Medulla oplongata 22 04-16

10.  Dorsal nucleus of Vagus(motor nucleus )-
 Is a long vertical column .
 Upper end lies deep to the vagal triangle in the floor of the
fourth ventricle.
 Traced downwards in the closed part, it occupies a position
in the lateral part of central grey matter dorsal to the
hypoglossal nucleus.
 Main source of parasympathetic fibres of vagus nerve.

11. The upper part of the nucleus lies in the reticular formation,-
ventrolateral to the dorsal nucleus of vagus.
Traced downwards lies dorsomedial.
The rostral portion of the nucleus-Gustatory –VII,IX, AND X
cranial nerves nuclei terminate in it.
The caudal portion-receives-IX AND X cranial nerve nuclei.
 Nucleus of tractus solitarius:

12.  Nucleus ambiguus:
 Elongated column of typical motor neuron.
 Is so named because it is not clearly defined in
sections of the medulla.
 Occupies a position dorsal to the inferior olivary
nucleus,ventromedial to the nucleus of spinal tract of
Vth nerve.

13.  Hypoglossal nucleus:
 Elongated motor cells,
 Extends in the paramedian plane ,
 The medial longitudenal bundle lies ventral to it.
 The upper part lies deep to hypoglossal triangle,
 In the closed part,lies in the grey matter ventral to the
central canal
 The fibres course ventrally,emerge on ventral aspect a
series of 12 rootlets in the sulcus between pyramid and
olive

14.  Inferior Olivary nucleus :
 1.receive input from the wide areas of cerebral cortex,
red nucleus and from the periaqueductal region.
 Medial accessory
 Dorsal accessory olivary nucleus receive input from the
spinal cord ,red nucleus,

16. TRANSVERSE SECTION AT THE LEVEL
OF PYRIMIDAL DECUSSATION

17. TRANSVERSE SECTION AT SENSORY
DECUSSATION

18. TRANSEVERSE SECTION AT THE ,LEVEL
OF SENSORY DECUSSATION
 The section passes through
the middle of medulla:
 The central grey matter
contains-
1.Hypoglossal nucleus
2.Dorsal nucleus of vagus
3.Nucleus of tractus
solitarius.

19. TRANSVERSE SECTION AT THE LEVEL
OF SENSORY DECUSSATION
 The nucleus gracilis and
nucleus cuneatus become
more pronounced and
are separated from the
central grey matter.
 The fibres of fasciculus
gracilis and fasciculus
cuneatus occupy the
broad posterior white
column and terminate in
the nucleus

20.  Sensory Decussation of
the internal arcuate
fibres ;
 In this decussation the
gracile fibres are medial
to that of cuneate fibres
 The internal arcuate
fibres cut off the spinal
nucleus and tract of
trigeminal nerve from
the central grey matter.

21.  Immediately dorsolateral to the cuneate nucleus lies the
accessory cuneate nucleus-receive the more lateral fibres
(derived from the cervical segments) of the fasciculus
cuneatus –posterior external arcuate fibres conveying
proprioceptive impulses to the cerebellum of the same
side through inferior cerebellar peduncle.

22.  The separated spinal nucleus and tract of trigeminal nerve lies
ventrolateral to the cuneate nucleus.
 The lower part of the olivary nucleus is seen.
 The pyramids lie on either side of the anterior median fissure.
 Medial longitudinal bundle lies posterior to the medial
leminiscus.
 Spinocerebellar and lateral spinothalamic tracts lie in the
anterolateral area of lateral white column.
 Lateral and anterior spinothalamic tracts-spinal leminiscus.

23. TRANSVERSE SECTION AT THE
LEVEL OF OLIVE

24. 1. AT THE LEVEL OF OLIVE
 The central grey matter spread over the floor of the fourth ventricle from
medial to lateral-1.hypoglossal2.nucleus intercalatus 3.dorsal nucleus of
vagus 4.vestibular nuclei.(inferior and medial).
 The nucleus of tractus solitarius lies ventral to vestibular nuclei.
 The nucleus ambiguus lies deep within the reticular formation and give
origion to the motor fibres of IX,X, AND XIth cranial nerves.

25.  On either side of the midline from dorsal to ventral lie-
 1.medial longitudinal fasciculus
 2.tecto spinal tract,
 3.medial leminiscus
 4.pyrimidal tract.
 The arcuate nuclei-inferiorly displaced pontine nuclei are
situated on the anteromedial aspect of the pyramids.
 Laterally from dorsal to ventral-inferior cerebellar peduncle
and inferior olivary nucleus. Close to it lies medial and
dorsal accessory olivary nucleus.

26. BLOOD SUPPLY
 The medulla is supplied
by-
 Two vertebral arteries.
 Anterior and Posterior
spinal arteries.
 Anterior and Posterior
inferior cerebellar
arteries.
 Basilar artery.

27. VASCULAR DISORDERS
 Are Lateral Medullary syndrome(syndrome of wallenberg).
 Medial medullary syndrome(Dejerine’s anterior bulbar
syndrome)
 Lateral medullary syndrome-
 Due to the Thrombosis of Posterior inferior cerebellar artery,
Which supplies the dorsolateral part of the medulla and inferior
surface of the cerebellum.

28.  Medial medullary syndrome:
 The paramedian region of medulla is supplied by the
branches of vertebral artery.

29. VASCULAR DISORDERS
 Lateral medullary
syndrome:
 1.controlateral loss of
pain and temperature
sensation-spinothalamic
tract.
 2.Ipsilateral loss of pain
and temperature over
the face-spinal nucleus
and spinal tract of
trigeminal nerve.

30.  3.Ipsilateral paralysis of
muscles of palate pharynx
and larynx-nucleus
ambiguus.
 4.Ipsilateral ataxia-inferior
cerebellar peduncle and
cerebellum
 Giddiness-vestibular nuclei.
 Horner’s syndrome-
descending sympathetic
pathway of reticular
formation of medulla.

31. HORNER’S SYNDROME
Occurs due the interruption of sympathetic pathway
of head and neck.
Common sites of lesion are-brain stem,cervical part of
spinalcord or stellate ganglion

32. HORNER’S SYNDROME contd…
CHARACTERISTIC FEATURES:
 Miosis-Due to the paralysis of dilator pupillae, and
unopposed action of sphincter pupillae.
 Partial ptosis-Due to the paralysis of smooth muscle
fibres (muller’s) of levator palpebrae superioris.
 Anhidrosis-(loss of sweating)-Due to involvement of
sudomotor fibres.
 Enophthalmos-(sunken eyeball)-Due to paralysis of
ORBITALIS muscle.
 Flushing of the face-Due to the involvement of
vasoconstrictors fibres of face.

33.  Medial medullary
syndrome
 Controlateral hemiplegia
due to damage of
pyramid.
 Ipsilateral paralysis and
atrophy of half of the
tongue- hypoglossal
nerve.
 Controlateral loss of
position and vibration
sense-medial lemniscus.

34.  Transverse section at the level of pyrimidal
decussation(picture and label the parts with brief
explanation).
 Transverse section at the level of sensory decussation.
 Lateral medullary syndrome.