Chapter 4: Skin and Body Membranes
Classification of Body Membranes
 Epithelial Membranes: covering and lining membranes
o Cutaneous Membranes
o
o
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Mucous Membranes
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Lines body cavities that open to the outside, such as:
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Adapted for _______________ or ________________________.
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The lining of the RESPIRATORY and DIGESTIVE tracts secrete large amounts of:
Serous Membranes
 Lines body cavities that are closed to the exterior.
 Occur in pairs
 Parietal:
 Visceral:
 Serous Fluid:
 Function/Importance of Serous Fluid:
Connective Tissue Membranes
o Synovial Membranes
The Skin
 Functions of the Skin
o Protection from
 Mechanical Damage
 Chemical Damage
 Bacterial Damage
 Ultraviolet Radiation
 Temperature Damage
 Desiccation/Drying out
o Temperature control: sweat and goosebumps
o Excretion of urea and uric acid
o Synthesis of vitamin D

Structure of the Skin
o Epidermis
composed of 5 layers/strata
1) Innermost: stratum basale (s. germinativum) = ONLY living/dividing layer of epidermis
2) s. spinosum
3) s. granulosum
4) s. lucidum
5) Outermost: s. coreum
 Avascular: lacks a rich blood supply
 Most cells are keratinocytes, which produce KERATIN.
o
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The average person sheds about 40 pounds of skin in a lifetime
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We have a completely new epidermis every 25 to 45 days.
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Melanin production is performed by melanocytes (melanin producing cells) in response to UV
exposure. This pigment is produced and deposited into the s. basale and will move up
through the layers as new cells are produced underneath.
Dermis
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AKA hide
Strong and elastic
Made of dense fibrous connective tissue
2 regions
o
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Papillary layer = Most superficial layer of the dermis
o Dermal papillae attaches DERMIS to s. basale
o Forms fingerprints which provide gripping action for fingers
o Provides nourishment to the s. basale to keep those cells dividing.
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Reticular layer = Deepest layer of the dermis
o Contains blood vessels, sweat and oil glands, and pressure receptors.
o Phagocytes prevent bacteria from entering deeper into the body =
NONSPECIFIC
o Collagen protein provide toughness for attachment
o Elastin protein provides flexibility and elasticity.
o Maintains body temperature by promoting sweat production and release
and contraction of muscles for goosebumps.
Hypodermis: made of adipose tissue = Deepest layer of the skin
 Anchors skin to underlying tissues/organs.
 Provides shock absorption and insulation
Skin Color: 3 main pigments contribute to skin color
o Melanin: yellow, reddish brown, dark brown, black. Protection from UV light.
o
Carotene: orange-yellow fat soluble vitamin that can be stored in adipose tissue.
o
Hemoglobin: red; found in red blood cells. The more blood in the area, the more red the skin
appears.
o
Abnormal Skin colorations
 Erythema: redness due to blushing, inflammation, fever, high blood pressure
 Pallor: pale skin due to anemia (low RBC), low blood pressure, loss of blood flow.
Could lead to Cyanosis: blue discoloration due to lack of blood supply.
 Jaundice: yellow cast due to bile build up; signifies liver damage
 Bruises: loss of blood due to injury. Color changes to bruise occur as pigments are
broken down.
Appendages of Skin
o Cutaneous Glands: Exocrine glands: secrete products onto skin surface via ducts.
 Sebaceous glands: oil glands
 Found all over the skin except palms and soles
 Empty into hair follicle
 Sebum: product of sebaceous glands
o Acts as lubricant; keeps skin soft
o Kills bacteria
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Sudoriferous glands: sweat glands
 2.5 million per person, found ALL OVER the body
 Eccrine/Merocrine = most numerous and widespread. Produces sweat
o Highly efficient temp control mechanism
o Sweat: mostly salt water and some wastes.
 Weak acidic pH from 4-6
 Can lose up to 7 liters of sweat on a hot day.
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Apocrine
o Only found in axillary and genital regions
o Only becomes active @ puberty.
o Odorless by bacteria feed off the oily secretion producing an odor.