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Chapter 5: Skin and the Integumentary System (5-6: Hair (Kertiniation…
Chapter 5: Skin and the Integumentary System
Skin and Tissues
Skin Functions
Dermis
Subcutaneous
Epidermis
General Structure
4.Cutaneous Sensation
Light touch detection
Meissner's Corpuscles
Pressure detection
Pacinian Corpuscles
5.Vitamin D Synthesis
UV rays in sunlight activate its synthesis. Vitamin D is required for bone homeostasis
3.Regulation of Body Heat
6.Blood Reservoir
The dermis houses about 10% of the body's blood vessels. Skin only requires 1-2% of the body's blood
2.Excretion (minimal, most through kidneys)
Urea
Uric Acid
7.Immunity
Langerhan's cell (macrophages); interact with T-helper cells in immune responses.
1.Protection
Chemical Barrier
Biological Barrier
Langerhans Cell (Epidermis)
Macrophages & Mast Cells (Dermis)
Physical barrier
5-2: Skin Color
Environmental Factors
Chemicals
Drugs (antihistamines & Antibiotics)
UV rays
Physiologic Factors
Lack of Hb in dermal blood vessels =blue (cyanosis)
Inability to breakdown Hb (liver problems) =yellow (jaundice)
Hemoglobin (Hb) in dermal blood vessels =pink
Carotene may accumulate in corneum =orange
Genetic Factors
People of different races have essentially the same # of melanocytes, but the amount of melanin produced varies (determined by DNA)
5-5: Subcutaneous (beneath the skin)
Structure
Adipose tissue & blood vessels
Function
Insulation
5-6: Hair
Kertiniation
Cells in follicle - maturing & accumulating keratin
Cells in epidermis - dead epithelial cells; full of keratin
Cells in root - active mitosis
Cells are epithelium
Pigment (melanin decrease with age
Genetically determined
White hair / gray (lack of melanin and air bubbles)
Growth
0.3 mm per day
2.5 million on body / 500,00 hair on the head
Grows for 2-5 years / new cycle pushes old hair out
Hair Papilla
Peg of connective tissue (nerves and capillaries)
Structure
Hair root
Hair shaft
Cortex
Medulla
Cuticle
Arrector Pili Muscle
A bundle of smooth muscle associated with every hair follicle
5-10: Life Span Changes
5-3: Vitamin D Synthesis
Skin Cancers
Squamos cell carcinoma
Malignant melanoma
Basal cell carcinoma
Prevention
Avoid mid-day sun, & wear sun block
5-8: Nails
Functions
Manipulation
Protection of digit ends
Structure
Nail root
Nail production by an epithelial fold
Lunula: pale crescent near nail root
Cuticle (fold of stratum corneum)
Nail body covers the nail bed
Epithelium undergoing keratinization (active mitosis in lunula)
5-9: Regulation if Body Heat
Heat production and loss
Heat loss is by four methods
Conduction
Less heat loss
Convention
Heat loss to surrounding air
Radiation
Most heat loss by this mode
Evaporation
Heat loss varies
Low body temperature require heat loss to be minimized
The hypothalamus signals for sweating to decrease (decreasing heat loss by evaporation) and dermal vasoconstriction (decreasing heat loss by radiation). Usually this brings the body temperature back to normal.
Heat loss in controlled by regulating dermal blood flow
Vasoconstriction
Decreases dermal blood flow which decreases heat loss.
Vasodilation
Increases dermal blood flow, which also increases heat loss.
If the body temperature remains low after the above action
Heat must be produced.
Shivering occurs and the tiny muscle contractions involved produce heat.
Heat Production is mostly a by-product of cellular metabolism
Problems in temperature regulation
Hyperthermia - elevated body temperature.
Humid air decreases evaporation
Air temperature exceeds body temperature, thus heat is gained not lost
Hypothermia - low body temperature
Very dangerous if core body temperature drops below 94 F
Limbs can withstand about 65 F because they contain no vital organs.
5-1: Epidermis
Main Function (Protection)
Prevents moisture loss (waterproof) 2. Prevents injury by penetration
Prevents microorganisms/chemical entry
Pigment
Structure
Stratum Granulosum
Stratum Spinosum
Stratum Lucidum
Stratum Basale (germinativum)
Stratum Corneum
5-7: Sebaceous Glands
Secretion (holocrine)
Fat
Cellular material
Sebum
Sebum is secreted into hair follicles
Associated with every hair follicle
Function : Sebum keeps skin & hair soft, pliable and virtually waterproof
Holocrine gland (simple cuboidal epithelium)
Disorders
Acne (hypersecretion of sebum; ducts clog & inflame
Seborrhea (hyperproduction of sebum; oily scales
5-4: Dermis
Structure
Papillary layer (20%)
Meissner's Corpuscles
Reticular layer (80%)
Pacinian Corpuscles
Main Function
Nourishment of the epidermis
5-7: Skin Glands (Sweat Glands)
Merocrine
Structure
Duct in dermis
Pore at surface
Coil in deep dermis
Characteristics
Function throughout life
Not associated with hair follicles
No odor in secretion
Location - forehead, neck, and back
Respond to elevated temperature / exercise
Secretion (99% water)
Salt
Wastes (urea and uric acid)
Apocrine
Characteristics
Secretion
Structure
Modified Apocrine Glands