Lab Manual - Brain, Cranial Nerves, and Cranial Cavity

Assignments:

• Before lab:
  1. Complete the learning module entitled Cranial Nerves.
  2. Review the Prelab Learning Module.
  3. Review the Steps of Dissection and Dissection Videos.
• During lab:
  1. Follow the steps of the dissection procedure in the Lab Manual (this page).
  2. Be certain to identify all of the Review Items.
• After lab:
  1. Read the Dissector Answers to cover the Learning Objectives for this lab.
  2. Read the Clinical Case for this lab.
  3. Review the Practice Questions for this lab.

Learning Objectives:

Upon completion of this session, the student will be able to:

1. Identify the three cranial fossae and openings for the spinal cord, cranial nerves, arteries (internal carotid and middle meningeal), and the internal jugular vein.
2. Identify the following surface features of the brain: cerebrum, cerebellum, brainstem; longitudinal fissure; lateral sulcus (including opercula) and central sulcus; and the pre- and post-central gyri; frontal, parietal, temporal, occipital and insular lobes.
3. Identify the following features on an axially sliced brain: gray and white matter; cerebral cortex; lateral ventricles; third ventricle.
4. Identify each of the 12 pairs of cranial nerves, both on the brain and in the anterior, middle and posterior cranial fossae.

Procedure:

1. Review the osteology of the skull. (Play movie; View images: N 2, 6, 7A, 7B, 8, 9, 11, TG 7-05B, 7-05C, 7-06, 7-07, 7-08, 7-57)

Distinguish between the calvaria and the base of skull. Identify the anterior, middle, and posterior cranial fossae, crista galli, greater and lesser wings of sphenoid, sella turcica, clivus, petrous ridge of temporal bone, internal occipital protuberance, and foramen magnum.

Find the following openings: cribriform plate of ethmoid, optic canal, superior orbital fissure; foramen rotundum, f. ovale, f. spinosum, f. lacerum; internal acoustic meatus, jugular foramen, hypoglossal canal; foramina of condyloid and mastoid emissary veins. Examine the base of the skull and the interior of the calvaria for sulci or grooves produced by various sinuses and arteries.

2. Identify the cranial nerves within the cranial cavity. (Play movie; View images: N 11, 104, 114, 115, 118, 126, TG 7-07, 7-47, 7-55A, 7-55B)

On the brain, identify the twelve pairs of cranial nerves: olfactory (I), optic (II), oculomotor (III), trochlear (IV), trigeminal (V), abducens (VI), facial (VII), vestibulocochlear (VIII), glossopharyngeal (IX), vagus (X), spinal accessory (XI), hypoglossal (XII). Identify these nerves at their exit foramina on the base of the skull. What cranial nerves exit the skull through the jugular foramen? Identify cervical fibers of the accessory nerve. Identify the internal carotid artery as it perforates the dura and the vertebral arteries in the foramen magnum.

3. Identify the major features of the brain and the ventricular system. (Play movie; View images: N 99, 105, 107, 108, 109, 115, TG 7-49, 7-50A, 7-50B, 7-53B, 7-53C, 7-54

Identify the frontal, parietal, occipital and temporal lobes of the cerebrum, and the longitudinal fissure. On the inferior side find the cerebellum, midbrain, pons and medulla oblongata. Compare the brain to the cranial fossae, note how the lobes fit in the fossae and relate to the dural folds.

Examine the sectioned brain. Note the cavities of the brain, the ventricles, identifying the lateral ventricles, separated by the septum pellucidum, interventricular foramina, third ventricle, cerebral aqueduct and fourth ventricle. Note the choroid plexus; where is it found and what is its function? Can you trace the flow of cerebrospinal fluid (CSF) from its secretion until it is reabsorbed by the venous system? See Objectives Trace the circulation of cerebrospinal fluid from its production at the choroid plexuses in the ventricles to its reabsorption into the venous system at the arachnoid granulations of the superior sagittal sinus.

Brain structures in MRI

Ventricles of the brain