integumentary system part 2

hair

consists of dead keratinized cells

none located on palms , soles , lips , nipples , and portion of external genitalia

functions

• warn of insects on skin

• hair on head guards against physical trauma

• protect from heat loss

• shield from sunlight

structure of hair

also called pili- flexible strands of dead kerantized cells

produce by hair follicles

contains hard keratin

• together and more durable

• cells do not flake off

2 regions of hair

shaft - area that extends above scalp , where keratinization is complete.

root- area within scale , where keratinization is still going on

3 parts of the shaft

1. medulla (inner or middle)- central core of large cellls and air spaces

2. cortex(outer) several layers of flattened cells surrounding medulla

3. cuticle (outer ) consist of overlapping layers of single cells

hair pigment is made by

melanocytes

• combinations of different melanin (yellow, rust, brown, black) create al the hair colors

• red hair has additional phenomena in pigment

• gray and white hair is a result of air bubbles in melanin in shaft

structure of hair follicle

extends from epidermal surface to dermis

• hair bulb- deep end of follicle

• hair follicle receptor(root hair plexus) - sensory nerve ending thats wrap around bulb

• hair matrix - actively dividing area of bulb that produces hairs cells, makes new cells pushes old cells upward

• arrector pili- smooth muscle attached to follicle, responsible for goosebumps - involuntary

• hair papilla - dermal tissue containing knot of capillaries that supplies nutrients to growing hair

types of growth of hair

vellus hair - pale fine bod hair of children and adult females

terminal hair - coarse , long hair

• scalp and eyebrows

• puberty - appear in axillary (armpit) and pubic regions of both sexes

______ and ______ affect hair grow

nutrition and horomones

true (frank) baldness

genetically determines and sex influenced condition

male patter baldness cause by follicular response to DHT

growth cycles are shortened - follicles shed before reaching the surface

nails

contain hard keratin

protective cover for distal, dorsal surface of fingers

nail bed is epidermis underneath keratinized nail plate

matrix - thickened portion of bed responsible for nail growth

nail folds - skin that overlaps border of nail

epinychium (in nail)

nail folds that projects onto surface of nail body

• also called cuticle

• nils normally appear pin because of underlying capillaries

• lunule- thickened nail matrix appears white

hyponchium (in nail)

area of under free edges of plate that accumulates dirt

abnormal color or shape can be an indicator of disease

clinical homeostatic imbalance 5.6

nails appearance can help diagnosing some diseases

yellow - tinged

may indicate respiratory or thyroid gland disorder

thickened yellow nails can be due to fungle infection of nail

koilonchya

spoon nail - outward concavity of nail

may single iron deficiency

beau’s line

horizontal line across nails may indicate severe illnesses such as uncontrolled diabetes, heart attach or cancer chemotherapy

sweat glands (sudoriferous glands)

all skin except nipples part of. external genitalia contains sweat glands

3 million per person

two types of sweat glands

eccrine (merocrine ) sweat glands

apocrine sweat glands

eccrine (merocrine ) sweat glands

• most number type

• abundant on plasm , soles , and forehead

• ducts connect pores

• function in thermoregulation - allow for vapor action

  1. regulated by sympathetic nervous system

their secretion is sweat

1. 99% water

2. salts

3. vitamin c

4. dermcidin (microbe - killing peptide )

5. Matoblic waste

apocrine sweat glands

confined to axillary and anegential areas

secrete vicious milky or yellowish sweat that contains fatty substances and proteins

• bacteria breaks down sweat leading to body odor

larger then eccrine sweat glands with ducts into hair follicles

begin at puberty

• function unknown but may act as sexual scent gland

sebaceous (oil ) glands

widely distributed, except for thick skin of palms and soles

most devolve from hair follicles and secrete into hair follicles

relatively inactive until puberty

• stimulated by hormones, especially androgens

secrete sebum

• oily HOLOCRINE secretion

• glands accumulate products then rupture

• bactericidal ( bacteria - killing ) properties

• soft skin and hair

Know Table 5.1  Summary of Cutaneous Glands

clinical homeostatic imbalance 5.7

acne is usually infectious inflammation of sebaceous glands, resulting in pimples (pustules or cysts)

