Transcript C. Glands of the skin

Chapter 6
Skin and the Integumentary
System
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 Introduction:
A. Organs are body structures composed of
two or more different tissues.
B. The skin and its accessory organs make up
the integumentary system.
Organization p. 122
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 6.1 Skin and Its Tissues
A. Function of skin:
1. Regulate temperature
2. Protective barrier
3. Retain body fluids
4. Location of sensory receptors
5. To synthesize certain chemicals
6. Eliminate waste products
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B. Integument & cutaneous layer
1. area 15 – 20 sq ft
2. thickness
a. eyelids 1/50 in (<0.5 mm)
b. soles of feet 1/8 in (6 mm)
3. Skin is made of two main layers:
epidermis & dermis
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4. Layers are firmly bonded together –
basement membrane
a. excessive rubbing can cause
layers to separate
b. fluid fills area causing a blister
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C. Epidermis - made up of stratified
squamous epithelium and lacks blood
vessels.
Four or five layers:
1. Outer layer (stratum corneum) made
of cells which are kertinized or cornified
(cytoplasm replaced by keratin)
a. cells are flattened and scalelike
and are constantly being lost
b. 1st line of defense (gases & lipid
soluble substances pass easily)
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2. Stratum lucidum is present in thick
skin only (named because of the
translucent material eleidin- forms
keratin)
3. Stratum granulosum (named
because of granules in the cytoplasm
of the cells)
a. melanocytes in this layer
produce melanin, pigment that
gives skin color & protects deeper
cells from UV rays
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Melanin cont.
1. 4-6 pairs of genes
2. sunlight increases
production
3. pituitary gland hormones
can also influence production
4. hemoglobin & cerotene also
contribute to skin color
b. Albinism – genetic defect
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4. Stratum spinosum – flattened cells
with spines or processes
5. Stratum germinativum (stratum
basale) is made up of germinating cells
continually divinding to replace the
outer layers.
a. no direct blood supply
b. gets nutrients, water, etc by
diffusion from vessels of the
dermis below
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D. Dermis
1. The dermis consists of two layers of
connective tissue with collagen and
elastic fibers within a gel-like ground
substance.
a. papillary layer – composed of
loose connective tissue, fine elastic
fibers and capillaries
(dermatoglyphics – skin ridges)
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dermis cont.
b. reticular layer – thicker & made
of dense irregular connective
tissue giving it strength & elasticity
2. The dermis also contains nerve fibers,
sensory fibers, hair follicles, sebaceous
glands, and sweat glands.
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E. Subcutaneous Layer
1. The subcutaneous layer
(hypodermis) is composed of loose
connective tissue and insulating
adipose tissue.
2. It binds the skin to underlying organs
and contains the blood vessels that
supply the skin.
3. wrinkles – less adipose tissue and
fewer elastic fibers
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6.2 Accessory Organs of the Skin
A. Nails
1. Nails are protective coverings over
the ends of fingers and toes.
2. Nails consist of stratified squamous
epithelial cells overlying the nail bed,
with the lunula as the most actively
growing region of the nail root.
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3. As new cells are produced, older
ones are pushed outward and become
keratinized.
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B. Hair Follicles
1. Hair can be found in nearly all
regions of the skin.
2. Individual hairs develop from cells at
the base of the hair follicle, an
invagination of the lower epidermis
that dips down into the dermis.
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3. As new cells are formed, old cells
are pushed outward and become
keratinized, and die forming the hair
shaft.
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4. A bundle of smooth muscle cells,
called the arrector pili muscle, attaches
to each hair follicle. These muscles
cause goose bumps when cold or
frightened.
5. Hair color is determined by genetics;
melanin from melanocytes is
responsible for most hair colors, but
red hair also contains the pigment
trichosiderin.
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C. Glands of the skin
There are two major types of cutaneous
glands associated with the skin.
