SKINDR. SADAF AZIZLECTURER, NORTHWEST COLLEGE OF PHYSICAL THERAPYPESHAWAR, PAKISTAN

SKIN

The skin is also known as the cutaneous membrane covers the entire external surface of body.

5 pigments of skin1. Melanin2. Melanoid3. Carotene4. Haemoglobin5. oxyhaemoglobin

STRUCTURE OF SKIN

The skin consists of 2 main parts. The superficial, thinner portion, which is composed of

epithelial tissue, is the epidermis (epi=above). It is avascular.

The deeper, thicker portion is the dermis. It is vascular Deep to dermis, but not part of skin is the subcutaneous

layer, also known as hypodermis (hypo=below). This consists of adipose tissues.

The subcutaneous layer serves as a storage depot for fat and contain large blood vessels that supply the skin

EPIDERMIS

Superficial avascular layer of stratified squamous epithelium. Give rise to appendages of skin Structurally made of superficial cornified zone and a deep

germinative zone. The cells of deeper layer proliferate and pass towards the surface As they migrate, they become more and more flattened and lose

their nuclei In the germinative zone there are also melanocytes which

synthesize melanin It consists of 5 sub layers and 4 distinct types of cell

EPIDERMIS & ITS CELL

KERATINOCYTESMELANOCYTESLANGERHANS CELLMERKEL CELL

1. KERATINOCYTES(Keratino= horn-like, -cytes=cells)

• Arranged in 4-5 layers and produce the protein “keratin”• the most abundant cells

ARRANGEMENT

• formed in stratum basale and undergo continuous mitosis.• The cells push their way up to the surface where they are dead

cells filled with keratin and will slough off. • Regenerates every 25-45 days.

FORMATION

• protect the skin from entry of foreign particles and act as waterproofing material

• Keratin is s a tough, fibrous protein that helps protect the skin and underlying tissues from abrasions, heat, microbes and chemicals.

• Keratinocytes also produce lamellar granules which release a water-repellant sealent that decreases water entry and loss and inhibits the entry of foreign materials

FUNCTION

2. MELANOCYTES(Melano= black)

• 8% of epidermal cells are melanocytes• Produce the pigment melanin.• Melanin is a yellow-red or brown-black

pigment that contribute to skin color and absorbs damaging UV light

CHARACTERISTIC

• They are also present in stratum basale.• These cells have dendritic processes.

ARRANGEMENT

• Melanin accumulates in melanosomes and transported along dendrites of the melanocytes to keratinocytes.

• Inside keratinocytes the melanin granules cluster to form protective veil over nucleus on the side toward the skin surface.

• In this way, they shield the nuclear DNA from damage by UV light

• Melanocytes themselves are particularly suspectible to damage by UV light

FUNCTION

Yozae she

Chal e d

3. LANGERHANS CELLS

•Arise from red bone marrow and migrate to epidermis where they constitute a small fraction of epidermal cells

ARRANGEMENT & ORIGIN

•They participate in immune responses mounted against microbes that invade the skin and are easily damaged by UV light.•Their role in immune response is to help other cells of the immune system recognize an invading microbe and destroy it

FUNCTION

4. MERKEL CELLS•These are least numerous of the epidermal cells•They are located in the deepest layer of the epidermis where they contact the processes of sensory neuron.

ARRANGEMENT

•These detect touch sensations.

FUNCTION

LAYERS OF EPIDERMIS

LAYERS OF EPIDERMIS*

Thick & thin skin: 5 layers

1. Stratum basale 2. Stratum spinosum3. Stratum granulosm4. Stratum lucidum5. Stratum corneum

1.STRATUM BASALE* This is the deepest layer of the epidermis and is separated by dermis by a

basement membrane.

Composed of single row of keratinocytes

This layer is characterized by numerous mitotic figures, the stem cells, responsible for production of new keratinocytes which are constantly displaced into layer above.

It is also known as STRATUM GERMINATIVUM (germ=sprout) to indicate its role in forming new cells

It contain keratin intermediate filaments which bind cells of stratum basale to

lleach other and to cells of adjacent layers

2. STRATUM SPINOSUM Spinos= thorn-like Superficial to stratum basale Mainly consist of numerous keratinocytes arranged in 8-10 layers. The keratinocytes in the stratum spinosum produced by the stem cells in

the basal layer retain their ability to divide. Stratum spinosum when prepared for microscopic examination appear to

be covered with thorn-like spines At each spine like projection the keratin intermediate filaments tightly join

cells to one another. This arrangement provides both strength and flexibility to skin. Langerhan cells and projections of melanocytes are also present

Basale ki yo v

3. STRATUM GRANULOSUM* Granulos= little grains Consists of 3-5 layers of keratinocytes that undergo apoptosis The nuclei and other organelles begin to degenerate as they move farther from

their source of nutrition i-e the dermal blood vessels This layer consist of dark granules of protein called keratohyalin, that

assembles keratin intermediate filaments into keratin Also present lamellar granules that release lipid-rich secretion. This secretion

is deposited in the spaces between cells of the stratum granulosum, lucidum and corneum.

