Brainstem

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TRUNK BRAIN

The brainstem is interposed between the medulla and the diencephalon, lying ventrally to the cerebellum, that is, it connects the spinal cord with the superiorly located brain structures. Brainstem white matter includes tracts that receive and send motor and sensory information to the brain, as well as those coming from the brain. BRAIN TRUNK his friends. Scattered in the white matter of the brainstem are gray matter masses called nuclei, which exert intense effects on functions such as blood pressure and respiration. In its constitution enter bodies of neurons that are grouped in nuclei and nerve fibers, which in turn, are grouped in bundles called tract, fascicle or lemniscus.
Many of the brainstem nuclei receive or mimic nerve fibers that enter the constitution of the cranial nerves. Of the 12 pairs of cranial nerves, 10 make connection with the brainstem.

BULB (OBLONGA BULLET) - BRAIN TRUNK BRIDGE - BRAIN TRUNK MESENCÉPHALO - BRAIN TRUNK
Bulb   bridge   Midbrain

The brainstem is divided into: bulb, located caudally, midbrain, and the bridge between them.

BULB (OBLONGA MARROW):

BULB (OBLONGA BULLET) - BRAIN TRUNK BULB (OBLONGA BULLET) - BRAIN TRUNK BULB (OBLONGA BULLET) - BRAIN TRUNK

The oblong bulb or medulla is shaped like a cone whose smaller end continues caudally with the spinal cord. Since there is no line demarcating the separation between the medulla and bulb, it is considered that the boundary is in a horizontal plane that passes immediately above the most cranial root filament of the first cervical nerve, which corresponds to the level of the foramen magnum.

The upper limit of the bulb is made in a visible horizontal groove in the contour of this organ, bulb-pontine groove, which corresponds to the inferior margin of the bridge. The surface of the bulb is traversed by two parallel grooves that continue in the medulla. These grooves delimit what is anterior and posterior in the bulb. Seen from the surface, they appear as a continuation of the spinal cord funicles. The anterior median fissure ends cranially in a depression called blind form.

On either side of the anterior median fissure there is an eminence called the pyramid, formed by a compact bundle of descending nerve fibers that connects the motor areas of the brain with the motor neurons in the medulla. This tract is called the pyramidal tract or cortico-spinal tract.

In the caudal part of the bulb, the fibers of this tract obliquely cross the median plane and constitute the decussation of the pyramids. It is due to the decussation of the pyramids that the right cerebral hemisphere controls the left side of the body and the left cerebral hemisphere controls the right side. For example, in a right brain injury, the body will be affected throughout its left half.

BULB (OBLONGA BULLET) & #8211; BRAIN TRUNK & #8211; PREVIOUS VIEW

Source: NETTER, Frank H .. Atlas of Human Anatomy. 2 ed. Porto Alegre: Artmed, 2000.

Between the anterior lateral and posterior lateral grooves is the lateral area of the bulb, where an oval eminence, the olive, is formed, formed by a large amount of gray matter. Ventrally to the olive emerges from the anterior lateral sulcus, the reticular filaments of the hypoglossal nerve. From the posterior lateral sulcus emerge the root filaments that unite to form the glossopharyngeal and vagus nerves in addition to the filaments that constitute the cranial or bulbar root of the accessory nerve that joins with the spinal root.

BULB (OBLONGA BULLET) & #8211; BRAIN TRUNK & #8211; BACK VIEW
BULB (OBLONGA BULLET) - BRAIN TRUNK - REAR VIEW
Source: NETTER, Frank H .. Atlas of Human Anatomy. 2 ed. Porto Alegre: Artmed, 2000.

The caudal half of the bulb or closed portion of the bulb is traversed by a narrow canal, direct continuation of the central canal of the medulla, which opens to form the IV ventricle, whose floor consists of the rostral half or open portion of the bulb. The posterior median sulcus terminates at half height of the bulb, due to the retraction of its lips, which contribute to the formation of the lateral limits of the IV ventricle.

Between the posterior median sulcus and the posterior lateral sulcus, there is the continuation of the posterior medullary funicular, and in the bulb, it is divided into gracilic fascicle and cuneiform fascicle by the posterior intermediate sulcus. These fascicles are made up of ascending nerve fibers from the medulla that end in two masses of gray matter, the gracilis and cuneiform nuclei, located in the most cranial part of the corresponding fascicles.

