Lecture 2- Meninges, CSF, Ventricular system, Cerebral hemispheres Flashcards
3 brain coverings
Dura mata - subdural spaces (increased arteries) Arachnoid mata - subarachnoid space (CSF and increased veins) Pia mata - adheres directly onto brain
Dura mata layers
Fibrous endosteal
Meningeal
- dural venous sinuses in between some sites
Dural reflections
Falx cerebri (partial separation of cerebral
hemispheres)
Falx cerebelli (partial separation of cerebellar
hemispheres)
Tentorium cerebelli
Diaphragm sellae
Blood supply of dura
Ethmoidal artery (ant + post) Internal carotid artery Middle meningeal artery Maxillary artery Ascending pharyngeal artery Occipital artery Vertebral artery
Nerve supply of dura mata
Meningeal branches of
- Maxillary
- Mandibular
- Upper cervical nerves
Arachnoid mata
Thin, vascular membrane
Attaches to dura by several layers of flattened cells
Conforms to general shape of brain but does not fit into every sulcus
Separated from Pia by arachnoid trabeculae and subarachnoid space
Specialisations of arachnoid mata
Trabeculae
Villi
Barrier
Arachnoid trabeculae
Strands of collagenous connective tissue from arachnoid to pia
Arachnoid villi
For reabsorption of CSF
Outgrowths of arachnoid projecting through the dura into the sinuses
Form granulations with age
Arachnoid barrier
Cells of outermost arachnoid layer have tight junctions
Prevents spread of microbes from the dura into the subarachnoid space so that they don’t reach the brain
Pia mata
2-3 cells thick
Attaches to end feet of arachnoid trabeculae, helps to keep arachnoid space open
Closely follows all sulci and gyri of brain
Penetrated by arteries and veins when they enter or leave the brain substance (perivascular space)
Spinal meninges
Devoid of fibrous layer (endosteal) of dura which ends at margin of foramen magnum
Arachnoid mata stays relatively the same
Pia mata forms 21 pairs of denticulate ligaments and is thickened anteriorly to give a shiny appearance in the midline (linea splendens and filum terminale)
Ventricular system
Lateral ventricles (cerebrum) via intraventricular foramen to 3rd ventricle (diencephalon) via cerebral aqueduct to 4th ventricle (pons/medulla)
Parts of lateral ventricle
Anterior (frontal
Body
Posterior (occipital)
Inferior (temporal)
Walls of 3rd ventricle
Anterior wall Posterior wall Sides= Thalamus Roof Floor
Floor of 4th ventricle (Rhomboid Fossa)
Facial colliculus Inferior cerebral peduncle Hypoglossal trigone Vagal trigone Locus cerulus Stria medularis Cuneate tubercle Gracile tubercle
CSF formation
Produced by choroid plexus
Made in the floor of lateral ventricles and roof of 3rd + 4th ventricles
Made at rate of 0.35 ml/min
500 ml of total CSF made per day and replaced every 4-6 hours
Circulation of CSF
From lateral vent to 3rd vent via interventricular foramina of Monro
From 3rd vent to 4th vent via cerebral aqueduct of Sylvius
From 4th vent to subarachnoid space via median foramen Magendie (Cisterna Magna + lateral foramina of Luschka, and Pontine Cistern)
Absorption of CSF
Absorbed into dural venous sinuses through arachnoid villi/granulations
CSF has a higher pressure than venous blood (passive transfusion)
Arachnoid villi/granulations are a one-way valve, therefore collapse to prevent venous blood from entering subarachnoid space
Functions of CSF
Supports and cushions brain and spinal cord against trauma for shock absorption
Acts as a buoyant fluid, therefore allowing brain to weigh less
Maintains uniform pressure
Aids brain nutrition, choroid plexus secretes protein-rich CSF for neural tissues
Removes waste products of neural metabolism
Cerebrospinal cisterns and types
Sites of dilation of subarachnoid space with pooling of CSF Cerebello-medullary Pontine Interpenduncular Cistern Ambiens
Cerebello-medullary cistern
Largest cistern
Pontine cistern
Contains basilar artery
Interpenduncular cistern
Contains arterial circle of Willis
Pre- and post- chiasmic
Cisterna of lamina terminalis
Supracallosal cistern