This secretion acts as water repellant and entry of foreign particles. The starum garnulosum marks the transition between the deeper active strata

and the dead cells of the superficial strata

Half of the spinous

Che pa bara zee nu death kege

Yo zae kawal kai

Lipis bara three layers ki deposited she Lipis secretion

Miyanz ki v da upper and da lover layer

4. STRATUM LUCIDUM*

Lucid=clear Present only in thick skin i-e fingertips, palms and

soles. 4-6 layers of dead keratinocytes Also large amount of keratin

One more than granulus

High meqdar ki v ( der xiyat )

5. STRATUM CORNEUM* Corne= horn 25-30 layers of dead keratinocytes, but may

vary depending on skin type The cells with each layer overlap one another

like scales on skin of snake Cells are continuously being shed and

replaced by cells from the deeper strata. Its multiple layers of dead cells help the

stratum corneum to protect deeper layers from injury and microbial invasion

Poo way

Ghorzege and raheje

MNEMONICS FOR SKIN LAYERS

Come, Let’s Get Sun Burned (from superficial to deep)

stratum Corneum stratum Lucidum stratum Granulosum stratum Spinosum stratum Basale.

DERMIS

Deep vascular layer of skin Made of connective tissue with

variable elastic fibers mixed with blood vessels, lymphatics and nerves.

Superficial papillary layer and deep reticular layer

APPENDAGES OF SKIN

APPENDAGES OF SKIN

1. Nails2. Hair3. Sweat glands4. Sebacous glands

NAILS Hardened keratin plates Each nail has the following parts

Root Free border Body Lunule Nail wall Nail bed

Germinative zone beneath root and lunule is thick and responsible for growth of nail

The corium is very vascular under body except lunule of nail.

HAIR Keratinous filaments – invagination of germinative layer of

epidermis into the dermis ROOT-the implanted part. Surrounded by hair follicle and expanded to form hair bulb.

The hair papilla forms the neurovascular hilum of hair. SHAFT-the projecting part

Hair grows at the hair bulb, Hair follicles lie obliquely to surface of skin and responsible for

characteristic hair streams in different body parts. The arrectores pilorum muscles produces goose skin Lanugo (primary skin) vellus (secondary hair) Hair growth rate 1.5-2.2mm per week.

SWEAT GLANDS

Sudoriferous/sweat glands distributed all over skin. These are of two types:1. THE ECCRINE GLANDS: Abundant. Distributed in every part of skin Single tube. Deep part is coiled called the body of the gland, lies in the deeper part

of corium. The straight part, the duct, traverses the dermis and epidermis and open on surface

of skin Large in axilla and groin, numerous in palms and soles, least in neck and back Merocrine in nature Cholinergic sympathetic nerves

2. THE APOCRINE GLANDS: Axilla, eyelids, nipple and external

genitalia. Larger than eccrine and produce

thicker secretion with characteristic odour.

Close association wit hair follicles. Ceruminous glands of external

auditory meatus Merocrine in nature but regulated by

dual autonomic control One liter of sweat secreted per day In hot climates the secretion

increases to 3-10 liters per day

SEBACOUS GLANDS Produce an oily secretion, called sebum, widely

distributed over dermis of skin Abundant in scalp, face, ear, nose mouth anus Small and sacculated appearance. Cluster of 2-5 piriform alveoli Ducts open into hair follicles Holocrine in nature Under hormonal control Lubricates skin and hair Bactericidal action Makes skin water proof.

FUNCTIONS OF SKIN

1. Protection2. Sensory3. Regulation of body temperature4. Absorption5. Secretion6. Excretion7. Regulation of pH8. Synthesis9. Storage10.reparative

SUPERFICIAL FASCIA

DEFINITION General coating of body

beneath of skin Made of loose areolar

tissue with varying amounts of skin

DISTRIBUTION OF FAT IN THIS FASCIA

Abundant in the gluteal , lumbar from of thighs, anterior abdominal wall below umbilicus, mammary gland, post deltoid region and cervicothoracic region

In females fat is more abundant and evenly distributed

Fat is absent from eyelids, external ear, penis and scrotum

Fats fill the hollow spaces like axilla orbits and ischiorectal fossa

Fats around kidney provide support

TYPES OF FATS

Yellow fat Brown fat

FUNCTIONS

Facilitates movement of skin Passage of vessels and nerves Conserves body heat

DEEP FASCIA

DEFINITION

Fibrous sheet. Invests the body beneath the superficial fascia Devoid of fat Inelastic and tough

DISTRIBUTION

Best-defined in limbs and neck Ill-defined on trunk and face

IMPORTANT FEATURES

Extensions-intermuscular septa Thickenings-retinacula & aponeurosis Interruptions on the subcutaneous bones

FUNCTIONS

Keeps underlying structures in position Extra surface for muscular attachments Helps in venous & lymphatic return Assists muscles in their action Retinacula prevent loss of power and minimize

friction.

Discussion

Differentiate brown & yellow fat.

THE END…!!!