Comparison of the different levels of the pons The midbrain 2 cm in length It connects the po...
Comparison of the different levels of the pons
The midbrain
- 2 cm in length
- It connects the pons & the cerebellum with the forebrain
- It’s traversed by a narrow channel called cerebral aqueduct (Filled with CSF)
The anterior surface
- There’s a deep depression in the midline (Inter peduncular fossa)
- Inter peduncular fossa is bounded on either side by the crus cerebri
- Many blood vessels perforate the floor of the IPF & it’s called the posterior perforated substance
- Occulomotor nerve emerges from the groove on the medial side of the crus cerebri
The posterior surface
- There are 4 colliculi (2 superior & 2 inferior)
- Superior colliculi : Centers for visual reflexes
- Inferior colliculi : Lower auditory centers
- In the midline below the inferior colliculi, the trochlear nerve emerges
- The lateral surface : Superior & inferior brachia ascend in an antero – lateral direction
- Superior brachium : Connects superior colliculus to the lateral geniculate body (Nuclei of the thalamus) & the optic tract
- Inferior brachium : Connects inferior colliculus to the medial geniculate body (Nuclei if the thalamus)
Internal structure of the midbrain is considered at 2 levels
- The mid brain has 2 lateral halves : Cerebral peduncles
- Cerebral peduncles are divided into 2 parts by substantia nigra (Pigmented band of grey matter)
- Anterior part : Crus cerebri
- Posterior part : Tegmentum
- There’s a narrow cavity in the midline : Cerebral aqueduct (Connects 3rd & 4th ventricles)
- It’s lined by ependyma
- It’s surrounded by the central grey matter
- Tectum : part of the midbrain posterior to the cerebral aqueduct
- Tectum has superior & inferior colliculi
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