Medulla_oblongata

Brain: Medulla oblongata
Medulla oblongata labeled at bottom left
Section of the medulla oblongata at about the middle of the olive.
Latin	medulla oblongata
Gray\'s	subject #187 767
Part of	Brain stem
NeuroNames	hier-695
MeSH	Medulla+Oblongata
Dorlands/Elsevier	m_06/12519731

The medulla oblongata is the lower portion of the brainstem. It deals with autonomic functions. The cardiac center is the part of the medulla oblongata responsible for controlling the heart rate.

Contents 1 Location 2 Anatomy 2.1 Two parts: open and closed 2.2 Landmark fissures and sulci 2.3 Between the anterior median sulcus and the anterolateral sulcus 2.4 Between the anterolateral and posterolateral sulci 2.5 Between the posterior median sulcus and the posterolateral sulcus 2.6 Lower part 2.7 Base 3 Functions 4 Blood supply 5 Additional images 6 Popular Culture 7 External links

Location

By anatomical terms of location, it is rostral to the spinal cord and caudal to the pons, which is in turn ventral to the cerebellum.

For a human or other bipedal species, this means it is above the spinal cord, below the pons, and anterior to the cerebellum.

Anatomy

Two parts: open and closed

The medulla is often thought of as being in two parts:

• an open part (close to the pons)
• a closed part (further down towards the spinal cord).

The opening referred to is on the dorsal side of the medulla, and forms part of the fourth ventricle of the brain.

Landmark fissures and sulci

The medulla has an anterior median fissure and a posterior median sulcus corresponding to the structures seen in the spinal cord.

On each side, the anterolateral sulcus lies in line with the ventral roots of the spinal nerves. The rootlets of cranial nerve XII (the hypoglossal nerve) emerge from this sulcus.

The posterolateral sulcus lies in line with the dorsal roots of the spinal nerves. It gives attachment to the rootlets of the glossopharyngeal, vagus and the accessory nerve or the IX, X, and the XI cranial nerves from above downward in order.

Between the anterior median sulcus and the anterolateral sulcus

The region between the anterior median sulcus and the anterolateral sulcus is occupied by an elevation on either side called as the pyramid of medulla oblongata. This elevation is caused by the corticospinal tract.

In the lower part of the medulla some of these fibers cross each other thus obliterating the anterior median fissure. This is known as the decussation of the pyramids.

Some other fibers that originate from the anterior median fissure above the decussation of the pyramids and run laterally across the surface of the pons are known as the external arcuate fibers.

Between the anterolateral and posterolateral sulci

The region between the anterolateral and posterolateral sulci in the upper part of the medulla is marked by a swelling known as the Olivary_body.

It is caused by a large mass of gray matter known as the inferior olivary nucleus.

Between the posterior median sulcus and the posterolateral sulcus

The posterior part of the medulla between the posterior median sulcus and the posterolateral sulcus contains tracts that enter it from the posterior funiculus of the spinal cord. These are the fasciculus gracilis, lying medially next to the midline, and the fasciculus cuneatus, lying laterally.

These fasciculi end in rounded elevations known as the gracile and the cuneate tubercles. They are caused by masses of gray matter known as the nucleus gracilis and the nucleus cuneatus.

Just above the tubercles, the posterior aspect of the medulla is occupied by a triangular fossa, which forms the lower part of the floor of the fourth ventricle. The fossa is bounded on either side by the inferior cerebellar peduncle, which connects the medulla to the cerebellum.

Lower part

The lower part of the medulla, immediately lateral to the fasciculus cuneatus, is marked by another longitudinal elevation known as the tuberculum cinereum.

It is caused by an underlying collection of gray matter known as the spinal nucleus of the trigeminal nerve.

The gray matter of this nucleus is covered by a layer of nerve fibers that form the spinal tract of the trigeminal nerve.

Base

The base of the medulla is defined by the commissural fibers, crossing over from the ipsilateral side in the spinal cord to the contralateral side in the brain stem; below this is the spinal cord.

Functions

The medulla oblongata controls autonomic functions, and relays nerve signals between the brain and spinal cord. It is also responsible for controlling several major points and autonomic functions of the body:

• respiration (via dorsal respiratory group and ventral respiratory group)
• blood pressure
• heart rate
• swallowing
• vomiting
• defecation

Blood supply

Blood to the medulla is supplied by a number of arteries.

• Anterior spinal artery: The anterior spinal artery supplies the whole medial part of the medulla oblongata. A blockage (such as in a stroke) will injure the pyramidal tract, medial lemniscus, and the hypoglossal nucleus. This causes a syndrome called medial medullary syndrome.
• Posterior inferior cerebellar artery (PICA): The posterior inferior cerebellar artery, a major branch of the vertebral artery, supplies the posterolateral part of the medulla, where the main sensory tracts run and synapse. (As the name implies, it also supplies some of the cerebellum.)
• Direct branches of the vertebral artery: The vertebral artery supplies an area between the other two main arteries, including the nucleus solitarius and other sensory nuclei and fibers. Lateral medullary syndrome can be caused by occlusion of either the PICA or the vertebral arteries.
• (ceribellar artery is suppelyed by the medulla)

