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INFORMATION - BRAIN - THE HUMAN BRAIN-5

STRUCTURE OF BRAIN

BRAIN CELLS:

Microscopically, brain is made up of two types cells, Neurons and Neuroglia.

Neurons are main brain cells. They send and receive nerve impulses or signals.

Neuroglia provide structural support, protection, and nourishment to neurons. Neuroglia are mainly of three types: Astroglia or astrocytes, oligodendroglia, and ependymal cells.

BRAIN COVERINGS:

Our brain is protected from injury inside a bony covering called the Cranium. Cranium is part of the skull.

Actually, brain and spinal cord are covered by three layers of tissue called Meninges.

The inner most layer closest to the surface of the brain is called the Pia Mater. It covers the entire surface of the brain as well as it follows the folds of the brain. The pia mater has many blood vessels which goes deep into the surface of the brain.

The middle layer of the meninges is called the Arachnoid. It covers the entire brain. It is elastic membrane.

The space between the pia mater and the arachnoid is called the Subarachnoid space, which contains the Cerebrospinal fluid (CSF).

The outer most layer of the meninges is called the Dura Mater. In the brain, the dura mater is made up of two layers. The outer layer is called the periosteum. The inner of the two, the Dura itself, lines the inside of the entire skull. It also creates folds from the top and from the sides. One, the Falx, separates the right and left half of the brain. Another, the Tentorium, separates the upper and lower parts of the brain. The dura mater is inelastic membrane.

The space between the dura and the arachnoid membranes is called the Subdural space.

CSF:

Cerebrospinal fluid - CSF - is a clear watery liquid that helps to cushion the brain and spinal cord from injury. It circulates through channels around the spinal cord and brain. It also is within hollow channels or cavities, called Ventricles, in the brain. The Choroid Plexus in the ventricles produces most of the CSF. CSF is constantly being formed and absorbed.

VENTRICULAR SYSTEM:

The Ventricular System is made up of Ventricles and their connections.

There are four ventricles. They are connected by holes and tubes. The holes are called Foramen.

Two Lateral Ventricles (first and second), one in each Cerebral Hemisphere, are connected to the Third Ventricle by a separate opening called the Foramen of Munro.

The third ventricle is flat and in the center of the brain. Its walls are made up of the Thalamus and Hypothalamus. Third ventricle connects with the Fourth Ventricle through a long tube called the Aqueduct of Sylvius.

The fourth ventricle is in the back of the brain. Through its openings CSF gets around the brain and spinal cord.

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