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 | medullla 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.
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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
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' is referred to on the dorsal side of the medulla, and forms part of the fourth ventricle of the brain.
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 the 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 downwards in order.
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 fibres which originate from the anterior median fissure above the decussation of the pyramids and run laterally across the surface of the medulla are known as the external arcuate fibers.
The region between the anterolateral and posterolateral sulci in the upper part of the medulla is marked by a swelling known as the olive. It is caused by a large mass of gray matter known as the inferior olivary nucleus.
The posterior part of the medulla between the posterior median sulcus and the posterolateral sulcus contain 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.
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.
The base of the medulla is defined by the commissural fibres, 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
It controls autonomic functions and relays nerve signals between the brain and spinal cord.
The Medulla oblongata is responsible for controlling several major autonomic functions of the body:
- respiration (via dorsal respiratory group and ventral respiratory group)
- blood pressure
- heart rate
- reflex arcs
- vomiting
[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 fibres. Lateral medullary syndrome can be caused by occlusion of either the PICA or the vertebral arteries.
[edit] In Popular Culture
- (1996) In Billy Bob Thornton's Sling Blade, one of the members of Doyle's band recites lyrics that mention the Medulla Oblongata.
- (1996) In Fight Club the Narrator discovers a series of articles written by organs in the first person. The first one is the medulla oblongata.
- (1998) The Adam Sandler movie The Waterboy has a comedic line that references the function of the Medulla Oblongata, where a professor made to resemble Colonel Sanders says (of Sandler's Waterboy character) that "there's something wrong with his Medulla Oblongata".
- (2001) In one episode of Farscape (Infinite Possibilities Part I: Daedalus Demands), protagonist John Crichton tells Harvey the Neural Clone to "kiss my medulla oblongata".
- (2001) In the Futurama episode, Parasites Lost, Fry, during an attempt to rid his body of worms from the inside by using micro-droids threatens to destroy his medulla oblongata, therefore killing himself and the worms.
- (2002) In The Adventures of Jimmy Neutron: Boy Genius episode Time is Money, Sheen Estevez comments on a t.v. show, "It wasn't all that bad Jimmy, I liked the part about the Medulla oblongata. I don't don't know what it means, but it sure sounds cool. Back! Or I will slay thee with my medulla oblaongata"
- (2003) In singer/songwriter Alicia Keys album "The Diary of Alicia Keys," the song "Slow Down" features the line: "It's like I known you forever, my medulla oblongata is electrified."
- (2003) In the video game SSX 3, one of the character Mac's responses to a wipeout is a cry that his medulla oblongata hurts.
- (2007) Commenting on his resurgence in mid-season 2007, NBA star Shaquille O'Neal stated: "I'm on a mission. And I know the older I get, I may lose a step or two, but it's all up in the medulla oblongata. I've got a lot up there. I've got a lot of knowledge . . . in this medulla oblongata."
[edit] Additional images
 Beginning of medulla oblongata in the human brain |
 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 |
 Transverse section of medulla oblongata below the middle of the olive. |
 Mesal aspect of a brain sectioned in the median sagittal plane. |
 Base of brain. |
 Diagram showing the positions of the three principal subarachnoid cisternæ. |
