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(mĭnĭn`jēz), three membranous layers of connective tissueconnective tissue,
supportive tissue widely distributed in the body, characterized by large amounts of intercellular substance and relatively few cells. The intercellular material, or matrix, is produced by the cells and gives the tissue its particular character.
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 that envelop the brain and spinal cord (see nervous systemnervous system,
network of specialized tissue that controls actions and reactions of the body and its adjustment to the environment. Virtually all members of the animal kingdom have at least a rudimentary nervous system.
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). The outermost layer, or dura mater, is extremely tough and is fused with the membranous lining of the skull. In the brain it forms a vertical sheet that separates the cerebral hemispheres and a horizontal sheet that lies between the cerebrum and the cerebellum. The thin arachnoid membrane lies below and in close contact with the dura mater. The innermost layer, or pia mater, is in direct contact with the brain and spinal cord and contains the blood vessels that supply them. The pia mater and arachnoid membrane are separated by the subarachnoid space containing the cerebrospinal fluid, which carries nutrients, absorbs the impact of shocks, and acts as a barrier to disease organisms. Thus, the meninges provide a fluid-filled jacket for the protection of neural tissues and allow for the flexing and twisting of the vertebral column about the spinal cord.



the connective-tissue membranes enveloping the brain and spinal cord in vertebrates and man.

A primitive meninx develops in the embryo and differentiates into dura mater (adjoining the periosteum) and primary pia mater (adjoining the brain and forming the folds of the brain’s vascular plexuses). Three meninges are distinguished in adult mammals and man. In the brain region, dura mater, the outer membrane, forms the periosteum of the inner surface of the skull and passes longitudinal and transverse processes into the cranial cavity. The principal processes are the falciform, wedged between the two cerebral hemispheres (a rudiment is found in birds), and the tentorium cerebelli, which separates the cerebellum from the lower surface of the occipital lobes of the cerebrum. Sinuses form, when the dura mater splits, in certain places in the cranium; venous blood flows into them from the brain. In the spinal cord region, the dura mater consists of two layers, outer (periosteum) and inner. These are divided by the epidural space, which is filled with adipose tissue and venous plexuses.

The primitive pia mater in mammals splits into arachnoid and vascular or secondary, meninges. The arachnoid is internal to the dura mater. In the cranial cavity, it adjoins the surface of the gyri of the cerebral cortex, without entering the sulci or other depressions (thereby forming cisternae). In the spinal cord region, the arachnoid adheres firmly to the inner layer of the dura mater.

The innermost of the membranes is the meninx vasculosa, which adheres to the surface of the spinal cord and brain and extends into the brain’s sulci and depressions, containing the blood vessels that feed the brain. The subarachnoid space, between the arachnoid and the meninx vasculosa, is filled with cerebrospinal fluid. The arachnoid and the meninx vasculosa, which join near the cerebral cortex, are given the common name of “pia mater.”


The membranes that cover the brain and spinal cord; there are three in mammals and one or two in submammalian forms
References in periodicals archive ?
In some cases the bacteria multiply in the blood and this results in septicaemia before the bacteria can infect the meninges.
Moderate mononuclear infiltrates and edema were present throughout the meninges, most severely over the cerebellum.
The author has organized the main body of his text in twenty-two chapters devoted to developmental anatomy, the structure and function of neurons and neuroglia, the anatomy of the canine brain, meninges and the ventricular system, the spinal cord, spinal reflexes, and a wide variety of other related subjects.
Washington, July 7 (ANI): Researchers at North Carolina State University say that comparing human and canine genomes, they have come to the conclusion that a gene commonly believed to be involved in meningiomas-tumours-which affect the meninges (thin covering) of the human brain, and account for one out of four adult brain tumours-may not be as crucial for tumour formation as previously thought.
From the meninges, brain, spleen, and blood a spore-bearing aerobe was grown in pure culture.
He has also reorganized the material so learners can progress in a more sequential manner; added new material on the visual system, the meninges, the venous system, and the limbic system; and increased the radiological images and other illustrations by about 10%.
Upon the microscopic examination of the brain, the researchers observed that the blast from certain weapons produces small haemorrhages (bleeding) in the brain tissue and the meninges (lining of the brain).
The meninges within the brain and all spinal cord sections except those from the sacral spinal cord had stasis of heterophils within the blood vessels and perivascular infiltration of mild numbers of heterophils (Figure 1).
This is a tumour of the meninges, which are the protective membranes around the brain and spinal cord.
Something sets off a chain of events that begins with leakage of fluid from blood vessels into the meninges, the protective covering of the brain and spinal cord, followed by swelling, which in turn leads to seizures.
immitis to be in the yeast phase in the CSF and meninges of patients with coccidioidal meningitis (8).