The Brain - Protection

Skull

The skull forms a protective bony armour around the brain that will prevent the brain to be hit by any external object.

Meninges

Meninges are three layers of tough, elastic tissues that surround the brain, providing it nourishment and protection. There are three types of meninges in mammals: the outer layer is known as the dura mater, than comes the arachnoid layer, and the inner layer is called pia mater. 

Blood-brain barrier 

The blood that reaches the brain is not the same as the blood that passes through the body. There is a barrier, created by the meninges, that prevent this contact between the brain and the blood. These blood-brain barrier prevents the entrance of infectious particles, however, is permeable to necessary substances like oxygen and other nutrients. 

Some harmful substances are able to pass through the blood-brain barrier, like alcohol and other molecules generated by the consumption of drugs.

Cerebrospinal Fluid

Between the arachnois layer and the pia mater, a special fluid floats around, nourishing the brain and being able to absorb the impact, therefore protecting the brain. This fluid is called Cerebrospinal fluid.