Brain Stem

Question 1

Brain stem is composed of ?

Answer 1

1- mid brain
2- pons
3- medulla oblongata

Question 2

The extent of medulla ? & its long

Answer 2

It is 3 cm , above it is continous with pons below it is continous with the sc at the foramen magnum

Question 3

Parts of medulla

Answer 3

1- closed medulla : the lower half of it that encloses the central canal that is continous with spinal cord in it
2- opened medulla : the upper half that opens in to the 4 th ventricle

Question 4

Anterolateral external features of the medulla ?

Answer 4

1.The anterior median fissure.
2. The pyramid: formed by the pyramidal (corticospinal) tract.
3. Pyramidal decussation.
4. The anterolateral sulci: gives exit to the hypoglossal nerves.
5.The olive: formed by the inferior olivary nucleus.
6. The posterolateral sulci: gives exit to the glossopharyngeal,vagus and cranial accessory nerves.
7. The inferior cerebellar peduncle.

Question 5

Posterior external features of medulla ?

Answer 5

1- medullary striae
2-Posterior median sulcus
3-Inferior fovea.
4-Hypoglossal trigone (triangle).
5-Vagal trigone.
6-Vestibular trigone ( area)
7- gracile tubarcle ( gracile nuclei is the cause)
8- cuneate tuburcle ( cuneate nuclei is the cause)
9 gracile tract
10-cuneate tracts

Question 6

Extent of the pons ?

Answer 6

It extends from the medulla below till the midbrain above and lies infront of cerebullem abd 4th ventricle

Question 7

Anterior external features of the pons ?

Answer 7

1-The basilar groove: for basilar artery.
2. transverse striations
3-The middle cerebellar peduncle.
4-The trigeminal nerve: that emerges between the bailar part & middle cerberlar pedunle
5-The abducent nerve &The facial nerve& The vestibule-cochlear nerve : that emerge at the pontomedullary junction
6-cerebelopontine angle : where the 7&8 nerves come out from

Question 8

Posterior external features of the pons ?

Answer 8

1. The median posterior sulcus
2. The medial eminence : abducent n is the cause
3. The facial colliculus : 5 ((nerve ))is the cause
   4-Superior fovea
   5- upper vestibular area

Question 9

Extend of the midbrain ?

Answer 9

It extends from the pons till the diencephalon

Question 10

How the midbrain plays a role for ventricles in brain

Answer 10

It contains a narrow cavity called cerebral aqueduct that connects 3rd and 4th ventricules together

Question 11

Anterior external features of the midbrain

Answer 11

1- cerebral peduncles : anterior part is called crus cerebri
2- oculomotor nerve : that energes medual to cerebral peduncles
3- interpedunculer fossa : that contains
* tuber cinereum
* mamillary bodies
* posterior perforeted substance
4- optic chiasm
5- optic tract

Question 12

Posterior external features of the midbrain ?

Answer 12

1. Four colliculi which include:
   a. Two superior colliculi (Visual function).
   b. Two inferior colliculi (Auditory function).
2. Two superior cerebellar peduncles.
3. Superior medullary velum (membrane): lies between the two superior cerebellar peduncles.
4. The trochlear nerve : that is special as it is the
   * smallest
   * the only crossing cranial nerve
   * the only cranial nerve coming from posterior midbrain

Question 13

Lateral external features of the midbrain?

Answer 13

• Superior brachium
• Inferior brachium
• Medial geniculate body
•lateral geniculate body
• Trochlear nerve
• Optictract
• Basal vein
• posterior cerebral artery

Question 14

Talk about the interpeduncler fossa ( boundries- content)

Answer 14

Boundaries :

antero-superior : optic chiasma
inferior : upper border of pons
laterally : cerebral peduncle
Contents :
• • • • •
tuber cinerum
mammillary bodies
posterior perforated substance
oculomotor nerve
end of basilar artery

Question 15

Internal structures in medulla ?

Answer 15

At the level of pyramid decussation ( lower part of medulla ) there is :-
1- no motor nuclei for cranial nerves
2- gracile nuclei
3- cuneate nuclei
4-accessory cuneate nuclei
5- spinal nuclei

6- ventral spinocerebellar tract
7- dorsal spinocerebellar tract
8- spinal tract of trigiminal

At the level of sensory decussation ( middle of the medulla)
1- inferior olivary nuclei

2-spinal leminisci
3-dorsal and ventral spinocerebellar tracts
4-corticospinal tracts

At the level of the open medulla
1- inferior cerebrallar peducle
2- inferior olivary nuclei
3- motor nuclei ( 10 and 9 doesnot appear in one time )
4- reticular formation

5- medial luminisci
6- spinal luminisci
7- ventral spinocereballer tract
8- pyrimadal tracts

Question 16

Internal structures in pons ?

Answer 16

Anterioly
1- pontine nuclei : it forms a part of corticopontocerebellar pathway
2-pontocerebellar fibers as transverse fibers
3- pyramidal ((bundles )) and corticopontine ( frontocerebellar- paretocerebellar )fibrs as longitodinal fibres

4- medial , trigrminal, lateral and spinal leminsci

Note ❣️❣️ there is no dorsal spinocerebellar or cenuocerebellar or vestibulocerebellar tracts 😉

Posteriorly ( tegmentum )
Motor nuclei
( cut section at middle -> 5 th nerve only
Cut section at low -> 6,7,8 nerves only 😉)
Middle cerebullar peduncle