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CHAPTER 4
Skin and Body Membranes
Function of Body Membranes
Line or cover body surfaces
 Protect body surfaces
 Lubricate body surfaces

Classification of Body
Membranes

Epithelial Membranes – are simple
organs
– Cutaneous membranes
– Mucous membrane
– Serous membrane

Connective Tissue Membranes
Cutaneous Membrane

Cutaneous
Membrane = skin
– A dry membrane
because it is exposed
to air
– Outermost protective
boundary

Superficial Epidermis
– Keratinized stratified
squamous epithelium

Underlying Dermis
– Mostly dense
connective tissue
Mucous Membranes
“Wet” or moist
membranes
 Surface Epithelium

– Type of epithelium depends
on its location


Has a layer of underlying
loose connective tissue
called the lamina propria
Lines all body cavities
that open to the exterior
body surface
– Respiratory, Digestive, and
Reproductive organs

Adapted for absorption or
secretion
Serous Membranes
Serous Membranes = “Serosa”
 Surface simple squamous epithelium
with underlying areolar connective
tissue
 Lines open body cavities that are closed
to the exterior of the body
 Serous membranes occur in pairs:

– Parietal = lines the cavity wall
– Visceral = covers the outside of the organ
contained in the cavity
Serous Membranes
Serous layers are separated by serous
fluid which helps to reduce friction
between organs.
 Specific Serous Membranes:

– Peritoneum = covers the abdominal cavity
– Pleura = surrounds the lungs
– Pericardium = surrounds the heart
Connective Tissue Membrane

Synovial Membrane
– Made of connective tissue only
– Lines fibrous capsules surrounding joints
Synovial Membrane
Integumentary System

Components include:
– Skin = cutaneous membrane
– Sweat glands
– Oil glands
– Hairs
– Nails
Integumentary System

Protects deeper tissues from:
– Mechanical Damage
– Chemical Damage
– Bacterial Damage
– Thermal Damage
– UV Radiation
– Drying Out
Integumentary System

The skin aids in:
– Heat Regulation
– Excretion of urea and uric acid
– Synthesizing vitamin D
Skin Structure

Has 3 layers:
– Epidermis = outermost layer
• Stratified squamous epithelium
• Often keratinized (hardened by keratin)
– Dermis = middle layer
• Dense connective tissue
• Firmly connected to epidermis
– Hypodermis = aka “subcutaneous” tissue; deep to
the dermis
• Not part of the skin
• Anchors skin to underlying organs
• Composed mostly of adipose tissue
Skin Structure
Layers of the Epidermis

Stratum Basale
– Layer lying next to the dermis and is undergoing
mitosis

Stratum Spinosum
 Stratum Granulosum
 Stratum Lucidum
– Occurs only in thick skin

Stratum Corneum
– 20 to 30 cell layers thick
– Shingle-like dead cells
– Have a totally “new” epidermis every 25-45 days
Melanin
Pigment produced by melanocytes
 Color is yellow to brown to black
 Found mostly in the stratum basale
 Amount produced depends upon
genetics and the exposure to sunlight

Layers of the Dermis

Papillary Layer
– Have projections called dermal papillae
– Contain pain receptors (Meissner’s
corpuscles) and capillary loops

Reticular Layer
– Deepest skin layer
– Contains blood vessels, glands, and
pressure receptors (Pacinian corpuscles)
Normal Skin Color Determinants
Melanin = yellow, brown, or black
pigments
 Carotene = orange-yellow pigment from
some vegetables
 Hemoglobin = red coloring from blood
cells in the dermis capillaries; oxygen
content determines the extent of red
coloring

Accessory Organs of the Skin

Sebaceous Glands = produce oil
– Acts as a lubricant for skin and kills
bacteria
– Most have ducts that empty into hair
follicles
– Glands are activated at puberty
Accessory Organs of the Skin

Sweat Glands = widely distributed in
skin
– 2 types:
• Eccrine = open via duct to pore on skin
surface
• Apocrine = ducts empty into hair follicles
– Composition of sweat:
• Mostly water, some metabolic waste
• Only in apocrine glands – fatty acids &
proteins
– Function:
• Helps get rid of excessive heat
• Excretes waste products
• Its acidic nature inhibits bacteria growth
– Odor is from associated bacteria
Accessory Organs of the Skin

Hair – produced
by hair follicle
– Consists of hard
keratinized
epithelial cells
– Melanocytes
provide pigment
for hair color
Hair
– Has a central
medulla, a cortex
that surrounds it, and
a heavily keratinized
cuticle on the outside
of the cortex
Hair
– Arrector Pili =
muscle that contracts
when we are cool to
give the appearance
of “goose bumps”
because it is
attached to the hair
follicle
Accessory Organs of the Skin

Nails = scale-like modifications of the
epidermis that are heavily keratinized
– Have a lack of pigment that makes them
colorless
– Stratum basale extends beneath the nail
bed so that the nail grows
Nails
Skin Homeostatic Imbalances

Infections (page 107):
– Athlete’s Foot = caused by fungal infection
– Boils & Carbuncles = caused by bacterial
infection
– Cold Sores = caused by a virus
– Contact Dermatitis = exposures cause an
allergic reaction
– Impetigo = caused by bacterial infection
– Psoriasis = cause is unknown but is
triggered by trauma, infection, and stress
Burns (pages 108 – 109)
Tissue damage and cell death caused
by heat, electricity, UV radiation, or
chemicals
 Dangers of burns include dehydration,
electrolyte imbalance, and circulatory
shock
 “Rule of Nines” is a way to determine
the extent of burns

– Body is divided into 11 areas for quick
estimation and each area represents about
9%
Severity of Burns

1st Degree Burns = only epidermis is
damaged
– Skin is red and swollen

2nd Degree Burns = epidermis and
upper dermis are damaged
– Skin is red with blisters

3rd Degree Burns = destroys entire skin
layer
– Burn is gray-white or black
Burns

Burns are considered critical if:
– Over 25% of the body has 2nd degree
burns
– Over 10% of the body has 3rd degree burns
– There are 3rd degree burns of the face,
hands, or feet
Skin Cancer

Skin Cancer = most common type of
cancer; abnormal cell mass; 2 types:
– Benign – does not spread
– Malignant – metastasized (moves) to other
parts of the body
Basal Cell Carcinoma
Least malignant
 Most common type arises from stratum
basale

Squamous Cell Carcinoma
Early removal allows a good chance of
cure
 Arises from stratum spinosum
 Metastasizes to lymph nodes

Malignant Melanoma
Most deadly of skin cancers
 Cancer of melanocytes
 Metastasizes rapidly to lymph and blood
vessels

Detection of Skin Cancer

Uses ABCD rule:
– A = Asymmetry
• 2 sides of pigmented mole do not match
– B = Border irregularity
• Borders of mole are not smooth
– C = Color
• Different colors in pigmented area
– D = Diameter
• Spot is larger than 6mm in diameter