INTEGUMENTARY SYSTEM
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I. Integumentary Structure and Function
A.
The integument is the largest organ of the
body, and together with its epidermal structures
(hair, glands and nails) it is the integument
system.
1. The skin is considered an organ since it
consists of several kinds of tissues that function
together.
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2. The skin varies in thickness, the thickest
parts of the body exposed to wear and
abrasion, soles of feet and palms of hands.
3. The thinnest is the eyelids, external
genitalia and tympanum.
4. Skin variations help to identify some
underling problem. Example – pale skin- shock,
red skin- infection.
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B. Development of the Associated Structures
1. Hair, glands and nails develop from the
germinal layer of the epidermis and are
ectodermal in organ.
2. Before hair can form, a hair follicle must be
present.
3. Each hair follicle begins to develop about 12
weeks.
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4. Sebaceous glands and sweat glands
are both two important aspects of the
integumentary system. Both develop from
the germinal layer of the epidermis.
5. Mammary glands are modified sweat
glands, which develop like sweat glands.
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6. Nails begin developing at about ten
weeks.
7. The thickened area of epidermis is
called the nail field.
8. The nail itself is called the nail plate.
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C. The integumentary system has two major
components: the cutaneous membrane and the
accessory structures.
1. Cutaneous membrane or skin is an organ
composed of epidermis and the underlying
connective tissues of the dermis.
2. Large stem cells or germinative cells,
culminate the stratum germinativum
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3. The accessory structures include hair,
nails and endocrine glands.
4. Beneath the dermis, is the
subcutaneous layer or the hypodermis,
which attaches the integument to muscles
or bones.
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5. Five functions of the integument are:
protection, temperature maintenance,
synthesis and storage of nutrients,
sensory reception and
excretion/secretion.
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D. The Epidermis
1. The epidermis consists of a stratified squamous
epithelium of several different cell layers.
2. In thick skin (the thickest found on palms of your
hands and soles of the feet) have five layers.
3. Thin skin only has three layers.
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E. Layers of the Epidermis
1. Stratum Germinativum- The deepest epidermal
layer. Also called stratum basale. The stratum
germinativum forms epidermal ridges.
2.
Stratum granulosum consists of cells
displaced. they make amounts of keratin.
Keratin is water-resistant.
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3. The most superficial layer of the
epidermis is the stratum corneum,
consists of 15-30 layers of flattened and
dead epithelial cells that have
accumulated large amounts of keratin.
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F. The color of your skin is caused by epidermal
pigmentation and dermal blood supply.
1. The epidermis contains two skin pigments
carotene (orange-yellow) and Melanin (brown,
yellow- brown or black pigmentation)
2. Melanocytes make and store melanin.
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3. Melanocytes activity slowly increases in
response to sunlight.
4. Freckles are areas of larger than
average melanin production.
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5. Sunlight contains significant amounts of
Ultraviolet radiation (UV). A small amount of
UV is necessary for the production of vitamin D.
6. Vitamin D is absorbed by the liver and then
converted by the kidneys into calcitriol, a
hormone essential for the absorption of calcium
and phosphorous. Low levels of Vitamin D can
lead to abnormal bone growth
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7. To much exposure to UV can cause
serious burns or cancer
8. Despite the presence of melanin, longterm damage can result form repeated
exposure, even in darkly pigmented
individuals.
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G. Dermal Circulation
1. Blood with abundant oxygen is bright red,
which is apparent in lightly pigmented
individuals.
2. Skin takes on a bluish color when it has low
levels of oxygen or when the skin is very cold.
This condition is called cyanosis. It can occur
for poor circulatory disorders (blue lips, skin)
and heart conditions.
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H. Skin Cancer
1. Skin cancers are the most common form of
cancer.
2. Basal cell carcinoma is a malignant cancer that
originates in the stratum basal layer. This is the
most common skin cancer.
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3. Less common are
squamous cell
carcinomas.
Metastasis
(spreading) seldom
occurs in either
cancer, and most
people survive these
cancers.
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4. Melanomas are extremely dangerous.
5. Melanomas usually begins from a mole
but may appear anywhere in the body.
This type of cancer grows quickly and
metastasizes through the lymphatic
system.
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6. The outlook for long-term survival
depends on when the condition was
detected and treated.
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II. The Dermis
A. Layers of the dermis
1.
The papillary layer consists of loose connective tissue
that supports ad nourishes the epidermis.
2.
The deeper reticular layer consists of irregular
connective tissue.
3.
The dermis contains a mixed cell population that
include small of the cells of connective tissue.
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B. The subcutaneous layer
1. The subcutaneous layer (hypodermis)
consists of loose connective tissue with many
fat cells.
2. These adipose (fat) cells provide infants and
small children with a layer of baby fat, which
helps them reduce heat loss.
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4. Subcutaneous fat acts as in insulator
and also serves as energy reserve and a
shock absorber.
5. As we grow where we store fat
changes.
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6.
Men tend to
store it in the neck,
upper arms and
along the lower back
and over the
buttocks.
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7. Women store in their breasts,
buttocks, hips and thighs.
8. Both men and women can also store
adipose tissue in the abdominal region,
“pot belly.”
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C.
1.
