Introduction to the Integumentary System

The integument is the largest system of

the body

16% of body weight

1.5 to 2 m2 in area

The integument is made up of two parts

______________________ membrane (skin)

Accessory structures (hair, nails, exocrine glands)

Introduction to the Integumentary System

Fig 5–1

Introduction to the Integumentary System

Origin

Ectoderm

Cells that respond to FGF2 turn into nervous tissue. Cells

that don’t turn into skin

Connections

Cardiovascular system

Blood vessels in the papillary layer of the dermis

Nervous system

Sensory receptors for pain, touch, and temperature

Introduction to the Integumentary System

Functions of Skin

Protects underlying tissues and organs (U.V., invaders)

Excretes salts, water, and organic wastes (glands)

Maintains body temperature (insulation and evaporation)

Synthesizes vitamin D3

Stores lipids

Detects touch, pressure, pain, and temperature

Epidermis

The most abundant cells of the epidermis are ____________.

Contain large amounts of keratin

Epidermis is avascular stratified squamous epithelium

Nutrients and oxygen diffuse from capillaries in the dermis

Thin Skin: Covers most of the body

Has four layers of keratinocytes

Thick Skin: Covers the palms of the hands and soles of the

feet

Has five layers of keratinocytes

Lacks hair and sebaceous glands

Epidermis

Fig 5-3

The S. coreum would be thinner in thin skin. The S. lucidum is found only in thick skin.

Epidermis

Stratum Germinativum (Stratum Basale) The “germinative layer”

Has many germinative (stem) cells or basal cells

Is attached to basal lamina by hemidesmosomes

Forms a strong bond between epidermis and dermis

Forms ____________________(e.g., fingerprints)

Dermal papillae (tiny mounds) Increase the area of basal lamina

Strengthen attachment between epidermis and dermis

Epidermis

Fig 5-4

Fig. 5-2

Dermal papilla: Tiny mounds that (1) increase the area of the basal lamina and (2) strengthen the attachment between the epidermis and the dermis

Epidermis

Specialized Cells of Stratum Germinativum

______________________(1% of cells in the skin)

Found in hairless skin (sensory function)

Respond to touch (trigger nervous system)

______________________ (3% of cells in the skin)

Contain the pigment melanin

Scattered throughout stratum germinativum

Epidermis

Stratum Spinosum

The “spiny layer”

Produced by division of stratum germinativum

Eight to ten layers of keratinocytes bound by desmosomes

Cells shrink until cytoskeletons stick out (spiny)

Continue to divide, increasing thickness of epithelium

Contain dendritic (______________) cells, active in

immune response

Epidermis

Stratum Granulosum

The “grainy layer”

Cells stop dividing, produce protein fibers, dehydrate,

and die

Keratin:

– a tough, fibrous protein

– makes up hair and nails

Keratohyalin :

– dense granules

– cross-link keratin fibers

Epidermis

Stratum Lucidum

The “clear layer”

Found only in thick skin

Covers stratum granulosum

Epidermis

Stratum Corneum

The “horn layer”

Exposed surface of skin

15 to 30 layers of keratinized cells

Water resistant

Shed and replaced every 2 weeks

Epidermis

Keratinization

The formation of a layer of dead, protective

cells filled with keratin

Occurs on all exposed skin surfaces except

eyes

Skin life cycle

It takes 15–30 days for a cell to move from

stratum germinativum to stratum corneum

Dandruff is caused by excessive shedding of cells from the outer layer of skin in the scalp. Thus

dandruff is composed of cells from which epidermal layer?

1. Stratum germinativum2. Stratum spinosum3. Stratum corneum4. Stratum granulosum

Skin Color Skin color is influenced by

Two pigments ______________________:

– orange-yellow pigment– found in orange vegetables– accumulates in epidermal cells and fatty tissues of the

dermis– can be converted to vitamin A

______________________:– yellow-brown or black pigment– produced by melanocytes from tyrosine in the stratum

germinativum– stored in transport vesicles (melanosomes)– transferred to keratinocytes

Blood circulation (red blood cells)

Skin Color

Fig 5-5

(contains melanin)

(in melanosome)

Skin Color

Function of Melanocytes

Melanin protects skin from sun damage

Ultraviolet (UV) radiation

Causes DNA mutations and burns that lead to cancer and

wrinkles

Production of cholecalciferol (Vit. D3) within epidermal cells

Stimulates secretion of melanocyte stimulating hormone from

keratinocytes (this gives you a tan)

Skin color depends on melanin production (bigger

melanosomes), ____________ number of melanocytes

Skin Color

Localized differences in rates of melanin production by melanocytes: Freckles:

Small pigmented areas with irregular borders on relatively pale skin.

Most abundant on surfaces with greater exposure to the sun (e.g., face).

Lentigos: Similar to freckles, but have regular borders and contain

abnormal melanocytes.

