The human brain weighs about 3 lbs. and contains 100 billion neurons and even more glial cells, according to Neuroscience For Kids, a University of Washington website. The brain has three major divisions, which contain different structures and two types of brain tissue. Protecting the brain is a covering tissue, the meninges, and a fluid that flows around the brain.
Forebrain
The forebrain, also called the prosencephalon, is the largest division of the brain. The forebrain has two parts: the telencephalon and diencephalon. The telencephalon has the neocortex, which is the outer layer of the cerebral cortex. It also contains internal structures such as the basal ganglia, amygdala and hippocampus, as well as the lateral ventricles, which are the fluid filled structures of the brain. The diencephalon has the thalamus, hypothalamus, epithalamus and the third ventricle.
Midbrain
The midbrain, the second division of the human brain, is also known as the mesencephalon. The tectum, tegmentum and the cerebral aqueduct all are found in the midbrain. The cerebral aqueduct contains the third and fourth ventricles.
Hindbrain
The last major division of the brain, the hindbrain, is also known as the rhombencephalon. The hindbrain also has two divisions: the metencephalon and myelencephalon. The metencephalon contains the cerebellum and pons. The metencephalon and myelencephalon both have the fourth ventricle. The medulla oblongata is also in the myelencephalon.
White and Gray Matter
The University of Maryland Medical Center states that the brain has two types of tissues that make up the brain matter. The gray matter, also known as the substantia grisea, contains the cell bodies in the brain while the gray color comes from the nuclei in the cell bodies. The white matter, also known as the substantia alba, contains the nerve fibers and the white color comes from the myelin that surrounds the axons of the nerve fibers.
Cerebrospinal Fluid
The cerebrospinal fluid, or CSF, surrounds the brain and fills the ventricles. The University of Washington states that the CSF has four major functions. The CSF protects the brain from injury during an impact. The CSF also provides buoyancy for the brain, and removes waste products that can harm the brain. The last major function of the CSF is to transport hormones to other areas of the brain.
Meninges
The meninges is the covering of the brain that separates the brain from the environment. Three layers make up the meninges: dura mater, arachnoid and pia mater. The dura mater protects the brain, which can prevent blood vessels from being damaged during an abnormal movement. The arachnoid layer has a spider-like appearance, and the pia mater is the meninges layer closest to the brain.
