INTEGUMENTARY SYSTEM
- Body’s outer layer: skin, nails, hair, glands, & nerves of skin
- Protects body from infection & injuries from external environment
- Body’s coat of armor & first line of defense against viruses, bacteria, & other microbes
- Shields body from harmful light & regulates body temp
- Stores fat, water, glucose, & vit D
Skin
-
Largest organ of human body
Largest & heaviest organ (around 6lbs & 2mm thick); thinner on sensitive areas like
eyelids; thicker on surfaces that take more stress like soles of feet
One inch of skin contains 19 million cells
Protects body from extreme temps, maintains balance in fluids, synthesizes vit D
Made up of stratified squamous epithelial tissue
➔ has protective function; prevents microorganisms from getting
underneath skin; prevents water loss
microscopic view
5 Layers of Skin:
1) Epidermis
2) Dermis
3) Hypodermis
4) Fascia
5) Muscle
3 Layers of Skin: (based on most sources)
1) Epidermis - outermost layer; thin; constantly shedding dead skin cells; layer that
we can feel
Different Cells:
● Keratinocytes - building blocks of tough fibrous protein
- gives durability, structure, & waterproof properties
- executors of epithelialization process
- these cells die, laging may kapalit
-
moves upwards pag namamatay kasi may bagong cells so
nagkakathick skin (?)
● Melanocytes - synthesizes melanin (pigment)
● Langerhan cells - star-shaped found in stratum spinosum
- from bone marrow
- ingests invaders
- Antigen; for immunity; protects integ by producing antibodies to
prevent infection
● Merkel cells - found in stratum basale
- at boundary of epidermis & dermis
- creates sensory receptors
Layers of Epidermis: from superficial to deep
1. Stratum corneum - outermost layer; roughest; 20-30 layers of dead
keratinocytes; basic protection; waterproof layer of skin
2. Stratum lucidum - clear layer; 2-3 rows dead keratinocytes; thick skin on
hands & feet soles
3. Stratum granulosum - alive keratinocytes; forms keratins; grainy; the
deeper itis, the younger the cells
4. Stratum spinosum - cell regeneration is active; contains filaments help
hold each other; 8-10 row of cells mainly keratinocytes
5. Stratum basale (germinativum) - deepest; thinnest; where most new cell
productions happen; connects dermis to epidermis; single row of cells
attached to basement of membrane
Why do wounds itch?
- Most cells that accumulate at site of injury release histamines to repair the
skin, which irritate it, triggering an itchy sensation. Process involves tissue
growth & skin tightening
2) Dermis - true skin; thicker than epidermis
- middle layer
- contains blood vessels, nerves, hair follicles, & sweat glands
- sweating, circulating blood, sensation
- has collagen & elastin fibers w/c makes skin strong & elastic
- contains nerve fibers that registers sensation (temp, pressure, pain, hair
glands, sweat glands)
Layers of Dermis:
● Papillary layer - thin top layer; has areolar connective tissue & blood
vessels that give nutrients to the epidermis & help control the temp of skin
★ Areolar connective tissue - beneath epidermis; underneath
epithelial tissue of all body systems that has external openings;
makes skin elastic & helps withstand pulling pain
★ Papillary ridges - protrusions on skin; overlay epidermal
protrusions into dermis called intermediate ridges; sa tip ng ridges,
ay may receptor cells (merkel)
● Reticular Layer - thick bottom layer; has blood vessels & connective
tissue that supports the skin; 80% of dermis; made up of dense irregular
tissue
4 Classifications of Somatosensory Receptors:
1) Thermoreceptors - perceive temp all over body; homeostasis occurs
2 Categories
a) Hot
b) Cold - in greater density in face & ears
2) Thigmoreceptors/Mechanoreceptors - perceives sensation: pressure,
vibrations, texture
- most sensitive: merkel cells on non hairy skin
3) Nocireceptors/Pain Receptors - noci means injurious or hurt in latin
- 3 million receptors all over
Types of Wounds:
❖ Abrasion
❖ Avulsion
❖ Puncture
4) Propioreceptor - propio means ones own in latin
- sense sensation in relation to other parts of joints, muscles
- sends signals that something is wrong
3) Hypodermis (Subcutaneous tissue - SQ/SC) - deepest layer of skin
- consists of fat & connective tissue that attaches to the skin to underlying
muscles
- insulates & cushions
- Stores energy, connects dermis to muscles & bones
- Insulates body & protect body from harm
- Mostly adipose connective tissue
★ Adipose connective tissue - fat
- provides insulation, energy storage, shock absorption, &
helps anchor skin
-
Composed of fat cells or adipocytes (energy storing cells)
Stretch marks develop when skin stretches w/c causes connective tissue (collagen
& elastin fibers) to break so nagkakastretch marks