These nuclei determine the emergence of two eminences: the more medial gracile tubercle and the more lateral cuneiform tubercle. By virtue of the IV ventricle, the gracile and cuneiform tubercles move apart laterally as two branches of one & #8220; V & #8221; and gradually continuing upward with the inferior cerebellar peduncle (restiform body). This is formed by a thick bundle of fibers that form the lateral edges of the caudal half of the IV ventricle, flexing dorsally to penetrate the cerebellum.

BULB (OBLONGA BULLET) & #8211; BRAIN TRUNK & #8211; POSTER SIDE VIEW
 BULB (OBLONGA BULLET) - BRAIN TRUNK - POSTER SIDE VIEW
Source: NETTER, Frank H .. Atlas of Human Anatomy. 2 ed. Porto Alegre: Artmed, 2000.

In the bulb is located the respiratory center, very important for the regulation of the respiratory rhythm. Also located are the vasomotor center and the vomiting center. The presence of the respiratory and vasomotor centers in the bulb makes lesions in this organ particularly dangerous.

Because of its importance with respect to vital functions, the bulb is often called the vital center. Because these structures are fundamental to the body, you can understand the seriousness of a fracture at the base of the skull. The bulb is also extremely sensitive to certain drugs, especially narcotics. An overdose of narcotic causes bulb depression and death because the person stops breathing.

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BRIDGE:

BRIDGE - BRAIN TRUNK - SIDE VIEW BRIDGE - BRAIN TRUNK - REAR VIEW BRIDGE - BRAIN TRUNK

Bridge is the part of the brainstem interposed between the bulb and the midbrain. It is located ventrally to the cerebellum and rests on the basilar part of the occipital bone and the back of the sphenoid turgical saddle. Its ventrally located base presents a transverse striation due to the presence of numerous transverse fiber bundles that run through it.

These fibers converge on either side to form a massive bundle, the middle cerebellar peduncle, which penetrates the corresponding cerebellar hemisphere. The boundary between the bridge and the middle cerebellar peduncle (bridge arm) is considered to be the emergence point of the trigeminal nerve (V cranial nerve). This emergence is made by two roots, one larger, or sensory root of the trigeminal nerve, and another minor, or motor root of the trigeminal nerve.

BRIDGE & #8211; BRAIN TRUNK & #8211; POSTER SIDE VIEW
 BRIDGE - BRAIN TRUNK - POSTER SIDE VIEW
Source: NETTER, Frank H .. Atlas of Human Anatomy. 2 ed. Porto Alegre: Artmed, 2000.

Running along the ventral surface of the bridge is a groove, the basilar sulcus, which usually houses the basilar artery.
The ventral part of the bridge is separated from the bulb by the bulbous groove.BRIDGE pontine, from which emerges on each side from the midline, the VI, VII and VIII cranial pair.

The VI pair, the abducent nerve, emerges between the bridge and the bulb pyramid. The VIII cranial pair, the vestibulo-cochlear nerve, emerges laterally near a small lobe called a floccule. The VII cranial nerve, the facial nerve, emerges laterally with the VIII cranial nerve, the vestibulo-cochlear nerve, with which it maintains close relationships. Between the two emerges the intermediate nerve, which is the sensory root of the seventh cranial nerve.

BRIDGE & #8211; BRAIN TRUNK & #8211; PREVIOUS VIEW
 BRIDGE - BRAIN TRUNK - PREVIOUS VIEW
Source: NETTER, Frank H .. Atlas of Human Anatomy. 2 ed. Porto Alegre: Artmed, 2000.

The dorsal part of the bridge has no demarcation line with the dorsal part of the bulb, both constituting the floor of the IV ventricle.

Bridge Cores:

 Trigeminal Nerve Motor Core (V cranial pair) - is located on the lateral margin of the fourth ventricle.

 Sensitive Nuclei of the Trigeminal Nerve (V cranial pair) Cephalic continuation of the spinal cord sensitive spine. The fibers that penetrate the bridge from the trigeminal ganglion are divided into ascending and descending branches.

