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Dr. Ahmed Fathalla Ibrahim BRAIN STEM VENTRAL SURFACE DORSAL SURFACE CAUDAL MEDULLA (LEVEL OF PYRAMIDAL DECUSSATION) FG DMS FC GN ST5 Central grey matter CN SN5 Central canal DSC PD VSC P VMF CAUDAL MEDULLA (LEVEL OF PYRAMIDAL DECUSSATION) • • • • • • • • • • • • DMS: Dorsal median sulcus FG: fasciculus gracilis GN: Gracile nucleus FC: Fasciculus cuneatus CN: Cuneate nucleus SN5: Spinal nucleus of trigeminal nerve ST5: Spinal tract of trigeminal nerve P: Pyramid PD: Pyramidal decussation DSC: Dorsal spinocerebellar tract VSC: Ventral spinocerebellar tract VMF: Ventral median fissure CAUDAL MEDULLA (LEVEL OF PYRAMIDAL DECUSSATION) • • GREY MATTER: Sensory nuclei: Gracile, cuneate, spinal nucleus of trigeminal • WHITE MATTER: 1. Ascending tracts: Gracile, cuneate, spinal tract of trigeminal, dorsal & ventral spinocerebellar, spinal leminiscus 2. Descending tracts: Pyramidal & extrapyramidal tracts CAUDAL MEDULLA (LEVEL OF PYRAMIDAL DECUSSATION) • Pyramidal decussation: Most of the fibers of pyramid decussate then pass laterally & dorsally to form the lateral corticospinal tract that descend in the lateral white column of spinal & terminate in ventral horn cells of opposite side • Spinal nucleus of trigeminal: It lies in the lower part of pons, the whole medulla & extends to the 2nd cervical segment of spinal cord where it is continuous with substantia gelatinosa. It receives pain & temperature sensations from the face along trigeminal nerve CAUDAL MEDULLA (LEVEL OF PYRAMIDAL DECUSSATION) • Dorsal & ventral spinocerebellar tracts: They carry proprioceptive fibers to the cerebellum through inferior cerebellar peduncle (dorsal) & superior cerebellar peduncle (ventral) • Gracile &Cuneate tracts: They carry proprioceptive & fine touch sensations & end in Gracile & Cuneate nuclei (2nd order neurones in dorsal column tract) MID MEDULLA (LEVEL OF SENSORY DECUSSATION) DMS FG FC GN CN Central grey matter Central canal ST5 SN5 DSC M L VSC Internal Arcuate Fibers Sensory Decussation P VMF MID MEDULLA (LEVEL OF SENSORY DECUSSATION) • • GREY MATTER: Sensory nuclei: Gracile, cuneate, spinal nucleus of trigeminal • WHITE MATTER: 1. Ascending tracts: gracile, cuneate, spinal tract of trigeminal, dorsal & ventral spinocerebellar, spinal leminiscus 2. Descending tracts: Pyramidal & extrapyramidal tracts MID MEDULLA (LEVEL OF SENSORY DECUSSATION) • Gracile & cuneate nuclei: They are more prominent. Axons of cells of gracile & cuneate nuclei curve around the central canal as internal arcuate fibers then decussate forming the sensory decussation & ascend in the brain stem as medial leminiscus that end in the ventral posterolateral nucleus of thalamus • Pyramid: They are more prominent BRAIN STEM VENTRAL SURFACE DORSAL SURFACE ROSTRAL MEDULLA DCN 4TH V MV LV VH S VCN ICP A D Vagus Nerve Hypoglossal Nerve I.O. M L F M ML P VMF • • • • • • • • • • • • • • • • ROSTRAL MEDULLA H: Hypoglossal nucleus V: Dorsal vagal nucleus S: Nucleus solitarius A: nucleus ambiguus MV: Medial vestibular nucleus LV: Lateral vestibular nucleus DCN: Dorsal cochlear nucleus VCN: Ventral cochlear nucleus ICP: Inferior cerebellar peduncle I.O.: Inferior olive D: Dorsal accessory olive M: Medial accessory olive MLF: Medial longitudinal fascisulus ML: Medial leminiscus P: Pyramid VMF: Ventral median fissure ROSTRAL MEDULLA • GREY MATTER: 1.Motor nuclei: Hypoglossal, dorsal vagal, nucleus ambiguus 2.Sensory nuclei: Nucleus solitarius, medial & lateral vestibular nuclei, dorsal & ventral cochlear nuclei, spinal nucleus of trigeminal 3.Extrapyramidal nuclei: Inferior olive, medial & dorsal accessory olive ROSTRAL MEDULLA • WHITE MATTER: 1.Ascending tracts: Medial leminiscus, spinal leminiscus, spinal tract of trigeminal, ventral spinocerebellar tract 2.Descending tracts: Pyramidal & extrapyramidal tracts 3.Both ascending & descending tract: Medial longitudinal fasciculus 4.Inferior cerebellar peduncle: fibers connecting medulla to cerebellum ROSTRAL MEDULLA • Hypoglossal nucleus: It lies in the medial part of floor of 4th ventricle. It contains motor neurones innervating muscles of tongue (except palatoglossus) through hypoglossal nerve • Dorsal vagal nucleus: It lies in the floor of 4th ventricle , lateral to hypoglossal nucleus. It contains preganglionic parasympathetic neurones running in the vagus nerve • Nucleus Solitarius: It lies ventrolateral to dorsal vagal nucleus. It receive taste fibers from facial, glossopharyngeal & vagus nerves ROSTRAL MEDULLA • Nucleus ambiguus: It lies dorsal to inferior olivary nucleus. It contains motor neurones innervating muscles of pharynx, palate & larynx through glossopharyngeal, vagus & cranial part of accessory nerves • Medial & lateral vestibular nuclei: They lie in the floor of 4th ventricle, lateral to dorsal vagal nucleus. They receive afferent fibers from vestibular nerve • Dorsal & ventral cochlear nuclei: They lie dorsal (dorsal nucleus) & lateral (ventral nucleus) to ICP. They receive afferent fibers from cochlear nerve ROSTRAL MEDULLA • Olivary nuclear complex: It is formed of a large nucleus (inferior olive) & 2 smaller nuclei (medial & dorsal accessory olive). 1. Afferents: From cerebral cortex & spinal cord 2. Efferents: To cerebellum through ICP 3. Function: They are concerned with control of movement ROSTRAL MEDULLA • Medial longitudinal fasciculus: It consists of both ascending & descending fibers: 1. Ascending fibers: connect vestibular nuclei to nuclei supplying extraoccular muscles (occulomotor, trochlear & abducent nuclei). It coordinates movements of head & eyes 2. Descending fibers: connect vestibular nuclei to nuclei of ventral horn of spinal cord (medial vestibulospinal tract). It control body posture & balance ROSTRAL MEDULLA • Spinal leminiscus: It carries pain, temperature & touch sensations from the opposite side of body to ventral posterolateral nucleus of thalamus • Inferior cerebellar peduncle: It is formed of fibers connecting medulla to cerebellum