Question

Which of the following structures is present characteristically only in the mammalian brain?
A. Corpus fibrosum
B. Corpus striatum
C. Corpus luteum
D. Corpus callosum

Answer 1

Hint:-A brain is an internal organ that is complex in nature and serves as the centre of the nervous system in all vertebrates and most invertebrates. It supervises all sensory and motor functions of the body.

Complete Answer:-
A mammalian brain is differentiated into three regions viz., cerebrum or forebrain, cerebellum or midbrain, and medulla or hindbrain. The cerebrum is divided into two cerebral hemispheres. A long distinct groove is present between the two hemispheres and is called a medial longitudinal fissure. A large C-shaped bundle of nerve fibres stretching across the midline of the brain is found under the cerebral cortex. It consists of white matter and is called the corpus callosum. It measures approximately 10 cm in length. It integrates both left and right cerebral hemispheres. It facilitates the transfer of information between the two cerebral hemispheres. This aids in the processing of sensory, motor, and cognitive signals in the brain. The Corpus callosum is a unique characteristic feature of the mammalian brain.
Thus, the right option is D.

Additional information:-
The average weight of an adult human brain is about 1.2–1.4 kg which is almost 2 percent of the total body weight. It has a volume of about 1260 cm${}^3$ in men and 1130 cm${}^3$ in women.

Note:- Corpus callosum is composed of about 200 million heavily myelinated nerve fibres. Basically, the development of the corpus callosum gets completed in the initial four years of childhood but its growth continues at a slower pace till the late thirties. A condition in which a person is born without a corpus callosum is known as agenesis of corpus callosum.