Integumentary System
Facts about your Skin
• Inegument = means covering
• Integumentary System- skin, nails, hair,
membranes, sweat, & oil glands
Surface Area = 1.2 to 2.2 square meters
Weight = 4 to 5 kg
Thickness 1.5 - 4.0 mm
7% of average body weight for an adult
Functions of Skin
Cushions and insulates and is waterproof
Protects from chemicals, heat, cold
 Not helpful against organic solvents, heavy metals or plant
oils from poison oak
Screens UV
Acid Mantel keeps down bacteria ~pH 5
Macrophages gobble up invaders
Synthesizes vitamin D with UV
Functions of the Skin
Regulates body heat
Prevents unnecessary water loss
Sweat 500ml a day if about 31-32 C
vessel dilate & constrict
But Lipid soluble – Vitamins and steroids in
Sensory reception (nerve endings)
Pacinian receptors
• Bumps and deep pressure
Meissner’s corpuscles & Merkel disks
• Aware of caress of clothing
Layers of the Skin
1) Epidermis
2) Dermis
3) Hypodermis
1) Epidermis
• Epi = Upon
• Keratinized stratified squamous epithelium
• nutrients reach by diffusion/ avascular
• Outer layer of dead skin cells called cuticle with living
level underneath
“Ashiness” is caused by this layer of dead skin cells being
very rough and raggedy
• DUST you see around is made up of dead skin cells!
Epithelium: layers (on left) and cell types (on right)
• Four basic types of tissue
– Epithelium – epidermis just discussed
– Connective tissue - dermis
– Muscle tissue
– Nervous tissue
tough, leathery, flexible layer
Made of connective tissue
Vascularized – contains blood vessels
Anchors the epidermis
Critical in Temperature regulation – contract and expand
In the dermis:
• Oil glands
• Sweat glands
• Hair follicles
• Fat tissue
• Nerves
• Connective tissue
• Blood vessels
Two layers
Papillary – areolar connective tissue; includes dermal
Reticular – “rticulum” (network) of collagen and
reticular fibers
Fingerprints, palmprints, footprints
Dermal papillae lie atop dermal ridges
Elevate the overlying epidermis into epidermal ridges
Are “sweat films” because of sweat pores
Genetically determined
Flexion creases
• Deep dermis
from continual folding
Finger Print
• Subcutaneous Tissue /Hypodermis / superficial
– not really part of skin, but helps with protective
– superficial to connective tissue around bones
– loose enough for free movement
– Adipose tissue – different patters of accumulation for
men and women (grows when we gain weight)
– shock absorber & insulator
– Deep pressure receptors
Cells of the Epidermis
• Keratinized stratified
squamous epithelium
• Four distinct cell
Merkel Cells
Epidermal Dendrite
o Most epidermal / superficial cells
o Produce keratin – “kera”= horn . Fibrous protein
that gives stretch
o Constantly in mitosis & pushed upwards
o By the time they are on the surface they are dead
o New epidermis every 25-45 days
o Friction= keratin formation is accelerated
therefore callus- a thickening of the epidermis
o Spider shaped
epithelial cells that
make Melanin
o Deepest layers of the
o Melanin made &
collects in granules
called melanosomes
o Actin filaments move
them along till they
are taken up by
o Granules accumulate
on the superficial
“sunny side” of the
Keratinocytes nuclei &
protect nucleus from
harmful UV rays
Merkel Cells
o Shaped like a spiky hemisphere
o Help with sensory of touch
Langerhans’ Cells /
Epidermal Dendrite Cells
Macrophages (pac mans) that help activate
our immune system
Layers of the Epidermis
• Thick skin= covers
palms, fingertips, and
soles of the feet
– FIVE layers/ strata
• Thin Skin= rest of the
– FOUR layers (no
stratum lucidum)
Deep to Superficial:
stratum basal
stratum spinosum
strata granulosum
strata lucidum
strata corneum
Epidermis and dermis of (a) thick skin and (b) thin skin
(which one makes the difference?)
Stratum basale/ stratum germinativum/
Basal Layer
Deepest epidermal layer
Single row of cells
Attached to dermis w/ a wavy boarder line
10-25% of cells are melanocytes & their
– undergoing mitosis
stratum spinosum/
Prickly Layer
• several cell layers thick
• keratinocyte in this layer are spiny
strata granulosum/
Granular Layer
• 3-5 cell layer
• keratinocyets flatten & start to die
– not enough oxygen and nutrients b/c pushed
away from blood source
strata lucidum/
Clear Layer
thin translucent band
only in thick skin
start making distinct layer
strata corneum/
Horny Layer
• 20-30 cells thick
• ¾ of epidermal thickness
• thickened plasma membrane of cells protects
from abrasion & penetration
• glycolipid acts as a “water proof”
• protects body from heat and water loss
• “dandruff” 18kg= 40 lbs in a lifetime
Skin Color
1. Melanin
• same # of melanocytes
• kind + amount of melanin made & retained
– Darker = more darker melanosomes & retain longer
• Freckles & pigment moles are accumulation of
• Sunlight causes melanin buildup
– to protect from UV
Skin Color
2. Carotene
Yellow-orange pigment
Accumulate in the stratum corneum
Palms of hands, soles of feet
Eat lots of rich carotene foods- becomes more obvious
3. Hemoglobin
– Pinkish hue of light skin b/c can be seen through light
Skin Appendages
• Derived from
epidermis but extend
into dermis
• Include
– Hair and hair follicles
– Sebaceous (oil) glands
– Sweat (sudoiferous)
– Nails
• Hair growth: averages 2 mm/week
– Active & Resting phase then Shed
– At the base of the follicle, hair papilla
• Contains blood vessels and nerves
• Contains matrix – epithelial cells responsible for
– Contains melanocytes
• Functions of hair
– Warmth
– Sense light touch of the skin
– Protection – scalp
• Hair color
– Amount of melanin for black or brown; distinct
form of melanin for red
– White: decreased melanin and air bubbles in the
– Genetically determined though influenced by
hormones and environment
Hair and hair follicles: complex
Derived from epidermis and dermis
Everywhere but palms, soles, nipples, parts of genitalia
Hair papilla
is connective
*“arrector pili” is smooth muscle
Hair bulb: epithelial
cells surrounding
• hard keratin
• Corresponds to hooves and claws
• Grows from nail matrix
Sebaceous (oil) glands
• Entire body except palms and soles
• Oils and lubricates
Sweat Glands
• Entire skin surface
– except nipples and
part of external
• Prevent overheating
• 500 ml to 12 L /day!
• Humans most
efficient (only
mammals have)
• Produced in response
to stress as well as

Integumentary Power Point