Medulla oblongata Flashcards
What is the medulla oblongata?
The lowest part of the brainstem, continuous with the spinal cord.
Where does the medulla extend from and to?
From the lower border of the pons to just above the first cervical nerve.
Where is the medulla located?
In the anterior part of the posterior cranial fossa.
What structure does the medulla extend down to?
The foramen magnum.
What lies anterior to the medulla?
The clivus and meninges.
What lies posterior to the medulla?
The vallecula of the cerebellum.
What part of the brain does the medulla belong to?
The hindbrain.
What space does the medulla occupy?
The infratentorial space.
What are the two parts of the medulla?
Open (superior) part and closed (inferior) part.
What forms the dorsal surface of the open part of the medulla?
The fourth ventricle.
What happens to the fourth ventricle at the closed part of the medulla?
It narrows at the obex and continues as the central canal.
What divides the medulla into right and left halves?
The anterior and posterior median fissures.
What is the anterior median fissure?
A groove that divides the medulla in the midline.
Where does the anterior median fissure end?
At the foramen caecum at the junction with the pons.
What further divides each half of the medulla?
The anterolateral and posterolateral sulci.
What is the anterior region of the medulla called?
The pyramid.
What fibres make up the pyramid?
Corticospinal and corticobulbar fibres.
What happens to many fibres in the lower part of the pyramid?
They cross at the midline to form the pyramidal decussation.
What are the anterior external arcuate fibres?
Transverse fibres at the upper part of the pyramid that end in the cerebellum.
What is the olive?
An oval elevation in the lateral region of the upper medulla.
What forms the olive?
The inferior olivary nucleus.
What is the circumolivary bundle?
A bundle of fibres curving around the lower edge of the olive.
Where do the rootlets of the hypoglossal nerve emerge?
The anterolateral sulcus between the pyramid and the olive.
Which nerves emerge from the posterolateral fissure?
Cranial nerves IX, X, and the cranial part of XI.
What lies between the posterolateral sulcus and posterior median fissure?
The posterior region of the medulla.
What is the V-shaped depression in the upper posterior region of the medulla?
The lower part of the floor of the fourth ventricle.
What are the three longitudinal elevations below the floor of the fourth ventricle?
Fasciculus gracilis, fasciculus cuneatus, and inferior cerebellar peduncle.
What forms the gracile and cuneate tubercles?
The nucleus gracilis and nucleus cuneatus.
What is lateral to the cuneate nucleus?
The accessory cuneate nucleus.
What fibres relay in the accessory cuneate nucleus?
Unconscious proprioceptive fibres of the upper limb.
What is the function of fasciculus gracilis and fasciculus cuneatus?
Convey discriminative touch, pressure, vibration, position, and movement sense.
What does fasciculus gracilis contain?
Fibres from the lower limb and lower trunk.
What does fasciculus cuneatus contain?
Fibres from the upper limb and upper trunk.
What is the tubercinerium?
An elevation lateral to the fasciculus cuneatus.
What forms the tubercinerium?
The spinal nucleus of the trigeminal nerve.
What are the two parts of the medulla based on the central canal?
Closed (lower) part with a central canal and open (upper) part forming the fourth ventricle.
What separates the anterior horn from the central grey matter at the pyramidal decussation?
Decussating pyramidal fibres.
What is the lateral part of the spinal nucleus of the accessory nerve?
The separated anterior horn.
Where is the supraspinal nucleus located?
Medially within the separated anterior horn.
What is continuous with the central grey matter in the lower medulla?
Nucleus gracilis and nucleus cuneatus.
What lies lateral to the central grey matter?
The nucleus of the spinal tract of the trigeminal nerve.
What forms the spinal tract of the trigeminal nerve?
A bundle of fibres overlying its nucleus.
What is the most important feature of the lower medulla?
The decussation of pyramidal tracts.
Where do the decussating pyramidal fibres go?
To the lateral corticospinal tract.
Where are fasciculus gracilis and fasciculus cuneatus located?
The posterior white column.
What replaces Clarke�s column in the medulla?
The accessory cuneate nucleus.
Where is the medial lemniscus formed?
By internal arcuate fibres crossing in the sensory decussation.
What is the representation pattern of the medial lemniscus?
Head posteriorly and feet anteriorly.
Where are the pyramidal tracts located?
Anteriorly.
What lies posterior to the medial lemniscus?
The medial longitudinal bundle.
What tracts lie in the anterolateral medulla?
Spinocerebellar, lateral spinothalamic, and other tracts.
Which cranial nerve nuclei are in the floor of the fourth ventricle?
Hypoglossal, dorsal vagus, tractus solitarius, and vestibular nuclei.
What does the nucleus ambiguus supply?
Motor fibres of IX, X, and XI cranial nerves.
What do the dorsal and ventral cochlear nuclei receive?
Fibres of the cochlear nerve.
Where is the inferior olivary nucleus located?
At the upper medulla.
What does the inferior olivary nucleus contribute to?
The olive elevation.
What is the function of olivocerebellar fibres?
Terminate in the cerebellum as climbing fibres.
What are the visceral centres of the medulla?
Respiratory, cardiac, and vasomotor centres.
What supplies the medial part of the medulla?
The anterior spinal artery.
What supplies the posterolateral medulla?
The posterior inferior cerebellar artery.
What causes medial medullary syndrome?
Blockage of the anterior spinal artery.
What are the features of medial medullary syndrome?
Contralateral hemiplegia, loss of vibration sense, ipsilateral tongue paralysis.
What causes lateral medullary syndrome?
Blockage of the posterior inferior cerebellar artery.
What are features of lateral medullary syndrome?
Ipsilateral soft palate paralysis, facial pain/temp loss, contralateral body pain/temp loss, ataxia, Horner�s syndrome.
Why is injury to the lower medulla fatal?
It affects vital centres like respiratory and vasomotor centres.
What is bulbar palsy?
Weakness of muscles supplied by VII�XII cranial nerves.
What is pseudobulbar palsy?
Bilateral corticonuclear fibre lesion causing tongue, lips, pharynx, and palate paralysis.
What does the medulla develop from?
The myelencephalic part of the rhombencephalon.
