Our skin
The components of the integumentary system…
Skin – a.k.a. the integument OR cutaneous
Accessory organs
Sweat glands
Oil glands
Without our skin, we would quickly fall prey to bacteria and
perish from water and heat loss!!!
A little more information about our skin…
The skin ordinarily receives very little respect from its
inhabitants, but architecturally it is a marvel
Some of its uniqueness includes:
It covers the entire body
 It has a surface area of 1.5 – 2.0 m2
 Weighs ~4 kg (9 lbs)
 Accounts for about 7% of the total body weight
 Consists of ~1/2 million cells that are constantly dying and
being replaced
 It is pliable yet tough
The major functions of the skin
Protection – the skin covers and protects
underlying tissue and organs from impacts,
chemicals, and infections, while preventing the loss
of body fluids
Temperature maintenance – the skin maintains
normal body temperature by regulating heat gain
or loss to the environment
The major functions of the skin con’t
Storage of nutrients – the deeper portions of the
dermis typically contains a large reserve of lipids
in the form of adipose tissue
Sensory reception – receptors in the integument
detect touch, press, pain, and temperature stimuli
and relay that information to the nervous system
The major functions of the skin con’t…
5. Excretion and secretion – the integument excretes
salt, water, and organic wastes (sweat) and
produces milk (a specialized exocrine secretion)
Bell Ringer…
Why is temperature regulation so important for
the body
How does our skin protect us – there is more than
one way
The skin consists of two distinct regions:
The epidermis – the superficial epithelium
The dermis – underlying dense connective tissue
The subcutaneous tissue just below the skin is
known as the hypodermis or superficial fascia but
strictly speaking, it is not considered part of the skin
– it attaches to deeper structures such as muscles or
The epidermis…
The epidermis is composed entirely of stratified
squamous epithelium in 5 zones called strata
The epidermis is avascular - no blood supply
Most cells of the epidermis are keratinocytes –
produce keratin, a fibrous protein that makes the
epidermis a tough protective layer
The strata of the epidermis…
There are 5 strata zones – listed from inside to
Stratum basale – contain epidermal pegs to help
from this layer from slipping
Stratum spinosum
Stratum granulosum
Stratum lucidum – found only in hairless area such
as our palms and soles of feet
Stratum corneum
Stratum basale…
Deepest cell layer of the epidermis
Lies closest to the dermis, separated by basement
Contains the only epidermal cells that receive
adequate nourishment via diffusion from the
connective tissue
Constantly undergoing cell division, producing
millions of new cells daily, which make their way up
to the superficial layer of the skin
Life cycle of a skin cell produced in the
basale layer…
As the cell moves away from the basale layer, it
moves through the other layers of the skin, picking
up more and more keratin along the way
It eventually reaches the outermost strata – stratum
corneum, where it dies and is eventually shed
We have totally “new” epidermis every 25 to 45
The cell membranes of older skin cells (the ones
nearer the surface) thicken and develop many
desmosomes that fasten them to each other
While this is happening, the cells begin to harden
due to strands of tough, fibrous, waterproof keratin
proteins being synthesized and stored within the cell
Stratum Spinosum
Called this because the keratinocytes in this layer
appear “spiny”
Scattered among the keratinocytes are melanin
granules and Langerhans’ cells, which are most
abundant in this layer
 Melanin
granules – give skin its color and protects us
from UV radiation
 Langerhans’ cells – help in immune responses
Stratum Granulosum
Consists of 3 – 5 layers where the keratinocytes
appearance changes drastically
 They
become flatten and fill with waterproofing
lamellated granules
All cells above this layer are to far from the
capillaries and therefore die
Stratum corneum…
The outermost layer of skin composed of dead,
completely keratinized cells
It is 20 – 30 cells layer thick and accounts for ~ ¾ of
the epidermal thickness
Keratin is an exceptionally tough protein – its
abundance allows this layer to provide a durable
“overcoat” for the body, which protects deeper cells
from the hostile environment and water loss
This layer rubs and flakes off slowly but is steadily
replaced by cell produced by the stratum basale
Bell Ringer…
List the layers of the epidermis in order from
deepest to most superficial
What layer is only seen in the palms of our hands
and the soles of our feet?
The dermis…
The layer just below the basement membrane of the
The boundary between the dermis and epidermis is
usually uneven
This is because the epidermis has ridges projecting
inward and the dermis has conical dermal papillae
passing into the spaces between the ridges,
prevents the dermis from slipping laterally
The dermis…
The dermis binds the epidermis to the underlying
It is largely composed of irregular dense connective
tissue that includes tough collagenous fibers and
elastic fibers in a gel-like substance
 These
fibers give the skin toughness and elasticity
On average, the dermis is 1.0 – 2.0 mm thick, it
may be as thin as 0.5 mm or less on the eyelids or
as thick as 3.0 mm on our soles
The dermis…
Contains smooth muscle fibers, such as the arrector
pili muscle which causes hair to stand on end
Nerve cell processes are scattered through out the
dermis, which pick up on sensations from the outer
It also contains blood vessels, hair follicles,
sebaceous glands and sweat glands
Medicine delivery through our
There are several ways medication can be
administered through our skin
Intradermal injections
Injected within the skin
Subcutaneous injections
Injected through a hollow needle into the subcutaneous
a.k.a hypodermic injections
Transdermal patches
The patch is attached to the skin where the medication diffuses
through the epidermis and dermis entering the capillaries
What are the 5 functions of our skin?
How would you distinguish a mucous and a serous
Where is the subcutaneous layer located? Is it part
of the skin?

Introduction to the Integumentary System