Sensory nerves are abundant in top layer of skin (epidermis); these nerves
transmit feelings of:
● Pain
● Heat
● Other sensation experienced by the skin
Acne - blemishes on face, neck, shoulders, back
- Common in teen years but still occur in adulthood
- to keep hair & skin lubricated, body depends on sebaceous glands (just under
skin)
➔ Secretes sebum (coats skin &
hair to prevent drying out
➔ Sebum travels up hair
follicles, out the pores, onto
surface of skin
➔ Hair follicles routinely shed
dead skin cells w/c sebum
carries out of body
➔ When body produces extra
sebum & dead skin cells, they
clog pores resulting skin
blemishes + bacteria =
inflammation
- acne may appear as whiteheads (clogged follicles closed off from air),
blackheads (clogged follicles that go darker when exposed to air), pustules (inflamed
follicles w/ pus or cyst, which is larger, painful, pus-filled lumps deep under skin)
Factor contributing to acne:
● Hormonal changes - testosterone
● Bacteria
● Certain meds
● Genetics
For mild acne, doctors may prescribe over the counter lotion with some of the
ffg:
● Benzoyl peroxide - kills bacteria, dries excess oil, removes dead skin cells
clogging pores
● Salicylic acid - slows loss of skin cells to prevent clogged pores; may
break down whiteheads & blackheads
● Alpha hydroxy acids - like lactic acid; help remove dead skin cells, reduce
inflammation & stimulate growth of new smoother skin
● Sulfur - removes dead skin cells & dries excess oils
For moderate to severe acne, doctors may prescribe stronger prescription lotion
with some of the ffg:
● Vitamin A - reduces build up of dead skin cells
● Topical antibiotics - kill bacteria
● Benzoyl peroxide + topical antibiotics
For moderate to severe acne, doctors may prescribe oral medication alone or with
topical treatment some of the ffg:
● Oral antibiotics - kill bacteria & reduce inflammation
● Isotretinoin - for most severe cases
● Corticosteroid injection - to relieve pain & help clear up a large legion
● Birth control pill w/ estrogen - to minimize effects of testosterone
Tips for good skin care:
● Wash twice daily with mild soap
● Wash gently w/o scrubbing
● For dry skin, use water based moisturizer
● Use oil-free (non comedogenic - wont clog pores) products
● Avoid picking/squeezing blemishes to avoid infection and scarring
● Avoid touching face with hands, hair, or items like cellphone
Hair - composed of keratinized thread of cells w/c develops in epidermis
- Since its from skin, its considered an appendage of skin
Function of Hair:
● Insulation against cold in scalp
● Against glare in eye brows
● Screen against foreign particles (eye lashes)
● In nostrils, trap dust particles in inhaled hair
● Protect openings from foreign particles
● Help protect skin
● Regulate body temperature
● Lend itself to evaporation & perspiration process
● Help with nerve sensing functions of integumentary system
3 Parts of Hair:
● Hair shaft - part of hair you can see, touch, & style
● Hair follicle - tube-like structure that keeps hair in skin
● Hair bulb - located under skin & responsible for hair growth
-
Hair has a hard cortex, w/c surrounds a softer center, the medulla. Cortex
is covered by the cuticle, a single layer of overlapping cells that holds hair
in the hair follicle.
● Hair papilla - extension of dermis that protrudes into the hair bulb. Blood
vessels within the papilla supply the hair bulb with the nourishment
needed to produce the hair. Hair is produced in cycles of growth & rest.
● Hair color - determined by varying amounts & types of melanin.
Production & distribution of melanin by melanocytes occur in hair bulb by
same method as in the skin.
● 2 types of Pigments : w/c blend to form a wide range of color; hormonal &
environmental factors can also contribute to color
1) Eumelanin - darker
2) Pheomelanin - lighter
● Hair in the scalp can live up to 2-6 yrs then die & be replaced with new
hair. As we get older, hair production slows down, mainly bc of heredity.
Hair grows 5 inches per year.
● 2 Types of Hair:
1) Terminal - hair sa ulo; may pigment
2) Vellus - hair sa face; peach fuzz; slightly pigmented
● Arrector pili - associated w/ each hair follicle; arrector means “arises”
- Contraction of this causes hair to become more perpendicular to
skin’s surface, or to “stand on end” (arrector pili pushes skin
upwards) & it produces a raised area of skin called “goosebumps”
(piloerection)
➔ Involuntary reaction
from sympathetic
nervous system
(nerves that control
fight or flight
response) control the
skin muscles
● Hair is primarily comprised of fibrous protein & contains small amount of
lipids (fats) & water. Hair comes from follicles, w/c are simple organs
made up of cells called epithelial cells.
