Medulla oblongata

Last updated

Medulla oblongata
1311 Brain Stem.jpg
Medulla oblongata part of the brain stem (purple colored)
Gray694.png
Section of the medulla oblongata at about the middle of the olivary body
Details
Part of Brain stem
Identifiers
Latin medulla oblongata, myelencephalon
MeSH D008526
NeuroNames 698
NeuroLex ID birnlex_957
TA98 A14.1.03.003
TA2 5983
FMA 62004
Anatomical terms of neuroanatomy

The medulla oblongata or simply medulla is a long stem-like structure which makes up the lower part of the brainstem. [1] It is anterior and partially inferior to the cerebellum. It is a cone-shaped neuronal mass responsible for autonomic (involuntary) functions, ranging from vomiting to sneezing. [2] The medulla contains the cardiac, respiratory, vomiting and vasomotor centers, and therefore deals with the autonomic functions of breathing, heart rate and blood pressure as well as the sleep–wake cycle. [2]

Contents

During embryonic development, the medulla oblongata develops from the myelencephalon. The myelencephalon is a secondary vesicle which forms during the maturation of the rhombencephalon, also referred to as the hindbrain.

The bulb is an archaic term for the medulla oblongata. [1] In modern clinical usage, the word bulbar (as in bulbar palsy) is retained for terms that relate to the medulla oblongata, particularly in reference to medical conditions. The word bulbar can refer to the nerves and tracts connected to the medulla, and also by association to those muscles innervated, such as those of the tongue, pharynx and larynx.

Anatomy

Medulla oblongata (animation) Medulla oblongata small.gif
Medulla oblongata (animation)
Medulla and parts (10-16) - (10) pyramid; (11) the anterior median fissure; (15) is the choroid plexus in the fourth ventricle; (13) olive and (7) the pons Human brainstem anterior view description.JPG
Medulla and parts (10-16) - (10) pyramid; (11) the anterior median fissure; (15) is the choroid plexus in the fourth ventricle; (13) olive and (7) the pons
Medulla-animated as it protrudes from the foramen magnum of the skull-base, after which it gives rise to the spinal cord. Medulla oblongata and foramen magnum animation small.gif
Medulla-animated as it protrudes from the foramen magnum of the skull-base, after which it gives rise to the spinal cord.

The medulla can be thought of as being in two parts:

External surfaces

The anterior median fissure contains a fold of pia mater, and extends along the length of the medulla oblongata. It ends at the lower border of the pons in a small triangular area, termed the foramen cecum. On either side of this fissure are raised areas termed the medullary pyramids. The pyramids house the pyramidal tracts–the corticospinal and the corticobulbar tracts of the nervous system. At the caudal part of the medulla these tracts cross over in the decussation of the pyramids obscuring the fissure at this point. 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 anterior external arcuate fibers.

The region between the anterolateral and posterolateral sulcus in the upper part of the medulla is marked by a pair of swellings known as olivary bodies (also called olives). They are caused by the largest nuclei of the olivary bodies, the inferior olivary nuclei.

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 gracile fasciculus, lying medially next to the midline, and the cuneate fasciculus, 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 gracile nucleus and the cuneate nucleus. The soma (cell bodies) in these nuclei are the second-order neurons of the posterior column-medial lemniscus pathway, and their axons, called the internal arcuate fibers or fasciculi, decussate from one side of the medulla to the other to form the medial lemniscus.

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 cuneate fasciculus, 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 trigeminal nucleus. 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 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.

Blood supply

Blood to the medulla is supplied by a number of arteries. [3]

Development

The medulla oblongata forms in fetal development from the myelencephalon. The final differentiation of the medulla is seen at week 20 gestation. [4] [ full citation needed ]

Neuroblasts from the alar plate of the neural tube at this level will produce the sensory nuclei of the medulla. The basal plate neuroblasts will give rise to the motor nuclei.

Function

The medulla oblongata connects the higher levels of the brain to the spinal cord, and is responsible for several functions of the autonomous nervous system which include:

Clinical significance

A blood vessel 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.

Lateral medullary syndrome can be caused by the blockage of either the posterior inferior cerebellar artery or of the vertebral arteries.

Progressive bulbar palsy (PBP) is a disease that attacks the nerves supplying the bulbar muscles. Infantile progressive bulbar palsy is progressive bulbar palsy in children.

Other animals

Both lampreys and hagfish possess a fully developed medulla oblongata. [6] [7] Since these are both very similar to early agnathans, it has been suggested that the medulla evolved in these early fish, approximately 505 million years ago. [8] The status of the medulla as part of the primordial reptilian brain is confirmed by its disproportionate size in modern reptiles such as the crocodile, alligator, and monitor lizard.

