3. Integumentary System - Skin, hair, and nails
protect our insides from the outside.
The epidermis is the outer layer of
skin. The outer cells are dead, and all
the cells are filled with keratin, a
protein that gives the skin its rough,
leathery texture, and makes it
waterproof.
The dermis is the inner layer of skin.
The cells that make it up are alive,
and it contains nerves, blood, and
lymph vessels. The nerves allow the
reception of environmental signals.
The blood vessels help regulate body
temperature, and the lymph helps
protect against infection. A layer of
fat below the dermis stores food for
energy.
The Integumentary System
5. A hair root is produced at the base of
the hair follicle, which is a deep
pocket that extends into the dermis.
The hair shaft (the part of the hair
outside the skin) is made of keratin
and needs no nourishment, because
it is no longer alive. Oil from glands
in the skin keeps the hair shaft from
drying out and breaking off.
Hair
6. Nails form from root cells in the
epidermis. As new cells form, the
nail grows longer. Nails are also
made up of keratin.
Nails
7. Glands release
secretions through
ducts. The main glands
are the sweat glands
and the oil glands.
Sweat glands release
excess salts, water,
and urea to regulate
body temperature. If
the body is too hot, the
sweat glands release
sweat, which
evaporates and cools
the body.
The oil glands release
sebum, which helps
keep the skin soft and
waterproof.
Glands
Urea carries
excess heat
away from the
body
8. A pigment, determines if the skin will
be light or dark, and it protects the
skin from harmful ultraviolet light by
absorbing it.
Melanin - Skin Pigment
Melanocyte - Melanin producing cells
Melanin
