Honors Anatomy & Physiology
INTEGUMENTARY SYSTEM
ESSENTIAL QUESTION

What are the ways skin protects the
body?
INTEGUMENTARY SYSTEM
functions:
1. protecting the body
2. helping to regulate body temperature
3. allows you to sense stimuli in your
environment
4. stores blood
5. synthesis of vit. D
6. excretion & absorption of materials

STRUCTURE OF THE SKIN
skin = cutaneous membrane
 largest organ of body


in adults: covers ~ 2 m² & weighs ~ 4.5 – 5 kg (10
– 11 lb)
2 parts:
1. epidermis
2. dermis
3. sub Q below dermis & not technically part of
skin: contains fat (insulation), & blood
vessels, nerves that supply the skin

LAYERS OF THE EPIDERMIS
EPIDERMIS
keratinzed stratified squamous epithelium
 4 main cell types:
1. keratinocytes
2. melanocytes
3. Langerhans cells
4. Merkel cells

KERATINOCYTES
~ 90% of all epidermal cells
 produce fibrous protein: keratin:

 protects
 heat
skin & underlying tissue from
 microbes
 chemicals

also release a water-repellant sealant
from lamellar granules
 decreases
water entry/loss
 inhibits entry of foreign materials
KERATINOCYTES
MELANOCYTES
~8% of epidermal cells
 produce melanin  keratinocytes

 pigment
(yellow-red to brown-black) that
contributes to skin color
 * absorbs UV radiation
 “covers” nucleus in keratinocyte
LANGERHANS CELLS
arise in red bone marrow then migrate to
epidermis
 easily damaged by UV radiation
 function: immune response vs. microbes
that invade

MERKEL CELLS
least numerous of epidermal cells (>1%)
 deep in epidermis
 in contact with Merkel disc (tactile disc)
 together detect different aspects of
touch

THIN SKIN
covers most of body
 4 layers:
1. stratum basale
2. stratum spinosum
3. stratum granulosum
4. stratum corneum

THICK SKIN
found in areas where exposure to friction
is the greatest
 “thick” because has 1 extra layer:

 stratum
lucidum (between stratgum granulosa
& a thicker stratum corneum)
PSORIASIS

common & chronic skin disorder in which
keratinocytes divide & move more quickly
than normal from stratum basale 
stratum corneum
 make
abnl keratin  flaky, silvery scales @
skin surface
 most often over knees, elbows, or scalp
DERMIS
2nd, deeper layer of skin
 composed mostly of CT
 2 regions:
1. papillary region
2. reticular region

PAPILLARY REGION OF DERMIS
~ 1/5th of total dermis
 surface area greatly increased by fingerlike structures: dermal papillae that
project into epidermis

 contain:
 capillary
loops
 tactile receptors: Meissner corpuscles
 free nerve endings (temp, pain, tickle, itch)
EPIDERMAL RIDGES
develop during 3rd month of fetal
development
 pattern is genetically determined & unique
to individuals (x identical twins)
 on finger tips ridges deeper  finger
prints

 allow
you to grasp things by increasing
surface area
RETICULAR REGION OF DERMIS
attached to subcutaneous layer beneath
 contains:

 dense
irregular CT
 hair follicles
 sebaceous glands
 sudoriferous (sweat) glands
 collagen & elastic fibers (gives skin its
elasticity, strength): extreme stretching 
striae (stretch marks)
BASIS OF SKIN COLOR
3 pigments contribute:
1. Melanin
2. Hemoglobin (hgb)
3. Carotene

MELANIN
made from a.a. tyrosine using enzyme
tyrosinase then stored in organelle called
a melanosome
 exposure to UV light increases enzymatic
activity & more (& darker) melanin
produced
 melanin absorbs UV radiation preventing it
from damaging DNA which  skin cancer

HEMOGLOBIN
in RBCs  rosy color to lighter skinned
individuals
 blushing: due to increased blood flow
(autonomic nervous system at work)

CAROTENE
yellow-orange pigment
 precursor of vit. A

ALBINISM
inherited inability to produce melanin
 most due to cell’s inability to produce
tyrosinase

VITILIGO
partial or complete lack of melanocytes
from patches of skin produces irregular
white spots
 ? Immune system malfunction?

SKIN COLOR AS DIAGNOSTIC CLUE
 cyanotic: when blood not adequately
oxygenated mucous membranes, nail beds
& skin appears bluish
SKIN COLOR AS DIAGNOSTIC CLUE

jaundice: due to build up of bilirubin
(yellow pigment) in skin, sclera; usually
indicates liver disease
SKIN COLOR AS DIAGNOSTIC CLUE

erythema: redness of skin caused by
engorgement of capillaries due to: injury,
infection, inflammation, allergic reaction
SKIN COLOR AS DIAGNOSTIC CLUE

pallor: paleness of the skin, seen in shock
& anemia
ACCESSORY STRUCTURES OF THE SKIN
all develop from embryonic epidermis
 include:

