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THE INTEGUMENTARY SYSTEM The Integumentary system • Skin is the largest organ in the body • The Integumentary system consist of: 1. the skin 2. its derivatives. These include hair, nails, and several types of glands. FUNCTIONS • • • • • Protection regulation of body temperature excretion of waste materials synthesis of vitamin D reception of various stimuli perceived as pain, pressure and temperature. Skin • LAYERS OF THE SKIN: 1. epidermis 2. Dermis 3. hypodermis. Epidermis • • • • 1. 2. 3. 4. 5. the outer layer of the skin made of stratified squamous epithelium no blood supply Epidermis contains 4-5 strata. stratum cornium Stratum lucidium Stratum granulosum Stratum spinosum Stratum basale,. 5 LAYERS OF EPIDERMIS • Stratum cornium is the outer, dead, flat, Keratinized and thicker layer. • Stratum lucidium is next to stratum cornium. It consists of flat, translucent layers of cells. This stratum found in thick skin only. • Stratum granulosum lies just below stratum lucidium. The cells in this layer are in the process of keratinization • Stratum spinosum: next down to stratum granulosum. The cells in this stratum have a poly-hydral shape and they are in the process of protein synthesis. • Stratum basale rests on the basement membrane, and it is the last layer of epidermis next to stratum spinosum. LAYERS OF DERMIS-1 • Dermis is also referred to as the true skin 1. • • • Papillary layer is next to stratum basale of the epidermis. contains loose connective tissue with in the bundles of collagenous fibers loose capillaries that nourish the epidermis. In some areas papillary layer have special nerve endings that serve as touch receptors . LAYERS OF DERMIS-2 2-Reticular layer: • next to papillary layer. • made of dense connective tissue with course of collagenous fiber • bundles that crisscross to form a storma of elastic network. • many blood and lymphatic vessels, nerves, fat cell, sebaceous (oil) glands and hair roots are embedded. • Receptors of deep pressure are distributed through out the dermis. Hypoderms • found beneath the dermis. • subcutaneous layer (under the skin). • Hypodermis is composed of loose, fibrous connective tissue • richly supplied with lymphatic and blood vessels and nerves • much thicker than dermis. With in it coils of ducts of sweat glands, and the base of hair follicles. Functions of Skin • 1. Protection: against harmful microorganisms, foreign material and it prevents excessive loss of body fluid. • 2. Temperature regulation: with the sweat, heat leaves the body. • 3. Excretion: Small amount of waste products from the body such as urea. • 4. Synthesis: By the action of UV. Vitamin D is synthesized in the skin. Vitamin D is necessary for absorption calcium from intestine. • 5. Sensory reception: it contains sensory receptors of heat, cold, touch, pressure, and pain. Color of the skin determined by 3 factors :1. presence of melanin- a dark pigment produced by specialized cell called melanocyte. 2. The accumulation of yellow pigment carotene. 3. The color of blood reflected through the epidermis. * • The main function of melanin is to screen out excessive ultraviolet rays. • All races have some melanin in their skins although the darker races have slightly more melanocyte. • The person who is genetically unable to produce any melanin is an albino. Glands of the Skin • sweat glands:• Types: Eccrine and Apocrine glands . Eccrine glands are small, simple coiled tubular • glands distributed over nearly the entire body • absent over nail beds, margins of lips of vulva, tips of male genital organ. • numerous over the palms and soles • sweat they secret is colorless, aqueous fluid containing neutral fats, albumin, urea, lactic acid and sodium chloride • excretion helps body temperature to be regulated. GLANDS OF SKIN Apocrine glands • • • • • • • Odiferous found at the armpits, in the dark region around nipples, the outer lips of the vulva, and the anal and genital regions larger and deeply situated than eccrine sweat glands apocrine sweat gland becomes active at puberty respond to stress The female breasts are apocrine glands that have become adapted to secret and release milk instead of sweat. The glands in the outer ear canal are also apocrine skin glands. Sebaceous (Oil) glands • Sebaceous glands are simple branched alveolar glands found in the dermis • main functions are lubrication and protection • connected to hair follicles • secret oily secretion called sebum. It is a semi fluid substance composed of entirely lipids • functions as a permeability barrier, skin softening and a protective agent against bacteria and fungi • found all over the body Hair • Hair is an appendage of the skin • composed of Keratinized threads of cells • develops from the epidermis • It covers the entire body except the palms, soles, lips, tip of male genital organ, inner lips of vulva and nipples. Function • - Insulation against cold in scalp • - Against glare in eye brows • - Screen against foreign particles (eye lashes) • - In the nostrils trap dust particles in the inhaled air • - Protect openings from foreign particles. Structure of Hair • Hair has two parts, the shaft the part above skin and the root embedded in the skin. • The lower portion of the root, located in the hypodermis enlarges to form the bulbs. The bulb forms a papilla of blood rich connective tissue • Part of the hair follicle is attached with the bundle of smooth muscle called arrecter pili muscles. • When it contracts it pulls the follicles and its hair to an erect position. • Hair grows and when it finishes its growth sheds. The growth rate of hair depends on its position. The fastest growth rate occurs over the scalp of women aged 16 to 24 years. Nail • Nails, like hair are modifications of the epidermis. They are made of hard keratin. Nails are composed of flat, cornified plates on the dorsal surface of the distal segment of the fingers and toe. The proximal part of nail is lunula, which is white in its color because of the capillaries underneath are covered by thick epithelium. Nail has body and root. The body is the exposed part and the root is hidden under the skin. The nail ends with a free edge that overhangs the tip of the fingers. Epithelial layer covering underneath of the fore-hang nail is hyponychyem. The nail rests on an epithelial layer of skin called nail bed. The thicker layer of skin beneath the nail root is the matrix, where new cells are generated. Nail grows 0.5 m.m a week. Thin layers of epidermis called eponychium originally cover the growing nail. Our nail protects our fingers and toes. It also allows picking up and grasping objects as well we use them to scratch. Effects of Aging on the Integumentary System • Blood flow to the skin is reduced, the skin becomes thinner, and elasticity is lost. • Sweat and sebaceous glands are less active, and the number of melanocytes decreases.