The Integumentary System

skin is the boundary that separates the

human body from the outside world.

“SKIN” - the single largest organ in the

Body

it comes from a Latin word that means to

cover, reflecting the fact that the skin and

its accessory structures form a covering

over the entire body.

What make up the

Integumentary

System?

The skin and its accessory

organs --- the hair, nails,

Sweat & sebaceous glands.

Dermatology is the medical

specialty for the diagnosis

and treatment of disorders

of the integumentary

system.

Functions of the IntegumentarySystem▪ Protection – chemical, physical, and mechanical barrier

▪ Body temperature regulation is accomplished by:

▪ Cutaneous sensation – exoreceptors sense touch and pain

▪ 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

▪ Consists of three major regions

▪ Epidermis – outermost superficial region

▪ Dermis – middle region

▪ Hypodermis (superficial fascia) – deepest region

Epidermis

Keratinized stratified squamous epithelium

Four types of cellsKeratinocytes –deepest, produce keratin (tough fibrous protein)

Melanocytes - make dark skin pigment melanin

Merkel cells –associated with sensory nerve endings

Langerhans cells –Macrophage-like dendritic cells

(see figure on next slide)

Epidermis is the outermost layer of the skin.

Most of the cells of the epidermis undergo

rapid cell division (mitosis). As new cells

are produced, they push the older cells to

the surface of the skin. Here are the older

cells become flattened, lose their cellular

contents. And begin making keratin.

What is keratin?

- a tough fibrous protein

In humans, it forms the basic structure of

hair, nails, and calluses.

Keratinocytes, the keratin-producing

cells, die and form a tough, flexible

waterproof covering on the surface of the

skin. This outer layer of dead cells is shed

or washed away at a surprising rate – once

over 14 to 28 days.

The epidermis also contains

melanocytes, or cells that produce melanin,

a dark pigment. Although light-skinned and

dark-skinned people have roughly the

same number of melanocytes, the

difference in their skin color is caused by

the amount of melanin the melanocytes

produce and distribute. There are no blood

vessels in the epidermis, which explains

why a slight scratch will not cause bleeding.

What is dermis?

It is the innermost layer of the skin. It lies

beneath the epidermis and contains blood

vessels, nerve endings, glands, sense

organs, smooth muscles, and hair follicles.

DermisStrong, flexible connective tissueCells: fibroblasts, macrophages, mast cells, WBCs

Fiber types: collagen, elastic, reticular.Rich supply of nerves and vesselsCritical role in Temperature regulation (the vessels)

Remember…

Four basic types of tissue

Epithelium –epidermis just discussed

Connective tissue - dermis

Muscle tissue

Nervous tissue

Fingerprints, palmprints, footprints

Dermal papillae lie atop dermal ridgesElevate the overlying epidermis into epidermal ridgesAre “sweat films” because of sweat poresGenetically determined

The dermis is the receptive site

for the pigment of tattoos

Fingerprints, palmprints, footprints

Flexion creases

Deep dermis, from continual folding

Fibers

Collagen: strength and resilience

Elastic fibers: stretch-recoil

Striae: stretch marks

Tension lines

The direction the bundles of fibers are

directed

Beneath the dermis is the hypodermis,

a layer of fat and loose connective tissue

that insulates the body.

Subcutaneous layer deep to the skin

Skin Color

▪ Three pigments contribute to skin color

▪ Melanin – yellow to reddish-brown to black

pigment, responsible for dark skin colors

▪ Freckles and pigmented moles – result from local

accumulations of melanin

▪ Carotene – yellow to orange pigment, most

obvious in the palms and soles of the feet

▪ Hemoglobin – reddish pigment responsible for the

pinkish hue of the skin

Hair

▪ Filaments of dead keratinized cells produced by hair follicles

▪ Contains hard keratin

▪ Made up of the shaft projecting from the skin, and the root embedded in the skin

▪ called the medulla, a cortex, and an outermost cuticle

▪ Pigmented by melanocytes at the base of the hair

Hair Distribution

▪ Hair is distributed over the entire skin surface except:

▪ Palms, soles, and lips

▪ Nipples and portions of the external genitalia

Types of Hair

▪ Vellus – pale, fine body hair found in children and

the adult female

▪ Terminal – coarse, long hair of eyebrows, scalp,

axillary, and pubic regions

CLEAVAGE (TENSION) LINES

ANDSTRIAE• Cleavage (tension) lines:

elastin and collagen fibers

oriented in some directions

more than in others

• Important in surgery

• If incision parallel tolines, there is lessgapping, faster healing,less scar tissue

• If skin is overstretched,striae (stretch marks) occur

NAILS

Nails are composed of hard, keratinizedepidermal cells located over the dorsalsurfaces of the ends of fingers and toes

Each nail consists of:

free edge

transparent nail body (plate) with a whitish

lunula at its base

nail root embedded in a fold of skin

NAILS

What are the two major types of glands contained

in the dermis?

Sweat glands and Sebaceous or oil glands

These glands pass through the epidermis

and release their products at the surface of

the skin. Sweat glands produce the watery

secretion known as sweat, which contains

salts, water, and other compounds.

Sebaceous (oil) glands

Entire body except palms and soles

Produce sebum by holocrine secretion

Oils and lubricates

Sweat glands

Entire skin surface except nipples and part of external genitalia

Prevent overheating

Disorders of the integumentary systemBurns

Threat to life

Catastrophic loss of body fluids

Dehydration and fatal circulatory shock

Infection

Types

First degree –epidermis: redness (e.g. sunburn)

Second degree –epidermis and upper dermis: blister

Third degree - full thickness

Infections

Skin cancer

BurnsFirst-degree(epidermis only; redness)

Second-degree(epidermis and dermis,

with blistering)

Third-degree(full thickness, destroying

epidermis, dermis, often

part of hypodermis)