Cerebral protection

 The brain has several barriers of protection against accidents and illnesses; firstly it has the skull, but also a liquid that serves as buffer against blows and biological barrier, and the meninges to protect against infections.

  The skull is a bone, which is a structure not expandable in the adult, covered by leather scalp and formed by the combination of 8 juxtaposed bones, 2 pairs (temporal and parietal), and odd 4 (frontal, sphenoid, ethmoid and occipital), forming a box of bone to ensuring the protection of the brain and their shells.

The skull has two distinct regions: the dome and the base. The first consists of the frontal, occipital, and parietal bones together by sutures (coronal, sagittal and lambdoid) and presented two solid bone layers, the outer and inner separated by a spongy tissue called the diploe.

During the first year of life, due to the presence of the fontanels and the non-consolidation of the sutures may be an increased the brain product of an increase in intracranial pressure.

Around 18 months of life, the anterior fontanel is closed and skull begins to be a little distensible rigid box. The frontal bones, ethmoid, sphenoid, temporal and occipital, form the base of the skull and it is crossed by numerous holes where they exit nerves and veins and where it penetrates the nutrient arteries of the brain. The dome and the base limit the cavity endocranial containing the brain itself .

Other means of protection is the cerebrospinal fluid, this occupies 20% of the volume of the cranial vault, and is a liquid that flows into the central nervous system including the spinal cord. The average volume in children is 90 ml, with a production of 0.35 ml per minute. In situations of increased pressure endocranial this fluid is responsible for maintain intracranial pressure within normal limits by moving its volume to reserve spaces.

The following protective barriers are the meninges that are 3 membranes surrounding the central nervous system. From the outermost to the innermost are: dura mater, arachnoid, and Pia mater. The dura mater is also known as paquimeninge and the two together are called also leptomeningess.

The dura mater is the wrapper more external of the brain, composed of fibrous, solid and thick fabric, usually attached to the inner table of the bone forming independent magazines that protect the brain from mass displacement during shocks or sudden deceleration situations.

Another barrier is known as arachnoid: is a transparent and avascular membrane that covers the brain going as a bridge between the grooves and convolutions. There is a space where the cerebrospinal fluid circulates between the brain and the arachnoid. 

Finally, the pia mater is very tenuous and highly vascularized membrane attached closely to the cerebral cortex followed up in its most minimal crease.

While all these means of protection were developed to take care of the structures of the brain, there are situations for which it was not designed, for example, evolutionarily brain was not designed for the deceleration that occurs when a car brakes sharply, which creates a movement that sends the head first was forward and then backward, causing the brain to bounce on the walls of the skull which is lethal because it can break the connection between the spinal cord and the brain structures, before this, it is essential, in the absence of other form of care, the use of the safety belt when you are in a car that you can stop at any moment after high speed.

References:


  Bingmei, MF. (2012) Experimental methods and transport models for drugs delivery across blood-brain barrier. Current Pharmaceutical Biotechnology. 13 (7) 1346-1359. 

Sabogal Barrios, R.,  y Moscote Salazar, L. (2007) Neurotrauma: Fundamentos para un Manejo Integral. Cartagena. España.

Saunders, NR.Liddelow, SA., and Dziegielewska, KM. (2012) Barrier mechanisms in the developing brain. Frontiers in Pharmacology. Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3314990/