 Abducent Nerve Nucleus (VI Cranial Pair) - forms part of the dorsal gray matter of the medial eminence of the fourth ventricle floor, deep to the facial colliculus.

 Facial Nerve Nucleus (VII Cranial Pair) - is located deep in the reticular formation, laterally to the abducens nerve nucleus. They emerge from the caudal border between the olive and the inferior cerebellar peduncle.

 Vestibulocochlear Nerve Nucleus (VIII Cranial Pair) - The nucleus of the vestibular division occupies a large area in the lateral portion of the fourth ventricle. The nucleus of the cochlear division is located in the caudal portion of the bridge.

BRIDGE & #8211; BRIDGE CORE SCHEME & #8211; BRAIN TRUNK & #8211; SIDE VIEW
BRIDGE - BRIDGE CORE DIAGRAM - BRAIN TRUNK - SIDE VIEW
Source: NETTER, Frank H .. Atlas of Human Anatomy. 2 ed. Porto Alegre: Artmed, 2000.

Ventricle Room: is located between the bulb and the bridge on its posterior face and ventrally to the cerebellum. It continues caudally with the central canal of the bulb and cranially with the cerebral aqueduct, the midbrain cavity that communicates the III and IV ventricles. The IV ventricle cavity extends on either side to form the lateral recesses, situated on the dorsal surface of the inferior cerebellar peduncle.
Ventricle RoomThis recess communicates on either side with the subarachnoid space through the two lateral openings of the IV ventricle. There is also a median opening of the IV ventricle called the Magendie Forme, or median foramen, situated in the middle of the caudal half of the IV ventricle roof. Through this cavity, cerebrospinal fluid, which fills the ventricular cavity, passes into the subarachnoid space.

BRIDGE & #8211; FOURTH VENTRICLE & #8211; BRAIN TRUNK & #8211; SIDE VIEW
 BRIDGE - FOURTH VENTRICLE - BRAIN TRUNK - SIDE VIEW
Source: NETTER, Frank H .. Atlas of Human Anatomy. 2 ed. Porto Alegre: Artmed, 2000.

The floor of the IV ventricle or rhomboid fossa is formed by the dorsal part of the bridge and the open portion of the bulb.

IV ventricle ceiling: The cranial half of the roof of the IV ventricle consists of a thin lamina of white matter, the superior medullary veil, which extends between the two superior cerebellar peduncles. In the constitution of the caudal half we have the following formations:

 A small part of the white matter of the cerebellum nodule.

 The inferior medullary veil, bilateral formation consisting of a thin white lamina attached medially to the lateral edges of the cerebellum nodule.

 Choroidal IV ventricle, which joins the two anterior formations to the edges of the caudal half of the floor of the IV ventricle.

BRIDGE & #8211; FLOOR OF THE FOURTH VENTRICLE & #8211; BRAIN TRUNK & #8211; BACK VIEW
 BRIDGE - FOURTH VENTRICLE FLOOR - BRAIN TRUNK - REAR VIEW
Source: NETTER, Frank H .. Atlas of Human Anatomy. 2 ed. Porto Alegre: Artmed, 2000.

The choroidal mesh is formed by the union of the ependymal epithelium, which internally lines the ventricle with the pia mater and externally reinforces this epithelium. This screen emits irregular and highly vascularized projections for the formation of the IV ventricular choroid plexus. This choroid plexus has the shape of & #8220; T & #8221; It produces cerebrospinal fluid, which accumulates in the ventricular cavity and passes into the subarachnoid space through the lateral openings and the median opening of the IV ventricle.

The bridge plays a key role in regulating breathing pattern and rhythm. Injuries to this structure can cause severe respiratory rhythm disturbances.

Midbrain:

Midbrain - Side View Midbrain - Posterior View Midbrain

They interpose between the bridge and the brain, which is represented by a plane that connects the two nipple bodies, belonging to the diencephalon, to the posterior commissure. It is crossed by a narrow channel, the cerebral aqueduct. The part of the midbrain located dorsally to the aqueduct is the midbrain ceiling. Ventrally, we have the two cerebral peduncles, which in turn are divided into a dorsal part, the tegment and another ventral part, the base of the peduncle.

