VAN 121: Veterinary Gross Anatomy-II (2+2)

PIAMATER

• It is a very delicate vascular membrane that closely invests the brain and the spinal cord and sends processes into the brain substance.
• The cerebral piamater accurately moulds itself on the brain by dipping itself into all the sulci and fissures. Its external face forms the inner boundary of the subarachnoid space and is lined by endothelium. From its deep face trabeculae are given off which dip into the substance of the brain. The smaller blood vessels ramify in the piamater forming plexuses.
• Folds of piamater extend into two of the fissures of the brain. One of these is the telachorioidea of the third ventricle that enters the transverse fissure and forms the roof of the third ventricle. Another fold passes into the space between the cerebellum and medulla and forms the telachorioidea of the fourth ventricle.
• The spinal piamater is thicker and denser. It sends a fold into the ventral median fissure of the spinal cord and also helps to form the dorsal median septum. Along the mid ventral line it forms a thickening the linea splendens in which runs the ventral spinal artery. On each side it gives off a strong longitudinal band, the denticulate ligament lying between the dorsal and ventral roots of the spinal nerves.