hair from becoming dry.
• Sebum is somewhat bacteriostatic and fungistatic and consists mainly of lipids.
• These glands depend on sex hormones, particularly testosterone, to regulate sebum secretion and production.
• Sebum secretion varies according to sex hormone levels.
• Sebaceous glands are present on all areas of the skin except the palms and the soles.
• These glands are most abundant on the face, scalp, upper chest, and back.
• The apocrine sweat glands are located in the axillae, breast areolae, umbilical and anogenital areas, external auditory canals, and eyelids.
• The eccrine sweat glands are widely distributed over the body, except in a few areas, such as the lips.
Functions of Integumentary System• Regulates body temperature– regulates heat loss
• Helps regulate fluid balance – absorbs water – prevents excessive water & electrolyte loss. – Slow loss up to 600 ml daily by evaporation
• Immune Response Function
• Vitamin production – exposure to UV light allows for the conversion of
substances necessary for synthesizing vitamin D – Necessary to prevent osteoporosis, rickets
• Excretion:Partial excretion of metabolic wastes occurs through the skin.
• Transmits sensation – nerve receptors
• allows for feelings of temperature, pain, light touch and pressure
Functions of hair:
Head:o UV protectiono Cushion from traumao InsulationNostrils, Ear canals, Eyelashes:• Prevent entry of foreign materialBody Hair:• sensory detection