Midbrain In a cross section of the midbrain, it is seen that the tegment is separated from the base by a dark area, the substantia nigra. Next to the substantia nigra there are two longitudinal grooves: one lateral, lateral sulcus of the midbrain, and another medial, medial sulcus of the cerebral peduncle. These grooves mark the boundary between the base and the tegment of the cerebral peduncle. From the medial sulcus emerges the oculomotor nerve, III cranial pair.

Ceiling of the midbrain: In dorsal view the mesencephalic ceiling has four rounded eminences called superior and inferior colliculi, separated by two cross-shaped perpendicular grooves. The anterior part of the longitudinal branch of the cross houses the pineal body, which belongs to the diencephalon. Caudally at each inferior colliculus emerges the IV cranial nerve, the trochlear nerve.

MESENCÉPHAL (DIDACTIC SCHEME) & #8211; MESENCÉPHAL CROSS SECTION
 MESENCÉPHAL (DIDACTICAL DIAGRAM) - CROSS SECTION OF THE MESENCÉPHAL
Source: AX, Angelo. Functional Neuroanatomy. Rio de Janeiro / Sao Paulo: Atheneu, 1991.

Each colliculus connects to a small oval eminence of the diencephalon, the geniculate body, through a superficial bundle of nerve fibers that forms its arm. Thus the inferior colliculus connects to the medial geniculate body by the lower colliculus arm, and the superior colliculus connects to the lateral geniculate body by the superior colliculus arm, which has its hidden path between the thalamus pulvinar and the medial geniculate body. The lateral geniculate body is at the end of the optic tract.

MESENCÉPHALO & #8211; COLLICULES AND GENICULATED BODIES & #8211; POSTER SIDE VIEW
 MESENCÉPHAL - COLLICULES AND GENICULATED BODIES - POSTER SIDE VIEW
Source: NETTER, Frank H .. Atlas of Human Anatomy. 2 ed. Porto Alegre: Artmed, 2000.

Brain Peduncles: Viewed ventrally, the brain peduncles appear with two large bundles of fibers that appear at the upper edge of the bridge and diverge cranially to penetrate deep into the brain. They thus delimit a deep triangular depression, the interpeduncular fossa, previously limited by two eminences belonging to the diencephalon, the nipple bodies. The bottom of the interpeduncular fossa has small holes for the passage of vessels. It is called posterior perforated substance.

Red Core - occupies much of the tegment. It is an oval-shaped mass extending from the caudal limit of the superior colliculus to the subthalamic region. It is circular in cross section.

LOWER VIEW OF MESENCÉPHAL
 LOWER VIEW OF MESENCÉPHAL
Source: NETTER, Frank H .. Atlas of Human Anatomy. 2 ed. Porto Alegre: Artmed, 2000.

Midbrain Cores:

 Mesencephalic Root Nucleus of the Trigeminal Nerve (V cranial pair) - forms a scattered region on the lateral portion of the central gray matter surrounding the aqueduct.

 Trochlear Nerve Nucleus (IV Cranial Pair) - is at the level of the inferior colliculus.

 Oculomotor Nerve Nucleus (III Cranial Pair) - appears in a cross section. It extends to the superior colliculus.

MESENCÉPHALO & #8211; SCHEME OF CORES & #8211; BRAIN TRUNK & #8211; BACK VIEW
 MESENCÉPHAL - CORE DIAGRAM - BRAIN TRUNK - REAR VIEW
Source: NETTER, Frank H .. Atlas of Human Anatomy. 2 ed. Porto Alegre: Artmed, 2000.

Review of Cerebellar Peduncles:

 Lower Cerebellar Peduncle: originates from the bulb.

 Middle Cerebellar Peduncle: originates from the bridge.

 Superior Cerebellar Peduncle: originates in the midbrain.

Lower Cerebellar Stalk
Origin: Bulb
  Medium Cerebellar Stalk
Origin: Bridge
  Superior Cerebellar Peduncle
Origin: Mesencephalon
Lower Cerebellar Stalk Medium Cerebellar Stalk Superior Cerebellar Peduncle

 

 

Structures of
Nervous system
Nervous tissue

Spinal cord

Cerebellum

Diencephalon

Telencephalon

Meninges and CSF

Brain Vascularization

Peripheral Nervous System

 

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