Describe the three layers of meninges covering the brain.

Brain is covered with three meninges namely dura mater, arachnoid mater and pia mater. The tough dura mater, avascular arachnoid mater and delicate pia mater together protect the brain from any injury.

Explanation:

The three layers of meninges covering the brain are dura mater, arachnoid mater and pia mater.  

Dura mater: The outer most meninx of the brain is called dura mater. It is a tough and fibrous covering of the brain. Dura mater is made of dense irregular connective tissue and is continuous with epineurium.  

Arachnoid mater: The middle meninx present between pia mater and dura mater is the arachnoid mater. Arachnoid mater is avascular layer and is rich in collagen and elastic fibers.  

Pia mater: The deepest meninx is called pia mater. It is the delicate layer of connective tissue. Pia mater is rich in the blood vessels that deliver nutrients and oxygen to the spinal cord.

prophase: we can observe the chromosomes to coil up and condense. they become visible. nuclear membrane and envelope disintigrate.s

metaphase: chromosomes align at the center, the metaphase plate. spindle fibers attach to centromeres of the sister chromatids. they meet at kinetochores.

anaphase: sister chromatids are pulled towards each opposing centromere, set on different poles.

telophase: chromosomes are now clustered up only on either sides of the cell. nuclear membranes reform, and a new cell wall forms along the cell plate. this will lead to cytokinesis, the process that divides the cell membrane and forms the cell wall.