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Coordination in animals

(d) Synthesis of vitamin D: the skin Mammalian ear
synthesise vitamin D when exposed Task 2.9
to sunlight. The cholesterol in the
skin is converted into inactive form Search from the library and internet
of vitamin D under the influence of sources for the information about the
FOR ONLINE READING ONLY
sunlight. The vitamin D is further mammalian ear. Write short notes about
processed in the liver and kidney into the searched information.
active form. The ear is the organ for hearing and
(e) Sensation: the skin is responsible for maintenance of body balance. It detects
sensation of pain, pressure, touch, and sound waves and vibration. It also
temperature change. provides information on the position
of the organism. The mammalian ear is
Adaptation of skin to its function composed of three parts; the outer ear, the

Human skin is adapted to its functions as middle ear and the inner ear as shown in
the sensory organ by having the following Figure 2.16.
features:
1. Skin has sweat glands which produce Outer ear
sweat that helps to cool the body. In The outer ear is made up of an external
hot environment, the glands produce flap of skin covering by an elastic cartilage
sweat through pores on the skin. called pinna. The pinna collects sound
Evaporation of sweat lowers body waves and directs them into the ear canal.
heat and hence helps to cool the body. The canal is called external auditory meatus
2. It has hair erector muscles which and its function is to pass sound waves to
controls the erection and lying down the middle ear. Across the end of ear canal
of hairs depending on the changes of is a tympanic membrane or ear drum which
temperature in the environment. separates the outer ear from middle ear. The
opening of the auditory canal is lined with
3. It is supplied with nerve endings which fine hairs and glands which secrete ear wax.
transmit impulses to central nervous The glands are located in the upper wall of
system for interpretation. the auditory canal. Ear wax protects the ear

4. Presence of the blood vessels which against entrance of foreign materials such
dilate when the body temperature is as dust and microorganisms.

high to facilitate heat loss by radiation
and constrict when the temperature Middle ear
is low to reduce heat loss. The blood The middle ear is positioned between
vessels also supply food and oxygen tympanic membrane and a bony wall
to the skin and remove excretory containing two small openings covered
products. by membranes. The two openings are oval
window which is also called fenestra ovalis

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