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Skin and Body Membranes
Skin and Body Membranes
Function of body membranes
o
Line or cover body surfaces
o
Protect body surfaces
o
Lubricate body surfaces
Classification of Body Membranes
Epithelial membranes
o
Cutaneous membrane
o
Mucous membrane
o
Serous membrane
Connective tissue membranes
Cutaneous Membrane
Cutaneous membrane = skin
o
A dry membrane
o
Outermost protective boundary
Superficial epidermis
o
Keratinized stratified squamous epithelium
Underlying dermis
o
Mostly dense connective tissue
Mucous Membranes
Surface epithelium
o
Type depends on site
Underlying loose connective tissue (lamina propria)
Lines all body cavities that open to the exterior body
surface
Often adapted for absorption or secretion
Serous Membranes
Surface simple squamous epithelium
Underlying areolar connective tissue
Lines open body cavities that are closed
to the exterior of the body
Serous layers separated by serous fluid
Specific serous membranes
o
Peritoneum

o
Pleura

o
Abdominal cavity
Around the lungs
Pericardium

Around the heart
Connective Tissue Membrane
Synovial membrane
o
Connective tissue only
o
Lines fibrous capsules surrounding joints
Integumentary System
Skin (cutaneous membrane)
Skin derivatives
o
Sweat glands
o
Oil glands
o
Hairs
o
Nails
Skin Functions
Protects deeper tissues from:
o
Mechanical damage
o
Chemical damage
o
Bacterial damage
o
Thermal damage
o
Ultraviolet radiation
o
Desiccation (Drying out )
o
Aids in heat regulation
o
Aids in excretion of urea and uric acid
o
Synthesizes vitamin D
Skin Structure
Epidermis – outer layer
o
Stratified squamous epithelium
o
Often keratinized (hardened by keratin)
Dermis
o
Dense connective tissue
Deep to dermis is the hypodermis
o
Not part of the skin
o
Anchors skin to underlying organs
o
Composed mostly of adipose tissue
Layer of Epidermis
Stratum basale
o
Cells undergoing mitosis
o
Lies next to dermis
Stratum spinosum
Stratum granulosum
Stratum lucidum
o
Occurs only in thick skin
Stratum corneum
o
Shingle-like dead cells
Melanin
Pigment (melanin) produced by melanocytes
Color is yellow to brown to black
Melanocytes are mostly in the stratum basale
Amount of melanin produced depends upon genetics and exposure to sunlight
Dermis
Two layers
o
o
Papillary layer

Projections called dermal papillae

Pain receptors

Capillary loops
Reticular layer
Skin Structure

Blood vessels

Glands

Nerve receptors
Normal Skin Color Determinants
Melanin
o
Yellow, brown or black pigments
Carotene
o
Orange-yellow pigment from some vegetables
Hemoglobin
o
Red coloring from blood cells in dermis capillaries
o
Oxygen content determines the extent of red coloring
Appendages of the Skin
Sebaceous glands
o
Produce oil

Lubricant for skin

Kills bacteria
o
Most with ducts that empty into hair follicles
o
Glands are activated at puberty
Sweat glands
o
Widely distributed in skin
o
Two types

Eccrine
 Open via duct to pore on skin surface

Apocrine
 Ducts empty into hair follicles
Sweat and Its Function
Composition
o
Mostly water
o
Some metabolic waste
o
Fatty acids and proteins (apocrine only)
Function
o
Helps dissipate excess heat
o
Excretes waste products
o
Acidic nature inhibits bacteria growth
Odor is from associated bacteria
Appendages of the Skin
Hair
o
Produced by hair bulb
o
Consists of hard keratinized epithelial cells
o
Melanocytes provide pigment for hair color
Hair Anatomy
Central medulla
Cortex surrounds medulla
Cuticle on outside of cortex
o Most heavily keratinized
Associated Hair Structures
Hair follicle
o
Dermal and epidermal sheath surround hair root
Arrector pilli
o
Smooth muscle
Sebaceous gland
Sweat gland
Appendages of the Skin
Nails
o
Scale-like modifications of the epidermis

o
Stratum basale extends beneath the nail bed

o
Heavily keratinized
Responsible for growth
Lack of pigment makes them colorless
Nail Structures
Free edge
Body
Root of nail
Eponychium – proximal nail fold that projects onto the nail body
Skin Homeostatic Imbalances
Infections
o
Athletes foot

o
Boils and carbuncles

o
Caused by fungal infection
Caused by bacterial infection
Cold sores

Caused by virus
Infections and allergies
o
Contact dermatitis

o
Impetigo

o
Exposures cause allergic reaction
Caused by bacterial infection
Psoriasis

Cause is unknown

Triggered by trauma, infection, stress
Burns
o
Tissue damage and cell death caused by heat, electricity, UV radiation, or
chemicals
o
Associated dangers

Dehydration

Electrolyte imbalance

Circulatory shock
Rule of Nines
Way to determine the extent of burns
Body is divided into 11 areas for quick estimation
o
Each area represents about 9%
Severity of Burns
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
Critical Burns
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
Skin Cancer
Cancer – abnormal cell mass
Two types
o
Benign
Does not spread (encapsulated)
o
Malignant
Metastasized (moves) to other parts of the body
Skin cancer is the most common type of cancer
Skin Cancer Types
Basal cell carcinoma
o
Least malignant
o
Most common type
o
Arises from statum basale
Squamous cell carcinoma
o
Arises from stratum spinosum
o
Metastasizes to lymph nodes
o
Early removal allows a good chance of cure
Malignant melanoma
o
Most deadly of skin cancers
o
Cancer of melanocytes
o
Metastasizes rapidly to lymph and blood vessels
o
Detection uses ABCD rule
ABCD Rule
A = Asymmetry
o
Two sides of pigmented mole do not match
B = Border irregularity
o
Borders of mole are not smooth
C = Color
o
Different colors in pigmented area
D = Diameter
o
Spot is larger then 6 mm in diameter
Aging of Skin
Effects:
o Thinner skin
o Basal cell layer (epidermis) in disarray
o Decreased number of collagen fibers (strength)
o Decreased functioning of elastic fibers (elasticity)
o Blood vessels in dermis leak
o Loss of hair, nerve cells, sweat ducts & sebaceous glands
o Lengthening of cell generation time
Causes:
o Intrinsic chronological aging – genetic
o Extrinsic environmental damage – exposure to sunlight, etc.

Damage to collagen & elastin

Damage to proteins & DNA

Formation of oxygen free radicals
O2
O- + O-
Treatment: (Antioxidants to eliminate oxygen free radicals)
o Tretinol or Retin-A (retinoic acid)
o Beta carotene
4-Year Old Skin
The red color in the dermis shows
high levels of Collagen Type 3
63-Year Old Skin
The Dermis shows loss of Collagen
Type 3 and thinning of the Epidermis.