EXERCISES, LESSON 3
REQUIREMENT. The following exercises are to be answered by completing the
incomplete statements.
After you have completed all the exercises, turn to "Solutions to Exercises," at
the end of the lesson and check your answers.
1. The envelopes of the body are like an air conditioner; they help to remove
.
The envelopes are like a blanket; they help to retain
when the surrounding air is
_____d. The skin is like a chemical factory; it manufactures v
in the
presence of sunlight. The skin is like an umbrella; it helps to protect us from the s and
the r
.
2. The mitotic activity of the epidermis occurs in the
l layer. At any given time,
about
percent of the cells in this layer are involved in m
s. As cells migrate to
the surface, they change shape from
r to
l and finally to
s. As
the cells become squamous, they also become h
d, or c
d.
3. The color of the skin is due to special chemicals called
s. Special cells
located in the dermis provide the p
s of pigments to the basal cells. As basal cells
migrate to the surface, the precursors are gradually converted to the actual p
s.
The type of color for each individual is controlled by
s.
4. The integumentary system is the boundary between the organism and the
surrounding e
t. For this reason, the integumentary system has a number of
functions related to the
t.
Friction against the integument is reduced by
s and outer dead
s. When
subjected to friction, the integument tends to become
er.
The outer layers of cells are kept flexible by
l from the sebaceous glands. This
forms an essentially w
f covering for the body. This is important in preventing
general d
n of the body.
Because of pigments and outer layers of dead cells, the integument helps to
protect the body from excessive
r radiation.
Receptor organs in the integument and the subcutaneous layer continuously
inform the
n of conditions immediately surrounding the body.
MD0007
3-14
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