Meninges, ventricles and cerebro spinal fluid
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Transcript of Meninges, ventricles and cerebro spinal fluid
MENINGES
ANATOMY AND PHYSIOLOGY
Dr SHAROJ KHANMBBS (NGMC)
• Brain n and spinal cord are completely surrounded by three layers of tissue, the meninges, lying between the skull and the brain, and between the vertebral foramina and the spinal cord.
• The meninges are three layers of protective tissue called the dura mater, arachnoid mater, and pia mater.
• Named from outside inwards the layers of meninges are the:
• Dura mater• Arachnoid mater• Pia mater.
• Dura and arachnoid maters are separated by a potential space, the subdural space.
• Arachnoid and pia maters are separated by the subarachnoid space, containing cerebrospinal fluid.
DURA MATER
• The dura mater is the most superior of the meningeal layers.
• This forms several structures that separate the cranial cavity into compartments and protect the brain from displacement.
• The falx cerebri separates the hemispheres of the cerebrum.
• The falx cerebelli separates the lobes of the cerebellum.
• The tentorium cerebelli separates the cerebrum from the cerebellum.
• The dura mater also forms several vein-like sinuses that carry blood (which has already given its supply of oxygen and nutrients to the brain) back to the heart.
• Venous blood from the brain drains into venous sinuses between the two layers of dura mater.
• Spinal dura mater forms a loose sheath round the spinal cord, extending from the foramen magnum to the 2nd sacral vertebra.
• Thereafter it encloses the filum terminale and fuses with the periosteum of the coccyx.
Arachnoid mater• Arachnoid mater is the middle layer of the meninges.
• In some areas, it projects into the sinuses formed by the dura mater.
• These projections are the arachnoid granulation/arachnoid villi. They transfer cerebrospinal fluid from the ventricles back into the bloodstream.
• Subarachanoid space lies between the arachnoid and pia mater.
• It is filled with cerebrospinal fluid. All blood vessels entering the brain, as well as cranial nerves pass through this space.
• It continues downwards to envelop the spinal cord and ends by merging with the dura mater at the level of the 2nd sacral vertebra.
• The term arachnoid refers to the spider web like appearance of the blood vessels within the space.
Pia Mater• Pia mater is the innermost layer of the meninges.
• Unlike the other layers, this tissue adheres closely to the brain, running down into the sulci and fissures of the cortex.
• It fuses with the ependyma, the membranous lining of the ventricles to form structures called the choroid plexes which produce cerebrospinal fluid.
Ventricles of the brain andthe cerebrospinal fluid
• The brain contains four irregular-shaped cavities, or ventricles, containing cerebrospinal fluid (CSF)
• They are:• Right and left lateral ventricles• Third ventricle• Fourth ventricle
• The lateral ventricles:These cavities lie within the cerebral hemispheres, oneon each side of the median plane just below the corpuscallosum.• They are separated from each other by a thin
membrane, the septum lucidum, and are lined with ciliated epithelium.
• They communicate with the third• ventricle by interventricular foramina.
• The third ventricle• Third ventricle is a cavity situated below the lateral
ventricles between the two parts of the thalamus. It communicates with the fourth ventricle by a canal, the cerebral aqueduct.
• The fourth ventricle- The fourth ventricle is a diamond-shaped cavity
situated below and behind the third ventricle, between the cerebellum and pons.
• It is continuous below with the central canal of the spinal cord and communicates with the subarachnoid space by foramina in its roof.
Cerebrospinal fluid (CSF)
• CSF is clear, colorless and transparent fluid Circulates through cavity of the Brain Subarachnoid space Central canal of spinal cord.
Functions of the Cerebrospinal Fluid
• Cushions and protects the central nervous system from trauma
• Provides mechanical buoyancy and support for the brain • Serves as a reservoir and assists in the regulation of the
contents of the skull • Nourishes the central nervous system • Removes metabolites from the central nervous system