Senile lentigos (liver spots/age spots): Variable pigmented areas on sun-exposed skin in older

individuals with pale skin.

Skin Color

Capillaries and Skin Color Oxygenated red blood contributes to skin

color Blood vessels dilate from heat, skin reddens

Blood flow decreases, skin pales

Cyanosis Bluish skin tint

Caused by severe reduction in blood flow or

oxygenation

Skin Color

Illness and Skin Color Jaundice

Buildup of bile produced by liver Yellow color (i.e., yellow pigment accumulates in

body fluids)

Addison disease A disease of the pituitary gland Skin darkening (i.e., secretion of large qunatities of

ACTH, a hormone structurally similar to MSH)

Vitiligo (1% of population) Loss of melanocytes (attacked by lymphocytes) Loss of color

Skin Cancer

Basal cell carcinoma = most common. Squamous cell carcinomas = restricted to areas

of sun-exposed skin.

Malignant melanomas = metastasize through the lymphatic system. A = Asymmetry B = Border C = Color D = Diameter

Why does the skin of a fair-skinned person appear red during exercise in hot weather?

1. Sunlight stimulates erythrocyte production in skin.

2. Blood is diverted to the superficial dermis to eliminate heat.

3. Sunlight bleaches fair skin, allowing blood to be seen.

4. Heat stimulates cutaneous blood vessels, causing leaks.

Vitamin D3

Vitamin D3

Epidermal cells in s. spinosum and s. basale produce cholecalciferol (vitamin D3)

In the presence of UV radiation

Liver and kidneys convert vitamin D3 into

calcitriol To aid absorption of calcium and phosphorus

Essential for bone maintenance and growth

Insufficient vitamin D3

Can cause __________________ in children and osteomalacia in adults.

Vitamin D3

Fig 5-7

In some cultures, women must be covered completely, except for their eyes, when they go

outside. Explain why these women exhibit a high incidence of problems with their bones.

1. UV light prevents calcium deposition in bones.

2. Melanin production is necessary for bone growth.

3. Cloth prevents oxygen from diffusing into skin and bones.

4. UV light is necessary to produce the hormone cholecalciferol (vitamin D3).

Epidermal Growth Factor (EGF)

Is a powerful peptide growth factor

Is produced by glands (salivary and duodenum)

Is used in laboratories to grow skin grafts

Functions of EGF Promotes division of germinative cells

Accelerates keratin production

Stimulates epidermal repair

Stimulates glandular secretion

The Dermis

The Dermis

Is located between epidermis and

subcutaneous layer

Anchors epidermal accessory structures (hair

follicles, sweat glands)

Has two components Outer papillary layer

Deep reticular layer

The Dermis

The Papillary Layer Consists of areolar tissue Contains smaller capillaries, lymphatics, and sensory

neurons Has dermal papillae projecting between epidermal

ridges

The Reticular Layer Consists of dense irregular connective tissue Contains larger blood vessels, lymph vessels, and

nerve fibers Contains collagen and elastic fibers Contains connective tissue proper

The Dermis

Dermatitis

An inflammation of the papillary layer

Caused by infection, radiation, mechanical

irritation, or chemicals (e.g., poison ivy)

Characterized by itch or pain (due to

abundance of sensory receptors in skin.

The Dermis

Dermal Strength and Elasticity Presence of two types of fibers

Collagen fibers:– very strong, resist stretching but bend easily

– provide flexibility

Elastic fibers:– permit stretching and then recoil to original length

– limit the flexibility of collagen fibers to prevent damage to tissue

Properties of flexibility and resilience

Skin turgor:

Skin Damage (dermal level) Sagging and wrinkles (reduced skin elasticity)

are caused by: Dehydration (loss of skin turgor) Age Hormonal changes UV exposure

Stretch Marks (Thickened tissue resulting from excessive stretching of skin due to): Pregnancy Weight gain/loss Note: Tetinoin (Retin-A), a derivative of Vit. A,

increases blood flow to dermis and stimulates dermal repair leading to a decrease in wrinkles.

The Dermis

Lines of Cleavage

Collagen and elastic fibers in the

dermis Are arranged in parallel bundles

Resist force in a specific direction

Lines of cleavage establish important

patterns A parallel cut remains shut, heals well

A cut across (right angle) pulls open and

scars

Fig 5.8

The Hypodermis

The __________________ layer or hypodermis Lies below the integument

Is connected to the reticular layer of integument by connective tissue fibers

Is made of elastic areolar and adipose tissues

(Subcutaneous fat deposits can be reduced by lipoplasty)

Has few capillaries and no vital organs (only the superficial region or reticular layer of the dermis has large arteries and veins.

