normal skin color determinants - jefferson county public ... · pdf filenormal skin color...

1

Body Bugs

NOVA | Bugs That Live on You

Follicular Mites – found in

all hair follicles

Dust Mites – found

on your body, your

bed, any fluffy

surface that you

spend time with

Skin color

Slide 4.14

Normal Skin Color Determinants

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

• Determined by a combo of:

•Types of pigments present

•Blood circulation

•Stratum corneum thickness

Slide 4.14

Normal Skin Color Determinants


• 3 different pigments that contribute to overall skin color

• Melanin

• Carotene

• hemoglobin

Normal Skin Color Determinants• Melanin

• Only pigment of the 3 produced in skin

•Yellow, brown or black pigments produced in melanocytes found in stratum basale – transferred to keratinocytes

•Local accumulations form freckles & pigmented moles

•Amount of melanin produced depends upon genetic and exposure to sunlight

•Solar elastosis – clumping of elastinfibers = leathery looking skin

2

A closer look at Melanin

• Despite the protective action of melanin,

excessive and/or cumulative exposure

eventually can cause damage to the skin and

various types of cancer

START BEING CAREFUL

NOW!!!

• Effects are most obvious in palms & soles of feet where stratum corneumis thickest

• Carotene

• Orange-yellow pigment from some vegetables (carrots, squash, tomatoes)

• Vitamin A precurser – vitamin A forms retinal which is needed for sight

• Accumulates in adipose and stratum corneum cells

Normal Skin Color DeterminantsNormal Skin Color Determinants• Hemoglobin & blood circulation

•Found in red blood cells

•Bright red coloring from oxygenated blood cells in dermis capillaries

•Oxygen content determines the extent of red coloring

•Poorly oxygenated blood is blue

•More obvious in fair skinned individuals (give pinkish hue)

Blood flow

• Vasodilation causes increase in flow

• Vasoconstriction causes decrease in flow

Skin as a Diagnostic

• Skin color is influenced by emotional &

disease states: You should know the states that cause these.• Cyanosis – bluish color - lack of oxygen

• Seen in lips or nail beds (choking)• Erythema – redness – blushing, heat,

inflammation, fever, hypertension, allergies• Add this -Pallor – paleness – lack of blood

flow – fear, anger, anemia, low BP• Jaundice – yellowish color – liver damage

• Bile pigments accumulate in blood & deposited in body tissue

• Bronzing – bronze (tan) – Addison’s disease

• Hematomas (bruise) – black & blue – blood under skin

3

End of Worksheet #1 Material

Skin Derivatives

Appendages of Skin

• These are oil and sweat glands, hair & hair

follicles, & nails

• What is Hair (pili)?

– Strand of keratin

– This keratin is hard & tougher & more durable

than soft keratin in skin

Hair & Hair Follicles

• In mammals is primarily for warmth, but also

help to sense insects on skin

• Scalp hair protects us from physical trauma,

heat loss, & sun

• Eye lashes keep debris out of eyes

• Eyebrows keep sweat out of eyes

• Nose/ear hair filters debris & insects

Hair Anatomy• Central medulla

• Cortex surrounds medulla

• embedded with pigment granules made by melanocytes @ base of hair follicle

• Color, shape, distribution of the granules provide important points of forensic comparison

• Cuticle on outside of cortex• Single layer of overlapping cells

heavily keratinized• Split ends – cuticle flakes off –

fibers in cortex fray out

4

a)a) HumanHuman b) Dogb) Dog c) Deerc) Deer

d) Rabbitd) Rabbit e) cate) cat f) Horsef) Horse

Hair anatomy

• Hair shaft –

above skin

• Hair root –

below skin

Slide 4.18

Appendages of the Skin


• Hair

•Shaft – projects from skin

•Add in margins: Shape determines hair curliness

•Flat = curly

•Oval = wavy

•Round = straightFigure 4.7c

Slide 4.18

Hair Follicle

• Hair - Extends into dermis & hypodermis

• Produced by hair bulb- expanded end surrounded by nerve endings

• Papilla contains capillaries in bulb for hair nourishment

• Matrix = growth zone – directly surrounds papilla

Figure 4.7c

Slide 4.20

Associated Hair Structures


• Arrector pilli

• Smooth muscle regulated by emotions (cold/scared)

• Contraction pulls hair upright (normally at angle) causing skin surface to dimple

Figure 4.7a

Arrector Pili Muscle

5

Slide 4.19

Hair Color


• Caused by proportions of 3 types of melanin

• Determined by genetics

• Melanin is replaced by air bubbles in gray/white hair –causes different texture

Figure 4.7b

Hair Types

• Vellus hair – softer body hair – pale/fine

• Terminal hair – coarser hair found in axillary & anogenital regions & other body regions

• Scalp, eyebrows, pubic areas, chest, face, arms of men after puberty

• Lanugo – newborn baby fuzz

• Only hairless part of body are the lips, nipples, external genitalia & thick skinned areas

Interesting Facts• There are over 1 million hairs covering the body

– 100,000 + on scalp

– 30,000+ in an adult male’s beard

• Hair density & growth are primarily related to nutrition

& hormones

• Over-active hormones can lead to additional terminal

hair growth

• Poor nutrition can result in hair loss or slow hair growth

• MISCONCEPTION: hair does not grow faster after it’s cut

Slide 4.20

Hair Growth


• Grows ~ 2mm/wk or ~ 1cm/month

• Taking vitamins can help

• Influenced by (in order):

•Nutrition: main influence

•hormones

•Blood flow

Figure 4.7a

Cycles

6

Androgenetic Alopecia

• Male pattern baldness• Begins @ anterior

hairline• Growth cycles of hair

follicles severlyshortened

• Sex linked, recessive trait• Punnett Square!

