anatomyphysiologyblog - Brainstem - Gross Anatomy of Medulla Oblongata, Pons in addition to Midbrain
BRAINSTEM: GENERAL CONSIDERATIONS
Components:
The brainstem consists of (from inward a higher house downward):
Midbrain (continuous amongst the cerebral hemisphere above)
Pons
Medulla (continuous amongst the spinal cord below)
Location:
The brainstem is located inward posterior cranial fossa
Above, midbrain is continuous amongst the cerebral hemisphere.
Below, medulla is continuous amongst the spinal cord.
Posteriorly, the pons in addition to medulla are separated from the cerebellum past times the quaternary ventricle.
The quaternary ventricle is continuous,
below, amongst the fundamental canal, which traverses the lower percentage of the medulla in addition to is continuous amongst the fundamental canal of spinal cord and
above, amongst the cerebral aqueduct of midbrain.
The midbrain, pons in addition to medulla are connected to the cerebellum past times superior, middle in addition to inferior cerebellar peduncles, respectively.
Cranial nerves related to the brainstem
The 3rd in addition to quaternary nerves emerge from the surface of the midbrain;
The 5th from the pons;
The sixth, 7th in addition to 8th nerves emerge at the junction of the pons in addition to medulla;
The ninth, tenth, eleventh in addition to 12th nerves emerge from the surface of the medulla.
Functions:
The brainstem has iii wide functions:
1. Serves equally a conduit for the ascending tracts in addition to descending tracts connecting the spinal cord to the dissimilar parts of the higher centers inward the forebrain;
2. Contains of import reflex centers associated amongst the command of respiration in addition to the cardiovascular organization in addition to amongst the command of consciousness; in addition to
3. Contains the of import nuclei of cranial nerves III through XII.
GROSS ANATOMY OF MEDULLA OBLONGATA
The medulla oblongata is conical inward shape. Its wide percentage joins the pons inward a higher house in addition to narrow percentage becomes continuous amongst the spinal cord. The junction betwixt medulla in addition to spinal cord coincides amongst the degree of the upper edge of Atlas (first cervical vertebra).
Its length is virtually 3 cm in addition to its width is virtually 2cm at its upper end.
It is divided into
1. A lower unopen percentage amongst fundamental canal in addition to
2. An upper opened upward percentage posteriorly which is related to the lower percentage of the 4th ventricle
Features on the anterior surface of Medulla Oblongata
Anterior median fissure, is an upward continuation of like cleft acquaint on the spinal cord
Anterolateral sulcus, on each side, is inward trouble amongst the ventral roots of spinal cord
- Gives attachment to the rootlets of the hypoglossal nerve
Pyramid is an elevation on each side of the midline betwixt anterior median cleft in addition to anterolateral sulcus.
- Composed of bundles of nervus fibers of corticospinal tract that descends from the cerebral cortex to the spinal cord
- Tapers inferiorly where the bulk of fibers cross over to the contrary side, obliterating the medulla. These crossing fibers found the decussation of the pyramid.
Olive is a prominent, elongated oval swelling that lies inward the upper percentage of medulla posterolateral to the pyramid separated past times anterolateral sulcus.
The elevation is produced past times the underlying inferior olivary nucleus.
Features on posterior surface of the medulla oblongata
Posterior median sulcus is upward continuation of the like cleft on the spinal cord.
Posterolateral sulcus lies inward trouble amongst the dorsal roots of spinal nerves.
- Gives attachment to the rootlets of 9th, 10th in addition to 11th cranial nerves.
Between the posterior median sulcus in addition to posterolateral sulcus, the medulla contains tracts (asccending) that come inward it from the posterior funiculus of the spinal cord.
- Fasciculus gracilis lies medially in addition to fasciculus cuneatus lies laterally
- Both fasciculi cease inward rounded elevations called gracile tubercle (nucleus gracilis) in addition to cuneate tubercle (nucleus cuneatus) respectively.
Just inward a higher house these tubercles, medulla is occupied past times a triangular fossa which forms the lower percentage of the 4th ventricle.
This fossa is bounded on each side past times inferior cerebellar peduncle which connect the medulla to cerebellum.
Features on the posterior percentage of the medulla that forms the flooring of the 4th ventricle:
Presents median sulcus, on each side of which at that spot is a longitudinal elevation called the median eminence (continuous inward a higher house inward the pontine percentage of the flooring of 4th ventricle). The eminence is bounded laterally past times sulcus limitans.
The sulcus limitans is marked past times a depression called inferior fovea. The percentage of the medulla below fovea presents hypoglossal triangle medially in addition to vagal triangle laterally.
Between the vagal triangle, inward a higher house in addition to gracile tubercle, below lies a little expanse called area postrema.
The lowest percentage of the flooring is called the calamus scriptorius (for its resemblance to a nib).
The inferior angle where the lateral margins of the flooring run into is called obex.
GROSS ANATOMY OF PONS
Pons has a convex anterior surface marked past times transversely running fibers which laterally forms a parcel called middle cerebellar peduncle.
Main Features
- The trigeminal nerve emerges from the anterior surface at its junction amongst middle cerebellar peduncle.
- Presents a basilar sulcus inward the midline which lodges basilar artery
- In the groove betwixt Pons in addition to the medulla oblongata, at that spot emerge, from medial to lateral, abducent, facial in addition to vestibulocochlear nerves.
Posterior surface of the pons is express laterally past times superior cerebellar peduncle in addition to forms the upper percentage of the flooring of the 4th ventricle.
Main Features:
- The flooring is divided into symmetrical halves past times a median sulcus.
- Lateral to this sulcus is an elongated elevation, the medial eminence, which is bounded laterally past times a sulcus limitans.
- Inferior cease of medial eminence is slightly expanded to shape facial colliculus, which is produced past times facial nerve
- The upper cease of sulcus limitans presents a bluish-gray coloration in addition to the expanse is called substantia ferruginosa.
- Area foyer lies lateral to sulcus limitans.
Parts of the Pons
· a posterior part, the tegmentum, and
· an anterior basilar part
GROSS ANATOMY OF MID-BRAIN
Anteriorly, it presents 2 large bundles of fibers, ane on each side of the midline, called crus cerebri.
- The oculomotor nerve emerges from the medial appear of the crus of the same side
- The crura bounds from behind the interpeduncular fossa.
Posteriorly, the midbrain presents iv rounded swellings called colliculi.
- Superior in addition to inferior colliculi ane on each side
- Each colliculus is laterally related to a ridge called brachium
o Superior in addition to inferior brachium from respective colliculi
o Superior brachium connects the superior colliculus to lateral geniculate body
o Inferior brachium connects the inferior colluculus to medial geniculate body
o In the midline below the inferior colliculus, the trochlear nerve emerges which hence winds circular the side of the midbrain to accomplish its ventral aspect.
Parts of the midbrain
The midbrain comprises 2 lateral halves, called the cerebral peduncles; which is ane time to a greater extent than divided into an anterior part, the crus cerebri, in addition to a posterior part, tegmentum, past times a pigmented band of grayness matter, substantia nigra.
The tectum is the percentage of the midbrain posterior to the cerebral aqueduct; it has iv little surface swellings referred to previously; these are two superior in addition to 2 inferior colliculi.
REFERENCES:
Following resources are used piece preparing this postal service (readers are strongly recommended to cash inward one's chips through them for to a greater extent than details):
Snell’s Clinical Neuroanatomy 7th Edition
Lange Clinical Neuroanatomy 25th Edition