Download shaw ch 5 ppt - Spring

Shaw
 Includes:
◦ Skin
◦ Accessory Organs
 Hair follicles
 Nails
 Sebaceous (oil) Glands
 Sweat Glands
1) Protection – first line of defense
A) Chemical
 Melanin – protection against UV light
 Kills bacteria because of a bactericidal substance in sebum
(acidic & antiseptic)
 Skin secretes antibiotic (human defensin)
B) Physical/Mechanical
 Hardness of keratinized cells creates a barrier
 Skin is waterproof – slows water loss
C) Biological
 Rapid mitotic rate and cell shedding minimizes pathogen
entry
 Immune cells in the epidermis and dermis
2) Body temperature regulation:
A) High Body Temp
◦ Blood Vessel Dilation (allows for cooling)
◦ Increasing sweat gland secretions to cool
the body
B) Low Body Temp
◦ Blood Vessel Constriction (allows for
warming b/c blood bypasses the skin so
that its temp can drop to that of external
environment)
3) Cutaneous sensation – skin contains sensory
receptors for basic skin sensations
◦ Meissner’s corpuscles: light touch (ex. Your
clothing on your skin)
◦ Pacinian corpuscles: heavy pressure; pain (ex.
Someone bumping into you)
◦ Thermoreceptors: temperature (warm & cold)
◦ Pain receptors

Other sensations (itching, tickling, softness,
hardness, wetness) caused by the stimulation
of 2 or more receptors described above and a
blending of their sensations
4) Metabolic functions – synthesis of
vitamin D in dermal blood vessels when
exposed to sunlight
5) Blood reservoir – skin blood vessels
store up to 5% of the body’s blood
volume
6) 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
Hair shaft
Pore
Dermal papillae
(papillary layer
of dermis)
Epidermis
Meissner's corpuscle
Free nerve ending
Reticular layer of dermis
Sebaceous (oil) gland
Arrector pili muscle
Dermis
Sensory nerve fiber
sweat gland
Pacinian corpuscle
Artery
Hypodermis
(superficial
fascia)
Hair root
Hair follicle
Sweat gland
Vein
Adipose tissue
Hair follicle receptor
(root hair plexus)

Structure:
◦ Contains no nerves
◦ Not vascularized –gets nutrients by diffusion through
blood vessels in dermis
◦ Composed of 30-50 rows of stratified squamous
epithelium
 As these cells grow & divide, the older cells are pushed up
and out to the surface; dead skin cells get rubbed away
◦ Contains:
 Melanocytes produce melanin which protects cells from
damaging effects of UV (natural sunscreen!)
 Keratinocytes produce keratin which waterproofs the skin

Structure
◦ Made of strong, fibrous connective tissue
 Dense irregular connective tissue
◦ Dermal Papillae= peg-like projections on upper
edge of dermis that indent the overlying epidermis
◦ Very vascularized
 Accounts for blushing and pink cheeks
◦ Also contains:
 Sensory Receptors(nerve fibers), hair follicles, glands
◦ Responsible for the dermal ridges that produce
whorled ridges on the dermal papillae, or the
epidermal surface of fingertips (fingerprints)
 Fingerprints are genetically determined
 No 2 people have the same fingerprint though twins are
similar


Not technically considered part
of the skin but shares some of
its protective functions
Definition:
◦ Subcutaneous layer deep to the
skin

Structure:
◦ Composed of primarily of adipose
(fat) tissue

Functions:
◦ Anchors skin to muscles & organs,
◦ Shock absorber & Insulator b/c its
made of adipose

3 pigments contribute:
◦ Melanin: produced by melanocytes in the epidermis
 Skin color is determined by amount of melanin
produced
 Function: protect skin cells from UV radiation/natural
sunscreen
 Fair-skinned people have less melanin and are more likely
to get skin cancer
◦ Carotene: yellow-orange pigment that accumulates
in hypodermis; found in carrots
◦ Hemoglobin: pigment in red blood cells; gives
pinkish hue of fair skin
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

Albinism – lack of melanin pigment
Freckles or pigmented moles – accumulation of
melanin
Cyanosis – bluish color to skin resulting from
poor oxygenation of hemoglobin in blood
◦ Occurs during heart failure & severe respiratory
disorders

Black-and-blue marks (bruises) – blood escaped
from circulation and clotted beneath the skin
◦ Hematoma – clotted blood mass

Jaundice – abnormal yellowish skin due to a liver
disorder (bile pigments accumulate in blood)
 Include
the following:
◦Nails
◦Sweat (Sudoriferous) Glands
◦Oil (Sebaceous) Glands
◦Hair Follicles
◦Hair



Up to 3 million per person
Location: abundant on palms of hands, soles of
feet, and forehead
Function: prevents overheating of body
◦ Body’s response to pain or stress



