10/11/2011
Skin and Body Membranes Chapter 4
Body Membranes
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Functions of Membranes
• Line or cover body surfaces • Protect body surfaces • Lubricate body surfaces
Classification of Membranes
• Epithelial membranes • Connective tissue membranes
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Epithelial Membranes • •
Called ‘epithelial’ but they also contain a basement membrane made from connective tissue Types:
• Cutaneous membrane • Mucous membrane • Serous membrane
Cutaneous Membranes • Also called ‘skin’ • A dry membrane • Outermost protective boundary
• Superficial epidermis •
Keratinized stratified squamous epithelium
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Keratin - a tough, insoluble protein fiber that coats human skin
• Underlying dermis •
Mostly dense connective tissue
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Mucous Membranes •
Has a surface epithelium
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Type depends on site
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Underlying loose connective tissue (lamina propria)
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‘Wet’ or moist membranes continuously bathed in mucus secretions (or urine, in the urinary tract)
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Lines all body cavities that open to the exterior body surface
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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
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Serous layers (in pairs)
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Parietal layer
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Lines cavity wall Visceral layer
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Lines organ Space in between contains serous fluid
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Reduces friction between organs
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Serous Membranes, Cont’d •
Specific serous membranes
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Peritoneum
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Abdominal cavity
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Pleura
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Around the lungs
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Pericardium
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Around the heart
Connective Tissue Membranes •
Also called synovial membranes
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Only made of connective tissue
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Location:
• • • •
No epithelial cells at all
Lines fibrous capsules surrounding joints Line small sacs called ‘bursae’ Line tube-like ‘tendon sheaths’
Function:
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Cushion organs moving against each other during activity
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Integumentary System
Skin Functions •
Protects deeper tissues from:
• • •
• • •
Mechanical, chemical, bacterial and thermal damage Ultraviolet radiation Desiccation (drying out)
Regulates temperature Aids in excretion Makes Vitamin D
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Skin Structure •
Epidermis – outer layer
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Often keratinized (hardened by keratin) Dermis
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Dense connective tissue Hypodermis (subcutaneous tissue)
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Adipose tissue Not part of the skin - acts as the anchor to underlying organs
Epidermal Layers 5 Layers - from superficial to deep
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Stratum Corneum
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Dead skin cells
Stratum Lucidum
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Only occurs in thick skin
Stratum Granulosum Stratum Spinosum Stratum Basale
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Cells undergo mitosis in this layer Melanocytes are located in this layer
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Stratum Corneum
Stratum Granulosum
Stratum Spinosum Stratum Basale
Melanin •
Pigment produced by melanocytes
• • • • •
Protects from UV rays Amount of pigment depends on genetics and exposure to sun More melanin = darker skin
Color is yellow to brown to black Melanocytes are mostly in the stratum basale
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Dermis 2 Layers:
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Papillary Layer
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Has projections called dermal papillae (creates fingerprints on palm and sole) Pain and touch receptors (Meissner’s corpuscles) Capillary loops
Reticular Layer
• • •
Blood vessels Sweat and oil glands Deep pressure receptors (Pacinian corpuscles)
Normal Skin Color Determinants
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Melanin
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Yellow, brown or black pigments
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Carotene
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• • • •
Orange-yellow pigment from some vegetables Skin will take on an orange-yellow color if large amounts of carotene-rich foods are eaten
Hemoglobin Red coloring from blood cells in dermis capillaries Oxygen content determines the extent of red coloring Oxygen poor people will be blue - cyanosis
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Happens in people with heart failure and breathing problems
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Blue People •
The Blue Fugates
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A family that had methemoglobinemia - their body could not convert methemoglobin to hemoglobin - giving them a perpetual blue color
A man named Paul Karason took too much colloidal silver in preparing for ‘Y2K’ and turned himself blue.
