Brainstem External Features PDF Lecture Notes

BRAINSTEM EXTERNAL FEATURES DR NADINE RAMPF | PHD [email protected] LECTURE OUTLINE Overview and functions 04 Features of the ventral surfaces 07 Features of the dorsal surfaces 13 Blood supply 19 02 OBJECTIVES...

BRAINSTEM EXTERNAL FEATURES DR NADINE RAMPF | PHD [email protected] LECTURE OUTLINE Overview and functions 04 Features of the ventral surfaces 07 Features of the dorsal surfaces 13 Blood supply 19 02 OBJECTIVES List the parts of the brainstem Describe the location of the brainstem Describe the relations between the different parts of the brainstem and their relations to the cerebellum Describe the external features of both ventral and dorsal surfaces of the brain stem List cranial nerves emerging from the brain stem Describe the site of emergence of each cranial nerve 03 LECTURE OUTLINE Overview and functions Features of the ventral surfaces Features of the dorsal surfaces Blood supply 04  OVERVIEW corpus quadragemina Have 4 colliculi Midbrain The brainstem is the region of the brain that connects the cerebrum with the spinal cord Pons LOCATION Medulla On the basilar part of the occipital bone (clivus) Body PARTS (superior to inferior) Midbrain Pons Medulla oblongata CONNECTIONS WITH CEREBELLUM Each of the 3 parts of the brainstem is connected to the cerebellum by a pair of cerebellar peduncles (superior, middle and inferior) 05 FUNCTIONS It is a pathway of tracts between the cerebral cortex and spinal cord It is a site of origin of nuclei of cranial nerves (from 3rd Body to 12th) It is a site of emergence of cranial nerves (from 3rd to 12th) It contains groups of nuclei and related fibres known as the reticular formation which is responsible for: Control of level of consciousness Perception of pain Regulation of cardiovascular system Regulation of respiratory system 06 LECTURE OUTLINE Overview and functions Features of the ventral surfaces Features of the dorsal surfaces Blood supply 07  MEDULLA VENTRAL SURFACE Ventral median fissure Continuation of ventral median fissure of spinal cord Divides the medulla into 2 halves Its lower part is masked by decussation of most of the pyramidal (corticospinal) fibres (75% -90%) Pyramid Body An elevation on either side of the ventral median fissure Produced by the corticospinal tract 08  MEDULLA VENTRAL SURFACE nucleus (inferior olivery nucleus) vestibular system below Olive olive Body An elevation, located lateral to the pyramid Produced by inferior olivary nucleus (important in control of movement) CN nerves emerging from medulla (4 nerves) Hypoglossal (12th) Emerge from sulcus between the pyramid and the olive Glossopharyngeal (9th), vagus (10th) and cranial part of accessory (11th) Emerge from sulcus dorsolateral to olive (from above downwards) 09  PONS VENTRAL SURFACE Basilar sulcus Body Divides the pons into 2 halves Occupied by the basilar artery Transverse pontine (pontocerebellar) fibres Originate from pontine nuclei 1. Cross the midline 2. Pass through the contralateral middle cerebellar peduncle 3. Enter the opposite cerebellar hemisphere 10  PONS VENTRAL SURFACE CN nerves emerging from pons (4 nerves) Trigeminal (5th) Body Emerges from the middle of ventrolateral aspect of pons as 2 roots: a small motor medial root a large lateral sensory root Abducent (6th) Emerges from sulcus between pons and pyramid Facial (7th) and vestibulocochlear (8th) Body Emerge from the cerebellopontine angle (junction between medulla, pons and cerebellum) Both nerves emerge as 2 roots (from medial to lateral): 7th (motor root and sensory root) 8th (vestibular part and cochlear part) 11  MIDBRAIN VENTRAL SURFACE Crus cerebri (basis pedunculi/cerebral peduncles) Body Large column of descending fibres Separated on either side by a depression called the interpeduncular fossa CN rerve emerging from midbrain (one) Oculomotor (3rd) Emerges from medial aspect of crus cerebri 12 LECTURE OUTLINE Overview and functions Features of the ventral surfaces Features of the dorsal surfaces Blood supply 13 MEDULLA DORSAL SURFACE The features differ in the caudal part (closed medulla) and the cranial part (open medulla) Open part Closed part 14  