Neuroanatomy.pdf

Neuroanatomy Meninges, Ventricular System, Brain Blood Supply Protection of CNS 1. BONE – skull, vertebral column 2. CONNECTIVE TISSUES Meningeal Layers a. Dura mater – tough outer layer b. Arachnoid mater – wed-like middle layer c. Pia mater – delicate/thin inner layer 3. FLUID a. CSF *From superfi...

Neuroanatomy Meninges, Ventricular System, Brain Blood Supply Protection of CNS 1. BONE – skull, vertebral column 2. CONNECTIVE TISSUES Meningeal Layers a. Dura mater – tough outer layer b. Arachnoid mater – wed-like middle layer c. Pia mater – delicate/thin inner layer 3. FLUID a. CSF *From superficial à deep* Meninges of Brain Meninges of Spinal Cord SKULL VERTERBRAL COLUMN (boney layer is vertebrae instead of skull) EPIDURAL SPACE (only present pathologically) SPACE 1: EPIDURAL SPACE – filled with fat for additional LAYER 1: DURA MATER (2 layers) protection due to exposure of more forces (shock 1. PERIOSTEAL (adhered to bone) absorber) 2. MENINGEAL (forms folds for venous sinuses) - True space in spinal cord whereas only present pathologically in brain SUBDURAL SPACE (only present pathologically) LAYER 1: DURA MATER (1 layer) LAYER 2: ARACHNOID MATER - Thicker than other meninges – ‘tough mother’ - ‘Web’ extensions all the way down to pia mater - Arachnoid villus/arachnoid granulations (small SUBDURAL SPACE (only present pathologically) protrusions of arachnoid through dura mater) LAYER 2: ARACHNOID MATER – ‘web’ SPACE 1: SUBARACHNOID SPACE – CSF location - Sits between arachnoid + pia mater SPACE 2: SUBARACHNOID – CSF location LAYER 3: PIA MATER - Tightly adhered to neural tissue itself - Protects outer layer of cortex (adhered + attached that if peeled off = damage to skull) Periosteal Dura: attached to bone thus outer layer Meningeal Dura: inner layer – folds away from periosteal - Forms folds of tissues that separate cranial cavity into sections - Separated by ‘venous sinuses’ - Thus gives rise to dural reflections + continues into foramen magnum as spinal dura LAYER 3: PIA MATER – tightly adhered to neural tissue itself Dura Mater: sac that covers spinal cord with bony attachments at foramen magnum, C1-C2 + @ the level of S2 ‘dural sleeve’ - Surrounding this layer is the EPIDURAL SPACE which contains FAT + Connective Tissue + BV - Sac extends below spinal cord to protect the final spinal nerves @ base of spine Arachnoid: middle layer of avascular CT with collagen + elastic fibers - Deep to arachnoid layer = subarachnoid space containing CSF **TOGETHER THEY FORM SOCK = completely covers spinal cord from beginning to end; thus fused together** Dural Reflections – folds that separate the cranial cavity into compartments which isolate any trauma/damage and prevent it from spreading into other areas 1. FALX CEREBRI: divides 2 hemispheres of cerebrum 2. TENTORIUM CEREBELI: divides cerebrum from cerebellum 3. FALX CEREBELI: divides 2 hemispheres of cerebellum - Large veins within the dura mater reflections of the skull (within the folds) are ENSURED to be left OPEN for continuous drainage Dura Sinuses Superior SS: receives blood from superior aspect of cranium + drains into the confluence of sinus (sits at top of falx cerebri) Inferior SS: collects blood deep within cranium near diencephalon + meets up with SSS at confluence using SS SS: receives blood from IFF + drains into confluence Confluence receives blood from: SSS, ISS, SS - Here we are outside the skull completely Transverse sinus: receives dumped blood from COS à takes an “S” turn à becomes SIGMOID SINUS à drains into internal jugular vein à headed to superior vena cava Cavernous sinus: drains regions of skull (mouth, nose, eyes) à inferior petrosal à intrajugular vein à superior vena cava Arachnoid Granulations - Extend through dura mater into venous sinuses PIA MATER (dural sac opened) - DENTICULATE LIGAMENTS: thickening of pia mater that suspend the spinal cord in the middle of its dural sheath - Located between ventral + dorsal nerve roots - Protect spinal cord against shock + sudden displacement/trauma *Extends off surface of cord + forms tooth like extensions called denticulate ligaments to anchor cord to dural sac/sheath* Termination of Spinal Cord 1. CONUS MEDULLARIS - End of spinal cord (L4 in children, L1/2 in adults) - Dural sleeve extends way beyond bcs spinal nerves are exiting @ conus medullaris - Protected from dural