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Called argyria
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Skin Appendages
• Structure which rises from the skin and assists in maintaining homeostasis
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Cutaneous Glands • • • • •
Sebaceous (oil) glands Produce sebum, empty into hair follicles Lubricant for skin Kills bacteria Glands become very active at puberty
Cutaneous Glands • • • • • • • •
Sweat glands Produce sweat Widely distributed in skin Two types Eccrine Empty to pores on skin surface, widely distributed, mostly on palms and soles Apocrine Empty into hair follicles in the armpits, around nipples and in the groin
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Sweat and its function • • • • •
• • • •
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Composition Mostly water Some metabolic waste Fatty acids and proteins (apocrine only) Slightly acidic (pH 4 to 6)
Function Helps dissipate excess heat Excretes waste products Acidic nature inhibits bacteria growth
Odor is from associated bacteria
Hair •
Hair
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Produced by hair follicle
• • •
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Grows from the hair bulb
Consists of hard keratinized epithelial cells Melanocytes provide pigment for hair color
Functions Provide insulation and protection
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Hair Anatomy • • • •
Central medulla Cortex surrounds medulla Cuticle on outside of cortex Most heavily keratinized
Associated Hair Structures • • •
• •
Arrector pilli Smooth muscle attached to hair follicle Makes hair stand on end
Sebaceous glands Apocrine sweat glands
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Nails
•Hardening of the epidermis •Heavily keratinized •As new skin cells die, the nail grows
•Lack of pigment makes them colorless
Nail Anatomy • Free edge • Body • Root of nail • Eponychium (cuticle)– proximal nail fold that projects onto the nail body
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Homeostatic Imbalances
• ‘Homeostatic imbalances’ is another term for ‘pathologies’ which is another term for ‘diseases’ or ‘sicknesses’
Homeostatic Imbalances of Skin • • •
Athletes foot Itchy, red, peeling of the skin between the toes Caused by fungal infection
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• • • • • •
Boils and carbuncles Inflammation of hair follicles and sebaceous glands Caused by bacterial infection
Cold sores Small fluid-filled blisters that itch and sting Caused by the herpes simplex virus
• • •
Contact dermatitis Itching, redness, and swelling of the skin - eventually become blisters Exposures cause allergic reaction
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• • •
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Impetigo Pink, water-filled, raised lesions (usually around the mouth) Caused by bacterial infection
Psoriasis Reddened lesions covered with dry, silvery scales - may be disfiguring Cause is unknown - chronic condition Triggered by trauma, infection, stress
Burns • • • • • •
Tissue damage and cell death caused by heat, electricity, UV radiation, or chemicals Associated dangers Infection is the leading cause of death in burn victims Dehydration Electrolyte imbalance Circulatory shock - low blood volume
• •
Can lead to kidney shut-down To save lives, lost fluids must be replaced immediately
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Rule of Nines • • • •
Way to determine the extent of burns Body is divided into 11 areas for quick estimation Each area represents about 9% Burned skin is sterile for 24 hours
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Fungi and bacteria will then invade and cause trauma
First-degree burns
Severity of Burns
Only epidermis is damaged Skin is red and swollen, generally heal in 2-3 days
Second degree burns Epidermis and upper dermis are damaged Skin is red with blisters
Third-degree burns (full-thickness burns)
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Destroys entire skin layer, nerve endings destroyed Burn is gray-white or black
Fourth-degree burns Destroys all skin and hypodermis Can extend to underlying muscle and bone
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• • • • • •
Critical Burns Burns are considered critical if: Over 25% of body has second degree burns Over 10% of the body has third degree burns There are third degree burns of the face, hands, feet, or genitals Accompanied with other complications (fractures, inhalation burn, immune diseases)
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These patients are transported to a specialty burn center.
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Tumors • • • •
Tumors (neoplasms) are abnormal growth of body cells Two types: Benign Does not spread (encapsulated)
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Ex: Warts, moles
Malignant (cancerous)
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Metastasize (moves) to other parts of the body Skin cancer is the most common type of cancer
Skin Cancer • • • • •
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Basal cell carcinoma Least malignant Most common type
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Arises from stratum basale 99% of cases are fully cured with removal of lesion
Squamous cell carcinoma Arises from stratum spinosum Metastasizes to lymph nodes Early removal allows a good chance of cure
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Skin Cancer • • • • •
Malignant melanoma Most deadly of skin cancers, 50% survival rate
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Cancer of melanocytes Metastasizes rapidly to lymph and blood vessels Detection uses ABCDE rule (with exception of nodular melanoma) QuickTime™ and a decompressor are needed to see this picture.
ABCDE Rule to test for Melanoma •
A = Asymmetry
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Two sides of pigmented mole do not match
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B = Border irregularity
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Borders of mole are not smooth
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C = Color
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Different colors in pigmented area
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D = Diameter
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Spot is larger than 6 mm in diameter
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E = Enlarging or Evolving
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