Is the site of subcutaneous injections using hypodermic needles

Hair

Hair, hair follicles, sebaceous glands,

sweat glands, and nails

Are integumentary accessory structures

Appendages of the skin that represent

specializations of keratinocytes that extend from

the connective tissue to the skin

Are derived from embryonic epidermis

Are located in dermis

Project through the skin surface

Hair

The Hair Follicle

Is located deep in dermis

Produces nonliving hairs

Is wrapped in a dense

connective tissue sheath

Base is surrounded by

sensory nerves (root hair

plexus)

Hair

Hair Shaft Structure

Medulla

The central core

Cortex

The middle layer

Cuticle

The surface layer

Cross-Section Through a Hair Follicle

Fig 5.10

Hair

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

Hair

Accessory Structures of Hair

_______________________

Involuntary smooth muscle

Causes hairs to stand up

Produces “goose bumps”

________________________

Lubricate the hair

Control bacteria

Fig 5.10

Hair Hair Color:

Produced by melanocytes at the hair papilla

Determined by genes

Alopecia Areata:

Ability to produce hair is gone (2% of population)

Due to immune system attack on the hair follicles

Male Pattern Baldness:

Hair growth is inhibited by testosterone receptor alterations (50% of

men over 50)

Rogaine can stimulate production of growth factors that stimulate

weakened hair follicles to create larger amounts of hair

Which two events are possible results of the contraction of the arrector pili muscle?

1. Goose bumps/release of sebum

2. Sweating/contraction of underlying muscles

3. Goose bumps/localized increase in blood flow

4. Localized pallor/release of sebum

Sebaceous Glands and Sweat Glands Exocrine Glands in Skin

Sebaceous glands (oil glands)

Simple branched alveolar glands are associated with

hair follicles

Holocrine glands

Secrete sebum (lipids and other stuff that lubricate and

protect the epidermis while inhibiting bacteria)

Sweat glands

Two types: apocrine glands and merocrine (eccrine)

glands

Watery secretions

Clinical Correlations

Folliculitis: Local inflammation of hair follicle as a result of a

bacterial infection.

Furuncle or “boil”: Abscess from blockage of a gland’s duct.

Acne: Due to increased concentration of sex hormones

during puberty.

Seborrheic dermatitis: Inflammation around abnormally active sebaceous

glands Sebaceous glands and sweat glands

Sebaceous Glands and Sweat Glands

____________________ sweat glands

Found in armpits (axillae), 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

Sebaceous Glands and Sweat Glands

__________________ (Eccrine) sweat glands Widely distributed on body surface Especially on palms and soles Coiled, tubular glands Discharge directly onto skin surface Sensible perspiration (water is excreted by sweat glands) Water, salts, and organic compounds Functions of merocrine sweat gland activity

Cools skin Excretes water and electrolytes Flushes microorganisms and harmful chemicals from skin

Other Integumentary Glands

Mammary glands: Anatomically related to apocrine sweat glands Sexual and pituitary hormones control their

development and secretion Produce milk

Ceruminous glands: Modified sweat glands in external ear Produce cerumen (earwax) Protect the eardrum

Control of Glandular Secretions

Control of Glands Autonomic nervous system

Controls sebaceous and apocrine sweat glands Works simultaneously over entire body

Merocrine sweat glands Are controlled independently Sweating occurs locally

Thermoregulation Is the main function of sensible perspiration Works with cardiovascular system Regulates body temperature

What are the functions of sebaceous secretions?

1. Inhibits the growth of bacteria

2. Lubricates and conditions the surrounding skin

3. Lubricates and protects the keratin of the hair shaft

4. All of the above

Nails

Nails protect fingers and toes

Made of dead cells packed with keratin

Metabolic disorder can change nail structure,

shape or appearance

Fig 5-13

Nails

Fig 5-13

(Cuticle)

Nails

Yellow nails: Chronic resp. disorders, thyroid gland disorders, or

AIDS

Blue-purple nails: Hypoxemia (e.g., congenital heart defect) Cynaosis

Pitted and distorted nails: Psoriasis

Concave (spoon) nails: Blood disorder (e.g., iron deficiency anemia)

Clubbing of nails: Hypoxemia (e.g., COPD, emphysema)

Repair of the Integument

Bleeding occurs

Mast cells trigger inflammatory response

A blood clot or scab stabilizes and protects the

area

Germinative cells migrate around the wound

Macrophages clean the area

Fibroblasts and endothelial cells move in,

producing granulation tissue

Repair of the Integument

Fig 5-14

1. Blood clot and scab formation

Repair of the Integument

Fig 5-14

2. Cellular migration

Repair of the Integument

Fig 5-14

3. Epidermis covers granulation tissue

Repair of the Integument

Fig 5-14

4. Epidermis covers scar tissue

Repair of the Integument

Fig 5-15

Fibroblasts produce scar tissueInflammation decreases, clot disintegratesFibroblasts strengthen scar tissueA raised keloid may form

Rule of Nines

Method for estimating the percentage of surface area affected by burns.

Importance of the Integumentary System

Importance of the Integumentary System

Importance of the Integumentary System

Importance of the Integumentary System