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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)
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