Download Brain stem

Brainstem
Dr. Sama ul haque
Objectives
 Identify the gross features of the brainstem.
 Briefly describe the internal structure of the brainstems
(ascending and descending pathways, sensory and motor cranial
nuclei, substantia nigra, red nucleus, olivary nucleus and reticular
formation).
 Describe the main connections of the sensory cranial nuclei.
Objectives
 Describe the main connections of the motor cranial nuclei.
 Describe lesions in the brainstem such as medial medullary
syndrome and lateral medullary syndrome.
 Describe the main connections of the substantia nigra and the red
nucleus.
Brainstem
 Composed of Medulla Oblongata, Pons and the Midbrain.
 It lies in the Posterior cranial fossa of the skull.
 Stalk like in shape.
 Connects spinal cord with forebrain.
 Functions:
 It is a channel for the ascending and descending tracts.
 It contains important centers associated with respiratory and
cardiovascular systems.
 It contains the nuclei of the cranial nerves.
Medulla Oblongata
Medulla Oblongata (External features)
 It connects Pons superiorly with Spinal Cord inferiorly.
 Begins caudally at foramen magnum.
 It is conical in shape.
 Central canal continues to the middle of the medulla
and then expand as cavity of 4th ventricle.
Medulla Oblongata (External features)
 Anterior median fissure
 Pyramids (Pyramidal Tract): Bundles of corticospinal fibers
 Decussation of pyramids: Inferior part of pyramids
 Anterior external arcuate fibers: Fibers emerging from anterior
median fissure above decussation and run laterally to enter the
cerebellum.
 Olives (Inferior Olivary Nuclei): Posterolateral to Pyramids
 Roots of hypoglossal nerve: Between Pyramid and Olive
Medulla Oblongata (External features)
Anterior View
Medulla Oblongata (External features)
 Inferior cerebellar peduncles: Posterior to olives connecting
medulla to the cerebellum.
 Roots of glossopharyngeal, vagus and cranial roots of accessory
cranial nerves: Between olive and inferior cerebellar peduncle.
 Posterior median sulcus
 Floor of 4th ventricle
 Hypoglossal triangle
 Vagal triangle
 Gracile tubercle
 Cuneate tubercle
Medulla Oblongata (External features)
Posterior View
Medulla Oblongata (Internal structure)
Level of decussation of Pyramids
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Decussation of corticospinal tracts
Gracile fasciculus and nucleus
Cuneate fasciculus and nucleus
Substantia Gelatinosa of posterior gray column
of cord continue as Nucleus of the spinal tract of
the trigeminal nerve.
 Anterior and posterior spinocerebellar tracts
 Lateral spinothalamic tract
 Medial accessory olivary nucleus
Medulla Oblongata (Internal structure)
Level of decussation of Pyramids
Medulla Oblongata (Internal structure)
Level of decussation of Medial Lemnisci
 Medial Lemniscus or Sensory Decussation
(Internal arcuate fibers from nuclei gracilis and
cuneatus).
 Nucleus of the spinal tract of the trigeminal
nerve.
 Spinal tract of the trigeminal nerve.
 Anterior and posterior spinocerebellar tracts
 Lateral and Anterior spinothalamic tracts
Medulla Oblongata (Internal structure)
Level of decussation of Medial Lemnisci
Medulla Oblongata (Internal structure)
Level of the Olives
 Inferior Olivary Nucleus: Gray matter is shaped
like a crumpled bag ,facing medially.
 This nucleus is responsible for the elevation
called Olive.
 Small dorsal and medial Olivary Nuclei.
 Medial Lemniscus
 Inferior cerebellar peduncle
Medulla Oblongata (Internal structure)
Level of the Olives
 Medial longitudinal fasciculus
 Tectospinal tract
 Hypoglossal nucleus
 Dorsal vagal nucleus
 Inferior vestibular nucleus
 Pyramids
Medulla Oblongata (Internal structure)
Level of the Olives
Medulla Oblongata (Internal structure)
Level just inferior to the Pons
 Lateral Vestibular Nucleus
 Cochlear Nuclei are anterior and posterior to
inferior cerebellar peduncle
Medulla Oblongata (Internal structure)
Level just inferior to the Pons
Pons
Pons (External features)
 Lies anterior to the cerebellum.
 Connects Medulla to Midbrain.
 Anterior Surface:
– Basilar groove
– Transverse fibers converging on each side to the Middle
Cerebellar peduncle.
– Trigeminal nerve (Motor and Sensory Roots).
– Between Pons and Medulla Abducent, Facial and
Vestibulocochlear arises.
– Superficial transverse pontine fibers
Pons (External features) Anterior Surface
Pons (External features)
 Posterior Surface:
– Forms the upper half of the floor of 4th ventricle
– Limited laterally by Superior cerebellar peduncle
– Divided by Median sulcus
– Lateral to Median sulcus lies Medial eminence
– Lateral to Medial eminence lies Sulcus limitans
– Lateral to Sulcus limitans lies Vestibular area
– The inferior end of Medial eminence is expanded to form
Facial colliculus
Pons (External features)
Pons (Internal structure)
Trapezoid body: It is a bundle of fibers and cells
in Pons. It is a part of the Auditory Pathway.
Pons is divided by transverse fibers of trapezoid
body into:
 The tegmentum posteriorly
 The basal part anteriorly
Pons (Internal structure)
Transvers section through caudal part
(Passing through Facial Colliculus)
 Medial Lemniscus
 Motor nucleus of facial nerve
 Motor nucleus of Abducent (Facial Colliculus)
 Cavity of 4th ventricle
 Medial longitudinal fasciculus
Pons (Internal structure)
Transvers section through caudal part
(Passing through Facial Colliculus)
 Medial Vestibular Nucleus
 Superior cerebellar peduncle
 Middle cerebellar peduncle
 Transverse pontine fibers
 Corticospinal and corticonuclear fibers
 Spinal nucleus of Trigeminal nerve
Pons (Internal structure)
Transvers section through caudal part (Passing through Facial Colliculus)
Pons (Internal structure)
Transvers section through cranial part
(Passing through Trigeminal Nuclei)
 Cavity of 4th ventricle
 Medial longitudinal fasciculus
 Motor Nucleus of the Trigeminal Nerve
 Principal Sensory Nucleus of Trigeminal Nerve
Pons (Internal structure)
Transvers section through cranial part
(Passing through Trigeminal Nuclei)
 Superior cerebellar peduncle
 Middle cerebellar peduncle
 Medial Lemniscus
 Trapezoid body
Pons (Internal structure)
Transvers section through caudal part (Passing through Trigeminal Nuclei)
Thank You