Brainstem: Midbrain

Question 1

Definition and size

Answer 1

Uppermost and shortest part of brain stem 2 cm long lying between pons and diencephalon

Question 2

Parts

Answer 2

Divided by a narrow canal (cerebral aqueduct of sylvius) into:
1. Anterior part (cerebral peduncle)
2. Posterior part (tectum)

Question 3

External features (surfaces)

Answer 3

1. Ventral surface
2. Dorsal surface
3. 2 lateral surfaces

Question 4

Ventral surface contents

Answer 4

1. 2 cerebral peduncles
2. Interpeduncular fossa

Question 5

2 cerebral peduncles

Answer 5

2 large bundles of nerve fibers emerging from pons upper surface and ascend to disappear in cerebral hemispheres substance

Question 6

Interpeduncular fossa

Answer 6

In median plane between the 2 cerebral peduncles

Question 7

Dorsal surface contents

Answer 7

1. 4 colliculi (corpora quadrigemina)
2. Superior cerebellar peduncles
3. Trochlear (4th cranial) nerve

Question 8

Corpora quadrigemina

Answer 8

4 rounded elevations
1. 2 superior colliculi: centers visual reflexes
2. 2 inferior colliculi: centers auditory reflexes

Question 9

Superior cerebellar peduncles

Answer 9

Bundles of nerve fibers running downwards, backwards, and laterally along 4th ventricle sides entering cerebellum

Question 10

Trochlear nerve

Answer 10

Emerges from midbrain below inferior colliculus
It is the only cranial nerve emerging from back of brain stem

Question 11

2 lateral surfaces

Answer 11

Lateral surfaces of cerebral peduncles and related to tentorial notch of Tentorium cerebelli

Question 12

2 lateral surfaces content

Answer 12

Superior and inferior brachia (brachia quadrigemina)

Question 13

Brachia quadrigemina

Answer 13

Connect superior and inferior colliculi with lateral and medial geniculate bodies respectively

Question 14

Structures crossing lateral surfaces

Answer 14

3 arteries
1. Posterior cerebral artery
2. Superior cerebellar artery
3. Anterior choroidal artery
2 nerves
1. Optic tract
2. Trochlear nerve
One vein
1. Basal vein in great cerebral vein

Question 15

Arterial supply

Answer 15

1. Posterior cerebral artery
2. Superior cerebellar artery (basilar artery)
3. Posterior communicating artery (ICA)