What Is the Metencephalon?

One of the three enlarged hollow parts of the neural tube of the mesencephalon (midbrain) vertebrate embryo, located between and connected to the pontine, cerebellum, and mesencephalon; its smaller form is in the brain stem The shortest part, about 2 cm long, cuts across the cerebellum.

One of the three enlarged hollow parts of the neural tube of the mesencephalon (midbrain) vertebrate embryo, located between and connected to the pontine, cerebellum, and mesencephalon; its smaller form is in the brain stem The shortest part, about 2 cm long, cuts across the cerebellum.

Chinese name

Midbrain

Foreign name

mesencephalon, midbrain

Function

Visual and auditory reflex centers

Location

Above the pons, is exactly the midpoint of the entire brain

Pinyin

Zhong Nao

Midbrain Anatomy

During the development and evolution of the human brain, the midbrain retains simple structural forms. The fourth ventricle has been narrowed into a thin tube called the middle cerebral aqueduct here, and the rear of the tube is called the top cap, including the superior and inferior colliculus, collectively called the quadruplex. The ventral side of the tube is the brain foot, and each side of the brain foot is divided into a dorsal cover and a ventral foot sole by the oblique black matter. In addition to the superior nuclei, inferior colliculus, and substantia nigra, there are also red nuclei, oculomotor nuclei, and trochlear nuclei.

Midbrain artery

Source of midbrain arteries

There are 7 sources of the middle cerebral artery: the posterior cerebral artery (PCA); the superior cerebellar artery (5CA); the humic artery (CA); the posterior communicating artery (PCOA); the accessory hypothalamic artery (ACA); the anterior choroid artery (ACHA) ); Posterior choroidal artery (PMCA). The posterior cerebral artery circulates around the upper part of the cerebral foot, with an average of 10.2 branches of the midbrain artery, 3.5 of which originate from the proximal segment of the posterior cerebral artery, called the posterior perforating artery or interstitial fossa artery. And the medial sulcus of the midbrain, and some also penetrate into the contralateral posterior perforating mass or anastomosis with the contralateral posterior perforating artery.

The average outer diameter of adults is 0.70 ± 0.23 (0.38 ~ 1.38) mm, and that of children is 0.5 ± 0.09 (0.41 ~ 0.75) mm. The mural arteries are more common in one branch type, and only two sides in two branch types. After the mural arteries are sent out, they surround the middle of the foot of the brain, and then bend upward to the lateral groove of the midbrain, and finally stop at the quadruplex.

Some are from the hypothalamic artery, some from the proximal segment of the posterior cerebral artery, some from the distal segment of the posterior cerebral artery, and some from the posterior choroidal artery. The average outer diameter of adults is 0.47 ± 0.14 (0.35 ~ 0.75) mm, and children's 0.46 ± 0.11 (0.18 ~ 0.55) mm. After the hypothalamic arteries are issued, they surround the brain feet between the posterior cerebral arteries and thalamic arteries, and finally stop at the lateral sulcus of the midbrain and the triangle of the thalamus. In the midbrain.

Some of the posterior choroidal internal arteries originate from the distal segment of the posterior cerebral artery, some from the proximal segment of the posterior cerebral artery, some from the humic artery, and some from the posterior cerebral artery together with the humic artery. The average outside diameter of adults is 0.76 ± 0.16 (0.50 ~ 1.0) mm, and children's 0.6 ± 0.16 (0.35 ~ 0.8) mm. After the posterior choroidal internal arteries are emitted, they are constantly accompanied by the posterior cerebral arteries, which surround the brain feet, pass through the quadrilateral pool, and finally stop at the choroid plexus of the third ventricle. An average of 9.9 mesencephalic arteries are issued during the stroke.

The superior cerebellar artery originates from the top of the basilar artery. After the superior cerebellar artery is issued, it travels along the midbrain sulcus of the pons, and is usually divided into the medial and lateral branches near the lateral sulcus of the midbrain, and some are divided into the medial, medial, and lateral branches. The upper cerebellar artery sent an average of 3.6 midbrain arteries through the anterior midbrain region, and the medial branch issued an average of 12.9 midbrain arteries in the lateral and posterior regions.

The branches of the posterior communicating artery mostly penetrate into the thalamus. In addition, an average of 1.4 mesencephalic arteries are distributed in the anterior area.

The anterior choroid artery originates from the internal carotid artery, and most of the time it crosses the optic tract twice, and the branches penetrate into the anterior penetrating mass, optic tract, and optic sulcus. In addition, an average of 1.1 mesencephalic arteries are issued and penetrate into the cerebral feet.

Surface segmentation of midbrain

The mesencephalic, lateral sulcus, and anterior margin of the hypothalamus are used as boundaries, and the surface of the midbrain can be divided into 4 regions. For convenience, the midbrain artery can also be divided into the anterior medial group, anterior lateral group, and lateral group. And after the group.

The anterior medial group artery mainly comes from the posterior cerebral artery and the thalamus artery, and a few from the superior cerebellar artery and posterior communicating artery. Adults have an outer diameter of 0.4 to 1.0 mm and children have 0.28 to 0.88 mm. The diameter of the tube is the thickest in each group of arteries, and the stroke is straight. The branches penetrate into the perforating mass, the medial sulcus of the midbrain, and the oculomotor nerve root.

The anterior lateral group arteries have the most sources, with an outer diameter of 0.25 to 0.63 mm in adults and 0.13 to 0.58 mm in children, all of which penetrate into the cerebral feet.

The lateral group arteries mainly come from the humic arteries, the superior cerebellar arteries and the posterior choroidal internal arteries, and a few come from the para-hypothelial arteries and posterior cerebral arteries (10.9%). The outer diameter of adults is 0.25 to 0.75 mm, and that of children is 0.13 to 0.55 mm. Enter the lateral sulcus and mound triangle of the midbrain.

Posterior group arteries come from the mural arteries. The upper cerebellar artery and posterior choroidal internal artery have an outer diameter of 0.13 to 0.53 mm in adults and 0.08 to 0.45 mm in children. They meander and oscillate on the surface of the superior and inferior colliculus, densely packed into plexus, and emitted by the mural arteries and posterior choroidal internal arteries. Posterior group arteries mostly penetrate into the superior colliculus, and posterior group arteries from the superior cerebellar artery mostly penetrate into the inferior colliculus.