Sectiunile trunchiului cerebral

Brainstem: 3 major divisions

•Midbrain

•Pons

•Medulla

Reticular Formation

• “Core” of brainstem (midbrain, pons and medulla) composed of loosely organized neurons, outside of the major nuclear groups of the brainstem.

• Medial-to-lateral: raphe nuclei, gigantocellular region, small cell region

• Participate in widespread connections

• Rostral continuation of interneuronal network found in spinal cord

Cerebellar pathways

Conduct impulses from the leg and trunk muscles for unconscious proprioception

• Dorsal & Ventral Spinocerebellar Tracts– Enter cerebellum via inferior cerebellar peduncle

Summary of Spinal Cord Tracts

Brainstem Internal Anatomy

Tracing through the brainstem: Dorsal Column/Medial Lemniscal

System

Corticospinal Tract

                                   

Decussation of pyramids. Scheme showing passage of various fasciculi from medulla spinalis to medulla oblongata. a. Pons. b. Medulla oblongata. c. Decussation of the pyramids. d. Section of cervical part of medulla spinalis. 1. Anterior cerebrospinal

fasciculus (in red). 2. Lateral cerebrospinal fasciculus (in red). 3. Sensory tract (fasciculi gracilis et cuneatus) (in blue). 3’. Gracile and cuneate nuclei. 4. Antero-lateral proper fasciculus (in dotted line). 5. Pyramid. 6. Lemniscus. 7. Medial longitudinal fasciculus. 8.

Ventral spinocerebellar fasciculus (in blue). 9. Dorsal spinocerebellar fasciculus (in yellow).

Caudal Medulla

                                                            

Section of the medulla oblongata at the level of the decussation of the pyramids. (Testut.) 1. Anterior median fissure. 2. Posterior median sulcus. 3. Motor roots. 4. Sensory roots. 5. Base of the anterior column, from which the head (5’) has been

detached by the lateral cerebrospinal fasciculus. 6. Decussation of the lateral cerebrospinal fasciculus. 7. Posterior columns (in blue). 8. Gracile nucleus.

Caudal Medulla

“Closed” medulla

                                                            

Section of the medulla oblongata through the lower part of the decussation of the pyramids. (Testut.) 1. Anterior median fissure. 2. Posterior median sulcus. 3. Anterior column (in red), with 3’, anterior root. 4. Posterior column (in blue), with 4’, posterior roots. 5.

Lateral cerebrospinal fasciculus. 6. Posterior funiculus. The red arrow, a, a’, indicates the course the lateral cerebrospinal fasciculus takes at the level of the decussation of the pyramids; the blue arrow, b, b’, indicates the course which the sensory fibers take.

                                                            

Section of the medulla oblongata at the level of the decussation of the pyramids. (Testut.) 1. Anterior median fissure. 2. Posterior median sulcus. 3. Motor roots. 4. Sensory roots. 5. Base of the anterior column, from which the

head (5’) has been detached by the lateral cerebrospinal fasciculus. 6. Decussation of the lateral cerebrospinal fasciculus. 7. Posterior columns (in

blue). 8. Gracile nucleus.

Caudal Medulla

Caudal Medulla

Medulla

Medulla

                          

Superior terminations of the posterior fasciculi of the medulla spinalis. 1. Posterior median sulcus. 2. Fasciculus gracilis. 3. Fasciculus cuneatus. 4. Gracile nucleus. 5. Cuneate nucleus. 6, 6’, 6’’. Sensory fibers forming the lemniscus. 7. Sensory

decussation. 8. Cerebellar fibers uncrossed (in black). 9. Cerebellar fibers crossed (in black).

                                             

Transverse section passing through the sensory decussation. (Schematic.) 1. Anterior median fissure. 2. Posterior median sulcus. 3, 3. Head and base of anterior column (in red). 4. Hypoglossal nerve. 5. Bases of posterior columns. 6. Gracile nucleus. 7. Cuneate

nucleus. 8, 8. Lemniscus. 9. Sensory decussation. 10. Cerebrospinal fasciculus.

Rostral Medulla

Rostral Medulla

                                                                           

Section of the medulla oblongata at about the middle of the olive.

                                                                                          

Transverse section of medulla oblongata below the middle of the olive.

                                             

The formatio reticularis of the medulla oblongata, shown by a transverse section passing through the middle of the olive. (Testut.) 1. Anterior median fissure. 2. Fourth ventricle. 3. Formatio reticularis, with 3’, its internal part (reticularis alba), and 3’’, its external part

(reticularis grisea). 4. Raphé. 5. Pyramid. 6. Lemniscus. 7. Inferior olivary nucleus with the two accessory olivary nuclei. 8. Hypoglossal nerve, with 8’, its nucleus of origin. 9. Vagus nerve, with 9’, its nucleus of termination. 10. Lateral dorsal acoustic nucleus. 11. Nucleus ambiguus (nucleus of origin of motor fibers of glossopharyngeal, vagus, and cerebral portion of spinal

accessory). 12. Gracile nucleus. 13. Cuneate nucleus. 14. Head of posterior column, with 14’, the lower sensory root of trigeminal nerve. 15. Fasciculus solitarius. 16. Anterior external arcuate fibers, with 16’, the nucleus arcuatus. 17. Nucleus lateralis 18. Nucleus

of fasciculus teres. 19. Ligula.

Medulla-Pons Junction

Caudal Pons

Caudal Pons

Pons

Rostral Pons

                                                                             

             

Coronal section of the pons, at its upper part.

Rostral Pons

Pons- Mesencephalon Junction

Mesencephalon

Mesencephalon

Mesencephalon- Diencephalon Junction