Brainstem:
The Brainstem occupies the posterior cranial fossa of the
skull and comprise of three parts:
- Medulla (Myelincephalon)
- The Pons (Metincephalon)
- The Midbrain (Mesencephalon)
The pons and medulla together form Rhombincephalon. The
brainstem connects the spinal cord inferiorly to the brain (diencephalon
specifically) superiorly. It has three
functions:
- it channels the ascending and descending tracts between the spinal cord and brain.
- it houses the reflex centers e.g. those associated with respiratory, cardiovascular system and with control of consciousness
- it contains the nuclei of all the cranial nerves except the first 2.
Medulla connects the pons superiorly with the
spinal cord. On its anterior surface is a fissure called Anterior Median
Fissure which continues with the fissure of spinal cord. Lateral to the
fissure, on either side are large elevations called Pyramids that houses
bundles of descending nerve fibers called Corticospinal Fibers. Lateral to
pyramids are Olives which marks the location of underlying Olivary Nuclei.
The
groove between the pyramids and the olives bear the rootlets of Hypoglossal (12th
cranial) Nerve. Posterior to olives, the
inferior cerebellar peduncles connect the medulla to the cerebellum. The grove
between the inferior cerebellar peduncle and the olives are rootlets for the glossopharyngeal
(9th), Vegas (10th) and cranial roots of accessory nerve
(11th). Posterior Surface of superior half medulla forms the
inferior part of the floor of the 4th ventricle. The posterior
surface possesses the posterior median sulcus, lateral to which are Gracile and
Cuneate tubercle respectively.
Pons connects the Midbrain to the Medulla. Its
anterior surface is convex and bears many transverse fibers the form the Middle
Cerebellar Peduncle. There is a shallow grove in the midline, the basilar grove
for the basilar artery. On the anterolateral surface of the pons, the sensory
and motor roots of trigeminal nerve emerge. At the pontomedullary junction,
from medial to lateral emerges the Abducent (6th), Facial (7th)
and Vestibulocochlear (8th) nerve. Posterior surface of the pons
form the superior part of the floor of the 4th ventricle. Posterior
median sulcus divides the posterior surface into symmetric halves, limited by
the superior cerebellar peduncles. Lateral to the sulcus are elevations called
medial eminence that are bounded laterally by Sulcus limitans. Inferior end of
median eminence is slightly expanded to form the Facial Colliculus.
Midbrain connects the pons and medulla to the
cerebrum. It is traversed by narrow channel, the cerebral aqueduct which is
filled with CSF. On the posterior surface are four Collicili (corpora
quadrigemina). The superior colliculi are centers for visual reflex while the
inferior colliculi are lower auditory centers. In the midline, below the
inferior Colliculus, the trochlear (4th) nerve emerges. On the
anterior surface of midbrain there is a deep depression called the
interpeduncular fossa which is bounded on either side by crus cerebri. The Occulomotor
nerve emerges for from the groove on the medial side of crus cerebri and passes
forward in the lateral wall of cavernous sinus.
This comment has been removed by the author.
ReplyDeleteThe 2 images under medulla are labelled wrong-- they should say middle 'cereBELLAR' peduncle and inferior 'cereBELLAR' peduncle NOT 'cerebral'. The cerebral peduncle connects the brainstem to the forebrain, whereas the superior, middle, and inferior cereBELLAR peduncles conenct the brainstem with the cereBELLUM (specifically the mid and caudal pons and rostral medulla, respectively).
ReplyDeleteDoes the diencephalon belong to the brainstem?
ReplyDeleteThis blog is pretty good to learn new information, you are doing well. Keep it up!
ReplyDeletehttps://blog.mindvalley.com/pons/
The stuff is very nice and helpful! Thanks to providing this info.
ReplyDeletehttps://blog.mindvalley.com/brain-stem/
Investment Companies in Dubai
ReplyDeleteFinancial Companies in Dubai
Financial Company in Dubai
jeux ps5 en Tunisie ,
ReplyDelete