Additional images

Related Research Articles

Articles related to anatomy include:

<span class="mw-page-title-main">Pons</span> Part of the brainstem in humans and other bipeds

The pons is part of the brainstem that in humans and mammals, lies inferior to the midbrain, superior to the medulla oblongata and anterior to the cerebellum.

<span class="mw-page-title-main">Brainstem</span> Posterior part of the brain, adjoining and structurally continuous

The brainstem is the stalk-like part of the brain that interconnects the cerebrum and diencephalon with the spinal cord. In the human brain, the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is continuous with the thalamus of the diencephalon through the tentorial notch.

<span class="mw-page-title-main">Trigeminal nerve</span> Cranial nerve responsible for the faces senses and motor functions

In neuroanatomy, the trigeminal nerve (lit. triplet nerve), also known as the fifth cranial nerve, cranial nerve V, or simply CN V, is a cranial nerve responsible for sensation in the face and motor functions such as biting and chewing; it is the most complex of the cranial nerves. Its name (trigeminal, from Latin tri- 'three', and -geminus 'twin') derives from each of the two nerves (one on each side of the pons) having three major branches: the ophthalmic nerve (V1), the maxillary nerve (V2), and the mandibular nerve (V3). The ophthalmic and maxillary nerves are purely sensory, whereas the mandibular nerve supplies motor as well as sensory (or "cutaneous") functions. Adding to the complexity of this nerve is that autonomic nerve fibers as well as special sensory fibers (taste) are contained within it.

<span class="mw-page-title-main">Glossopharyngeal nerve</span> Cranial nerve IX, for the tongue and pharynx

The glossopharyngeal nerve, also known as the ninth cranial nerve, cranial nerve IX, or simply CN IX, is a cranial nerve that exits the brainstem from the sides of the upper medulla, just anterior to the vagus nerve. Being a mixed nerve (sensorimotor), it carries afferent sensory and efferent motor information. The motor division of the glossopharyngeal nerve is derived from the basal plate of the embryonic medulla oblongata, whereas the sensory division originates from the cranial neural crest.

<span class="mw-page-title-main">Spinothalamic tract</span> Sensory pathway from the skin to the thalamus

The spinothalamic tract is a part of the anterolateral system or the ventrolateral system, a sensory pathway to the thalamus. From the ventral posterolateral nucleus in the thalamus, sensory information is relayed upward to the somatosensory cortex of the postcentral gyrus.

<span class="mw-page-title-main">Dorsal column–medial lemniscus pathway</span> Sensory spinal pathway

The dorsal column–medial lemniscus pathway (DCML) is a sensory pathway of the central nervous system that conveys sensations of fine touch, vibration, two-point discrimination, and proprioception from the skin and joints. It transmits information from the body to the primary somatosensory cortex in the postcentral gyrus of the parietal lobe of the brain. The pathway receives information from sensory receptors throughout the body, and carries this in nerve tracts in the white matter of the dorsal column of the spinal cord to the medulla, where it is continued in the medial lemniscus, on to the thalamus and relayed from there through the internal capsule and transmitted to the somatosensory cortex. The name dorsal-column medial lemniscus comes from the two structures that carry the sensory information: the dorsal columns of the spinal cord, and the medial lemniscus in the brainstem.

<span class="mw-page-title-main">Medial medullary syndrome</span> Medical condition

Medial medullary syndrome, also known as inferior alternating syndrome, hypoglossal alternating hemiplegia, lower alternating hemiplegia, or Dejerine syndrome, is a type of alternating hemiplegia characterized by a set of clinical features resulting from occlusion of the anterior spinal artery. This results in the infarction of medial part of the medulla oblongata.

<span class="mw-page-title-main">Olivary body</span>

In anatomy, the olivary bodies or simply olives are a pair of prominent oval structures in the medulla oblongata, the lower portion of the brainstem. They contain the olivary nuclei.

<span class="mw-page-title-main">Inferior olivary nucleus</span> Brain structure in the medulla that helps coordinate movement

The inferior olivary nucleus (ION), is a structure found in the medulla oblongata underneath the superior olivary nucleus. In vertebrates, the ION is known to coordinate signals from the spinal cord to the cerebellum to regulate motor coordination and learning. These connections have been shown to be tightly associated, as degeneration of either the cerebellum or the ION results in degeneration of the other.

<span class="mw-page-title-main">Spinocerebellar tract</span> Nerve tract in humans

The spinocerebellar tract is a nerve tract originating in the spinal cord and terminating in the same side (ipsilateral) of the cerebellum.