 Hair
 Nails
 Glands
HAIR (PILI)
present on most skin surfaces x palmar
surfaces of hands, soles & plantar
surfaces of feet
 genetic & hormonal influences determine
the thickness & pattern of distribution of
hair

HAIR
functions:
 protection

 scalp,
eyebrows, eyelashes: from getting
foreign objects in eyes
 nose, ear canals: trap foreign objects

sensitive to light touch
 touch
receptors in hair root plexus
ANATOMY OF A HAIR
HAIR

composed of columns of dead, keratinized
cells bonded together by extracellular
proteins
ANATOMY OF A HAIR
shaft: portion of hair that projects from
scalp
 root: portion below scalp
 follicle: surrounds root of hair
 arector pili: smooth muscle extends from
side of hair follicle  superficial dermis

TYPES OF HAIR



lanuga: grows on fetus @ ~ 5 months fetal
age; sheds b/4 birth
vellus hair: short, fine hair that grows
over baby @~ 2-3 months after birth
terminal hair: coarse hair that develops
after puberty
HAIR GROWTH CYCLE
HAIR COLOR
mostly due to amt & type of melanin in
keratinzed cells
 dark hair has eumelanin
 blondes & redheads have pheomelanin
 gray: loss of melanin
 white: loss of melanin + air bubbles in
shaft of hair

SKIN GLANDS
exocrine glands ass’c with the skin:
1. sebaceous glands
2. sudoriferous glands



eccrine sweat glands
apocrine sweat glands
SEBACEOUS GLANDS
“oil” glands
 most connected to hair follicles

 rest
secrete directly onto surface of skin
(lips, eyelids, genitals)
secrete oily substance called sebum onto
hair
 keeps hair from getting brittle

ACNE
inflammation of sebaceous glands
colonized with bacteria
 infection  cyst which destroys epidermal
cells (cystic acne)
 acne is not caused by eating chocolate or
fried foods

SUDORIFEROUS GLANDS
sweat glands
  sweat onto skin surface or hair follicles

CERUMINOUS GLANDS
modified sweat glands in external ear
canal skin (subQ layer)
 secrete cerumen (ear wax

 provides
a sticky barrier that impedes
entrance of foreign bodies
NAILS
plates of tightly packed, hard, dead,
keratinized epidermal cells that form a
clear, solid covering over the dorsal
surfaces of the distal portions of the 20
digits
 average growth ~ 0.04 in/wk

 fingernails
grow slightly faster than toe nails
FUNCTIONS OF A NAIL
help us grasp & manipulate small objects
 protect ends of digits
 allows scratching

PARTS OF EXTERIOR OF A NAIL
ANATOMY OF A NAIL
PARTS OF A NAIL
body: visible part
 root: part buried
 matrix: where cells divide to produce
growth

FUNCTIONS OF THE SKIN (#7)
1.
Thermoregulation


1.
the homeostatic regulation of body
temperature
skin achieves this in 2 ways:
sweating

2.
evaporation of sweat requires nrg (body heat) so
body cools down as sweat evaporates
adjusting flow of blood in dermis


vessels dilate when body too warm
vessels constrict when body too cold
FUNCTIONS OF THE SKIN
2. Blood Reservoir
 skin carries ~ 8 – 10% of total blood flow
in resting adult
FUNCTIONS OF THE SKIN
3. Protection






keratin protects underlying tissues from microbes,
abrasion, heat, & chemicals
lipids released retard evaporation of water from
skin surface guarding vs. dehydration & retard water
from entering thru skin
sebum moistens skin & has antibacterial properties
acidic pH of sweat bacteriostatic
melanin protects DNA in skin cells from UV damage
Langerhans cells alert immune system if microbes
does attack / macrophages ingest microbes
FUNCTIONS OF THE SKIN
4. Cutaneous Sensations
 skin contains variety of nerve endings &
receptors
 touch
 pressure
 vibration
 tickle
 pain
 temperature
FUNCTIONS OF THE SKIN
5. Excretion

elimination of wastes from the body

only small amt substances excreted from
skin
 ~400


mL water/day
~200 mL sweat (sedentary adult)
small amts salts, CO2, NH3, & urea
FUNCTIONS OF THE SKIN
6. Absorption



passage of materials from external environment
 body cells
absorption of water-soluble materials negligible
lipid-soluble materials do absorb:




fat-soluble vitamins (A, D, E, K)
certain drugs (can be administered transdermally)
gases: O2 & CO2
toxins: acetone, CCl4, salts of Hg, Pb, Ar, substances
in poison ivy & poison oak
FUNCTIONS OF THE SKIN
7. Synthesis of Vitamin D


requires activation of a precursor molecule in
the skin by UV rays in sunlight  modified by
enzymes in liver & kidneys  producing calcitriol
the most active form of vit. D
calcitriol: aids in absorption of calcium in GI
tract
SKIN WOUND HEALING
skin damage sets in motion a sequence of
events that repairs the skin to as normal
as it can in both structure & function
 depending on depth of wound 1 of 2
processes occur

 epidemal
wound healing
 deep wound healing
EPIDERMAL WOUND HEALING


abrasion: portion of skin has been scraped
away
in response to injury: basal cells of nearby
uninjured skin break contact with bm, enlarge, &
migrate across the wound


migration continues across wound until meet cells
advancing from other side of wound
contact inhibition: cells stop migrating when touch
another cell
DEEP WOUND HEALING
when injury extends deeper than
epidermis repair process more complex &
scars form
 healing occurs in 4 phases:
1. Inflammatory phase
2. Migratory phase
3. Proliferative phase
4. Scar formation

