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1 Ahmed Abdulwahab UG : (1330095)

Integumentary system

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Ahmed AbdulwahabUG : (1330095)

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3The skin and hypodermis

Skin – our largest organ Accounts for 7% of body weight The skin varies in thickness from 1.5 to 4mm

distinct region The superficial region is a thick epithelial

tissue Divided into two distinct layers

Epidermis Dermis

Hypodermis – lies deep to the dermis

4Skin structure

5Functions

Protection : Skin cushions and insulates the deeper body organs Protects the body from scrapes ,chemicals

and invading microorganisms The epidermis is waterproof, preventing

unnecessary loss of water across the body surface

produce pigment to protect the skin from the harmful effects of ultraviolet (UV) radiation

6Function

Body temperature regulation :The skin’s rich capillary networks and sweat glands regulate the loss of heat from the body

Excreation : The skin acts as a miniature excretory system when urea, salts, and water are lost through sweat.

Production of vitamin : The epidermal cells use UV radiation to synthesize vitamin D

Sensory reseption : touch, pressure, temperature, and pain

7Epidermis

A keratinized stratified squamous epithelium that contains four distinct types of cells Keratinocytes – most abundant

epidermis cell Produce keratin – a tough fibrous protein that

gives the epidermis its protective properties. Produce antibodies and enzymes Arise from deepest layer of epidermis Keratinocytes are dead at skin's surface

Merkel cells ,Tactile epithelial cells – associated with sensory nerve ending and function as a receptor for touch

8Epidermis

Melanocytes – secrete the pigment melanin Melanin is made in membrane-walled granules and then

transferred through the cell processes to nearby keratinocytes

Langerhans cells : macrophage like dendritic cells Millions of these dead cells rub off every day, giving us an

entirely new epidermis every 35 to 45 days—the average time from the birth of a keratinocyte to its final wearing away.

9Layer of the Epidermis

Stratum basale Deepest layer of epidermis Attached to underlying dermis Also called the Stratum

germinativum these Cells divide rapidly

Merkel cells – associated with sensory nerve ending

Melanocytes – secrete the pigment melanin

10Layer of the epidermis

Stratum spinosum (spiny layer) "Spiny" appearance caused by artifacts of histological preparation Contains thick bundles of intermediate filaments Contains star-shaped cells are part of the immune system Dendritic cells police the outer body surface, using receptor-mediated

endocytosis to take up foreign proteins (antigens) that have invaded the epidermis

Stratum granulosum Consists of one to five layers of flattened keratinocytes and intermediate

filaments intermediate filaments contain Keratohyaline granules – help form keratin Lamellated granules – contain a waterproofing glycolipid

11Layer of the epidermis

Stratum lucidum (clear layer) Occurs only in thick skin but not in thin skin Consists of a few rows of flat, dead

keratinocytes It is also named the transition zone

Stratum corneum (horny layer) Thick layer of dead keratinocytes and

thickened plasma membranes Protects skin against abrasion and

penetration

12Dermis

Second major layer of the skin Strong, flexible connective tissue Richly supplied with blood vessels and nerves fibers The deep dermal plexus is located between the

hypodermis and the dermis It nourishes the hypodermis and the structures located within

the deeper portions of the dermis subpapillary located just below the dermal papillae

perform a critical role in temperature regulation. These vessels are so extensive that they can hold 5% of all blood in the body.

13Dermis

The dermis has two layers papillary layer the superficial 20% of the

dermis is areolar connective tissue containing very thin

collagen and elastic fibers It includes the dermal papillae

increase the surface area for exchange of gases, nutrients, and waste products between these layers

reticular layer the deeper – 80% of thickness of dermis. is dense irregular connective tissue

14Hypodermis

Deep to the skin – also called superficial fascia

Contains areolar and adipose connective tissues

Besides storing fat, the hypodermis anchors the skin to the underlying structures

is also an insulator because fat is a poor conductor of heat, it helps prevent heat loss from the body

15Skin color

Three pigments contribute to skin color Melanin – most important pigment – made

from tyrosine Carotene – yellowish pigment from carrots

and tomatoes Hemoglobin – Caucasian skin contains

little melanin Allows crimson color of blood to show through

16Skin color

Melanin in granules passes from melanocytes (same number in all races) to keratinocytes in stratum basale Digested by lysosomes Variations in color Protection from UV light vs vitamin D?

Derived from epidermis but extend into dermis Include

Hair and hair follicles Sebaceous (oil) glands Sweat (sudoriferous) glands Nails

17Skin Appendages

Hair Minor protective functions (retain heat, decrease sunburn,

eyelashes protect eyes) Structure shaft – projects from skin follicle – extends into dermis root – lies within the follicle bulb – contains CT, vessels and nerves sebaceous gland – lubricates hair arrector pili muscle – attached to follicle and contracts to move

hair (hair growth, goosebumps)

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19Skin Appendages

Hair Growth influenced by: (in this order) nutrition - main influence hormones blood flow

Hair Pigmentcaused by proportions of 3 melanin types

• dark hair – true melanin• blonde and red – melanin with iron and sulfur• gray/white hair - melanin replaced by air bubbles in shaft

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21Skin Appendages

Nails Scale-like modifications of the epidermis Heavily keratinized Stratum basale extends beneath the

nail bed to form nail matrix Responsible for growth ( matrix region) Lack of pigment makes them colorless Lunula “little moon” – area of cell

growth (white semicircle at base of nail) Cuticle – area of skin that covers base

of nail

Nail Structures

22Skin Appendages

Sebaceous glands all over except palms and soles of feetProduce oil for waterproofingLubricant for skin & kills bacteriaMost with ducts that empty into hair folliclesGlands are activated at puberty: stimulated by hormones

23Skin Appendages

Eccrine glandsWidely distributed in skin: abundant on palms, soles, foreheadSweat composition: mostly water with a slightly acidic 4-6 pHFunction: thermoregulation

Apocrine glandsDucts empty into hair follicles Found mainly in anogenital & axillary regionBegin to function at puberty due to hormones / pheromonesOrganic contents: Fatty acids and proteins – can have a yellowish color that stains clothesOdor is from associated bacteria

Ceruminous glands

Modified apocrine gland Found in outer 1/3 of ear canalProduce ear wax to trap “invaders”

Sweat Glands

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Thank you for your attention

AHMED ABDULWAHABUG : (1330095)