Chapter 5

The Integumentary System

Integumentary System

The body’s covering

Includes: skin, nails, and hairs, oil & sweat

glands & sensory receptors.

Skin: cutaneous membrane

Structure

Two main parts

Epidermis - surface epithelial layer

Dermis - deeper connective tissue layer

Subcutaneous (subQ) layer or hypodermis

lies deep to dermis; is not part of the skin

Integumentary System

Epidermis

Epidermis

Keratinized stratified squamous epithelium

Cell types (4):

Keratinocytes (90%)

Melanocytes (8%)

Langerhans cells

Merkel cells

Epidermal Cells

Keratinocytes

90% of epidermal cells

4-5 layers

Produce keratin

Protects skin

Waterproofs skin

Epidermal Cells

Melanocytes

Produce melanin that gives color to skin, hairs

Transfer pigment to keratinocytes

Make up 8% of epidermal cells

Epidermal Cells

Langerhans cells

Immune response

Merkel cells

Sense of touch

Consist of tactile disc and neuron for touch sensation

Epidermal Layers Four Layers (strata)

Stratum basale (aka. Stratum germinativum) Includes stem cells; new cells arise here

Stratum spinosum: 8-10 cell layer Cells beginning to look flattened

Stratum granulosum makes keratin Losing cell organelles and nuclei

Have waterproofing lipid

Stratum Lucidum Present only in skin of fingertips, soles & palms

Stratum corneum: flattened dead cells Cells here consist mostly of keratin.

Cells here are shed and replaced from below.

Epidermal Layers

Epidermal Layers

Keratinization & Growth of epidermis

EGF (Epidermal growth Factor)

Plays a role in this mechanism

Dandruff (Seborrheic Dermatitis)

Excessive amount of keratinized cells shed from

the skin of the scalp

CLINICAL CONNECTION:

PSORIASIS Abnormal division of

keratinocytes

Rapid movement from

stratum basale to stratum

corneum

Flaky, silvery scales at the

skin surface

Topical ointments & UV

phototherapy

Skin Color

Melanin: dark color

Darkness depends on amount of melanin

produced.

From melanosome

Provides some protection against UV rays

Carotene: yellow orange

In stratum corneum and adipose layers-

Hemoglobin in blood: pink-red

Depends on blood flow

Skin Color

Albinism

Inablity to produce melanin

Inability to synthesize tyronase

Vitiligo

Partial or complete loss of melanocytes from

patches of skin. Irregular white spots

Cyanotic

Bluish discoloration of the skin

Skin Color

Erythema

Redness or the skin

Engorgement of the capillaries

Jaundice

Yellowish color

Pallor

paleness

Dermis

Second major skin region containing strong,

flexible connective tissue (Collagen & elastic

fibers)

Stretches & recoils

Cell types include fibroblasts, macrophages,

and occasionally mast cells and white blood

cells

Composed of two layers – papillary and

reticular

Layers of the Dermis: Papillary Layer

Papillary layer

1/5 of the total layer

Areolar connective tissue with collagen and elastic

fibers

Its superior surface contains peglike projections

called dermal papillae

Dermal papillae contain capillary loops,

Meissner’s corpuscles, and free nerve endings

Layers of the Dermis: Reticular Layer

Reticular layer (Net-like)

Accounts for approximately 80% of the thickness

of the skin

Collagen fibers in this layer add strength and

resiliency to the skin

Elastin fibers provide stretch-recoil properties

Striae (stretch marks)

Red silvery white streaks on the surface of the skin

Hypodermis

Subcutaneous layer deep to the skin

Composed of adipose and areolar connective

tissue

Accessory Structures

Hair

Skin glands

Nails

Hair Found on most skin surfaces

Not on palmar surfaces of hand and fingers or plantar

surfaces of feet

Made of fused keratinized cells

Consists of shaft and root

Surrounded by hair follicle

Base is bulb which includes growing matrix producing

cells

Nerves in hair root plexuses

Muscle that pulls on hair: arrector pili

Causes hair to stand on end

Hair

Hair

Filamentous strands of dead keratinized cells

produced by hair follicles

Contains hard keratin which is tougher and

more durable than soft keratin of the skin

Made up of the shaft projecting from the skin,

and the root embedded in the skin

Consists of a core called the medulla, a

cortex, and an outermost cuticle

Pigmented by melanocytes at the base of the

hair

Hair Function and Distribution

Functions of hair include:

Helping to maintain warmth

Alerting the body to presence of insects on the

skin

Guarding the scalp against physical trauma, heat

loss, and sunlight

Hair is distributed over the entire skin surface

except

Palms, soles, and lips

Nipples and portions of the external genitalia

Hair Follicle

Root sheath extending from the epidermal

surface into the dermis

Deep end is expanded forming a hair bulb

A knot of sensory nerve endings (a root hair

plexus) wraps around each hair bulb

Bending a hair stimulates these endings,

hence our hairs act as sensitive touch

receptors

Hair Follicle

Figure 5.6a

Hair Follicle

Figure 5.6c

Hair growth

Anagen

Growth

Cells of the hair matrix divide

Catagen

Regression stage

Cell division stops, hair follicles atrophies

Telogen

Resting stage

Old hair falls out

Types of Hair

Vellus – pale, fine body hair found in children

and the adult female

“peach fuzz”