Assessory structures
Accessory structures include hair follicles,
sebaceous glands, sweat glands and nails.
2. Hairs project above the surface of the skin
almost everywhere except over the sides and
soles of the feet, palms of the hands and sides
of the fingers and toes, lips and portions of the
external genital organs.
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3. Hairs are nonliving structures produced in
organs called hair follicles.
4. Hair follicles project deep into the dermis
and often extend into the underlying
subcutaneous layer.
5. Hair papilla is a peg of connective tissue
containing capillaries and nerves.
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6. A hair root is the portion that anchors
the hair into the skin.
7. The hair shaft is the part we see on
the surface
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8. We have over 5 million hairs on our body
and they all serve important functions.
9. The roughly 100,000 hairs on our head
protect our scalp from UV light, helps cushion a
light blow to the head and provides insulation
benefits for the skull.
10. Nose hairs, ear hairs and eyelashes protect
entry of foreign particles and insects.
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11. Arrector pili muscles extend from the
papillary dermis. When stimulated it makes the
hairs stand up. Could be caused by emotions
or response to cold.
12. Hair color reflects differences in the type
and amounts of pigment produced by
melanocytes.
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13. Hair color is genetically controlled by
environmental conditions or hormones may
make the hair lighter.
14. On average about 50 hairs are lost a day
but conditions could alter this; drug use, dietary
factors, radiation, high fever, stress or hormonal
factors regarding pregnancy.
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15. In males,
changes in he level of
circulating sex
hormones can affect
the scalp, causing a
shift in production
from normal hair to
peach fuzz- male
pattern baldness
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III. Sebaceous glands
A. The integument contains two types of
exocrine glands: sebaceous and sweat glands.
1. Sebaceous glands or oil glands discharge a
waxy, oil secretion into hair follicles or on to the
skin.
2. Sebum is oil squeezed into the hair shaft,
which inhibits the growth of bacteria.
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3. The skin contains
two different types of
sweat glands:
apocrine and
merocrine sweat
glands.
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B. Apocrine
1.
2.
Apocrine sweat glands secrete their
secretions into the hair follicles in the armpits,
around the nipples, and the groin.
At puberty these glands are active.
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C. Merocrine sweat glands
1.
Merocrine sweat glands or eccrine
sweat glands are far more numerous than
apocrine.
2.
The skin contains about 2-5 million
merocrine glands.
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3. Their secretion is called perspiration, cool
the surface of the skin and reduce body
temperature.
4. The skin also contains other modified sweat
glands- mammary glands that secrete milk.
5. Ceruminous gland secretes earwax
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D. Nails
1.
Nails form on the dorsal surface of
fingers and toes.
2.
Know the diagram of the finger fig 5.8
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IV. Local control and
homeostasis
A. Injury and repair
1.
The skin can regenerate effectively
even after considerable damage ahs
occurred.
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2. There are four steps in repair.
a. Bleeding occurs at the injury – tries to push
out all the possible bacteria. Mast cells in the
region trigger an inflammatory response.
b. A scab forms. Phagocytic cells remove the
debris and damaged cells. Clotting around the
edges begin.
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c. Phagocytic activity has ended, and the
blood clot is disintegrating,
d. Scab shed, depression is left where
the injury occurred but scar tissue is
forming.
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3. Burns are the most common injury
that result from exposure of the skin to
heat, radiation, electric shock or strong
chemical agents. The degree of damage
depends on how deep the burn goes.
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C. Aging and the Integumentary System
1.
Skin injuries and infections become more
common.
2.
The sensitivity of the immune system is
reduced.
3. Muscles become weaker, and bone strength
decreases.
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4. Sensitivity to sun exposure increases.
5. The skin becomes dry and often scaly.
6. Hair thins and changes in color.
7. Sagging and wrinkling of the skin
appears.
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8. The ability to lose heat decreases.
9. Skin repairs proceed relatively slow.
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V. Clinical considerations
A. Inflammatory Conditions
1. Immunological hypersensitivity or
infectious agents cause inflammatory skin
disorders. (Infection)
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2. Allergies is a hypersensitive reactionredness, itching and swollen symptoms.
3. Both benign and malignant neoplastic
conditions are diseases of the skin- skin
cancer.
4. Moles are a benign neoplastic growth.
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B. Burns
1. First degree burns- the epidermal layer
of the skin are damaged- redness, pain
and edema (swelling)
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2. Secondary degree burns- involves the
epidermis and the dermis, blisters may
appear and recovery is usually slow.
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3. Third degree burns destroy the entire
thickness of the skin and frequently some
underlying muscle. The skin appears
charred and is insensitive to touch.
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C. Frostbite
1. First degree- the skin will appear cyanotic (bluish)
and swollen.
2. Second degree- vesicle formation and hyperemia
(swollen blood)
3. Third degree- Severed edema, some bleeding and
numbness followed y intense throbbing pain and
necrosis of the affected tissue. Gangrene will follow
untreated third degree burns.
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D. Skin Grafts
1.
If extensive area is damaged new skin cannot
grow back.
2.
A skin graft is a segment of skin that has
excised from a donor site and is transplanted to
the recipient site or graft bed.
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The end- Integumentary
system: skin/hair/glands/nails
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