pia (pe'ah)

One of the cerebrospinal meninges, a delicate network of connective ti ue in immediate relation to the surface of the brain and of the spinal cord, cerebral p. The p. of the brain. It contains in its meshes the ramifications of the cerebral ve els, closely follows the convolutions and gyri of the brain surface, lines the great fi ures,* and by some of them is continued into the ventricular cavities, external p. The p. covering the exterior of the brain as distinguished from the part within the ventricles, internal p. The p. which extends into the ventricles of the brain, p. mater. See p. p. spinal is, spinal p. The p. of the spinal cord. It is prolonged within the anterior and posterior median fi ures, and forms the epineurium of each of the spinal nerves. [Lat., fem. of pi us, gentle, delicate.]