MEDULLA ICP: Inferior Cerebellar Peduncle DORSAL SURFACE - CLOSED PART Cavity: central canal ICP ICP Composition Open part Body Dorsal median sulcus Closed part Divides the closed medulla into 2 halves Fasciculus gracilis Located on either side of dorsal median sulcus Gracile tubercle An elevation produced at the upper part of ICP: Inferior Cerebellar Peduncle fasciculus gracilis, marks the site of gracile nucleus Fasciculus cuneatus ICP ICP Located on either side of fasciculus gracilis Cuneate tubercle An elevation produced at the upper part of fasciculus cuneatus, marks the site of cuneate nucleus VESIICULAR GRACULUS BELOW NUCLEUS Inferior cerebellar peduncle GRACILIS (SENSORY FIBRES PROPIOCEPTOR INFO FROM UPPER AND LOWER LIMB 15  MEDULLA DORSAL SURFACE - OPEN PART 23 22 Cavity: 4th ventricle 21 On either side of the median sulcus an inverted V- 20 Body shaped sulcus divides the area into 3 parts 19 (from medial to lateral): 18 Hypoglossal triangle 17 8 Overlies the hypoglossal nucleus 9 16 Vagal triangle Overlies dorsal vagal nucleus 13 Vestibular area 14 Overlies the vestibular nuclei 15 1: Middle cerebellar peduncle 6: Facial colliculus 12: Gracile tubercle 18: Stria medullaris of 4th ventricle 2: Superior cerebellar peduncle 7: Hypoglossal triangle 13: Posterolateral sulcus 19: Sulcus limitans 3: Inferior cerebellar peduncle 8: Vagal triangle 14: Posterior intermediate sulcus 20: Superior fovea 4': Vestibular area (medulla) 9: Area posterma NAUSEA CENTRE 15: Posterior median sulcus 21: Locus coeruleus 4": Vestibular area (pons) 10: Trigeminal tubercle 16: Obex 22: Trochlear nerve 5: Median eminence 11: Cuneate tubercle 17: Inferior fovea 23: Frenulum of superior medullary velum 16  PONS DORSAL SURFACE 23 22 Separated from the medulla by an imaginary line 21 passing between the caudal margins of the middle cerebellar peduncle 20 Body 19 On each side, a sulcus divides the area into 2 parts 18 (from medial to lateral): 17 8 Medial eminence and facial colliculus 9 16 Overlies abducent nucleus Vestibular area 13 Overlies vestibular nuclei 14 15 The dorsal surface of the open medulla and the pons forms the floor of the 4th ventricle 1: Middle cerebellar peduncle 6: Facial colliculus 12: Gracile tubercle 18: Stria medullaris of 4th ventricle 2: Superior cerebellar peduncle 7: Hypoglossal triangle 13: Posterolateral sulcus 19: Sulcus limitans 3: Inferior cerebellar peduncle 8: Vagal triangle 14: Posterior intermediate sulcus 20: Superior fovea 4': Vestibular area (medulla) 9: Area posterma 15: Posterior median sulcus 21: Locus coeruleus 4": Vestibular area (pons) 10: Trigeminal tubercle 16: Obex 22: Trochlear nerve 5: Median eminence 11: Cuneate tubercle 17: Inferior fovea 23: Frenulum of superior medullary velum 17  MIDBRAIN DORSAL SURFACE Marked by 4 elevations Two superior colliculi Body Concerned with visual reflexes Two inferior colliculi Forms part of the auditory pathway CN nerve emerging from midbrain (one) Trochlear (4th) Emerges just caudal to inferior colliculus The only CN emerging from dorsal surface of brainstem DORSAL COLUMN = SESORY MECH. FOR UPPER AND LOWER BODY 18 LECTURE OUTLINE Overview and functions Features of the ventral surfaces Features of the dorsal surfaces Blood supply 19 ARTERIAL SUPPLY TO THE MEDULLA The surface of the medulla is supplied by the branches of the vertebraland basilar arteries: Anterior spinal artery Posterior spinal artery Posterior inferior cerebellar artery Their branches that supply the substance of the medulla enter along the roots of the glossopharyngeal, vagus, accessory and hypoglossal nerves 20 ARTERIAL SUPPLY TO THE PONS Arterial supply The blood supply of the pons is formed by branches of the vertebrobasilar system Pontine arteries Anterior inferior cerebellar artery Superior cerebellar artery 21 ARTERIAL SUPPLY TO THE MIDBRAIN Arterial supply Basilar artery through its posterior cerebral and superior cerebellar arteries Basilar artery also supplies the midbrain through direct branches Branches of posterior communicating and anterior choroidal arteries 22  THANK YOU FOR YOUR ATTENTION Content for this lecture: Chapter 5 | Snell's Clinical Neuroanatomy, 8th Edition