Question

What is the sequence of three layers of the brain from outside to inside?
A. Dura mater- Arachnoid- pia mater
B. Pia mater- dura mater-arachnoid
C. Arachnoid- dura mater- pia mater
D. Duramater- pia mater- arachnoid

Answer 1

Hint: These are between the brain and the brain box. The layer immediately below the cranium will be tough and the layer in contact with the brain tissue will be soft and also vascular.

Complete Answer:
Humans have a well developed nervous system. The ability of the man to bring about conduction is the main function of this system.

The human nervous system is divided into two types :
1. Central Nervous System : This forms the central axis of the body
2. Peripheral Nervous System : This is at the periphery of the body.

Central Nervous System
- The CNS consists of Brain and Spinal Cord. Brain is protected by a bony structure called a Skull while the spinal cord is protected by a Vertebral Column.
- Skull consists of Facial bones and Cranium.
- Cranium is the main brain case that protects the brain. It is made up of 8 bones.
- Brain is the central information processing organ of our body. It is totally a wrinkled structure.
- Brain lies within the cranium but it is not directly inside the cranium.
- It is covered by protective layers known as meninges (Meninx means cover or membrane). Thus these meninges are between the brain and the cranium. These are three in number.
- The primary function is to protect the brain. The meninges from outer to inner are
a. Dura Mater : (dura means durable, mater means mother) It is the outermost layer. It is a tough layer made up of fibrous connective tissue.
b. Arachnoid : (Arach means web like) It is the middle layer. It is made up of delicate connective tissue. It consists of fibres in network form
c. Pia Mater : (pia means soft, mater means mother). It is the innermost layer. It is in contact with the brain tissue. It is the vascular layer (consists of blood vessels).

Hence the correct answer is option A.

Note: The arachnoid and pia mater are collectively known as Leptomeninges.
- Only Birds and mammals have three meninges.
- Amphibians and reptiles have two meninges.
- Pisces have only one primitive meninx.
- Meningitis is inflammation of Meninges. It can be bacterial or viral.