Identify the structure indicated by the black arrow in the image below:
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Options:
explanation: The image shows a stained axial section through the midbrain level of the brainstem. The midbrain can be differentiated from the pons or medulla levels of the brainstem by the presence of the large crus cerebri anteriorly (bottom of the image) and the colliculi posteriorly (top of the image). The substantia nigra is a band of pigmented neurons located between the crus cerebri and the tegmentum of the cerebral peduncles in the anterior part of the midbrain. However, the black arrow indicates the cerebral aqueduct, which is a cavity in the midbrain connecting the third and the fourth ventricles that allows the passage of CSF. The aqueduct is located anterior to the tectal plate (the superior and inferior colliculi of the midbrain).
name: Substantia nigra
label: d
answer: no
explanation: The image shows a stained axial section through the midbrain level of the brainstem. The midbrain can be differentiated from the pons or medulla levels of the brainstem by the presence of the large crus cerebri anteriorly (bottom of the image) and the colliculi posteriorly (top of the image). The inferior colliculi are the two rounded prominences located in the tectum of the midbrain, inferior to the superior colliculi, on the posterior surface. However, the black arrow indicates the cerebral aqueduct, which is a cavity in the midbrain connecting the third and the fourth ventricles that allows the passage of CSF. The aqueduct is located anterior to the tectal plate (the superior and inferior colliculi of the midbrain).
name: Inferior colliculi
label: e
answer: no
explanation: The image shows a stained axial section through the midbrain level of the brainstem. The midbrain can be differentiated from the pons or medulla levels of the brainstem by the presence of the large crus cerebri anteriorly (bottom of the image) and the colliculi posteriorly (top of the image). The black arrow indicates the cerebral aqueduct, which is a cavity in the midbrain connecting the third and the fourth ventricles that allows the passage of CSF. The aqueduct is located anterior to the tectal plate (the superior and inferior colliculi of the midbrain).
name: Cerebral aqueduct
label: a
answer: yes
explanation: The image shows a stained axial section through the midbrain level of the brainstem. The midbrain can be differentiated from the pons or medulla levels of the brainstem by the presence of the large crus cerebri anteriorly (bottom of the image) and the colliculi posteriorly (top of the image). The periaqueductal grey matter is the grey matter surrounding the midline structure indicated by the black arrow, which is the cerebral aqueduct. This is a cavity in the midbrain connecting the third and the fourth ventricles that allows the passage of CSF. The aqueduct is located anterior to the tectal plate (the superior and inferior colliculi of the midbrain).
name: Periaqueductal gray matter
label: b
answer: no
explanation: The image shows a stained axial section through the midbrain level of the brainstem. The midbrain can be differentiated from the pons or medulla levels of the brainstem by the presence of the large crus cerebri anteriorly (bottom of the image) and the colliculi posteriorly (top of the image). The crus cerebri are the anterior regions of the cerebral peduncles, allowing the passage of the fibres of the corticospinal tract. However, the black arrow indicates the cerebral aqueduct, which is a cavity in the midbrain connecting the third and the fourth ventricles that allows the passage of CSF. The aqueduct is located anterior to the tectal plate (the superior and inferior colliculi of the midbrain).
name: Crus cerebri
label: c
answer: no

Correct answer: a