➔ Cells that line the organs and provide a protective barrier
● Cutting hair is not painful bc hair shaft is made up of dead keratinocytes.
Hair shaft DOES NOT HAVE nerves.
● Hair pulling hurts bc the scalp/skin is being tugged along the hair and the
skin has nerves
Nail - consists of nail plate, nail matrix, & nail bed below it & grooves
surrounding it
-
Made up of hardened plates of keratin & surrounding tissues
Nail unit consists of fingernails & toenails & surrounding tissue that
makes up the distal & dorsal surface of fingers & toes
Function of Nails:
- Sensory assistance
- Tool functionality - capillary refill test w/c helps assess dehydration/blood
flow at extremities
- Ornament - manicure & pedicure
- Protection
● Healthy fingernail protects distal phalanx, & surrounding soft tissues from
injuries; Unusual nail characteristic: horizontal ridges & discoloration can
point to underlying health problems
● Enhances precise delicate movements of the distal digits through counter
pressure exerted on the pulp of the finger
● Reinforce & protect ends of fingers & toes
Parts of the Nail:
● Nail plate - hard part of nail you can see
● Nail bed - skin under nail plate
- found between germinal matrix & hyponychium
- gives nail pinkish color
● Cuticle - thin skin at base of nail plate
● Matrix - originates behind nail’s root
- responsible for nail growth
- creates new cells & goes forward
● Lunula - name means “little moon”
- white moon shape part
- distal part of nail matrix
- most visible on thumb
- if not visible, could be an underlying disease like kidney failure
● Nail fold - skin that borders at bottom of nail
● Nail root - proximal portion of nail that's hidden within the skin
● Nail body - aka sterile matrix
- hard, visible portion of nail that attaches to nail bed
- made up of dead keratinocytes (translucent)
● Free edge - grows beyond nail
- need to cut bc this isnt attached to nail bed
● Proximal Fold - fold of skin along proximal region (base) of nail plate
- bottom of nail
● Lateral Fold - fold of skin along sides of nail plate
● Eponychium -epo means over/upon; nychium means little claw
- thin layer of tissue on ventral surface of proximal fold
- living tissue that produces the cuticle
● Cuticle - thin, dead, transparent layer produced by eponychium
- extends onto proximal portion of the nail plate
● Paronychium - paro means alongside; nychium means little claw
- tissue along border of the nail at lateral folds
- infections here are called paronychia
● Hyponychium - hypo means below/under;
- below nail’s free edge & distal to nail bed
- seal out germs & rich in wbc
3 Main Layers:
1) Dorsal - top layer
2) Intermediate - middle layer
3) Ventral - bottom layer
\
Fun facts:
● Hair & nails are made up of same protein. Both made up of keratin. Nails
are much stronger than hair due to difference in arrangement of keratin
molecules w/c gives nails more resilient properties
● Fingernails grow faster than toenails
● Nails grow faster in the summer, slower in winter
● Nail plate is attached to bone by anterior ligament & posterior ligament
● Nails are accessory organ of skin
Glands - found throughout skin
- Release water, salt, oil from under skin to surface of skin
Functions of glands:
● Exocrine glands of integ system produce sweat, oil, was to cool, protect &
moisturize skin’s surface
Major Glands of Skin
● Sebaceous Gland - produce sebum, an oily, white substance rich in lipids
- sebum is released by holocrine secretion & lubricates the hair &
surface of the skin w/c prevents drying & protects against some
bacteria
● Sweat Gland - coiled tubular structures vital for regulating body temp
3 Types of Sweat Glands:
1) Eccrine glands - found almost in every part of skin especially in
palms & soles of feet
- Produce a secretion that is mostly water with few salt
- Have ducts open onto the surface of skin thru sweat pores
- When body temp starts to rise above normal levels, sweat
glands produce sweat w/c evaporates & cools the body
2) Apocrine glands - active at puberty bc of influence of reproductive
hormones
- Common in armpit & genital area (hair growth)
- Organic secretion, essentially odorless when released,
quickly broken down by bacteria into substances
responsible for what is commonly known as body odor
3) Apoeccrine glands - produces more sweat
-
Plays large role in axillary sweating
4 Types of Exocrine Glands:
● Sudoriferous glands - to emit perspiration to help cool off body
when body temp rises
● Sebaceous glands - very small tubular-shaped glands, located in
the dermis; produce sebum
● Ceruminous glands - cerumen (earwax) has a protective
mechanism; modified sweat gland
● Mammary glands - glands on person’s chest; modified apocrine
glands; active during & after pregnancy