ch .5

HAIR - Dead keratinized cells

  • Hard keratin

  • More durable

  • Does not flake off

  • Protect from physical trauma, heat loss, & sunlight

What produces hair color

  • Hair pigments

Forms - yellow,rust,brown,black

Pigment called - Pheomelanin

Gray.white - due to decrease in melanin production

Air bubbles - replace melanin in hair shaft

Hair type - shaft shape

  • Flat - kinky

  • Oval - wavy

  • Perfectly round - straight

 

Types of hair -

  • Vellus hair

    • Pale,fine, - body hair in children and adult females

  • Coarse

    • Long hair, scalp eyebrows, eyelashes

    • Puberty) stimulated by androgens (testosterone)

 

 

 

 

Nutrition and hormones affect hair growth

 hair matrix - divides

Active phase - followed by resting phase

  • In resting phase, reduces in time

  • 4 years in active phase (up to 1 meter during that time)

  • A few months - eyebrows

  • 1 month - eyelashes

 

 

Alopecia

Thinning of hair in both sexes - age 60-65

More shedding than replacing

  • Age 35 - more common in males (40%)

  • Age 60 - 85%

True baldness

Male pattern baldness

  • Genetically determined - sex linked

    • From mothers - sons

  • Hair follicles get shorter

    • Androgens

 

Hirsutism - hairy in females - excess androgens

  • PCOS

  • More testosterone

    • Hair in chest, increase muscle mass

 

Sudoriferous glands - sudor=sweat

 - all skin surfaces

3 million per person

  • Eccrine sweat glands

    • Abundant on palms soles and forehead

    • Duct connect to pores (look at PPTX)

    • THERMOREGULATION

      • Regulated by sympathetic nervous system

      • Hypotonic - secrete sweat , pH 4-6

      • Inhibits bacterial growth - DERMCIDIN

        • Salts , metabolic waste (urea)

      • Heat induced sweating

        • temperature

      • Emotionally induced sweating

        • Nervous

  • The skin is involved in the synthesis of a vitamin D precursor when exposed to sunlight. This precursor is then converted into active vitamin D in the liver and kidneys, which is essential for calcium absorption and bone health. The process involves the conversion of 7-dehydrocholesterol in the skin to cholecalciferol (vitamin D3) upon exposure to UVB radiation.

 

  • Apocrine sweat glands

    • Axillary

    • Anogenital regions

    • Odorless until bacteria break down organic compounds

      • Causes body odor

    • Duct empty into hair follicles

    • Puberty (androgens)

      • Precise function unknown

        • Assumption - sexual scent glands??

          • Activity increases during sexual form

          • Alert and receive according to cycles

          • Secretions may act as pheromones

    • Modified apocrine glands

      • Ceruminous glands

        • Secrete cerumen - earwax

      • Mammary glands

        • Secrete milk

(muscle) Myoepithelial cells - sympathetic nervous system - contract in, force sweat

 

Sebaceous (oil) glands

 - not found in thick skin - palms and soles

  • Most develop from & secrete into hair follicles

  • Secrete Sebum

    • Acidic oily substance

    • Function : lubricate, soften, waterproof skin, Bactericidal action

 

Intugementary system functions

Excretion - some nitrogenous waste, lost in sweat

Ammonia, urea, uric acid

Blood reservoir -

 

Metabolic function - modified form of cholesterol

Vitamin d precursor

  • Active form - required in the gut in order to absorb calcium

    • Calcium - blood clotting, muscle, action potential

 

Cutaneous sensation

Exteroceptors

  • Pain, pressure, touch, temperature stimuli

 

 

 

 

 

 

Critical if

  • 25% of body has 2nd degree burns

  • Over 10% of body has 3rd degree burns

  • 3rd degree burns - hands. Feet or face

Immediate threat to life - loss of fluids, proteins electrolytes

Dehydration and electrolyte imbalance

 

 

***

Dendritic cells - epidermis - phagocytes and APC

Present foreign antigents

 

Insensible perspiration

  • Unnoticeable sweat

Sensible perspiration

 - temp rises

  • Dermal vessels dilate

  • temp drops

    • Dermal vessels constrict

Cutaneous sensation

   - free nerve endings

  • Pain and temp

  • Laminar core puzzle

    • Deep pressure and vibration

  • Hair follicle receptor

    • Light touch, bending of hair

  • Meissner corpuscles

    • Dermal papillae

    • Detect light touch discriminative touch

  • Epithelial tactile complex

    • Light touch

  • Bulbous corpuscles

    • Dermis

    • Deep, continuous pressure

 

Skin cancer

  • 1/5 individuals

  • High uv = cells commit photodamage

Three major form of skin cancer

  • Basal cell carcinoma

    • Proliferation of stratum basale

    • 99% curable if detected early

    • Shiny dome shaped nodules

    • Slow growing

    • Metastasis not common

  • Squamous cell carcinoma

    • Proliferation of keratinocytes of stratum spinosum

    • Grows rapidly metastasizes

    • Bleed or ulcerate

  • Melanoma

    • Least common, most dangerous

    • Cancer of melanocytes

    • Spread brown to black patch

    • Metastasizes rapidly

    • Highly resistant to chemotherapy

    • 1/3 developed from pre-existing moles

    • Early detection

ABCDE

  • A = asymmetry

  • B = border irregularity

  • c= color

  • d= diameter

  • E = evolving

 

Burns

  • First degree burns (heal 2-4, 3-5 days)

    • Partial thickness burn

    • Epidermis damage

    • Redness, swelling, pain

  • Second degree burns (2-4 weeks to heal, skin graft)

    • Epidermis, Upper dermis

    • Blistering

    • Partial thickness burn

  • Third degree burns (skin graft)

    • Entire thickness

    • Nerve ending destroyed

    • Full thickness burned

 

Severity and extent of burns

  • Rule of nines

  • 9% of body

  • Dangerous/critical

    • 25% of body = 2nd degree

    • 10% of body = 3rd degree

    • 3rd degree burns on hand feets and face

  • Immediate threat to life

    • Loss of fluids - proteins and electrolytes

    • Dehydration & electrolyte imbalance