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

The correct answer is A. Dura mater - Arachnoid - Pia mater.
The brain and spinal cord are protected by three layers of connective tissue known as meninges. These layers surround and protect the central nervous system (CNS). The meninges are arranged in the following sequence, from outside to inside:
1. Dura Mater:
o The dura mater is the outermost and toughest layer of the meninges. It is a thick, fibrous membrane that provides the primary protection to the brain and spinal cord.
o It is closely attached to the inside of the skull and vertebral column.
2. Arachnoid Mater:
o The arachnoid mater is the middle layer. It is a delicate, web-like structure, named for its appearance, resembling a spider's web.
o Between the arachnoid mater and the pia mater is the subarachnoid space, which contains cerebrospinal fluid (CSF), providing cushioning for the brain.
3. Pia Mater:
o The pia mater is the innermost layer. It is very thin and closely adheres to the surface of the brain and spinal cord, following the contours of the neural tissue.
o This layer contains blood vessels that supply nutrients to the brain and spinal cord.
Why Other Options Are Incorrect:
• B. Pia mater - dura mater - arachnoid: This order is incorrect because the pia mater is the innermost layer, not the outermost. Dura mater is the outermost layer.
• C. Arachnoid - dura mater - pia mater: This is incorrect because the dura mater is the outermost layer, not the middle.
• D. Dura mater - pia mater - arachnoid: This is incorrect because the pia mater is the innermost layer, and the arachnoid mater is in the middle.
The correct sequence of the three layers of the brain from outside to inside is Dura mater - Arachnoid - Pia mater, making A. Dura mater - Arachnoid - Pia mater the correct answer.