Week 05 Objective Assignment
The Integumentary System
Name the tissue types composing the epidermis and dermis. List the major layers of
each and describe the function of each layer.
The epidermis is the outermost portion, which in subdivided into thin layers called strata.
epidermis is composed entirely of epithelial cells and contains no blood vessels.
As the surface
layer of skin, the cells of the epidermis are constantly lost through wear and tear.
are no blood vessels in the epidermis, the only living cells are in its deepest layer, the stratum
germinativum, where nourishment is provided by capillaries in the underlying dermis.
in this layer are constantly dividing and producing daughter cells, which are pushed upward
toward the surface.
As the surface cells die from the gradual loss of nourishment, they undergo
changes in that they develop large amounts keratin, a protein that serves to thicken and protect
By the time the epidermal cells reach the surface, they have become flat and horny, forming the
uppermost layer of the epidermis, the stratum corneum.
Between the stratum germinativum
and the stratum corneum, there are additional layers that vary in number and quantity
depending on the thickness of the skin.
Cells in the deepest layer of the epidermis produce
melanin, the dark pigment that colors the skin.
The dermis is our true skin, which has a framework of connective tissue and contains many blood
vessels, nerve endings, and glands.
What we see as our true skin, the dermis has a framework of
elastic connective tissue and is well supplied with blood vessels and nerves.
Because of its
elasticity, the skin can stretch with little damage.
Most of the appendages of the skin, including
the sweat glands, oil glands, and hair are located in the dermis and may extend into the
subcutaneous layer under the skin.
The thickness of the dermis also varies in different areas.
Some areas like the soles of our feet
and the palms of our hands are covered with very thick layers of skin.
Other areas like the eyelids
are covered with very thin delicate layers.
Portions of the dermis extend upward into the epidermis, allowing blood vessels to get closer to
the surface cells.
These papillae are extension that form a distinct pattern of ridges on the
surface of thick skin which help to prevent slipping, such as when picking up or grasping an
The unchanging patterns of the ridges are determined by heredity.
The skin has many functions; the main four functions are protection against infection, protection
against dehydration, regulation of body temperature, and collection of sensory information.
The skin forms a primary barrier against invasion of pathogens.