Human Brain - Structure

Structure

The adult human brain weighs on average about 3 lbs. (1.5 kg) with a volume of around 1130 cubic centimetres (cm3) in women and 1260 cm3 in men, although there is substantial individual variation. Men with the same body height and body surface area as women have on average 100g heavier brains, although these differences do not correlate in any simple way with IQ or other measures of cognitive performance.

The cerebral hemispheres form the largest part of the human brain and are situated above most other brain structures. They are covered with a cortical layer with a convoluted topography. Underneath the cerebrum lies the brainstem, resembling a stalk on which the cerebrum is attached. At the rear of the brain, beneath the cerebrum and behind the brainstem, is the cerebellum, a structure with a horizontally furrowed surface that makes it look different from any other brain area. The same structures are present in other mammals, although they vary considerably in relative size. As a rule, the smaller the cerebrum, the less convoluted the cortex. The cortex of a rat or mouse is almost perfectly smooth. The cortex of a dolphin or whale, on the other hand, is more convoluted than the cortex of a human.

The living brain is very soft, having a consistency similar to soft gelatin or soft tofu. Despite being referred to as grey matter, the live cortex is pinkish-beige in color and slightly off-white in the interior.