Medulla Oblongata

Three gross functions of the brainstem

1. Serves as a conduit for the ascending and descending tracts connecting the spina cord to the different parts of the brain

2. Contains Important reflex centers associated with the control of respiration and cardiovascular system and with the control consciousness

3. Contains important nuclei of CN III - XII

The medulla oblongata connects the ____ superiorly with the ____ inferiorly

pons superiorly with the spinal cord inferiorly

The junction of the medulla and spinal cord is at what level?

origin of anterior and posterior roots of the first cervical spinal nerve (foramen magnum)

The ______ of the spinal cord continues upward into the lower half of the medulla

Central Canal

In the upper half of the medulla, the central canal expands as the _______________

cavity of the fourth ventricle

These structures are found on each side of the medulla’s median fissure

pyramids of the medulla

The pyramids are composed of bundles of nerve fibers, called ____________

Corticospinal fiebrs

The pyramids taper inferiorly, and it is here that the majority of the descending fibers cross over to the opposite side, forming the _____________

decussation of the pyramids

Few nerve fibers that emerge from the anterior median fissure above the decussation and pass laterally over the surface of the medulla to enter the cerebellum

Anterior External Arcuate Fibers

Posterolateral to the pyramids are the ________

olives

The olives are oval elevations produced by the underlying ___________

inferior olivary nuclei

In the groove between the pyramid and the olive emerge the rootlets of which cranial nerve?

Hypoglossal Nerve

Posterior to the olives are the ____________

inferior cerebellar peduncles

What cranial nerve emerge from the groove between the olive and the inferior cerebellar peduncle?

• Glossopharyngeal

• Vagus Nerves

• Cranial Roots of the Accessory Nerve

The posterior surface of the superior half of the medulla oblongata forms the _______________

lower part of the floor of the fourth ventricle

The posterior median sulcus is found where?

Posterior surface of the inferior half of the medulla

On each side of the median sulcus, there is an elongated swelling, the ________

gracile tubercle (produced by the underlying gracile nucleus)

Lateral to the gracile tubercle is a similar swelling, the ________

Cuneate tubercle (produced by the underlying cuneate nucleus)

Olfactory nerves pass through what opening in the skull?

Cribriform plate

Optic nerve + opthalmic artery pass through what opening in the skull?

Optic Canal

What structures are transmitted through the superior orbital fissure?

• Lacrimal, Frontal, Trochlear, Oculomotor, Nasociliary, and abducent nerves

• Superior ophthalmic vein

What structure passes through the foramen rotundum?

Maxillary Division of the Trigeminal Nerve

What structure passes through the foramen ovale?

Mandibular division of the trigeminal nerve, lesser petrosal nerve

What structure passes through the foramen spinosum

Middle meningeal artery

What structure passes through the foramen lacerum?

Internal carotid artery

What structures pass through the foramen magnum?

• Medulla oblongata

• Spinal part of accessory nerve

• Right and left vertebral arteries

What structures pass through the jugular foramen

• Glossopharyngeal

• Valgus

• Accessory nerves

• Sigmoid sinus becomes internal jugular vein

What structures pass through the internal acoustic meatus

Vestibulocochlear and facial nerves

Rearrangement of structures in the medulla can be attributed to?

expansion of the neural tube to form the hindbrain vesicle, which becomes the fourth ventricle

The internal structure of the medulla oblongata is considered at four levels:

1. Level of decussation of pyramids

2. Level of decussation of lemnisci

3. Level of the olives

4. Level just inferior to the pons

Great Motor decussation

Decussation of the pyramids

Most of the corticospinal fibers cross the median plane and continue down the spinal cord in the lateral white column as the ____________

Lateral corticospinal tract

The _____________ and ___________ appear as posterior extensions of the central gray matter

Nucleus Gracilis and cuneatus

The fasciculus gracilis and cuneatus continue to ascent superiorly posterior to the _____________

central gray matter

The substantia gelatinosa in the posterior gray column of the spinal cord becomes continuous with?

the inferior end of the nucleus of the spinal tract of the trigeminal nerve

A short distance above the level of the decussation of the pyramids, passes through the ________________

decussation of lemnisci

Great sensory decussation

Decussation of lemnisci

The decussation of the lemnisci takes place where?

