Integumentary System

The Skin

Facts about the skin• Skin is the largest external

organ• 1mm thick when you’re born• Thickens to 2mm as you

age• Thins as you reach old age• Weighs on average between

6-10 lbs• Soles of your feet and palms

have no hair follicles• Majority of dust in your

house is made of skin flakes

Integumentary System

Tissues that make up skin• Epithelium of epidermis• Connective tissue of dermis(Dense Irregular CT)• Subcutaneous layer (AKA superficial fascia or

hypodermis)

Skin is the main organ of integumentary system but also consists of its derivatives

• Hair• Nails• Glands• Nerve endings

Layers of the skin

Functions of the Skin

• Regulation of body temperature

• Protection• Sensation• Excretion• Immunity• Blood reservoir• Vitamin Synthesis

Synthesis of Vitamin D

• An hour of sunlight per week is sufficient to activate the body's own vitamin D precursor

• The sun triggers cholesterol found in epidermal cells to convert into Vitamin D

• Vitamin D can also be consumed in fortified milk.

• Vitamin D is essential because it regulates Ca and Phosphorus and keeps skeleton strong

• Deficiencies can cause rickets, osteoporosis, osteomalacia

Components of the skin

Surface Film

• Protective barrier of skin is formed by a thin film of emulsified material spread on its surface

• Made out of sweat, sebum and shed epithelial cells

• Functions – Protect against irritants– Antimicrobial– Lubricate, hydrate

Cell of the EpidermisEpidermis is avascular and made up of keratinized

stratisfied squamous cells.

Keratinocytes– make up 90% of epidermal cells– Principal outer element of the skin– Become filled with tough fibrous keratin

Melanocytes– Contribute to color of skin– Keep UV light from penetrating deep

Langerhans cells– Play a role in immune defense– Function with white blood cells

Epidermis The epidermis is made up of five sub-layers:

• Basal layer (stratum basale) The basal layer is the inner layer of the epidermis, containing basal cells. Basal cells continually divide, forming new keratinocytes and replacing the old ones that are shed from the skin's surface.

• Spinous layer (stratum spinosum)So named because after preservation, tissue looks to have “spines.” These are desmosomes being formed to connect the epithelial cells.

• Granular layer (stratum granulosum)So named because they appear as grains under magnifications. Here the cells are beginning to deteriorate as keratin is forming inside of them. Granules are called keratohyalin.

• Clear Layer (stratum lucidum)So named because it is a clear layer of cells as they loose their cytoplasmic contents and become fully keratinized. Thicker skin has more of these cells, absent in thin skin.

• Horny layer (stratum corneum) This layer contains continually shedding, dead keratinocytes (the primary cell type of the epidermis). This is the dead skin that you shed. It makes up 70 -80% of the dust in your house.

Layers of Epidermis

Stratum

Germinativum

(growth layer)

Dermal-Epidermal Junction

• Cements epidermis to dermis• Polysaccharide gel holds layers together• Any large detachment can result in severe

infection and death

The dermis is made up two layers1. The papillary layer is areolar

connective tissue containing fine elastic fibers, dermal papillae and corpuscles of light touch (Meissner's corpuscles).

2. The reticular layer is irregular connective tissue containing collagen and elastic fibers.

– blood vessels (body temp)– lymph vessels – hair follicles – sebaceous (oil) glands – sweat glands(ducts of

sudoriferous)– Adipose tissue

Dermis The dermis is the middle layer of the skin.

Papillary Layer

• Dermal papillae- bumps which form on superficial layer of the dermis

• In thick skin papillae line up in parallel lines which epidermis binds to, forming finger and toe prints

• In thin skin papillae are randomly placed so no ridges form.

Reticular Layer

• Tough layer of thick white collagenous fibers

• Few elastic fibers• Attachment point of

skeletal and smooth muscles

• Arrector pili muscles attach to each hair follicle, give you goose bumps

• Sensory receptors are located in this layer

Growth and Repair of Dermis• Strength, extensibility, and

elasticity are provided to the skin by collagen and elastin.

• Lines of cleavage (tension lines) indicate the direction of collagen fiber bundles in the dermis and are considered in making surgical incisions.

• Flexure lines- deep attachment of skin to muscles. Causes deep wrinkles.

Langer's cleavage lines

Growth and Repair of Dermis

Scars– Fibroblasts

reproduce to heal a wound resulting in a mass of connective tissue

Stretch Marks– If elastic fiber are

stretched too much or too quickly they tear

Subcutaneous-superficial fascia-

hypodermis

• The subcutis is the deepest layer of skin and is also known as the subcutaneous layer.