Appearance: coiled, tubular glands
Some modified sweat glands secrete ear wax &
milk
Composition of Sweat: water, salts, ammonia,
vitamin C, other wastes, possibly pheromones

Definition: specialized
epithelial cells usually
associated with/attached
to hair follicles


Location: all over the
body except palms of the
hands and soles of the
feet
Function: secrete an oily
secretion called sebum
that lubricates the hair
and skin

The good?
◦ Makes hair and skin silky, soft, and shiny
◦ Waterproof

The bad?
◦ Causes acne when overactive
◦ Acne: active inflammation of sebaceous
glands that causes pimples on the skin
◦ Usually caused by bacterial infection



Definition: flexible strands that are produced
by hair follicles
Structure: made of hard keratin (dead cells) that
projects from the skin
Function: protection (from trauma & sun) &
provides minimal warmth
◦ Also helps to sense insects on the skin


Location: all surfaces of the skin except palms
of the hands, soles of the feet, lips, nipples,
and parts of the reproductive anatomy
Visible hair is all dead cells living cells found
only in dermis of skin




Hair shaft: part
that extends from
the skin surface
Hair root: part
embedded in the
skin dermis
Hair follicle: the
hair root is
embedded/
anchored here
Arrector Pili
muscle: attached
to the hair so their
contractions pull
hair into upright
postion, dimple
skin, and make
goosebumps

Texture: Determined by the shape of the hair shaft
 determined by genetics
◦ Curly hair: flat, ribbon-like hair shaft
◦ Wavy hair: oval hair shaft
◦ Straight hair: perfectly round hair shaft

Color: Genetic trait that is determined by the type &
amount of pigment (melanin) that is produced
Abundance of melanin  dark hair
No melanin  white hair
Intermediate amounts of melanin  blond hair
Individual hairs stop producing melanin as we age; mixture
of hairs with & without gray hair
◦ Iron containing pigment  red hair
◦
◦
◦
◦


Definition: Scale-like modification of the
epidermis that forms a clear, protective
covering on the dorsal surface of the distal part
of a finger or toe
Structure:
◦ Made of keratinized stratified squamous epithelial
cells
◦ Reproduction: Cells division takes place in the nail
root (whitish half-moon shape) called the lunula
◦ Free edgebody (visible)root (embedded in skin)

Function: tools to pick up small objects or to
itch

The three major types of skin cancer
are:
◦ Basal cell carcinoma: least malignant; most
common (30% of white people will get this;
full cure by excision in 99% of cases)
◦ Squamous cell carcinoma: grows rapidly &
metastasizes to lymph nodes
 More dangerous
◦ Melanoma: cancer of melanocytes
 Most dangerous because it is highly
metastatic and resistant to chemotherapy
Squamous Cell
Basal Cell
Melanoma

Melanomas have the following characteristics
(ABCD rule)
◦ A: Asymmetry; the two sides of the pigmented area
do not match
◦ B: Border is irregular and exhibits indentations
◦ C: Color (pigmented area) is black, brown, tan, and
sometimes red or blue
◦ D: Diameter is larger than 6 mm (size of a pencil
eraser)
◦ Some experts add E: Elevation of spot above skin
surface


Tissue damage inflicted by intense heat,
electricity, radiation, or chemicals that
can cause a denaturing of the cell’s
proteins and cell death
First-degree – only the epidermis is
damaged
◦ Symptoms include localized
redness, swelling, and pain
◦ Sunburn is usually 1st degree

Second-degree – epidermis and upper
regions of dermis are damaged
◦ Symptoms mimic first degree
burns (redness, swelling, pain),
but blisters also appear
◦ Skin regeneration can occur in 3-4
weeks if infection is prevented


Third-degree – entire thickness of the skin is
damaged
Also called “Full Thickness Burns”
◦ Burned area appears gray-white,
cherry red, or black
◦ There is no initial edema (swelling) or
pain (since nerve endings are
destroyed)
◦ Needs skin grafting

First & Most Immediate Threat: Loss of body
fluids
◦ Dehydration
◦ Electrolyte imbalance: can lead to renal shutdown
and circulatory shock
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

Infection: causes majority of deaths
First thing a treating physician must do is
replace lost fluids
The amount of fluid lost can be determined
by using the “Rule of Nines”
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

Estimates the severity of burns (percentage of
body surface that is burned)
Divides the body into 11 areas, each
accounting for 9% of the total body area + 1%
for the genitals
Burns considered critical if:
◦ Over 25% of the body has second-degree burns
◦ Over 10% of the body has third-degree burns
◦ There are third-degree burns on face, hands, or
feet
MUST
CONSIDER
BOTH THE
ANTERIOR &
POSTERIOR
SIDES OF
THE BODY