Download Chapter 7 notes version 2

Anatomy and Physiology
Chapter 7: Skin and Its Appendages Part 2 of 2
Skin Color
 Melanin
 Basic determinant of skin tone
 Types of melanin
o Eumelanin—group of dark brown (almost black) melanins
o Pheomelanin—group of reddish and orange melanins
o Melanocytes release melanin in packets called melanosomes
 Albinism—congenital absence of melanin
 Vitiligo-loss of brown pigment
 Cumulative effects of UV exposure may produce age spots
 Other Pigments
 Beta-carotene (group of yellowish pigments from food) can also
contribute to skin color
 Lipofuscin—accumulates in cells that have ceased mitosis in aging
skin, producing brown-yellow age spots
 Hemoglobin—color changes also occur as a result of changes in blood
flow
o Blushing: redder skin color when blood flow to skin increases
(vasodilation)
o Cyanosis—bluish color caused by darkening of hemoglobin
when it loses oxygen and gains carbon dioxide
(vasoconstriction)
o Bruising can cause a rainbow of different colors to appear in
the skin (
 Jaundice: pigments in blood from bile (comes from liver)
Appendages of the Skin
 Hair (Figure 7-17)
 Development of hair
o Distribution—over entire body
 Except palms of hands and soles of feet (other small
areas)
o Lanugo: Fine and soft hair coat existing before birth
o Vellus Hair: fine, barely noticeable, childhood
o Terminal hair: Coarse pubic and axillary hair that develops
o Make up of hair
o Hair follicles and hair develop from epidermis
o Root—part of hair embedded in follicle in dermis
o Shaft—visible part of hair
o Medulla—inner core of hair; cortex—outer portion
o Growth—hair growth and rest periods alternate; hair on head
averages 5 inches of growth per year
 Nails (Figure 7-20)
 Consist of epidermal cells converted to hard keratin
 Nail body—visible part of each nail
1
 Root—part of nail in groove hidden by fold of skin, the cuticle
 Lunula—moon-shaped white area nearest root
 Nail bed—layer of epithelium under nail body; contains abundant
blood vessels
o Appears pink under translucent nails
 Growth—nails grow in st. basale beneath the lunula; average growth
about 0.5 mm per week, or slightly over 1 inch per year
 Skin glands
 Two types of Sudoriferous (sweat) glands
o Eccrine glands
 Most numerous sweat glands; quite small
 Distributed over total body surface with exception of a
few small areas
 Simple, coiled, tubular glands
 Function throughout life
 Secrete perspiration, or sweat; eliminate wastes and
help maintain a constant core temperature
o Apocrine glands
 Large and Located deep in subcutaneous layer
 Limited distribution—axilla, areola of breast, and
around anus
 Simple, branched, tubular glands
 Begin to function at puberty
 Secretes thicker liquid filled with proteins and lipids
 Bacteria feeding results in Body Odor
 Closes thing to pheromones
o Modified Sweat glands
 Mammary glands: Secrete milk
 Ceruminous glands
o Empty contents into external ear canal
o Mixed secretions of sebaceous (oil) and
ceruminous glands called cerumen (wax)
 Sebaceous glands
o Secrete sebum—oily substance that keeps hair and skin soft and
pliant; prevents excessive water loss from skin
o Lipid components have antifungal activity
o Found in dermis except in palms and soles
o Secretion increases in adolescence; may lead to formation of
pimples and blackheads
Skin Function:
 Protection
 Physical barrier to microorganisms and barrier to chemical hazards
 Reduces potential for mechanical trauma
 Prevents dehydration
 Protects against excess UV exposure (melanin function)
2
 Surface film
 Functions
o Antibacterial, antifungal activity
o Lubrication
o Hydration of skin surface
o Buffer of caustic irritants
o Blockade of toxic agents
 Sensation
 Skin acts as a sophisticated sense organ
 Somatic sensory receptors detect stimuli like pressure, touch,
temperature, pain, and other general senses
 Flexibility
 Skin is supple and elastic, thus permitting change in body contours
without injury
 Excretion
 Water
 Urea/ammonia/uric acid (very small amounts)
 Hormone (vitamin D) production
 Exposure of skin to UV light helps synthesis vitamin D
 Vitamin D is transferred in blood so it’s technically a hormone
 Immunity
 Phagocytic cells destroy bacteria
 Homeostasis of body temperature
 Heat production
o By metabolism of foods in skeletal muscles and liver
o Amount of muscular work being performed
 Heat loss
o 80% of heat loss occurs through the skin; remaining 20%
occurs through the mucosa of the respiratory, digestive, and
urinary tracts
 Homeostatic regulation of heat loss
o Heat loss by the skin is controlled by a negative feedback loop
o Hypothalamus monitors the body’s internal temperature
 Hyperthermia (above normal temperature): fainting, cramps, heat
and heat stroke
 Hypothermia (below normal temperature): slowed metabolism,
fibrillation
Burns

Tissue damage and cell death caused by heat, electricity, UV
radiation, or chemicals
 Associated dangers
o Dehydration
o Electrolyte imbalance
o Circulatory shock

Severity of burns
3
First-degree burns
o Only epidermis is damaged
o Skin is red and swollen
 Second degree burns
o Epidermis and upper dermis are damaged
o Skin is red with blisters
 Third-degree burns
o Destroys entire skin layer
o Burn is gray-white or black
 Rule of nines
 Way to determine the extent of burns
 Body is divided into 11 areas for quick estimation
 Each area represents about 9%
 Burns are considered critical if:
o Over 25% of body has second degree burns
o Over 10% of the body has third degree burns
o There are third degree burns of the face, hands, or feet
 Eschar (scab-like): when skin is so damaged that it can lead to this
acting as a tourniquet
o Escharotomy: procedure performed to lessen damage of burn

Cycle of Life: Skin
 Children
 Skin is smooth, unwrinkled, and characterized by elasticity and
flexibility
 Few sweat glands
 Rapid healing
 Adults
 Development and activation of sebaceous and sweat glands
 Increased sweat production; can result in body odor
 Increased sebum production; can result in acne
 Old age
 Decreased sebaceous and sweat gland activity
o Wrinkling (Figure 7-24)
o Decrease in body's ability to cool itself
The Big Picture:
Skin and the Whole Body
 Skin is a major component of the body’s structural framework
 Skin defines the internal environment of the body
 Primary functions are support and protection
4