The Integumentary System

Chapter 5

Chapter 5 Outline

Epidermis, dermis, hypodermis- structure/function

Skin color

Sunlight & vitamin D3

Hair

Glands

Nails- structure

Integumentary System

Largest system of the body

16% of body weight

1.5 to 2 m2 in area

1st line of defense

Made up of 2 parts

Cutaneous membrane

Accessory structures

Cutaneous Membrane

Cutaneous membrane has 2 components

Epidermis (outer)

Superficial epithelium (epithelial tissues)

Dermis (inner)

Connective tissues

Accessory Structures

Originate in the dermis

Extend through the epidermis to skin surface

Hair

Nails

Multicellular exocrine glands

Introduction to the Integumentary System

Connected to other systems

Cardiovascular system

Blood vessels in the dermis

Nervous system

Sensory receptors for pain, touch, temperature

Integumentary System

Subcutaneous layer (superficial fascia or

hypodermis)

Loose connective tissue

Below the dermis

Location of

hypodermic injections

Components of the Integumentary System

Functions of Skin

Protects underlying tissues and organs

Excretes salts, water, and organic wastes (glands)

Maintains body temperature (insulation &

evaporation)

Synthesizes vitamin D3

Stores lipids

Detects touch, pressure, pain, and temperature

Basic Organization of the Epidermis

Avascular stratified squamous epithelium

Nutrients, oxygen diffuse from capillaries in dermis

Mechanical & pathogen protection

Cells of the Epidermis

Keratinocytes

Contain large amounts of keratin

Most abundant cells in epidermis

Basic Organization of the Epidermis

Thin SkinCovers most of body

4 layers of keratinocytes Thick Skin

Covers palms & soles

5 layers of keratinocytes

Structure of Thick Epidermis

.

1

2

3

4

5

Stratum Germinativum

Germinative layer

Many germinative cells (basal cells)

Attached to basal lamina by hemidesmosomes

Forms strong bond between epidermis & dermis

Forms epidermal ridges (fingerprints)

Dermal papillae (tiny mounds)

Increase area of basal lamina

Strengthen attachment between epidermis &

dermis

Epidermal Ridges of Thick Skin

Stratum Spinosum

Spiny layer

Produced by division of stratum germinativum

8 -10 layers of keratinocytes bound by desmosomes

Cells shrink until cytoskeletons stick out (spiny)

Continue to divide, increasing thickness of

epithelium

Stratum Granulosum

Grainy layer, 3-5 layers keratinocytes

Stops dividing, starts producing

Keratin- tough, fibrous protein makes up hair, nails

Keratohyalin- forms dense granules promote cross-

linking of keratin fibers

Stratum Lucidum

Clear layer

Found only in thick skin

Covers stratum granulosum

Stratum Corneum

Exposed surface of skin

15 - 30 layers keratinized cells

Water resistant

Shed & replaced every 2 weeks

Stratum Corneum

Keratinization- formation of layer of dead,

protective cells filled with keratin

Occurs on all exposed skin surfaces except eyes

15–30 days for cell to move from stratum

germinativum to stratum corneum

Each of the following is a function of the

integumentary system, except

A. Protection of underlying tissue

B. Excretion of salts & wastes

C. Synthesis of vitamin C

D. Maintenance of body temperature

Perspiration

Insensible perspiration

Interstitial fluid lost by evaporation through the

stratum corneum, pint/day

Sensible perspiration

Water excreted by sweat glands

Dehydration- damage to stratum corneum (burns,

blisters) increase rate insensible perspiration

Burns- reduce water barrier, dangerous fluid loss

Immersion in hypertonic solution (seawater- water flows

out of cells, osmosis)

Skin Color

Skin color is influenced by 2 pigments

Carotene: orange-yellow pigment

Found in orange vegetables

Accumulates in epidermal cells & fatty tissues of dermis

Can be converted to vitamin A

Melanin: yellow-brown or black pigment

Produced by melanocytes in stratum germinativum

Stored in transport vesicles (melanosomes)

Transferred to keratinocytes

Melanocytes

Manufacture melanin from tyrosine and

package it in intracellular vesicles-

melanosomes

Melanocytes- Pigment Transfer

Melanosome are transferred to keratinocytes- color temporary

Melansome will fuse with lysosome and be broken down

Skin Pigmentation

Pale skin- transfer occurs in

stratum germinativum &

spinosum, superficial layers lose

pigmentation

Dark skin- transfer occurs in

stratum granulosum as well,

darker pigmentation

Skin Pigmentation

Skin pigmentation differences generally

not number of melanocytes, different

levels of synthesis of melanin

Freckles

Rates of melanin production different by your own

melanocytes

Face, shoulders

Liver spots- senile lentigos

Function of Melanocytes

Melanin protects skin from sun damage

UV radiation causes DNA mutations & burns-

lead to cancer & wrinkles

Dermal Circulation

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

Illness and Skin Color

Jaundice- buildup of bile produced by liver, yellow

color

Addison disease- disease of pituitary gland,

produce ACTH, skin darkening

Vitiligo- loss of melanocytes, loss of color

Vitamin D3

Epidermal cells produce

cholecalciferol (vitamin D3)

in the presence of UV

radiation

Liver & kidneys convert

vitamin D3 into calcitriol

Aid absorption of calcium

& phosphorus

Insufficient vitamin D3 can

cause ricketsBending of weak

bones under weight

of body

Dermis

Located between epidermis & subcutaneous

layer

Anchors epidermal accessory structures (hair

follicles, sweat glands)

