Transcript 1. Protects deeper tissues from

Chapter 4
Skin and Body Membranes
Physiology
Essentials of Human Anatomy & Physiology, 7th ed.
by Elaine N. Marieb
Skin and Body Membranes: Integumentary System, Physiology
Skin Functions
1. Protects deeper
tissues
2. Aids in heat
regulation
3. Aids in excretion of
urea and uric acid
4. Synthesizes
vitamin D
Skin and Body Membranes: Integumentary System, Physiology
1. Protects deeper tissues
from:
 Mechanical damage
(blisters, callouses)
 Chemical damage
(lipid-rich lamellar
granules in the
keratinocytes of the
stratum granulosum)
 Bacterial damage
(Langerhan’s cells
throughout epidermis,
usually visible in the
stratum spinosum)
Popped blisters, with
epidermis removed,
revealing dermis
Skin and Body Membranes: Integumentary System, Physiology
1. Protects deeper tissues…
UV exposure stimulates melanin
production.
 Thermal damage
(hypodermis, edema)
 Desiccation (keratinocytes
produce keratin, as well as
skin oil)
 Ultraviolet radiation
(melanocytes produce
melanin)
Skin and Body Membranes: Integumentary System, Physiology
Normal Skin Color Determinants
 Melanin - yellow to brown to black pigments
 Carotene - Orange-yellow pigment from some
vegetables
 Hemoglobin - Red coloring from blood cells in
dermal capillaries (oxygen content determines
the extent of red coloring)
Skin and Body Membranes: Integumentary System, Physiology
1. Protects deeper tissues…
Innervation = Nerves present in tissues which
function to sense and/or instruct
 Free nerve endings – detect pain, itch, and
temperature (located in dermis)
 Meissner’s corpuscles – structured nerve endings;
detect touch (located in dermal papillae; most
numerous on hands and feet)
 Pacinian corpuscles – encapsulated nerve endings;
detect pressure, vibration (located in reticular dermis
and hypodermis; most numerous on hands and feet)
Skin and Body Membranes: Integumentary System, Meissner’s corpuscle
Meissner’s corpuscle
Pacinian
corpuscle
Pacinian
corpuscles
Skin and Body Membranes: Integumentary System, Physiology
1. Protects deeper tissues…
Oil Glands =
Sebaceous Glands
 Produce sebum (oil)
• Lubricant for skin
and hair
• Kills bacteria
 Most with ducts that
empty into hair follicles
 Glands are activated
at puberty
Skin and Body Membranes: Integumentary System, Physiology
2. Aids in heat regulation
 Small blood vessels in dermis
• Constrict in cold conditions
• Dilate in warm conditions
 Sweat Glands = Sudoriferous Glands
• Glands are located in the reticular dermis, ducts
open to the skin surface.
• Sweat is a hypotonic, watery solution containing
some metabolic wastes, and sodium, potassium,
and chloride ions. pH is neutral to slightly acid.
• Two types: eccrine & apocrine
Skin and Body Membranes: Integumentary System, Sweat Glands
 Eccrine
• More numerous; found all over body
• Open via duct to pore on skin surface
 Apocrine
• Ducts empty
into hair follicles
• Axillary and
genital areas
of the body,
active after
puberty
Skin and Body Membranes: Integumentary System, Sweat Glands
Eccrine gland
Apocrine gland
Odor is from
associated bacteria
Skin and Body Membranes: Integumentary System, Physiology
2. Aids in heat regulation
Hot environments
 Sweat absorbs body heat as it evaporates off of skin.
 Blood vessels dilate, bringing blood closer to surface
for more heat loss.
Cold environments
• Blood vessels constrict,
bringing blood away from
surface for less heat loss.
• Subcutaneous fat* provides
a layer of insulation.
Goosebumps occur only where we have hair.
They may have warmed our distant ancestors,
but they don’t seem to do much for us today.
Skin and Body Membranes: Integumentary System, Physiology
3. Aids in excretion of urea and uric acid
• Sweat is a hypotonic, watery solution containing
some metabolic wastes, and sodium, potassium,
and chloride ions. pH is neutral to slightly acid.
Skin and Body Membranes: Integumentary System, Physiology
Skin and Body Membranes: Integumentary System, Physiology
4. Synthesizes
vitamin D
Skin and Body Membranes: Integumentary System, Physiology