1. Sebaceous glands (holocrine glands)
a. Found in the dermis of nearly all
the skin except the palms of the
hands and soles of the feet.
b. Ducts open into the upper part
of the hair follicles.
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Sebaceous cont.
c. Produce and oily secretion
called sebum that prevents hair
from becoming dry and brittle.
~ underactive vs. overactive
~ Blackheads
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2. Sweat glands (sudoriferous glands)
are two general types:
a. Apocrine glands are associated
with hair follicles and are few in
number.
1) empty into hair follicles
2) milky, sticky secretion ->
bacteria -> odor of sweat
3) respond to body
temperature, stress, and
sexual arousal
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Other apocrine glands believed to
be related to sweat glands are:
~ ciliary glands of the eyelids
~ ceruminous (wax) glands of the
external ear
~ mammary glands
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b. Eccrine glands open as pores on
the surface of the skin and are the
most common type in humans.
1) coiled tubes that open onto
the surface of the skin
2) secretion is mostly water
with some salt
3) respond to body
temperature
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 6.3 Physiology of the skin
A. Protective Barrier
B. Temperature Regulation
1. Proper temperature regulation is
vital to maintaining metabolic
reactions.
2. The skin plays a major role in
temperature regulation with the
hypothalamus controlling it.
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3. Active cells, such as those of the
heart and skeletal muscle, produce
heat.
4. The body responds to excessive heat
by dilation of dermal blood vessels and
sweating.
5. The body responds to excessive
cooling by constricting dermal blood
vessels, inactivating sweat glands, and
shivering.
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C. Sense Receptors
1. Free nerve endings
a) touch, pain, & temperature
b) skin, cornea & surround
root of the hair follicles
2. Meissner’s corpuscles
a) touch
b) encapsulated nerve endings
found in hairless portions of
the skin
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3. Ruffini’s corpuscles
a) formerly thought to sense
heat ? touch
b) found at the border of
dermis and subcutaneous
4. Pacinan corpuscles
a) deep touch & pressure
b) encapsulated nerve
endings widely distributed in
the subcutaneous tissue
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5. Krause’s end bulbs
a) cold, touch
b) encapsulated nerve endings
near the surface of the skin
D. UV rays -> Vitamin D (epidermis) ->
absorb Calcium -> bone tissue
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 6.4 Pathology
A. Healing of Wounds
1. Inflammation, in which blood vessels
dilate and become more permeable is
the body's normal response to injury.
~ aids healing by providing more
nutrients & oxygen
B. Common Skin Disorders p. 123
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C. Cuts
1. Superficial cuts are filled in by
reproducing epithelial cells.
2. Deeper cuts are closed off by clots,
covered by scabs, and eventually filled
in by connective tissue. Blood vessels
extend into the area, injured tissues
are replaced, and the scab falls off.
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3. Large wounds leave scars and healing
may be accompanied by the formation
of granulations (blood vessel & cluster
of fibrobasts).
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D. Burns
1. One million people are burned
annually -> 7000 die
2. The depth of a burn is measured in
degrees.
a. 1st degree burn (superficial
partial-thickness)
~ reddened as dermal blood
vessels dilate
~ sunburn -> skin maybe shed
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b. 2nd degree burn (deep partialthickness
~ Redness and blisters common
~ Painful because nerves of the
dermis are irritated
c. 3rd degree burn (full-thickness)
~ charring of the skin
~ healing occurs only by growth of
epithelial cells inward
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Extensive burning – rule of nines
1. autograft (self)
a. unburned region & transplanted to
injured region
b. cultured human epithelial -> postage
stamp grows to bathmat size then
transplanted
2. homograft (person to person)
a. temporary – prevent infection
b. replaced with autograft
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3. Other
a. amniotic membrane
b. artificial membranes composed of
silicone, polyurethane or nylon with
collagenous fibers
E. Skin Cancer p. 119
1. cutaneous carcinomas
2. cutaneous melanomas
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