Lab Manual - Neuroanatomy 2

Assignments:

• Before lab:
  1. Download and review the Lab Overview PowerPoint.
  2. Complete the learning module entitled Introduction to the Autonomic Nervous System I.
  3. Complete the learning module entitled Introduction to the Autonomic Nervous System II.
  4. Review the Prelab Learning Module.
  5. Review the special instructions in the Brain Dissection Guide.
  6. 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. For the brain dissection, follow the steps of the dissection procedure in the PowerPoint presentation entitled Brain Dissection Guide.
  3. 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. Define the scalp, its structural layers, muscles, nerves, and vessels.
2. Identify the arterial supply of the brain.
3. Identify the venous drainage of the brain including the cerebral veins and dural venous sinuses.
4. Identify the parts of the ventricular system and trace the flow of cerebrospinal fluid from production to reabsorption.
5. Identify the following features on axial and coronal slices of the brain: gray and white matter; cerebral cortex; corpus callosum; septum pellucidum; internal capsule; thalamus; hypothalamus; basal nuclei, including the striatum (caudate nucleus, putamen), globus pallidus, substantia nigra, and the subthalamic nucleus.

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 or cranial vault and the base of skull.

Examine the base of the skull and the interior of the calvaria for sulci or grooves produced by various sinuses and arteries. Look for small pits on the inner aspect of the calvaria, the granular fovea, caused by the arachnoid granulations eroding into the inner table of bone.

2. Examine the structure of the scalp. (Play movie; View images: N 11, 26, 99, 101A, 101B, 113, 132, TG 7-07, 7-30, 7-46, 7-49, 7-55, 7-56)

Five layers of tissue cover the bones of the calvaria: (1) Skin, (2) dense subcutaneous Connective tissue, (3) an Aponeurotic layer, the galea aponeurotica with epicranius muscles (occipitalis and frontalis), (4) Loose connective tissue that allows the skin and galea to move, and (5) Pericranium, the periosteum of the skull (S-C-A-L-P). The scalp itself consists of the first three layers. Try to identify the layers on its cut edge. The spread of infection is mainly facilitated through what layer of the scalp?

3. Identify the blood supply to the brain. (Play movie; View images: N 101, 104, 136, 137, 138, 139, 140, 141, 142, TG 7-19, 7-46, 7-47, 7-56A, 7-56B)

Identify the arterial system at the base of the brain: vertebral, anterior and posterior spinal, posterior inferior cerebellar, basilar, anterior inferior cerebellar, superior cerebellar, posterior cerebral, posterior communicating, middle cerebral, anterior cerebral, anterior communicating, and internal carotid. What is the arterial circle of Willis? Consider the broad distribution of each to the brain. Note veins of the cerebral hemispheres.

	Blood vessels of the brain
	Vertebral arteries

4. Identify the features of the cranial cavity and meninges. Open the dural sinuses. (Play movie; View images: N 9, 11, 69, 70, 98, 99A, 99B, 101, 102, 103, 104A, TG 104B, 108, 109, 147, 7-07, 7-19, 7-35, 7-46, 7-47, 7-48, 7-49A, 7-49B, 7-50, 7-51, 7-73)

Examine the arachnoid mater, its extent and attachment to the pia mater (via trabeculae). Consider the subarachnoid space, continuities and content. Enlargements of the subarachnoid space at the base of the brain constitute cisterns. Consider the function of cerebellomedullary, pontine and interpeduncular cisterns. Look for arachnoid granulations (villi). What is their function? Note their impressions on the overlying calvaria. Examine the pia mater on the brain. How does it differ from the arachnoid mater in covering the brain?

Subarachnoid space

Observe the arrangement of the cranial dura mater. Note differences from spinal dura, continuities and layers. Note dural attachment to the calvaria and the base of the skull. Is there any difference? Examine falx cerebri and falx cerebelli (on the left side), tentorium cerebelli, and diaphragma sellae. Are these infoldings periosteal or meningeal? Define attachments and relationship of each and the compartmentalization of the cranial cavity produced by these infoldings. What does each compartment contain? What is the tentorial notch? Observe meningeal arteries in all cranial fossae. Which is the largest? How is it held within the dura? Relation to greater wing of sphenoid? (Significance?) What is the innervation of dura?

Identify superior cerebral veins draining the cerebral cortex into the superior sagittal sinus.

Open each of the following venous sinuses by removing part of its wall; remove the coagulated blood and trace completely: superior sagittal sinus, (lacunae, areas of arachnoid granulations, entrance of superior cerebral veins), inferior sagittal sinus, sinus rectus (straight sinus) (is a portion of the great cerebral vein attached to it?), confluens of sinuses (significance, location, pattern and variations), occipital sinus, transverse sinus (inferior cerebral veins), sigmoid sinus, cavernous sinus (ophthalmic vein, middle cerebral veins), superior petrosal sinus (connects what?), inferior petrosal sinus. Define emissary veins and the mastoid, condyloid, parietal, and ophthalmic emissary veins.

Identify the cavernous sinus on either side of the body of the sphenoid bone. Do the two sides communicate? As they enter the lateral wall of the cavernous sinus, locate the oculomotor nerve (III), trochlear nerve (IV), and the trigeminal nerve (V). Identify the severed end of the internal carotid artery (course? ). Identify the abducens nerve (VI) as it pierces the dura covering the inferior petrosal sinus. Enlarge the opening in the diaphragma sellae and remove the hypophysis (pituitary gland). Determine anterior and posterior lobes and stalk. Locate the middle meningeal artery beneath the dura of the middle cranial fossa, noting its position in the dura and its course and entrance through the foramen spinosum.

5. Identify the major features of 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)

Using a brain knife, cut the brain in the midline. 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.

	Ventricles of the brain
	Brain structures in MRI

6. Section the brain to examine the inner structure of the brain. (View images: NI27A, NI27B, NI48B, NII.87.3, NII.87.4, NII.87.5, NII.87.6, NII.87.7, NII.87.8, NII.87.9)

On the right half of the brain, section the brain transversely through the splenium of the corpus callosum, through the anterior commissure, and through the crus cerebri of the midbrain. Section the left half of the brain coronally through the interventricular foramen.

On the sectioned brain and the brain models, identify inner structures of the brain, including the gray and white matter, the cerebral cortex, the internal capsule (anterior and posterior limbs and genu), thalamus, hypothalamus. Nuclei located near the base of the brain are collectively referred to as the basal nuclei (or basal ganglia in older terminology). Identify the basal nuclei including: the caudate nucleus, putamen, globus pallidus, subthalamic nucleus, and the substantia nigra in the midbrain. The caudate nucleus and putamen are together referred to as the striatum. The putamen and globus pallidus together are referred to as the lentiform nucleus.