Answer
The brain is the most important organ in the body, but it is possibly the most easily damaged. Consequently ,there are elaborate structural arrangements to protect it from physical and chemical injury. If one ignores head hair and skin, there are four layers of protection for the brain. These are the bones of the cranium, the meninges, the cerebrospinal fluid(CSF), and the blood brain barrier(BBB).
Work Step by Step
The layers of protection of the brain.
1. Cranial bones t
There are eight cranial bones and and they are all important in protecting the brain in some way. However, the bones that are most likely to be impacted by a fall or a direct blow to the head are the large frontal, parietal, temporal, and occipital bones. These bone ar flat bones with a double layer of compact bone and a middle layer of cancellous bone. The hard matrix of the compact bone is the body's best defence against physical trauma. Compact bone absorbs shocks and resists the transmission of concussive forces.
2. Meninges: The meninges are three connective tissue membranes that cover and protect the brain. They are outside in the dura mater, the arachnoid mater and the pia mater. They also enclose and protect blood vessels and contain the cerebrospinal fluid
3. The cerebrospinal fluid. This is a fluid secreted by the choroid plexuses of the lateral and fourth ventricles. It surrounds and cushions the brain. In addition, it floats the brain so that the buoyancy of the brain in this fluid reduces the its weight by 97%. This ensures that the brain tissue is not crushed against the bones of the skull. The CSF also protects against potential concussive injury which is often the result of physical blows to the cranium.
4.The blood brain barrier is a mechanism to ensure a stable chemical environment for the brain.
Bloodborne substances must pass through three layers cells before reaching the brain neurons. .
These three layers are capillary endothelial wall, the basal lamina of the endothelium, and the feet of the astrocytes clinging to the capillaries. The blood brain barrier is formed by the tight junctions formed in the endothelial cells under the influence of the astrocytes. This constitutes a selective layer of cells that allows some substances to reach the neurons, keeps some from entering the CSF, and pumps some out, Glucose , essential amino acids, and some electrolytes pass in by diffusion freely through the capillary walls; blood borne metabolic wastes, proteins and certain toxins cannot pass through; non-essential amino acids and K+ ions are pumped out of the CSF ; fats, fatty acids, carbon dioxide, are not barred. Unfortunately, alcohol, nicotine and some anesthetics can freely cross the blood brain barrier.
