Meninges And Cerebrospinal Fluid
Question 1: Give a brief account of the meninges.
Answer. The brain and spinal cord are enclosed in three protective membranes called meninges. From outwards to inwards these are (1) dura mater, (2) arachnoid mater, and (3) pia mater.
The dura mater is mesodermal in origin, while the arachnoid and pia mater are ectodermal in origin.
Meninges Dura mater
The dura mater is the thick outermost covering of the brain and spinal cord. The part enclosing the brain is called cranial/cerebral dura, while the part enclosing the spinal cord is called spinal dura. It is the very tough, opaque, inelastic membrane of fibrous tissue (Greek, dura = tough, mater = mother). It is also called pachymeninx (pachy = thick).
Meninges Arachnoid mater
The arachnoid mater (Greek, arachnoid = cobweb-like, mater = mother) is a delicate avascular membrane deep to dura mater. Many thread-like trabeculae extend from its inner aspect to the pia mater.
Meninges Pia mater
The pia mater (Greek, pia = tender, mater = mother) is a thin, transparent, vascular membrane, closely adherent to the surface of the brain and spinal cord.
The arachnoid mater and pia mater together are termed leptomeninges (lepto = thin).
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