Causes thinning hair in

women

Androgenetic Alopecia

� Increased activity in androgen receptors

causes hair loss & increases other health risks

such as coronary heart disease and prostate

cancer in men and polycystic ovary syndrome in

women

�Terminal hair replaced by vellus hair -progresses posteriorly

�Treatment: drugs that inhibit testosterone production (Rogaine, Propecia)

Imbalance: FYI

• Thinning hair can be caused by an abundance

of factors.

– Heterozygous traits

– Nutrition

– Medications

– Stress (affects nutrition & hormones)

– Hormones

– Physical factors



• Nails: Just know diagram & these imp. facts – add to diagram:

• Scale-like modifications of the epidermis

• Heavily keratinized

• Stratum basale extends beneath the nail bed to form nail matrix

• Which is responsible for growth

• Lack of pigment makes them colorless

Nail StructureNail Structure

• Know all parts labeled on diagram

• Why is lunula white?

• What happens if matrix is damaged?

7

Sweat Glands

• Sudoriferous (sweat) glands

• Three types

• Eccrine glands

• Widely distributed in skin: abundant on palms, soles, forehead

• Open via duct to pore on skin surface

• Sweat composition: mostly water(from blood), contains NaCl, vitamin C & metabolic wastes with a slightly acidic 4-6 pH

• Function: thermoregulation

Sweat Glands• Apocrine glands (also sudoriferous)

• Ducts empty into hair follicles

• Found mainly in anogenital & axillary(under arm) region

• Larger than eccrine glands

• Begin to function at puberty due to hormones

• Organic contents: Fatty acids and proteins – can have a yellowish color that stains clothes

• Odor is from associated bacteria

Slide 4.17

Sweat Glands


Ceruminous glands

• Modified apocrine gland

• Found in outer 1/3 of ear canal

• Produce ear wax to trap “invaders”

Sweat Glands

• Mammary glands – ADD TO NOTES

– Specialized sweat glands that secret milk

Slide 4.15



• Sebaceous glands (all over except palms and soles of feet)

• Secrete oily substance called sebum, usually into hair follicles

• waterproofing

• Lubricant for skin & kills bacteria

• Most with ducts that empty into hair follicles

• Glands are activated at puberty: stimulated by hormones

Imbalances

– Upper right hand box in notes;

– Acne – active infection of sebaceous glands

• Accompanied by pimples/cysts on skin caused by bacterial infection

– Whitehead - Sebaceous gland duct blocked by sebum

– Blackhead – sebum oxidizes, dries, and darkens

– Seborrhea – “cradle cap” – Over activity of

sebaceous glands in infants

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Integumentary Functions

Protection - biological

• Biological – cells – macrophages &

Langerhan’s cells engulf invaders.

Protection - mechanical

• Mechanical – physical

– Continuity – skin is made impermeable through the tight junctions & desmosomes

– Keratin – physically blocks the passage of water and water soluble substances

– FYI: Molecules that can pass through your skin:

• Lipid soluble – O2, CO2, ADEK, steroids, nicotine, & other transdermal medications

• Oleoresins – poison ivy & poison oak, etc – you have less than 10 min to wash it off!

Protection - Chemical

• Chemical

– Skin secretions: tears, sweat, oil lower pH and

contain lysozyme (chemical that lyses cells)

– Melanin – pigment shield against UV radiation

Excretion

• Limited amounts of nitrogen containing

wastes (most is excreted in urine unless you

have a kidney disorder in which case urea will

be excreted in small amounts through skin)

• Sodium chloride through sweat

• Water through sweat

• Heat through sweat

9

Homeostasis of Body Temperature

• Heat production – chief determinant is muscle

activity

• Heat loss/gain

– 80% of heat transfer is through the skin – the rest

is through the mucosa (dogs are opposite!)

– Regulated by vasoconstriction & vasodilation since

heat is carried primarily in the water content of

the blood (reminder: on page 1 of notes)

Understand what is

happening in these

diagrams!!

Vitamin D Production• Vitamin D is important in

the uptake of Calcium from the food you eat.

– Ca has to be absorbed from your stomach into the blood to go anywhere

– Cholesterol molecules when exposed to UV light become a Vitamin D precurser

– Precurser becomes active in the liver & kidneys

Sensation – skin receptors

Don’t need to memorize

• Free nerve ending = pain

• Meissner’s corpuscles = discriminating touch, light pressure (think fly on your arm)

• Krause’s – cold

• Ruffini’s – heat

• Merkel Disc – Medium pressure

• Pacinian corpuscle – Deep pressure

See diagram in notes

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