sac 2. LUMBAR CISTERN - Filled with CSF - Enlargement of subarachnoid space between conus medullaris (L2) & end of dural sac (S2) - Site for lumbar puncture bcs can sample CSF 3. CAUDA EQUINA - Remaining spinal nerves exiting (horse tail) - Protected from dural sac 4. FILUM TERMINALE - Tethers spinal cord à coccyx - Extension of pia mater running from conus medullaris à down to coccyx - Anchors conus + dural sac to coccyx itself - NOT A NEURAL STRUCTURE - Allows CSF to move from subarachnoid space into venous circulation (thus takes same route as venous blood) *Superior Sagittal sinus separates the 2 layers of dura* Ventricular System of CNS – a communicating network of cavities deep within tissues of the brain - 2 LATERAL VENTRICLES: found in all 4 lobes of the brain - 3RD VENTRICLE: found between thalamic nuclei - CEREBAL AQUEDUCT: runs through midbrain - 4TH VENTRICLE: found between pons + cerebellum CHOROID PLEXUSES: specialized arterial plexuses located within the ventricular spaces which functions to produce cerebrospinal fluid ‘CSF’ from arterial blood - CSF: serves as a nutrient delivery + waste removal system for brain tissue - CSF: enters subarachnoid space to provide fluid cushion around brain + SC - UNIDIRECTIONAL FLOW OF CSF - Absorbed by venous system after it has performed its role within the CNS CNS is 1st secreted à dumped into ventricular system (flows deep inside) à when flowing in ventricular system it serves as a delivery system for nutrients à once finished circulating in ventricular system à enters subarachnoid space and provides fluid cushin around outside **SYNTHESIZED FROM ARTERIAL BLOOD à RETURNED BACK INTO VENOUS BLOOD = ALWAYS WITH BLOOD SYSTEM* Flow of CSF - Lateral ventricles are not the only location where CSF can be circulated, also the 3rd and 4th Flow is still the same, difference is how much CSF is in the system CSF gives nutrition to deep brain structures - CSF cushions EXTERNALLY to brain + spinal cord (not internally) CSF picks up waste products and returns it to the venous system (not connected to lymphatic system) Blood Supply of the Brain 1. VERTEBRO-BASILAR SYSTEM a. Vertebral Arteries b. Basilar A. c. Posterior Cerebral A. (PCA) (occipital lobe- cortical blindness) d. Posterior communicating Arteries e. Posterior Anterior Inferior Cerebellar Artery (PICA, also covers brainstem) – MOST COMMON TO CAUSE STROKE – PICA SYNDROME f. Superior cerebellar (also covers brainstem) 2. CAROTID SYSETM a. Middle Cerebral A. (MCA) b. Anterior Cerebral A. (ACA) c. Anterior communicating A. Circle of Willis § Fxn: all blood supply comes from here § If there is a blood clot, there is a ‘back up plan’ for it to travel in a circle BASILAR SYSTEM § Posterior Cerebral A. (PCA) (occipital lobe- cortical blindness) § Posterior communicating Arteries INTERNAL CAROTID SYSTEM § Anterior Cerebral A. (ACA) § Anterior communicating A. § Internal carotid artery - It is the base of brain and circles PITUITARY + MIDBRAIN + CN II CORTICAL VASCULAR TERRITORIES Anterior cerebral artery: serves frontal + parietal lobe Middle cerebral artery: serves frontal + parietal + temporal lobe Posterior cerebral artery: serves temporal + occipital + parietal lobe Arteries of Spinal Cord Blood supply of spinal cord: Note: BASILAR ARTERY = main artery that supplies blood to the back portion of the brain - Carries oxygen-rich blood to brainstem, cerebellum, and occipital lobes Anterior – ONE ARTERY - Vertebral arteries @ top from basilar artery + each give off an anterior spinal artery which travel down entire entire length of cord à - Vertebral arteries cannot supply blood to entire length of cord thus as we go along, the interspinal artery will receive some supplemented blood supply from other arteries (intercostal arteries in thoracic spine + lumbar arteries in lumbar spine) **REINFORCING BLOOD SUPPLY ALL DOWN THE CORD** **DOES ANTERIOR 2/3’S – ANTERIOR + LATERAL COLUMN** Column = divided into 3: anterior, lateral, posterior Posterior – TWO ARTERIES - 2 posterior à branch off of posterior cerebellar artery (a part of vertebral system) à - Run down back of cord in a pair all the way down à - Cannot pump all the way down thus receive reinforced blood supply from intercostal arteries in thoracic spine + lumbar arteries in lumbar spine **DOES ONLY 1/3 OF POSTERIOR SIDE OF COLUMN = MORE PRONE TO INJURY BCS LESS PROTECTED**