Medulla oblongata
From Wikipedia, the free encyclopedia
| Brain: Medulla oblongata | ||
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| Medulla oblongata labeled at bottom left | ||
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| 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, such as breathing and blood pressure. The cardiac center is the part of the medulla oblongata responsible for controlling the heart rate.
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[edit] 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.
[edit] Anatomy
[edit] 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.
[edit] 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.
[edit] 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.
[edit] 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.
[edit] 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.
[edit] 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.
[edit] 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.
[edit] 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
- swallowing
- vomiting
- defecation
[edit] 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.
[edit] Additional images
 Lobes |
 Scheme showing the connections of the several parts of the brain. |
 Anteroinferior view of the medulla oblongata and pons. |
 Section of the medulla oblongata through the lower part of the decussation of the pyramids |
 Section of the medulla oblongata at the level of the decussation of the pyramids. |
 Transverse section of medulla oblongata below the middle of the olive. |
 The formatio reticularis of the medulla oblongata, shown by a transverse section passing through the middle of the olive. |
 Transverse section passing through the sensory decussation. |
 Mesal aspect of a brain sectioned in the median sagittal plane. |
 Base of brain. |
 Diagram showing the positions of the three principal subarachnoid cisternæ. |
 Human cerebrum lateral view |
_section_description.JPG/120px-Human_brain_frontal_(coronal)_section_description.JPG) Human brain frontal (coronal) section |
[edit] 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.
- In a Mad TV skit starring character Coach Hines, he stated 'that's your medulla oblongata' to a student, as he held up a piece of a plant that he just ripped up that signified the students neck.
- In the movie Van Wilder, Van introduces the Lambda Omega Omega fraternity to Sherry and Terry, who are "utterly infatuated with men who have larger than normal medulla oblongatas."
- In the song We Takin' Over, a line in Lil Wayne's verse says "Touch it I will bust your medulla."
- In the movie "Money Talks", starring Chris Tucker and Charlie Sheen, Tucker says to Sheen in a phone conversation, "Tell 'em to shoot you in the medulla oblongata, right behind the ear, you won't feel shit."