Terminal – coarse, long hair of eyebrows,

scalp, axillary, and pubic regions

Hair Thinning and Baldness

Alopecia – hair thinning in both sexes

True, or frank, baldness

Genetically determined and sex-influenced

condition

Male pattern baldness – caused by follicular

response to DHT

Hirsutism

Abnormal hair growth

GLANDS: Sebaceous

A bundle of smooth muscles (arrector pili)

“Goose bumps” or “Goose flesh”

Simple alveolar glands found all over the

body

Soften skin when stimulated by hormones

Secrete an oily secretion called sebum

GLANDS: Sebaceous

Acne

Inflammation of sebaceous glands

Cystic Acne

Cyst or a scar of connective tissue

Clindamycin

isotretinoin

Glands: Sweat glands

Sudoriferous (sweat) gland

Eccrine sweat gland (palms, soles, forehead) “emotional Sweating”

Wide distribution- thermoregulation

Apocrine sweat gland (axilliary, anogenital areas)

Mammary glands (specialized sweat glands)

Ceruminous (wax) gland

Wax combines with sebum to produce earwax

Impacted cerumen

Nails

Plates of packed hard dead keratinized cells

Nail body: major visible portion

Free edge: part extending past finger or toe

Root: cells deep to here (in nail matrix) form

new nail cells

Nails

Nails

Temperature regulation

Dilation (cooling) and constriction (warming) of

dermal vessels

Increasing sweat gland secretions to cool the

body

Protection (chemical, physical, and

mechanical barrier)

Sensory reception – exoreceptors sense

touch and pain

Functions of the Integumentary

System

Functions of the Integumentary

System

Metabolic functions – synthesis of vitamin D

in dermal blood vessels

Blood reservoir – skin blood vessels store up

to 5% of the body’s blood volume

Excretion – limited amounts of nitrogenous

wastes are eliminated from the body in sweat

Synthesis of Vitamin D

Requires UV

Calcitriol

Most active form of Vitamin D

Absorption of Calcium

Skin Cancer

Most skin tumors are benign and do not

metastasize

A crucial risk factor for nonmelanoma skin

cancers is the disabling of the p53 gene

Newly developed skin lotions can fix

damaged DNA

Skin Cancer

The three major types of skin cancer are:

Basal cell carcinoma

Squamous cell carcinoma

Melanoma

Basal Cell Carcinoma

Least malignant and most common skin

cancer

Stratum basale cells proliferate and invade

the dermis and hypodermis

Slow growing and do not often metastasize

Can be cured by surgical excision in 99% of

the cases

Squamous Cell Carcinoma

Arises from keratinocytes of stratum

spinosum

Arise most often on scalp, ears, and lower lip

Grows rapidly and metastasizes if not

removed

Prognosis is good if treated by radiation

therapy or removed surgically

Melanoma

Cancer of melanocytes is the most

dangerous type of skin cancer because it is:

Highly metastatic

Resistant to chemotherapy

Melanoma

Melanomas have the following characteristics

(ABCD rule)

A: Asymmetry; the two sides of the pigmented

area do not match

B: Border is irregular and exhibits indentations

C: Color (pigmented area) is black, brown, tan,

and sometimes red or blue

D: Diameter is larger than 6 mm (size of a pencil

eraser)

E: Evolving

Melanoma

Treated by wide surgical excision

accompanied by immunotherapy

Chance of survival is poor if the lesion is over

4 mm thick

Burns First-degree – only the epidermis is damaged

Symptoms include localized redness, swelling, and pain

Second-degree – epidermis and upper regions of dermis are damaged

Symptoms mimic first degree burns, but blisters also appear

Third-degree – entire thickness of the skin is damaged

Burned area appears gray-white, cherry red, or black; there is no initial edema or pain (since nerve endings are destroyed)

Rule of Nines

Estimates the severity of burns

Burns considered critical if:

Over 25% of the body has second-degree burns

Over 10% of the body has third-degree burns

There are third-degree burns on face, hands, or

feet

Rule of Nines

Figure 5.8a

Rule of Nines

Figure 5.8a

Pressure Ulcers

Aka decibitus ulcers/bedsores

Caused by deficient blood flow to tissues

Developmental Aspects of the

Integument: Fetal Epidermis develops from ectoderm

Dermis and hypodermis develop from

mesoderm

Lanugo – downy coat of delicate hairs

covering the fetus

Vernix caseosa – substance produced by

sebaceous glands that protects the skin of

the fetus in the amnion

Skin and hair become oilier and acne may

appear

Skin shows the effects of cumulative

environmental assaults around age 30

Scaling and dermatitis become more

common

Developmental Aspects of the

Integument: Adolescent to Adult

Epidermal replacement of cells slows and skin

becomes thinner

Skin becomes dry and itchy

Subcutaneous fat layer diminishes, leading to

intolerance of cold

Developmental Aspects of the

Integument:

Old Age

Decreased elasticity and loss of subcutaneous

tissue leads to wrinkles

Decreased numbers of melanocytes and

Langerhans’ cells increase the risk of skin

cancer

Developmental Aspects of the

Integument:

Old Age

Aging

Adolescence: can develop acne

Most effects in dermis, with visible signs of aging by about age 40. These include:

Loss of collagen fibers

Loss of elasticity

Loss of immune responses

Decreased melanocyte functions: gray hair, skin blotches

Thinning of skin and hairs

Anti-aging treatments

Anti-aging Treatments

Topical products Hydroquinone

Retinoic acid

Microdermabrasions

Chemical peel Glycolic acid

Laser resurfacing

Fat transplantation Botox

Radio frequency nonsurgical facelift, browlift

Thread lifts

Medical Terminology

Medical Terminology