The skin, or cutaneous mem-
brane, covers the external sur-
the largest organ of the body in
terms of both surface area and weight. In adults, the
skin covers an area of about 2 square meters (22 square
feet) and weighs 4.5-5 kg (10-11 lb), about 16% of total
Let’s take a closer look at the structure of the skin.
Pertaining to the skin.
"above") The super-
ficial, thinner layer
of the skin, which is
composed of epithe-
Skin Is a Multilayered
The skin consists of two main parts
(see Figure 4.1a):
Dermis is the deeper, thicker
Deep to the dermis, but not part
of the skin, is the subcutaneous
(subQ) layer. This layer consists
of areolar connective tissue and
adipose tissue. Fibers that extend
from the dermis anchor the skin
to the subcutaneous layer, which,
in turn, attaches to underlying tis-
sues and organs. The subcutane-
ous layer serves as a storage depot
for fat and contains large blood
vessels that supply the skin.
is composed of
keratinized stratified squamous
epithelium. It contains four prin-
cipal types of cells: keratinocytes,
A layer of
dense irregular con-
nective tissue lying
deep to the epidermis.
ku-TA-ne-us) The layer
beneath the skin. Also
lar) A type of fibrous
connective tissue in
which the fibers are
arranged in a loose
net or mesh.
• Threads of fused, dead, keratinized
• Base is surrounded by living hair
follicle, nerve endings, blood vessels,
oil glands, and smooth muscle.
• Guard skin and scalp from sun injury,
protect eyes and nose from foreign
particles, and assist in temperature
Dermal root sheath
• Made of plates of packed, hard,
dead keratinized epidermal cells.
• Consists of visible nail body,
embedded nail root, and free
edge, which extends past the
• Nail matrix proximal to the root
contains dividing cells that allow
nail to grow.
• Help us grasp and manipulate
small objects, protect ends of
fingers and toes, and scratch
various parts of the skin.
Sagittal section showing internal detail
The Integumentary System Is Composed of Skin, Glands, Hair, Nails, and Nerve Endings