Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Medulla Oblongata Dorsal surface
Document related concepts
Transcript
بسم هللا الرحمن الرحیم The Brainstem The Brainstem Consists of • Midbrain • Pons • Medulla oblongata The brainstem has three broad functions: (1) it serves as a conduit for the ascending tracts and descending tracts connecting the spinal cord to the different parts of the higher centers in the forebrain (2) it contains important reflex centers associated with the control of respiration and the cardiovascular system and with the control of consciousness (3) it contains the important nuclei of cranial nerves lll through Xll. Ventral surface • • • • • Medulla oblongata Pyramid: contain pyramidal tract (corticospinal tract) Decussation of pyramid: formed by crossing fibers of corticospinal tract Olive: produced by underlying inferior olivary nucleus Anterolateral sulcus: rootlets of hypoglossal nerve emerge from it Retroolivary sulcus: rootlets of glossopharyngeal, vagus and accessory nerves emerge from it Medulla Oblongata Dorsal surface • Lower portion – Gracile tubercle: produced by gracile nucleus – Cuneate tubercle: marks the site of cuneate nucleus underlying – Inferior cerebellar peduncle – Obex • Upper portion: forms the lower half of rhomboid fossa Pons Ventral surface • Basilar part • Basilar sulcus • Bulbopontine sulcus : from medial to lateral, the abducent, facial and vestibulocochlear nerves appear • Middle cerebellar peduncle • Trigeminal nerve Pons Dorsal surface • Superior cerebellar peduncle • Superior medullary velum • Trochlear nerve Midbrain Ventral surface • Crus cerebri • Interpeduncular fossa oculomotor nerves emerge from medial of crus cerebri • Posterior perforated substance Midbrain Dorsal surface • Superior colliculus constitute centers for visual reflexes • Inferior colliculus associated with auditory pathway • Brachium of superior colliculi • Brachium of inferior colliculi Fourth ventricle Central canal →fourth ventricle →mesencephalic aqueduct→third ventricle Position • Situated ventral to cerebellum, and dorsal to pons and cranial half of medulla * * Boundaries • Inferolateral: gracile and cuneate tubercles, inferior cerebellar peduncle • Superolateral: superior cerebellar peduncle • Lateral recess Features • Median sulcus • Sulcus limitans • Vestibular area overlies vestibular nuclei • Acoustic tubercle • overlying dorsal cochlear nucleus • Medial eminence • Striae medullares • Facial colliculus: overlies nucleus of abducent n. and genu of facial nerve • Hypoglossal triangle overlying hypoglossal nucleus • Vagal triangle: overlies dorsal nucleus of vagus nerve • Area postrema • Locus ceruleus : Roof • Anterior part: formed by superior cerebellar peduncle and superior medullary velum • Posterior part: formed by inferior medullary velum and choroid plexus of fourth ventricle • Three apertures – Median aperture of fourth ventricle – Two lateral apertures of fourth ventricle Tela choroidea and choroid plexus The characters of internal structure of brainstem Medulla oblongata Lower part (closed part) • Two decussations– – Decussations of medial lemniscus – Decussations of pyramid Cuneatus n V nucleuos Medulla oblongata Upper part (open part) • Appearance of inferior olivary nuculeus and inferior cerebellar peduncle • Enlargement of central canal to form the fourth ventricle floor • • • • • Spinoolivary accessory olivary Cortico olivary inf. Olivary n. Central tegmental tract inf. Olivary n. Olivocerebellar fibers Inf. Olivary = center of coordination of afferents of cerebellum Internal structures Gray matter • Cranial nerve nuclei • Relay nuclei Relay nuclei • • • • • • • Gracile nucleus Cuneate nucleus Inferior olivary nucleus Superior olivery nucleus Pontine nucleus Nucleus of inferior colliculus Gray matter layers of superior colliculus • Red nucleus • Substantia nigra • Pretectal area Non-cranial nerve nuclei Nucleus Site Gracile nucleus Medulla (underneath gracile tubercle) Cuneate nucleus Medulla (underneath cuneate tubercle) Superior olivery nucleus Pons Pontine nucleus pons Nucleus of inferior colliculus Midbrain Gray matter layers of superior colliculus Midbrain Red nucleus Midbrain Substantia nigra Midbrain Pretectal area Midbrain White matter Ascending tracts • • • • Medial lemniscus Spinal lemniscus Trigeminal lemniscus Lateral lemniscus Medial lemniscus Spinal lemniscus Trigeminal lemniscus Descending tracts • • • • • Corticospinal tract Rubrospinal tract Tectospinal tract Vestibulospinal tract Reticulospinal tract Lateral lemniscus Reticular formation of brainstem • Ascending reticular activating system (ARAS) • Motor central and vital centres – Reticulospinal tract – Cardiovascular center and respiratory center • Serotonergic rapheal nuclei • Medial longitudinal fasciculus= medial vestibolospinal tract • Dorsal n of vagus =parasympathic part • Solitarious n= gustatory • Central tegmental tract