Additional images

Medulla oblongata.jpg Beginning of medulla oblongata in the human brain	Illu cerebrum lobes.jpg Lobes	Gray677.png Scheme showing the connections of the several parts of the brain.	Gray679.png Anteroinferior view of the medulla oblongata and pons.
Gray687.png Section of the medulla oblongata through the lower part of the decussation of the pyramids	Gray688.png Section of the medulla oblongata at the level of the decussation of the pyramids.	Gray695.png Transverse section of medulla oblongata below the middle of the olive.	Gray700.png The formatio reticularis of the medulla oblongata, shown by a transverse section passing through the middle of the olive.
Gray714.png Transverse section passing through the sensory decussation.	Gray715.png Mesal aspect of a brain sectioned in the median sagittal plane.	Gray724.png Base of brain.	Gray768.png Diagram showing the positions of the three principal subarachnoid cisternæ.

Popular Culture

• In the movie The Waterboy, when asked why alligators are so aggressive, Bobby Boucher responds "My mama says that alligators are ornery because they got all them teeth and no toothbrush." Science professor "Colonel Sanders" then informs him that aggressive behavior in alligators is caused by an enlarged Medulla Oblongata, and insults Boucher by saying that the waterboy\'s high aggression is also caused by an enlarged Oblongata. Boucher then angrily tackles Sanders.

• In the television series Futurama, in the episode "Parasites Lost", the worms leave Fry\'s body, after he threatens to sever the Medulla Oblongata, which would cause his death. The worms leave, but not until Fry had already done severe damage to his brain.

• In the television series Jimmy Neutron Boy Genius, in the episode "Time is Money", Sheen says his favorite part of a video about brains is the part about the Medulla Oblongata, even though he doesn\'t know what it is, he likes the way it sounds.

• In the movie Torment of the Wicked, the monster from the swamps eats a Medulla Oblongata off the head of Dr. Miles Poiinowski when he loses the challenge to cross the bridge to happy ville.

• In the video game SSX 3, if you play as Mac Fraser and make him crash into a tree or obstacle, he\'ll sometimes say "Ow, My Medulla Oblongata!"

• In Alicia Keys\' song "Slow Down", from her album "As I Am", she sings "my medulla oblongata is electrified..." at about 1:35.

• In Fight Club the narrator finds a series of articles written in the first person by organs, one of which begins "I am Jack\'s medulla oblongata without me Jack could not regulate his heart rate, blood pressure or breathing", which then inspires his "I am Jack\'s ..." monologues throughout the book.

External links

• BrainMaps at UCDavis medulla

v • d • e Brain: rhombencephalon (hindbrain)
Myelencephalon/medulla	anterior/ventral: Arcuate nucleus of medulla • Pyramid (Decussation) • Olivary body • Inferior olivary nucleus • Anterior median fissure • Ventral respiratory group posterior/dorsal: VII,IX,X: Solitary/tract • XII, X: Dorsal • IX,X,XI: Ambiguus • IX: Inferior salivatory nucleus • Gracile nucleus/Cuneate nucleus/Accessory cuneate nucleus • Area postrema • Posterior median sulcus • Dorsal respiratory group raphe/reticular: Sensory decussation • Reticular formation (Gigantocellular nucleus, Parvocellular reticular nucleus, Ventral reticular nucleus, Lateral reticular nucleus, Paramedian reticular nucleus) • Raphe nuclei (Obscurus, Magnus, Pallidus) tracts: Corticospinal tract (Lateral, Anterior) • Inferior cerebellar peduncle • Olivocerebellar tract • Spinocerebellar (Dorsal, Ventral) • Spinothalamic tract • PCML (Posterior external arcuate fibers, Internal arcuate fibers, Medial lemniscus) • Extrapyramidal (Rubrospinal tract, Vestibulospinal tract, Tectospinal tract)
Metencephalon/pons	anterior/ventral: Superior olivary nucleus • Basis pontis (Pontine nuclei, Middle cerebellar peduncles) posterior/dorsal: Pontine tegmentum (Trapezoid body, Superior medullary velum, Locus ceruleus, MLF, Vestibulocerebellar tract, V Principal Spinal & Motor, VI, VII, VII: Superior salivary nucleus) • VIII-c (Dorsal, Anterior)/VIII-v (Lateral, Superior, Medial, Inferior) raphe/reticular: Reticular formation (Caudal pontine reticular nucleus, Oral pontine reticular nucleus, Tegmental pontine reticular nucleus, Paramedian pontine reticular formation) • Median raphe nucleus Apneustic center • Pneumotaxic center
Metencephalon/cerebellum	Vermis • Flocculus • Arbor vitae • Cerebellar tonsil • Inferior medullary velum Molecular layer (Stellate cell, Basket cell, Parallel fiber) • Purkinje cell layer (Purkinje cell) • Granule cell layer (Golgi cell) • Mossy fibers • Climbing fiber Deep cerebellar nuclei (Dentate, Emboliform, Globose, Fastigial)
Fourth ventricle	apertures (Median, Lateral) • Rhomboid fossa (Vagal trigone, Hypoglossal trigone, Obex, Sulcus limitans, Facial colliculus, Medial eminence) • Lateral recess

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