• The subcutis, consisting of a network of collagen and fat cells, helps conserve the body's heat while protecting other organs from injury by acting as a "shock absorber."

Appendages of the SkinHair

– Follicles develop before birth

– Lanugo is hair that forms before birth

– Vellus hair-strong fine hair that covers the body(peach fuzz)

– Terminal Hair- forms pubic, under arm hair

– In males terminal hair replaces vellus hair on extremities, chest and beard

– Germinal matrix is highly mitotic and pushes cells up to form hair– Melanocytes are deposited into hair to give it color

Germinal Matrix

Male Pattern Baldness

Alopecia• Two conditions need

to me met– Genes for baldness,

polygenic– Sex influenced– Male Hormone

testosterone

Appendages of the SkinGLANDS• Sebaceous (oil) glands are

usually connected to hair follicles, they are absent in the palms and soles.– produce sebum, which

moistens hair, waterproofs and softens skin, and inhibits bacterial growth.

– Enlarged sebaceous glands may produce blackheads, pimples, and boils.

• Ceruminous glands – modified sudoriferous

glands that produce a waxy substance called cerumen. They are found in the external auditory meatus.

Appendages of the Skin

GLANDS• Sudoriferous (sweat) glands-

produce perspiration, maintains temperature, eliminates small amounts of wastes. – Eccrine(merocrine)- small

sweat glands found all over, not associated with hair.

– Apocrine(stinky) limited in distribution to the skin of the axilla, pubis, anal, and areola; ducts open into hair follicles.

Appendages of the Skin

Nails• Nails are hard, keratinized epidermal cells over the dorsal

surfaces of the terminal portions of the fingers and toes.• The principal parts of the nail are the body, free edge, root,

lunula, eponychium, and matrix• Lunula is latin for “little moon”

The Nail

Eponychium(cuticle)

Nail plate(body)

Thermoregulation• Body temperature fluctuates very

throughout the day.• You’re at the highest at days end

and lowest in the morning• Biochemical reactions and

enzymes function within a narrow range

• Hypothalamus is the body’s thermostat

Abnormal Body TemperatureHeat Exhaustion• Body temperature remains normal• Loss of large amount of fluids and electrolytes• Vertigo, nausea and loss of consciousness

Heat Stroke• Body temp rises above 105 F• Tacycardia(rapid heart rate)• Hot dry skin• Confusion, convulsions• Body must be cooled immediately or death can result

Hypothermia• Body temp below 95 F• Slowed heart rate• Treated by slowly warming persons body

Frosbite• Damage results from ice crystals forming in skin• Necrosis results and if left gangrene can set in

Disorders of the SkinAlbinism• Every race has about the

same number of melanocytes• Skin color is determined by

the amount of melanin produced(genetic)

• Carotene, yellow pigment that also contributes to skin color(fat cells)

• The enzyme tyrosinase is needed to create melanin

• Sun exposure cause melanocyte to produce more melanin

• In albinism tyrosinase is absent thus they lack pigment in hair, skin and eyes

Disorders of the SkinEpidermolysis bullosa • Mutation in the keratin

gene.– Epidermis and dermis is not

held together.– any friction causes them to

separate and leave open sores and blister.

– Cases can range from mild to severe.

– Bone marrow transplants have proven beneficial.

Disorders of the Skin

Vitiligo• Charaterized by white patches of skin• Melanocytes no longer produce pigment

Disorders of the SkinOnycholysis• Seperation of nails from the nail bed• Usually occurs after trauma to nail

Disorders of the SkinImpetigo• Caused by staph or strep infections• Blisters with yellowish or dark scabs

Tinea• Fungal infections• Ringworm, athletes foot, thrush, jock

itch

Warts• Bumpy projections caused by

papilloma viruses• Easily removed

Boils• Staph infection of follicles• Large pus filled lesions

Disorders of the Skin

Acne• Result of overactive secretion of

sebaceous glands(5-10X more than normal)

• Pores are clogged and can form infected pustules

Blisters• Desmosomes are damaged by injury or

irritation• Immune response to protect skin

Calluses• Hardened skin formed by continual

pressure/rubbing

Corns• Thick hardened skin usually form in bony

areas as a result of friction

Burns

Can be caused by heat, electricity, UV rays or chemicals

First Degree• Only the epidermis is damaged,

sunburns normally are first degreeSecond Degree• Epidermis and top layer of dermis are

damaged, blisters form, may have shiny appearance

Third Degree• Entire depth of skin destroyed, black or

grayish in color. Skin cannot heal itself, graphs normally needed

First Degree

Third Degree

Second Degree

“rule of nines”

• Used to estimate the amount of skin burned