<span class="mw-page-title-main">Inferior cerebellar peduncle</span>

The upper part of the posterior district of the medulla oblongata is occupied by the inferior cerebellar peduncle, a thick rope-like strand situated between the lower part of the fourth ventricle and the roots of the glossopharyngeal and vagus nerves.

<span class="mw-page-title-main">Vestibular nuclei</span>

The vestibular nuclei (VN) are the cranial nuclei for the vestibular nerve located in the brainstem.

<span class="mw-page-title-main">Cerebellar peduncle</span> Structure connecting the cerebellum to the brainstem

Cerebellar peduncles connect the cerebellum to the brain stem. There are six cerebellar peduncles in total, three on each side:

<span class="mw-page-title-main">Dorsal column nuclei</span> Nuclei in the dorsal column of the brainstem

In neuroanatomy, the dorsal column nuclei are a pair of nuclei in the dorsal columns in the brainstem. The name refers collectively to the cuneate nucleus and gracile nucleus, which are situated at the lower end of the medulla oblongata. Both nuclei contain second-order neurons of the dorsal column–medial lemniscus pathway, which convey fine touch and proprioceptive information from the body to the brain. The dorsal column nuclei project to the thalamus.

<span class="mw-page-title-main">Posterior spinal artery</span>

The posterior spinal artery arises from the vertebral artery in 25% of humans or the posterior inferior cerebellar artery in 75% of humans, adjacent to the medulla oblongata. It is usually double, and spans the length of the spinal cord. It supplies the grey and white posterior columns of the spinal cord.

<span class="mw-page-title-main">Medial vestibular nucleus</span>

The medial vestibular nucleus is one of the vestibular nuclei. It is located in the medulla oblongata.

<span class="mw-page-title-main">Spinal cord</span> Long, tubular central nervous system structure in the vertebral column

The spinal cord is a long, thin, tubular structure made up of nervous tissue that extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone) of vertebrate animals. The center of the spinal cord is hollow and contains a structure called central canal, which contains cerebrospinal fluid. The spinal cord is also covered by meninges and enclosed by the neural arches. Together, the brain and spinal cord make up the central nervous system (CNS).

<span class="mw-page-title-main">Anatomy of the cerebellum</span> Structures in the cerebellum, a part of the brain

The anatomy of the cerebellum can be viewed at three levels. At the level of gross anatomy, the cerebellum consists of a tightly folded and crumpled layer of cortex, with white matter underneath, several deep nuclei embedded in the white matter, and a fluid-filled ventricle in the middle. At the intermediate level, the cerebellum and its auxiliary structures can be broken down into several hundred or thousand independently functioning modules or compartments known as microzones. At the microscopic level, each module consists of the same small set of neuronal elements, laid out with a highly stereotyped geometry.

References

PD-icon.svgThis article incorporates text in the public domain from page 767 of the 20th edition of Gray's Anatomy (1918)

  1. 1 2 Webb, Wanda G. (2017-01-01), Webb, Wanda G. (ed.), "2 - Organization of the Nervous System I", Neurology for the Speech-Language Pathologist (Sixth Edition), Mosby, pp. 13–43, doi:10.1016/b978-0-323-10027-4.00002-6, ISBN   978-0-323-10027-4 , retrieved 2020-11-15
  2. 1 2 Waldman, Steven D. (2009-01-01), Waldman, Steven D. (ed.), "CHAPTER 120 - The Medulla Oblongata", Pain Review, Philadelphia: W.B. Saunders, p. 208, doi:10.1016/b978-1-4160-5893-9.00120-9, ISBN   978-1-4160-5893-9 , retrieved 2020-11-15
  3. Purves, Dale (2001). Neuroscience. 2nd edition. Sinauer Associates.
  4. Carlson, Neil R. Foundations of Behavioral Neuroscience.63-65
  5. Hughes, T. (2003). "Neurology of swallowing and oral feeding disorders: Assessment and management". Journal of Neurology, Neurosurgery & Psychiatry. 74 (90003): 48iii–52. doi:10.1136/jnnp.74.suppl_3.iii48. PMC   1765635 . PMID   12933914.
  6. Nishizawa H, Kishida R, Kadota T, Goris RC; Kishida, Reiji; Kadota, Tetsuo; Goris, Richard C. (1988). "Somatotopic organization of the primary sensory trigeminal neurons in the hagfish, Eptatretus burgeri". J Comp Neurol. 267 (2): 281–95. doi:10.1002/cne.902670210. PMID   3343402. S2CID   45624479.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  7. Rovainen CM (1985). "Respiratory bursts at the midline of the rostral medulla of the lamprey". J Comp Physiol A. 157 (3): 303–9. doi:10.1007/BF00618120. PMID   3837091. S2CID   27654584.
  8. Haycock, Being and Perceiving