CNS Anatomy Meninges, Cerebral Spinal Fluid and Blood Supply Contents:
❑Meninges
❑CSF and Ventricles
❑Blood supply of the brain MENINGES • The meninges functions to support, protect and nourishe CNS tissue. • the production of cerebrospinal fluid helps by acting as a shock absorber, by circulating nutrients, and by getting rid of waste products • three layers: dura mater, arachnoid mater and pia mater. • Between these two layers are DURA meter the dural venous sinuses. • the outermost layer of the • drain blood from the brain to the meninges, It is thick, tough and internal jugular veins, where it is inextensible. returned to the heart. • cranial cavity has two sheets: Periosteal layer – lines the inner surface of the cranium. Meningeal layer – deep to the periosteal layer inside the cranial cavity. It is the only layer present in the vertebral column. structure purpose Falx cerebri the largest, sickle-shaped; separates the cerebral hemispheres. Starts from the frontal crest of frontal bone and the crista galli running to the internal occipital protuberance. Inervated: ophthalmic division of Falx cerebri trigeminal (V1) Tentorium Tentorium the second largest, crescent-shaped; cerebelli cerebelli separates the occipital Falx lobes from cerebellum. The falx cerebri cerebelli attaches to it giving a tentlike appearance. Diaphragm Inervation: V1 a sellae Falx cerebelli vertical infolding; lies inferior to the tentorium cerebelli, separating the cerebellar hemispheres.
Diaphragma smallest infolding; covers the pituitary sellae gland and sella turcica. Clinical correlation Extradural and Subdural Haematomas • A haematoma is a collection of blood. Which cause a rapid increase in intra- cranial pressure • The dura mater receives its own vasculature; primarily from the middle meningeal artery and vein. • Extradural – arterial blood collects between the skull and periosteal layer of the dura. The causative vessel is usually the middle meningeal artery, a consequence of brain trauma. • Subdural – venous blood collects between the dura and the arachnoid mater. It results from damage to cerebral veins as they empty into the dural venous sinuses. Arachnoid space • The arachnoid mater is the middle layer of the meninges • is avascular, and does not receive any innervation. • Underneath the arachnoid is a space known as the sub-arachnoid space • Small projections of arachnoid mater into the dura (known as arachnoid granulations) allow CSF to re-enter the circulation via the dural venous sinuses. Pia mater • underneath the sub-arachnoid • choroid plexus: a network space. It is very thin, and tightly of capillaries and ependyma adhered to the surface of the (specialized ciliated epithelial brain and spinal cord. tissue) that produce • follow the contours of the brain: cerebrospinal fluid. the gyri and fissures. • outer layer consisting of collagen • highly vascularized fibers and an inner layer that encases the entire spinal cord. Meningeal layers and levels in the spinal cord
Contents:
✓Meninges
❑CSF and Ventricles
❑Blood supply of the brain The Ventricles NAME FROM TO interventricular foramina (Monro) lateral third ventricle ventricles cerebral aqueduct (Sylvius) third ventricle fourth ventricle median subarachnoid aperture (Magendie) space via fourth ventricle the cisterna magna lateral aperture right and left lateral median aperture aperture (Luschka) subarachnoid space via fourth ventricle the cistern of great cerebral vein CSF and the Ventricles
• The ventricles are filled with cerebrospinal fluid (CSF) which cushions the brain and spinal cord • CSF is produced by modified ependymal cells of the choroid plexus found in all components of the ventricular system EXCEPT for the cerebral aqueduct and the posterior and anterior horns of the lateral ventricles. • fluid then flows around the superior sagittal sinus to be reabsorbed via the arachnoid granulations into the venous sinuses, where it passes through the jugular vein and major venous system.
Clinical correlations
As cerebrospinal fluid is continually produced by the choroid plexus within the ventricles, a blockage of outflow leads to increasingly high pressure in the lateral ventricles. Which can commonly lead to hydrocephalus. Contents:
✓Meninges
✓CSF and Ventricles
❑Blood supply of the brain Blood supply
Circle of willis Basilary a. Formed by the: Branches of the Basilar Artery: 1. Internal carotid 1. Pontine 2. Anterior cerebral 2. Labyrinthine 3. Anterior communicating 3. Anterior-Inferior Cerebellar 4. Posterior cerebral 4. Superior Cerebellar 5. Posterior communicating 5. Posterior Cerebral “PLAISP” Remember NOT the middle cerebral
An easy to follow guide for the blood supply https://www.youtube.com/watch?v=uMMMqkVZAhk
The anterior cerebral artery
• extends upward and forward from the internal carotid artery. It supplies the frontal lobes • logical thought, • personality, • voluntary movement of the legs. • Stroke in the anterior cerebral artery results in opposite leg weakness The middle cerebral artery • is the largest branch of the internal carotid. • supplies a portion of the frontal lobe and the lateral surface of the temporal and parietal lobes • the primary motor and sensory areas of: • the face • throat • hand and arm • the dominant hemisphere, the areas for speech. The posterior cerebral arteries
• from the basilar artery. • supply the temporal and occipital lobes
• Clinical symptoms associated with occlusion depend on the location of the occlusion. may include: thalamic syndrome, thalamic perforate syndrome, Weber’s syndrome, contralateral hemplegia, hemianopsia and a variety of other symptoms, including including color blindness, failure to see to-and-fro movements, verbal dyslexia, and hallucinations. Ant. Cerebral a.
Ant. Communicating a. Opthalmic a.
Internal carotid a. Middle cerebral a. with branch of Ant. Chorodial a. Post. Communicating a.
Post. Cerebral a.
Sup. Cerebellar a. Basillary a. with pontine branches Labyrinthine a. Ant. Inf. Cerebellar a. Post. Inf. Cerebellar a. with branches of Post. Spinal a. Vertebral a. Ant. Spinal a.