Has 2 components:

Outer papillary layer

Deep reticular layer

Dermis- Papillary Layer

Areolar tissue- contains smaller capillaries, lymphatics, sensory neurons

Dermal papillae projecting between epidermal ridges

Dermis- Reticular Layer

Dense irregular connective tissue- contains larger blood vessels, lymph vessels, nerve fibers

Contains collagen and elastic fibers

Contains connective tissue proper

Dermatitis

Inflammation of papillary layer

Caused by infection, radiation, mechanical

irritation, or chemicals (poison ivy)

Characterized by itch or pain

Dermal Strength and Elasticity

Presence of 2 fibers:

Collagen fibers: very strong, resist stretching but

bend easily- provide flexibility

Elastic fibers: permit stretching & then recoil to

original length- limit flexibility of collagen fibers to

prevent damage to tissue

Skin turgor- properties of flexibility & resilience

Affected by water content

Skin Damage

Sagging and wrinkles (reduced skin elasticity) caused:

Dehydration

Age

Hormonal changes

UV exposure

Stretch Marks

Thickened tissue resulting from excessive stretching of

skin due to pregnancy, weight gain

Lines of Cleavage of the Skin

Collagen & elastic fibers in the dermis

Arranged in parallel bundles

Resist force in a specific direction

Establish important patterns

Parallel cut remains shut, heals well

Cut across (right angle) pulls open & scars

Dermal Circulation

Network of arteries

along reticular

layer

Capillary network

from small

arteries in

papillary layer

Capillary return deep to papillary plexus

Hypodermis

Subcutaneous layer

Lies below the integument

Stabilizes the skin

Allows separate movement

Made of elastic areolar & adipose tissues

Connected to reticular layer of integument by

connective tissue fibers

Has few capillaries and no vital organs

Site of subcutaneous injections using hypodermic

needles

The 2 major components of the dermis

are the

A. Papillary layer and reticular layer

B. Superficial fascia & cutaneous

membrane

C. Epidermis and hypodermis

D. Stratum germinativum & stratum

corneum

Integumentary Accessory Structures

Hair, hair follicles, sebaceous glands,

sweat glands, nails

Derived from embryonic epidermis

Located in dermis

Project through the skin surface

Hair

The human body is covered with hair, except

Palms

Soles

Lips

Functions of Hair

Protects and insulates

Guards openings against particles and insects

Sensitive to very light touch

Hair Follicle

Located deep in dermis

Produces nonliving hairs

Is wrapped in a dense

connective tissue sheath

Base is surrounded by

sensory nerves- root hair

plexus

Accessory Structures of Hair

Arrector pili

Involuntary smooth muscle

Causes hairs to stand up

Produces “goose bumps”

Sebaceous glands

Lubricate the hair

Control bacteria

Hair Follicles

[INSERT FIG. 5.10c]

Exocrine Glands in Skin

Sebaceous glands (oil glands)

Holocrine glands (rupture of secretory cell)

– Secrete sebum- oily lipid secretion, lubricates & protects

epidermis (inhibits bacterial growth)

Sebaceous follicles

Discharge directly onto skin surface

– Face, back, chest, nipples, external genitalia

Sweat glands (sudoriferous)

Two types: apocrine and merocrine (eccrine) glands

Watery secretions

Sweat Glands

Apocrine Sweat Glands- actually merocrine secretion

Found in armpits, around nipples, groin

Secrete products into hair follicles

Begin secreting at puberty

Produce sticky, cloudy secretions, break down & cause odors

Merocrine Sweat Glands

Widely distributed on body surface, especially palms & soles

More numerous than apocrine sweat glands

Discharge directly onto skin surface

Sensible perspiration

Functions: cool skin, excretes water & electrolytes, flushes

microbes & harmful chemicals from skin

Sweat Glands

.

Aprocrine

sweat

gland

Merocrine

sweat

gland

Other Integumentary Glands

Mammary glands

Produce milk

Ceruminous glands

Produce cerumen

(earwax)

Protect the eardrum

Nails

Protect fingers and toes

Made of dead cells packed with keratin

Metabolic disorders can change nail structure

Yellow- chronic respiratory disorder, thyroid disorder, AIDS

Concave- blood disorder

Structure of a Nail

Nail body- visible portion of the nail, covers nail bed

Lunula- pale crescent at base of nail

Sides of nails lie in lateral nail grooves

Surrounded by lateral nail folds

Important Concepts Ch 5

Know functions, structure, cell types of:

Cutaneous membrane

Epidermis- epithelial tissue

– Thin/thick skin, stratums

Dermis- connective tissue

– Outer papillary layer & deep reticular layer

Subcutaneous layer (superficial fascia or hypodermis)

Loose connective tissue below dermis

Skin color production

Cholecalciferol (Vitamin D3) production

Dermal Strength and Elasticity- fibers, damage, lines of

cleavage, circulation

Accessory structures- functions, structure