INFLAMMATORY PHASE

blood clot forms
 loosely

unites edges of wound
inflammation develops
 vascular
response
 vasodilation
 cellular
& increased permeability of vessels
response
 phagocytic
 fibroblasts
WBCs (neutrophils), macrophages
MIGRATORY PHASE
clot  scab
 epithelial cells migrate beneath scab to
bridge wound
 fibroblasts begin secreting collagen &
glycoproteins  scar
 *tissue filling wound called granulation
tissue

PROLIFERATIVE PHASE
extensive growth of epithelial cells
beneath scab & deposition of collagen in
random patterns (fibroblasts)
 growth of blood vessels

SCAR FORMATION
aka maturation phase
 scab falls off
 epidermis restored
 collagen fibers become more organized
 fibroblasts disappear
 blood vessels restored to normal
 scar tissue less elastic, fewer blood
vessels, +/- accessory structures of skin

SCARS
fibrosis: process of scar formation
 2 types raised scars
1. hypertrophic scar


2.
scar remains w/in boundaries of wound
keloid

extends boundaries of wound site
SCAR FORMATION
aka maturation phase
 scab falls off
 epidermis restored
 collagen fibers become more organized
 fibroblasts disappear
 blood vessels restored to normal
 scar tissue less elastic, fewer blood
vessels, +/- accessory structures of skin

BURNS
tissue damage caused by excessive heat,
electricity, radioactivity, or corrosive
chemicals that denature proteins in skin
cells
 destroy skin’s ability to maintain
homeostasis
 graded by their severity: 1st & 2nd degree
= partial thickness burns; 3rd degree = full
thickness

1ST DEGREE BURNS
only epidermis is damaged
 example: sunburn
 symptoms:

 localized
redness, swelling, & pain
tx: immediate flushing with cool water
(lessens pain)
 healing: 3 – 6 days +/- peeling of skin
 results: normal

2ND DEGREE BURN
epidermis & upper dermis damaged, some
skin function lost, ass’c structures not
damaged
 symptoms:

 same
as 1st degree + blisters (epidermis
separates from dermis due to accumulation of
tissue fluid)

example: any burn with blisters
2ND DEGREE BURNS
tx: if 2° infection: antibiotics
 lasts: 3 – 4 wks with +/- scarring


AVOID: WEAR SUNSCREEN!
3RD DEGREE BURNS
destroys epidermis, dermis, & subQ
 no initial edema or pain or sensations
(receptors destroyed)
 most skin functions lost
 as healing starts  marked edema
 regeneration: months, + scarring
 tx: +/- skin grafting

SYSTEMIC EFFECTS OF A BURN
greater threat to life than burn itself
 include:

1.
large loss of water, plasma, plasma proteins

2.
3.
4.
5.
 shock
bacterial infection
reduced circulation of blood
decreased urine production
diminshed immune response
MAJOR BURNS
used to estimate extent & severity of
burns
 major burn considered a 3° burn that
covers > 10% of body or a 2° burn that
covers > 25% of surface area of body or
any 3° burn on face, hands, feet, or
perineum
 if burn > 70% surface area  > ½ patients
die

RULE OF 9’S
SKIN CANCER
3 common forms:
1. Basal cell carcinoma
2. Squamous cell carcinoma
3. Malignant melanoma


1 & 2 50% more common in males
BASAL CELL CARCINOMA
> 78% all skin cancers
 arises in cells from stratum basale

 Sun-exposed

areas
rarely metastasizes.
SQUAMOUS CELL CARCINOMA
~20% of all skin cancers
 arise from squamous cells in epidermis
 variable tendency to metastasize

MALIGNANT MELANOMA
arise from melanocytes
 ~2% of all skin cancers
 deadliest form of skin cancer

 spreads

rapidly, can die w/in months of dx
~1/50 Americans will develop in their
lifetimes (was 1/500 in 1930’s)
 increase
partly due to hole in ozone layer
(more UV rads)
 main reason: more people spend more time in
sun &/or tanning beds
MALIGNANT MELANOMA
key to successful tx is early detection
 early warning signs: ABCD
 A: asymetrical lesion
 B: borders are irregular
 C: color is uneven; may have multiple
coloration
 D:diameter: ordinary moles <0.25 in (pencil
eraser)

DEVELOPMENT OF THE INTEGUMENTARY
SYSTEM