Medulla - Part 1 Flashcards
(46 cards)
Connects the pons superiorly with the spinal cord inferiorly
Medulla
Where is the junction of medulla and spinal cord?
at the origin of the anterior and posterior roots of the first cervical spinal nerve, which corresponds approximately to the level of the foramen magnum.
Blood supply of medulla
posterior inferior cerebellar artery (lateral part) vertebral artery (medial)
Continuous inferiorly with the anterior median fissure of the spinal cord
Anterior median fissure
Swelling on each side of the median fissure
o Composed of bundles of nerve fibers called corticospinal fibers, which originate in large nerve cells (pyramidal/Betz cells) in the precentral gyrus of the cerebral cortex
Pyramids
o Few nerve fibers that emerge from the anterior median fissure above the decussation
o Pass laterally over the surface of the medulla oblongata to enter the cerebellum
Anterior external arcuate fibers
o Posterolateral to the pyramids
o Oval elevations produced by the underlying
inferior olivary nuclei
Olives
Emerges in the groove between the pyramid
and the olive
Hypoglossal nerve
Roots of these nerves emerge in the groove
between the olive and the inferior cerebellar
peduncle
Glossopharyngeal
Vagus
Accessory
Forms the lower part of the floor of the fourth
ventricle
Superior half of the medulla oblongata
Continuous with the posterior aspect of the spinal cord and possesses a posterior median sulcus
Inferior half
o Elongated swelling located on each side of the
median sulcus
o Produced by the underlying gracile nucleus
Gracile tubercle
o Lateral to the gracile tubercle
o Produced by the underlying cuneate nucleus
Cuneate tubercle
Its extensive lateral spread resulted in an
alteration in the position of the derivatives of the
alar and basal plates of the embryo
Fourth ventricle
Alar and basal plates: situated lateral and medial to the sulcus limitans respectively (vs. in
the spinal cord, wherein the alar and basal plates are situated posterior and anterior to the sulcus limitans)
Fourth ventricle
Four levels of medulla
o Level of decussation of pyramids
o Level of decussation of lemnisci
o Level of the olives
o Level just inferior to the pons
o Seen in a transverse section through the inferior half of the medulla oblongata
o Also known as the decussation of pyramids
Great motor decussation
Part of the medulla where corticospinal fibers occupy and form the pyramid
Superior part of the medulla
About three-fourths of the fibers cross the median plane continue down the spinal cord in the lateral white column as the __________
lateral corticospinal tract
Continue to ascend superiorly posterior to the central gray matter
Fasciculus gracilis and fasciculus cuneatus
Appear as posterior extensions of the centralgray matter
Nucleus gracilis and nucleus cuneatus
Found in the posterior gray column of the spinal cord, which becomes continuous with the inferior end of the nucleus of the spinal tract of the trigeminal nerve (CN V)
Substantia gelatinosa
o Seen in the transverse section through the inferior half of the medulla oblongata
o Also known as the decussation of lemnisci
o Found a short distance above the level of the decussation of the pyramids
Great sensory decussation
o Where the lemnisci have been formed, which
have emerged from the anterior aspects of
nucleus gracilis and nucleus cuneatus
o First travel anteriorly and laterally around the
central gray matter
o They then curve medially toward the midline
where they decussate with the corresponding
fibers of the opposite side
Internal arcuate fibers
