- MEDULLA OBLONGATA
- Structural Components
- Vital center
- Cardiac center
- Vasomotor center
- regulation of distribution of blood flow in vessels
- Respiratory center
- regulation of respiration
- External features
- ANTERIOR OR VENTRAL (अग्र )
- divided in to longitudinal halves by ( दो भाग )
- Anterior median fissure; ventral median fissure ( परिखा )
- continuous with fissure of spinal cord
- just above joining ends in a triangular depression
- Foramen caecum of medulla oblongata
- at lower border of pons
- interrupted by decussation of pyramids
- Two elongated elevations on each half called as
- Pyramids
- caused by corticospinal ( pyramidal) fibers
- most of these fibers cross to opposite side in lower medulla
- Decussation of pyramids; motor decussation
- descend as lateral corticospinal tract
- in lateral white column ( पार्श्व श्वेत स्तम्भ )
- uncrossed fibers descend as
- anterior corticospinal tract
- in anterior white column ( अग्र श्वेत स्तम्भ )
- Oval elevations called ( अंडा )
- Olive
- caused by inferior olivary nucleus
- LATERAL OR SIDES
- divided in to longitudinal halves by
- ANTEROLATERAL SIDES
- Anterolateral sulcus; ventrolateral sulcus
- extends along lateral border of pyramid
- XII - rootlets of Hypoglossal nerve emerges
- POSTEROLATERAL SIDES
- Posterolateral sulcus; dorsolateral sulcus
- lies between olive and inferior cerebellar peduncle
- emerges from it are
- IX , X , XI cranial nerves
- Inferior cerebellar peduncle
- posterolateral to olive
- attach medulla with cerebellum
- DORSAL OR POSTERIOR
- divided in to longitudinal halves by
- Posterior median sulcus; dorsal median sulcus
- present only in lower half of medulla
- above it lips diverge to form
- boundaries of triangular area
- lower part of 4th ventricle
- Upper Open part
- Posterior median sulcus; dorsal median sulcus
- either side of sulcus
- more laterally and obliquely continuation of sulcus limitans of pons
- from stria medullares
- sulcus limitans converges towards the upper end of lower medulla
- depression at sides on sulcus limitans
- inferior fovea
- it divides it in to two areas
- hypoglossal triangle
- vagal triangle
- between vagal triangle and gracile tubercle
- area postrema
- function as chemoreceptor
- ependymal thickening
- funiculus separans
- separates both vagal triangle and area postrema
- lowermost point is called obex
- Lower Closed Part
- either side of sulcus
- 3 longitudinal elevations ( medial to lateral )
- fasciculus gracilis
- upper end expand to form gracile tubercle due to
- nucleus gracilis
- fasciculus cuneatus
- upper end expand to form cuneate tubercle due to
- nucleus cuneatus
- Tuber cinerum
- caused by spinal nucleus of trigeminal nerve
- inferior cerebellar peduncle
- INTERNAL FEATURES OF MEDULLA
- At the level of decussation of pyramids
- POSTERIORLY
- narrow strips nucleus gracilis and nucleus cuneatus
- posterior horn
- apex gets swollen to form
- nucleus of spinal tract of trigeminal nerve
- it is upward continuation of substantia gelatinosa of spinal cord
- posterior horn capped in white matter by
- fibers of spinal tract of trigeminal nerve
- runs backwards and laterally across midline ( from anterior to posterior )
- to reach lateral side
- ANTERIORLY
- LATERALLY
- in white column diffused network of fibers
- reticular formation
- At the level of decussation of medial lemnisci ( or Sensory decussation )
- ANTERIORLY
- lower part of inferior olivary nucleus
- pyramid
- POSTERIORLY
- posterior white column
- fibers of fasciculus gracilis and cuneatus
- nucleus gracilis and nucleus cuneatus are well seen and demarcated
- separated from central grey matter
- CENTRALLY
- central grey matter contains
- ventromedial
- hypoglossal nucleus
- dorsolateral
- dorsal nucleus of vagus
- dorsolateral
- nucleus of tractus solitarius
- SIDES
- Dorsolateral to cuneate nucleus
- accessory cuneate nucleus
- receives lateral fibers (derived from cervical segments of cord ) of fasciculus cuneatus
- gives rise to posterior external arcuate fibres
- through inferior cerebellar peduncle
- proprioceptive impulse to cerebellum
- same side
- spinal nucleus and tract of trigeminal nerve lies laterally side of cuneate nucleus
- Ventrolateral
- medial longitudinal bundle lies posterior to medial lemniscus
- spinocerebellar and lateral spinothalamic tract
- SENSORY DECUSSATION (POSTERIOR TO ANTERIOR )
- Arising from nucleus gracilis and cuneatus
- internal arcuate fibers
- course forward and medially around central grey matter
- decussate with opposite fibers in median plane
- ascend upwards as MEDIAL LEMNISCUS on opposite side
- most medial fibers come to lie anteriorly
- feet and leg
- relay in to the thalamus
- At the level of Olives ( across the floor of fourth ventricle )
- central grey matter is spread and broken
- over floor of fourth ventricle
- medial to lateral
- posteriorly
- hypoglossal nucleus
- nucleus intermedius
- dorsal nucleus of vagus
- vestibular nucleus
- middle or intermediate
- nucleus ambiguus
- gives origin to 9 , 10 , 11
- paramedian region ( either side of midline - from posterior to anterior)
- median longitudinal fasciculus
- tectospinal tract
- medial lemniscus
- corticospinal tract
- laterally
- dorsal to ventral
- inferior cerebellar peduncle
- dorsal accessory olivary nucleus
- medial accessory olivary nucleus
- inferior olivary nucleus
- anteromedially
- arcuate nuclei
- At the level just inferior to pons
- lateral vestibular nucleus replaces inferior vestibular nucleus
- cochlear nucleus
- hi/medulla_oblongata.txt
- 2023/06/23 13:41
- brahmantra
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