Hair grows from follicles found in the dermis and is a defining characteristic of mammals. A single hair has three layers - an external cuticle, inner horny cortex, and a central medulla. Hair functions include retaining body heat, magnifying the sense of touch, and is affected by sex hormones and pigmentation. Nails are horny plates on fingers and toes with a visible portion, free edge, and embedded root that grows as cells in the nail root push older cells away.

3. Hair is a filamentous biomaterial, that grows
from follicles found in the dermis. Hair is one
of the defining characteristics of mammals.

4. The especial funtions of hair include :
1. retencion of body heat
2. the magnification of the
sense of touch.
• the removal of hair from
hiary spots in the skin is
know to reduce their
sensitivity to touch.

5. The parts of a single hair include:
 SHAFTextending upward from a pint in or near the surface of epidermis
ROOT embedded in the corium and surrounded by an epidermal downgrowth
 HAIR FOLLICLE
 HAIR BULB; the expanded base of the root into which
 from underneat a DERMAL PAPILLA (conective tissue)  nerves
 capillaries projects.

6. A single hair has three layers of cells:
 the external layer, or cuticle
 the horny porcion, or cortex (actuallly consisting of several layers)
 and central row of cells the medulla (not present in the some hair).
Hair cells contain a pigment responsible for variation – in hair coloring; if the
pigmentation is inadequeate, the air between the cells reflects ligth tha
makes the hair appear silvery or gray.

7. • In the bulb of the hair root are the live germinating cells
wich multiply and cause the shaft to rise upward to be
replaced by younger cells
• Scalp hais grow at the rate of about five inches per year
during their life period of two to five years,eyebrows and
eyelashes can grow for several months at most, before
replacement.
• Sex hormones have a pronunce effect on the extent and
location of hair growth, as seen in the faces of males and
in the pubic and axillary region of males and females

8. • The hair follicle, surrounding the root , has an
inner, epithelial sheath and an outer, conective tissue
sheath.
• The inner sheath consists of three layers of cells:
the horny cuticle, huxley s layers of flat cells, and henle s
layer of tube-shaped cells and an outer layer merging
with the deep stratum geminativum of the epidermis.
• The outer connective tissue sheath, growing out of the
corium, surround the inner sheath

10. On the dorsal surfaces of
the digits and toes are
the nails, horny plates
cosisting of the following
parts: a visible portion
attached to the digit or
toe, which it protects; a
free edge in the distal
portion: and a root, the
covered portion
embedded in the skin.

11. NAILS
• The nails bed is the skin
under the nail; the nail wall
is the skin covering the root
and sides of the nail.
• The lunula is the white
portion at the base of the
nail.
• Cells in the stratum
germinativum near the nail
root fuse with the root cells
and push the older cells
away so that the nail grows.