• associated with propionibacterium acne infection

white heads are blocked sebaceous glands

• if secretion is oxidized , whitehead become a black head

overreactive sebaceous glands in infants can lead to seborrhea , aka “”crackle cap”

• begins as pink , raised lesions on scalp that turns yellow / brown and flake off

functions of skin

• protection

• body temp regulation

• cataneous sensation

• blood reservoir

• excretion of waste

protection has 3 barriers

1. Chemical barrier

2. Physical barrier

3. Biological barrier

Chemical barrier

• Skin secretes many chemicals, such as: 

o Sweat, which contains antimicrobial proteins

o Sebum and defensins, which kill bacteria

o Cells also secrete antimicrobial defensin

• Acid mantle: low ph of skin retards bacterial multiplication

• Melanin provides a chemical barrier against  UV radiation damage

Physical barrier

Flat, dead, keratinized cells of stratum corneum, surrounded by glycolipids, block most water and water-soluble substances

• Some chemicals have limited penetration of skin

o Plant oleoresins (e.g., poison ivy)

o Organic solvents (acetone, paint thinner)

o Salts of heavy metals (lead, mercury)

o Some drugs (nitroglycerin)

o Drug agents (enhancers that help carry other drugs across skin)

Biological barriers

Epidermis contains phagocytic cells 

o Dendritic cells of epidermis engulf foreign antigens (invaders) and present to white blood cells, activating the immune response 

• Dermis contains macrophages

o Macrophages also activate immune system by presenting foreign antigens to white blood cells

• DNA can absorb harmful UV radiation, converting it to harmless heat

Body Temperature Regulation

• Under normal, resting body temperature, sweat glands produce about 500 ml/day of unnoticeable sweat

o Called insensible perspiration 

• If body temperature rises, dilation of dermal vessels can increase sweat gland activity to produce 12 L (3 gallons) of noticeable sweat

• Called sensible perspiration (WHEN YOU WORK OUT)

▪ - designed to COOL BODY 

 Cold external environment

• Dermal blood vessels constrict 

• Skin temperature drops to slow passive heat loss

Cutaneous Sensations

 sensory receptors are part of the nervous system

o Exteroreceptors respond to stimuli outside body, such as temperature and touch

o Free nerve endings sense painful stimuli

 Metabolic Functions

• Skin can synthesize vitamin d needed for calcium absorption in intestine

• Chemicals from keratinocytes can disarm some carcinogens

• Keratinocytes can activate some hormones

• Example: convert cortisone into hydrocortisone

• Skin makes collagenase, which aids in natural turnover of collagen to prevent wrinkles

Blood Reservoir

****Skin can hold up to 5% of the body’s total blood volume(in dermis) *****

• Skin vessels can be constricted to shunt blood to other organs, such as an exercising muscle

Excretion

• Skin can secrete limited amounts of nitrogenous wastes, such as ammonia, urea, and uric acid

• Sweating can cause salt and water loss

Developmental Aspects of the Integumentary System

Fetal: by end of 4th month, skin of fetus is developed

• Lanugo coat: delicate hairs in 5th and 6th month

• Vernix caseosa: sebaceous gland secretion that protects skin of fetus while in watery amniotic fluid

Infancy to adulthood

skin thickens and accumulates more subcutaneous fat; sweat and sebaceous gland activity increases, leading to acne

• Optimal appearance during 20s and 30s

• After age 30, effects of cumulative environmental assaults start to show

• Scaling and dermatitis become more common

Aging skin

• Epidermal replacement slows; skin becomes thin, dry, and itchy 

• Decreased sebaceous gland activity

• Subcutaneous fat and elasticity decrease =  winkles and being cold 

• Increased risk of cancer  due to decreased numbers of melanocytes and dendritic cells 

• Hair thinning

Ways to delay aging

1.uv protection 

​2.good nutrition 

​3.lots of fluid 

​4.good hydride 

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