Structures Protecting the Brain

 

Structures Protecting the Brain

Which Structures Protect the Brain?

The brain is protected by the cranium and meninges. These two structures together make up the border system or defense system of the brain against injuries or any other attacks.

Cranium:

The cranium is a part of the skull and is made up of bony tissues which give protection to the brain.

Meninges:

Meninges are the three layers of tissues that surround and protect the brain and spinal cord. These three layers are discussed below;

1. Dura Mater: Dura mater is a tough outer layer below the skull. It is further divided into two layers i.e. outer periosteal layer made up of tough fibrous tissues and the inner meninges layer that forms the infoldings and divides the cranial cavity into different portions.

The space between these two layers is called the venous sinus which drains blood from the brain to the heart. Venous sinus has two types. One type is the superior sagittal sinus made by Falx cerebri and the other type is a straight and transverse sinus made by Tentorium cerebri.

  2. Arachnoid Mater: Arachnoid mater is a spiderweb-like layer in the middle of the dura mater and pia mater. It is made up of fibrous connective tissues.

The arachnoid mater has connective tissue projections called trabeculae that bind with the underlying pia mater.  

3. Pia Mater: The Pia mater is the most adherent layer of the brain of fibrous tissues that provide nutrients to the nervous tissues. It contains a choroid plexus that produces cerebrospinal fluid. 

The Spaces between the Skull and Meninges:

• The space between the skull and dura matter is called epidural or extradural space.

• The space between the dura mater and the arachnoid mater is called sub-dural space.

• The space between the arachnoid mater and the pia mater is known as the sub-arachnoid mater.

            Cerebrospinal Fluid:

   Cerebrospinal fluid is a glasslike and colorless fluid present within the tissues of the brain that circulates through the brain ventricles, sub-arachnoid space and central canal of the spinal cord. It constitutes 99.13% of water and 0.87% of solid substances. These substances are organic substances such as lactic acid, amino acid, uric acid, cholesterol, etc. and inorganic substances such as sodium, magnesium, potassium, chlorides, bicarbonates, etc.

Blood-Brain Barrier:

 The blood-brain barrier is made up of tightly packed endothelial tissues that block the entry of harmful chemicals and specialized protein pumps that pump out the toxic substances back into the bloodstream.

 Ventricles of the brain                                                                                                              There are four ventricles of the brain which play an important part in the                   protection of the brain. These are the following;

           Left lateral ventricle and right lateral ventricle
           3rd   ventricle 
           4th   ventricle
          Left lateral ventricle and right lateral ventricle
          The left and right lateral ventricles are located in the left cerebral hemisphere and right cerebral                hemisphere respectively. These are C-shaped and the largest ventricles located under the corpus             callosum. Both these ventricles are communicated with the 3rd ventricle via intraventricular                     opening.
         3rd ventricle
         The 3rd ventricle is the narrow space between the left and right diencephalon and is located                     between the thalamus and hypothalamus. 
        4th ventricle
        The 4th ventricle is present between the pons/medulla and cerebellum. The 4th ventricle                          continues to the central canal of the spinal cord.
        The 3rd and 4th ventricles are connected by a cerebral aqueduct.