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