3-4. INTRODUCTION TO INTEGUMENTARY DERIVATIVES
The integumentary derivatives include the glands, hairs, and nails associated
with the skin. All integumentary derivatives are formed from the tissues of the
integument proper (dermis and epidermis). All are appended (attached) to the
integument proper and are often known as the appendages of the skin. See figure 3-2.
Figure 3-2. The integumentary derivatives (appendages).
a. A hair follicle is formed by the extension of the skin (dermis and epidermis)
deeper into the surface of the body. Follicles may extend into the subcutaneous layer.
b. At the base of the hair follicle is the hair root. The hair shaft grows out from
the root. The hair shaft is made of cells from the outermost layers of the epidermis.
c. Scalp and facial hairs grow continuously. Other hairs of the body grow to
fixed lengths. The types and patterns of hairs are determined for each individual by
genetics, including his/her sex.