the integumentary system · integument - latin word meaning “to cover” skin and its accessories...
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RACHNA YADAVB.Tech.,M.Sc.(MLT),MBA
THE INTEGUMENTARY SYSTEM
INTEGUMENT - LATIN word meaning “to COVER”
SKIN and its accessories such as the HAIR, NAILS, and various associated glands, make up the integumentary system
INTRODUCTION
Acts as barrier against infection and injury Regulates body temperature Removes the waste products from the body Provides protection against ultraviolet radiation from
the sun Generates vitamin D
FUNCTIONS OF INTEGUMENTARY SYSTEM
One of the largest organs of the body, making up to 6-8% of the total body weight
Consists of two distinct layers, the EPIDERMIS and DERMIS
SKIN
Hirsute – thin, hairy skin which covers grater part of the body
Glabrous – which covers the surfaces of palms, soles and flexor surfaces of the digits
TYPES OF SKIN
PROTECTIONqPhysical, chemical and biological barriersqTight cell junctions prevent bacterial invasionqLipids released retard evaporationqPigment protects somewhat against UV lightqLangerhans cells alert immune system
FUNCTIONS OF SKIN
THERMOREGULATIONqPerspiration & its evaporation§ lowers body temperature§ flow of blood in the dermis is adjustedqEXERCISE§ moderate exercise brought more blood to surface which
helps to lower temperature§ extreme exercise leads to shunting of blood to muscles
and body temperature risesqSHIVERING AND CONSTRICTION OF SURFACE
VESSELS§ raise internal body temperature as needed
CONTD…
qCUTANEOUS SENSATIONS§ Touch§ Pressure§ Vibration§ Tickle(mild touch that causes discomfort)§ Heat & Cold (Thermal)§ Pain & Itch
(Noxious)(harmful/poisonous/unpleasant)
CONTD…
EXCRETION & ABSORPTIONqEXCRETION§ 400 ml of water/day,§ Small amounts Nacl,CO2,§ Ammonia and UreaqABSORPTION§ Water soluble – Negligible§ Lipid soluble Vitamins -A, D, E, K§ Organic solvents§ Heavy metals§ Topical medicines
CONTD…
EPIDERMIS DERMIS SUBCUTANEOUS LAYER- also called as
hypodermis, lies beneath dermis, not part of the skin
LAYERS OF SKIN
Thin Outer most layer of Skin Composed of many sheets of Flattened, Scaly
Epithelial Cells Made of mostly DEAD CELLS
EPIDERMIS
STRATUM CORNEUM- Outermost layer, made of 25-30 layers of dead flat keratinocytes , Lamellar granules provide water repellent action and are continuously shed & replaced
STRATUM LUCIDUM- Only found in the fingertips , palms of hands, & soles of feet, made up of 3-5 layers of flat dead keratinocytes
STRATUM GRANULOSUM- Made up of 3-5 layers of keratinocytes, site of keratin formation, keratohyalin gives the granular appearance
STRATUM SPINOSUM- Provide strength & flexibility to the skin
STRATUM BASALE- Deepest layer, made up of a single layer of cuboidal or columnar cells which constantly divide & move up to apical surface
LAYERS OF EPIDERMIS
TYPES OF EPIDERMAL CELLSq KERATINOCYTES§ Produce the protein keratin, which helps protect the skin and
underlying tissue from heat, microbes, and chemicals, and lamellar granules, which release a waterproof sealant
q MELANOCYTES§ Produce the pigment melanin which contributes to skin color
and absorbs damaging ultraviolet (UV) lightq LANGERHANS CELLS§ Derived from bone marrow§ Participate in immune responseq MERKEL CELLS§ Contact a sensory structure called a tactile (Merkel) disc and
function in the sensation of touch
Innermost thick layer of the skin composed of living cells
Lies beneath the Epidermis and contains blood vessels, nerve endings, glands, sense organs, smooth ,muscles , and hair follicles
DERMIS
qPAPILLARY LAYER Thin , superficial, dermal papillae found here Contains loose areolar CT
qRETICULAR LAYER§ 80% of dermis§ Dense irregular CT
LAYERS OF DERMIS
Not part of the skin, and lies below the dermis Attach the skin to underlying bone and muscle as well
as supplying it with blood vessels and nerves Consists of loose connective tissue and elastin Main cell types are fibroblasts, macrophages and
adipocytes (the hypodermis contains 50% of body fat) Fat serves as padding and insulation for the body Also known as the subcutaneous tissue
HYPODERMIS
ACCESSORY STRUCTURES OF SKIN
Develop from the embryonic epidermis
Cells sink inward during development to form:
§ Hair§ Oil & sweat glands§ Nails
Act as protective plates over the fingertips and toes Area under nail has many nerve endings, which allow
to receive more information about objects touched
NAILS
CONTD… Tightly packed keratinized
cellsqNAIL BODY visible portion pink due to
underlying capillaries free edge appears whiteqNAIL ROOT buried under skin layers lunula is white due to
thickened stratum basaleqEPONYCHIUM
(CUTICLE) stratum corneum layer
HAIRS Epidermal cells Tube-like depression Extends into dermis Three (3) parts:vHair root vHair shaft vHair papilla Melanin Arrector pili muscle
HAIR RELATED STRUCTURES
Arrector pili- smooth muscle in dermis, contracts with cold or fear, forms goosebumps as hair is pulled vertically
Hair root plexus- detect hair movement
Sebaceous (oil) glands
The human body is covered with hair, except§ Palms§ Soles§ Lips§ Portions of external genitalia FUNCTIONS OF HAIR§ Protects and insulates§ Guards openings against particles and insects§ Is sensitive to very light touch
CONTD…
SEBACEOUS GLANDS(OIL GLANDS)§ Holocrine glands§ Secrete sebum SWEAT GLANDS§ Two types: apocrine glands and merocrine (eccrine)
glands§ Watery secretions CERUMINOUS (WAX) GLANDS MAMMARY (MILK) GLANDS
EXOCRINE GLANDS IN SKIN
Simple branched alveolar glands Associated with hair follicles Sebaceous follicles:§ Discharge directly onto skin surface Sebum:§ Contains lipids and other ingredients§ Lubricates and protects the epidermis§ Inhibits bacteria
SEBACEOUS (OIL) GLANDS
Apocrine sweat glands Found in armpits, around nipples, and groin Secrete products into hair follicles Produce sticky, cloudy secretions Break down and cause odors Surrounded by myoepithelial cells:§ Squeeze apocrine gland secretions onto skin surface§ In response to hormonal or nervous signal
SWEAT GLANDS
Widely distributed on body surface Especially on palms and soles Discharge directly onto skin surface Sensible perspiration Water, salts, and organic compounds Functions of merocrine sweat gland activity:§ Cools skin§ Excretes water and electrolytes§ Flushes microorganisms and harmful chemicals from skin
MEROCRINE (ECCRINE) SWEAT GLANDS
Produce a waxy substance called cerumen Found in the external auditory meatus Barrier for entrance of foreign bodies
CERUMINOUS GLANDS
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