Integumentary System

Integument(Skin) Integument is nothing

but the skin. Integument(=to cover in

latin Skin and its appendages

are the largest organ of the body

Functions:1. Protection2. Heat regulation3. Sensation4. Synthesis and storage

of Vit D

Integumentary systemSkin along with the exocrine

gland(sebaceous gland

HairNailsAssociated blood

vessels and Associated nerves Comprise

integumentary system

SkinSuperficial epidermismiddle dermisDeep

hypodermis(superficial fascia)

EpidermisSuperficial layer

composed of keratinized stratified squamous epithelium

Avascular with no blood vessels or lymphatics

Has basal cells which has regenerative capacity

Thick skin has 5 layers of cells

Thin skin has 4 layers of skin

DermisMiddle layer

composed of Dense irregular connective tissue

Contains nerve endings,hair follicles, and glands

They nourish the avascular epidermis

Contains dermal papillae(projections of dermis into epidermis)

Langer(incision or tension) lines in skin

They are the direction in which the most collagen fibres run in any particular location in the skin.

Incision should be made parallel to the direction to avoid minimal scarring.

HypodermisDeepest layerStores fat and anchors

upper layers to other tissues

Composed of areolar and adipose connectieve tissue

Epidermal layersFrom base to topStratum basaleStratum spinosumStratum granulosumStratum lucidumStratum corneum

Stratum basaleSingle layer of columnar or cuboidal cells

resting on basement membraneThe epidermis is renewed every 15-30

days; proliferative activity takes place in this layer; cells are very mitotic

Stratum spinosumseveral layers of polygonal shaped cells

with spines.Spines are nothing but keratin filaments.It resists the effects of abrasion and the

layer is thicker in thick skin which is subjected to continuous friction and pressure(eg: soles and palms)

Stratum granulosum3-5 layers of flattened polygonal cells with

visible granulesCells undergo keratinization which is a

process in which nucleus shivels up, cells dies, and cell fills up with protein keratin

This layer acts as a barrier to penetration by foreign materials and provides sealing effect

Stratum lucidum2-3 layers of dead, anucleated, clear cells.

Only found in thick skin

Stratum Corneum20-30 layers of dead, anucleated cells.They are cornified( brittle, hardened).

These outer cells are constantly shed

Epidermal cellsKeratinocytes: most numerous(90%);found

in all layers; produces keratin which provides the protective barrier mechanically as well as immunologically

Melanocytes: 2nd most numerous(8%);found in stratum basale;produces melanin which is a photoprotector

Epidermal cellsMerkel cells: 3rd numerous(1%) found in

stratum basale;provides tactile(light touch) sensation

Langerhans cells: <1% found in stratum spinosum; phagocytic action

Dermal layersPappillary Layer: uppermost; composed of dermal papillae; contatains blood vessels, sensory receptors, ducts of glands; and hair shafts

Reticular Layer: deepest;contains blood vessels; sensory recptors(neurons); secretory poertions of glands and hair follicles

Epidermal derivatives(skin appendages)

Hair : contains bulb, root and shaft ; associated with arrector pili muscle; functions to protect UV light, trauma, and heat loss

Nails : formed from stratum corneum ; functions in protection and grasping

Exocrine Glands: 1. Sebaceous glands2. Sweat (sudoriferous) glands3. Ceruminous

Exocrine glands in skin

Sebaceous glands(sebum=oil):associated with hair follicles and functions in lubrication and bactericidal

Sweat(sudoriferous) glands: appocrine: in axiallary and pubic regions,

secreates onto hair shafts and release an odiferous secretion

Eccrine : found everywhere, funtioning to release perspiration

Ceruminous: modified sweat glands ; found in external auditory canal; cerumen is an insect repellent and a water proofing agent