Lab 2: Gross And Internal CNS II Flashcards
Medulla
Between the upper roots of C1 and the lower edge of the pons (pronto-medullary junction)
Pons
Has a large ventral bulge due to a bundle of transversely oriented fibers
Midbrain
Has a midline fossa between longitudinal bundles of fibers (the cerebral peduncles)
Ventral Medulla
Ventral (anterior) median fissure or sulcus: midline cleft
Pyramids: base or floor of the medulla, lateral to the ventral median fissure
Olive: bulge that is lateral to the hypoglossal nerve roots
IX (glossopharyngeal), X (vagus), XI (accessory) cranial nerves exit laterally to the olive
IV (abducens) cranial nerve exits through the medial area of the ponto-medullary junction
VII (facial) VIII (vestibulocochlear) cranial nerves exit at the lateral pontomedullary junction
Ventral View of Pons
Basilar pons: contains horizontal fibers en route to the cerebellum
Middle cerebral peduncle: lateral to the basilar pons and continuous with it
Trigeminal (V) nerve: pierces the middle cerebellar peduncle
Ventral View of the Midbrain
Cerebral Peduncles: base of the midbrain; contains fibers from the cerebral cortex
Interpeduncular fossa: midline space between cerebral peduncles
Trochlear (IV) nerve: exits the midbrain dorsally, then winds around the cerebral peduncle; often missing
Oculomotor nerve (III) exits the midbrain through the interpeduncular fossa
Rhomboid Fossa or Floor of 4th ventricle
Consists of the ventricular surfaces of the pons and medulla. the ponto-medullary transition is where the rhomboid fossa is the widest
Floor of 4th ventricle
Median sulcus: midline longitudinal groove
Sulcus limitans: lateral longitudinal groove that separates the positions of the motor (medial) and sensory (lateral) cranial nerve nuclei in the periventricular zone
Lateral recess: widest point of the fourth ventricle; opens into the SAS as lateral apertures or openings that permit the exit of CSF from the ventricular system
Facial colliculus: a bulge in the caudal pontine area of the floor of the 4th ventricle; marks the location of facial nerve fibers that bend around the bulge of the abducens nucleus
Obex: casual point of the widened part of the fourth ventricle. Below this level, the casual medulla has a narrow, cylindrical IV ventricle
Lateral walls of the 4th ventricle
Middle cerebellar peduncles (large fiber connections between the pons and cerebellum, lateral to the superior and inferior cerebellar peduncles
Superior cerebellar peduncles: fiber connections between the cerebellum and midbrain; they contribute to the lateral walls of the rostrum pons
Inferior cerebral peduncles: fiber connections between the cerebellum and medulla; they form the lateral walls of the medulla
Dorsal surface of the midbrain
Roof or tectum: formed mainly by superior and inferior colliculi
Superior colliculi: transmission of visual info
Inferior: transmission of auditory info
Trochlear nerves: caudal to the inferior colliculi
Brachium of the inferior colliculus: rod-like bundle of fibers lateral to the inferior colliculus (transmits auditory info to the thalamus)
Sagittal surface of the Brainstem
I.D cerebral aqeduct and IV ventricle
Roof: in the midbrain again contains colliculi (tectum). The pons and medulla have a thin roof plate mostly faces with the cerebellum
Tegmentum: a primitive core located ventral to widened IV ventricle and peripheral to the cerebral aqueduct and caudal IV ventricle
Periventricluar zone: contains many cranial nerve nuclei (called periaqueductal gray in the midbrain)
Reticular formation: area ventral to the periventricular zone that extends to the base in the pons, in the sagittal plane, to the ventral surface of the midbrain and medulla
Base: ventral area of the brainstem that contains descending fivers from the cerebral cortex; in the sagittal plane it’s visible in the pons but lateral to the midline in the rest of the brainstem
Transverse (axial) slice of the Medulla
Tegmentum: area between the IV ventricle and the inferior olivary nuclei
Periventricular zone: adjacent to the IV ventricle and contains cranial nerve nuclei
Reticular formation: primitive processing area, ventral to the periventricular zone
Lateral walls: lateral bundles of fibers passing to and from the cerebellum; those in the medulla are the inferior cerebellar peduncle
Base: ventral area containing descending myelinated fibers from the cerebral cortex; these are called pyramidal tracts in the medulla
internal landmarks of the medulla (transverse cut)
Inferior olivary nuclei: a group of nuclei between the tegmentum and base, look crumpled gray matter
Hypoglossal nucleus: GSE nucleus that is close to the midline in the periventricular zone
Hypoglossal nerve roots: pass ventral from the nucleus, exit the medulla between the olivary nuclei and the pyramids
Pyramidal tracts: fibers from the motor areas of the cerebral cortex that travel to motor neurons of the spinal cord
Inferior cerebellar peduncle fibers passing between the cerebellum and brainstem and spinal cord
Transverse Slice of Caudal Pons
Tegmentum: (both layers) between IV ventricle and the base
Base contains descending cortical fibers, scattered and pale pontine nuclei as well as horizontal fibers that travel to form the middle cerebellar peduncle
lateral wall: medial part of the middle cerebellar peduncle and lateral to the IV ventricle is the superior cerebellar peduncle with cerebellar fibers en route to the midbrain
Abducens nucleus: in the periventricular zone close but not adjacent to the midline
Abducens nerve roots: pass ventrally through the reticular formation and base to exit the brainstem at the ponto-medullary junction
Facial nucleus: a BE nucleus in the ventrolateral reticular formation
Facial (VII) and vestibulocochlear (VIII) nerves
Exit brainstem laterally and pass through the internal auditory canal
