Pons Flashcards
Location of the pons
Inferior to midbrain
Superior to medulla
What separates the medulla from the pons?
Transverse groove
What are the nerves of the transverse groove?
Abducent nerve (Above Pyramid)
Facial (Above Olive)
Vestibulocochlear (Above Olive)
What are the surfaces of the pons?
Anterior
Posterior
Describe the anterior surface of the pons
Convex
Purpose of the basilar sulcus
Contains basilar artery
Where is the trigeminal nerve attached?
Attached by two rootlets
What is the inferior posterior surface of the pons continuous with?
Upper part of the medulla
What is the median sulcus?
Divides the posterior surface of the pons into two halves
What is the medial eminence?
Elongated elevation bound by sulcus limitans
Where is the facial colliculus?
Lower part of the medial eminence overlying the abducent nucleus
What surrounds the facial colliculus?
Facial nucleus axons turned around abducent nucleus
What is the superior fovea?
Depression at the lower end of sulcus limitans at the level of facial colliculus
Where are the vestibular nuclei?
Lateral to the superior fovea
How many parts can the pons be divided into?
Basilar part
Tegmentum
What structure divides the pons?
Divided by transversely running fibers of trapezoid body
Where is the basilar part of the pons?
Anterior part of the pons
How do the contents of the basilar parts vary at each level?
Contents are the same at each level
Where is the tegmental part of the pons?
In the dorsal part of the pons
Includes the trapezoid body
How do the contents of the tegmentum vary at each level?
Vary in the three levels of the pons
What are the components of the basilar part of the pons?
Descending Tracts
What are the descending tracts in the basilar part of the pons?
Corticoponto Cerebellar Tract
Corticospinal Tract
Characteristics of the corticoponto cerebellar tract
Has numerous transverse pontocerebellar fibers which arise from pontine nuclei
Characteristics of the corticospinal tract
Small, separate bundles running longitudinally between the transverse pontine fibers
What are the levels of the tegmental part of the pons?
Lower level: Level of facial colliculus.
Mid-level: level of trigeminal nerve.
Upper level: level of 4 lemnisci
Where is the trapezoid body?
Anterior part of the tegmentum
What are the fibers of the trapezoid body responsible for?
Arise from cochlear body and are responsible for hearing
Tegmentum in Lower Pons
Components
Nuclei
Ascending Tracts
Tegmentum in Lower Pons
Nuclei
Anterior and posterior cochlear nuclei
Vestibular nuclei
Superior salivatory nucleus
Abducent nerve nucleus
Facial motor nucleus
Tegmentum in Lower Pons
What encircles the abducent nerve nucleus?
Fibers of facial nerve
Tegmentum in Lower Pons
What does the encircling of the Abducent Nucleus form?
Forms elevation in the floor of 4th ventricle called facial colliculous
Tegmentum in Lower Pons
Describe the pathway of the facial motor neurons
Efferent fibers encircle abducent nucleus
Pass antero-laterally
Emerge at the groove between pons & olive of medulla
Tegmentum in Lower Pons
Ascending Tracts
Medial Lemniscus (Gracile and Cuneate Tracts)
Spinal Lemniscus (Anterior and Lateral Spinothalamic Tracts)
ANTERIOR SPINOCEREBELLAR TRACT
Spinal Tract and Nucleus
Tegmentum in Lower Pons
Purpose of the spinal tract
Carries pain and temperature sensations of face and scalp
Tegmentum in Mid-Pons
Nuclei
Trigeminal motor nucleus
Trigeminal sensory nucleus
Tegmentum in Mid-Pons
Location of Trigeminal Motor Nucleus
Medial in position
Tegmentum in Mid-Pons
What do the axons of the Trigeminal Motor Nucleus form?
Form the motor root of trigeminal nerve which passes along mandibular nerve
Tegmentum in Mid-Pons
Location of the Trigeminal Sensory Nucleus
Lateral in position
Tegmentum in Mid-Pons
Names of Ascending Tracts
Medial, Trigeminal, Spinal and Lateral Lemnisci
Anterior Spinocerebellar Tract
What is the upper tegmentum composed of?
Lateral Lemniscus
Spinal Lemniscus
Trigeminal Lemniscus
Medial Lemniscus
Anterior Spinocerebellar Tract
Tegmentum in Upper-Pons
Location of Lateral Lemniscus
Most lateral lemniscus
Tegmentum in Upper-Pons
What fibers does the Lateral Lemniscus contain?
Ascending fibers carrying hearing sensations from both ears (mainly opposite side)
Tegmentum in Upper-Pons
Where does the Lateral Lemniscus end?
Auditory Area in Temporal Lobe
Tegmentum in Upper-Pons
Location of Spinal Lemniscus
Medial to lateral lemniscus
Tegmentum in Upper-Pons
What fibers does the Lateral Lemniscus contain?
Band of ascending fibers
Tegmentum in Upper-Pons
What sensations does the Spinal Lemniscus carry?
Pain, temperature and touch from opposite side of body
Tegmentum in Upper-Pons
Location of the Trigeminal Lemniscus
Medial to Spinal Lemniscus
Tegmentum in Upper-Pons
What sensations does the Trigeminal Lemniscus carry?
Touch, pain and temperature from the opposite side of the face and scalp
Tegmentum in Upper-Pons
Location of Medial Lemniscus
Most medial lemniscus
Tegmentum in Upper-Pons
What sensations does the Medial Lemniscus carry?
Carrying proprioceptive sensations from the opposite side of the body
Primary blood supply of the pons
Basilar Artery
Which branches of the basilar artery supply the medial part of the basis pontis?
Paramedian Pontine Branches
Which branches of the basilar artery supply the lateral part of the basis pontis?
Long and short circumferential pontine branches
Which branches of the basilar artery supply the tegmentum?
Paramedian pontine branches
Long circumferential pontine branches and superior cerebellar artery (cranial part)
Long circumferential pontine branches and anterior inferior cerebellar artery (caudal part)
What is the venous drainage of the pons?
Basilar Venous Plexus
Inferior Petrosal Sinus
What are the effects of extensive pontine haemorrhage?
Pin point pupil
Hyperpyrexia
Quadriplegia