Anterior to central gray matter

Posterior to the pyramids

The lemnisci have been formed from what fibers?

Internal Arcuate fibers

Internal arcuate fibers emerge from?

Anterior aspects of the nucleus gracilis and nucleus cuneatus

Pathway of the internal arcuate fibers

Nucleus gracilis and cuneatus → travels anteriorly and laterally around the central gray matter → curve medially toward midline → decussate with the corresponding fibers of the opposite side

The nucleus of ________________ lies lateral to the internal arcuate fibers

nucleus of the spinal tract of the trigeminal nerves

The spinal tract of the trigeminal nerve lies lateral or medial to the nucleus?

Lateral to the nucleus

These tracts occupy an area lateral to the decussation of the lemnisci

Lateral and anterior spinothalamic tracts

spinotectal

The lateral, anterior spinothalamic tracts and the spinotectal tracts are collectively known as the?

spinal lemniscus

These tracts are situated in the anterolateral region of the medulla oblongata

Spinocerebellar, vestibulospinal, and rubrospinal tracts

A transverse section through the olives passes across the ___________

inferior part of the fourth ventricle

At the level of the olives, the amount of ___________ has increased owing to the presence of the olivary nuclear complex

Gray matter

Parts of the Olivary nuclear complex

Nuclei of the vestibulocochlear, glossopharyngeal, vagus, accessory, hypoglossal nerves, and the arcuate nuclei

The largest nucleus of the olivary nuclear complex

inferior olivary nucleus

(olivary nuclear complex) the gray matter is shaped like a _____________

crumpled bag; with its mouth directed medially

The cells of the inferior olivary nucleus send fibers medially across the midline to enter the?

cerebellum through the cerebellar peduncle

Function of the olivary nuclei is associated with _____________

voluntary muscle movement

The vestibular nuclear complex is made up of the following nuclei:

1. Medial vestibular nucleus

2. Inferior vestibular nucleus

3. Lateral vestibular nucleus

4. Superior vestibular nucleus

Two Cochlear Nuclei:

Anterior & Posterior Cochlear nucleus

The anterior cochlear nucleus is situated on the _______________

anterolateral aspect of the inferior cerebellar peduncle

The posterior cochlear nucleus is situated where?

posterior aspect of the inferior cerebellar peduncle lateral to the floor of the fourth ventricle

The nucleus ambiguus consists of large motor neurons and is situated deep within the ____________

reticular formation

The emerging nerve fibers of the nucleus ambiguus join the?

Glossopharyngeal, vagus, cranial part of the accessory nerve

The central gray matter lies beneath the floor of the fourth ventricle at this level

Level of the Olives

Central Gray matter nuclei, medial to lateral

1. hypoglossal nucleus

2. dorsal nucleus of the vagus

3. nucleus of the tractus solitarius

4. medial and inferior vestibular nuclei

The arcuate nuclei are thought to be inferiorly displaced _____________

pontine nuclei

The arcuate nuclei send efferent fibers to the _______ through the anterior external arcuate fibers

cerebellum

Forms a flattened tract on each side of the midline posterior to the pyramid

Medial lemniscus

forms a small tract of nerve fibers situated on each side of the midline posterior to the medial lemniscus and anterior to the hypoglossal nucleus

Medial Longitudinal Fasciculus

The reticular formation is deeply placed posterior to the?

olivary nucleus

These nerves can be seen running forward and laterally thought the reticular formation

Glossopharyngeal, vagus, and cranial part of the accessory nerves

The hypoglossal nerves emerge where?

between the pyramids and the olives

What nerves emerge between the olives and the inferior cerebellar peduncle

Glossopharyngeal, vagus, cranial part of the accessory nerves