Prelab Images - Scalp, Cranial Cavity, Meninges & Brain

Prelab Images - Scalp, Cranial Cavity, Meninges & Brain

Prelab should consist of reading the lab manual and dissector answers and viewing the dissection video. To begin your study, you may find it useful to look over the Netter's Atlas images listed below.
1. Review the osteology of the skull. (Play movie)
Plate 7 identifies the calvaria of the skull and plates 8, 9, and 11 show the base of the skull from different angles. The anterior, middle, and posterior cranial fossae are identified in plate 9. Plates 6 and 9 label the crista galli, greater and lesser wings of the sphenoid bone, and sella turcica. Plate 9 shows the clivus, petrous ridge of temporal bone (labeled petrous part), and the internal occipital protuberance. Plates 6, 8, and 11 label the foramen magnum. Plates 6 and 9 idenitfy the cribriform plate of the ethmoid bone. Plate 2 (bottom) and 11 give views of the optic canal and superior orbital fissure. Plate 11 labels all of the following: foramen rotundum, foramen ovale, foramen spinosum, foramen lacerum, internal acoustic meatus, jugular foramen, hypoglossal canal, and the foramina of condyloid and mastoid emissary veins (labeled mastoid foramen and condylar canal). Plates 6, 7, 8, 9, and 11 review the base of the skull and interior of calvaria.
Step 2. Identify the major features of the brain and its ventricular system. (Play movie) The frontal, parietal, occipital, and temporal lobes of the cerebrum are identified in plate 105. The longitudinal fissure is identified in plate 107. This fissure divides the cerebrum into right and left halves (plate 99). Plate 115 shows the cerebellum, midbrain, pons, and medulla oblongata. The midbrain is not labeled, but it is the part of the brain with the cerebral aqueduct passing through it in plate 115. Plate 108 identifies the lateral veintricles, interventricular foramina, third ventricle, cerebral aqueduct, and fourth ventricle. The choroid plexus is also identified in plate 109. The CSF is reabsorbed into the venous system into the superior sagittal sinus via arachnoid granulations (also shown in 109).
Step 3. On the right side, remove the brain. (Play movie)
Plate 101 (top) shows the layers of the scalp (remember SCALP - Skin, dense subcutaneous Connective tissue, Aponeurotic layer composed of galea aponeurotica and epicranius muscles, Loose connective tissue, and Pericranium). The scalp itself consists of the first three layers. Plate 99 (top) also shows a good view of the layers of the scalp and also adds the meninges. See plate 26 for the epicranius (occipitalis and frontalis) muscle.

Other than observing and identifying structures, the dissection procedure involves removal of the brain. This can be accomplished by taking a scalpel and cutting around the head just above the brow ridge. Next, take a saw and saw through the bone that is deep to the cut that you just made to remove the top of the skull. Plate 101 (bottom) shows what it will look like once you have removed the top of the skull. Plates 99 and 101 show superior cerebral veins draining the cerebral cortex. The superior cerebral veins drain the blood into the superior sagittal sinus (midline structure seen in plates 99 and 101). To remove the right half of the brain you will need to lift it up and cut through the cranial nerves emerging from the brainstem on the inferior side of the brain (plate 113 bottom). See plate 11 for where these cranial nerves exit the skull. Next, you will need to cut through the carotid artery, vertebral artery, and spinal cord to remove the brain (see plate 132, top picture).
Step 4. Identify the cranial nerves within the cranial cavity. (Play movie)
Plates 114 and 118 show where the twelve cranial nerves emerge from the brainstem. Plate 115 also shows the trochlear nerve, the only cranial nerve emerging from the posterior side of the brainstem. Plate 11 shows where each cranial nerve leaves the cranium. Plate 104 (top) shows a view similar to the one you may have in lab after removing the brain. Plate 11 and plate 104 (top) both indicate that the glossopharyngeal, vagus, and accessory cranial nerves exit the skull through the jugular foramen. Plate 126 shows a schema of the accessory nerve receiving fibers from the cervical spinal cord. You can see these fibers traveling near the vertebral artery in the top picture of plate 104 (the vertrebal artery is not labeled, but it is the artery that is deep to the vein labeled great cerebral vein).
Step 5. Identify the features of the cranial cavity and meninges. Open the dural sinuses. (Play movie)
Plates 99 and 101 show the arachnoid matter and the trabeculae (not labeled) attaching the arachnoid mater to the pia mater. Plate 108 shows the subarachnoid space, and the cerebellomedullary, pontine, and interpeduncular cisterns. Plates 99 and 101 label arachnoid granulations (villi) poking into the superior sagittal sinus. Plates 99 and 101 both show the dura mater of the skull and its arrangement. Plate 109 also shows the dura mater of the skull and the dura of the spinal cord. Plate 102 labels the falx cerebelli and falx cerebri. Plate 104 labels the tentorum cerebelli. Plate 104 shows the hypophysis (pituitary gland). The stalk of the hypophysis pierces the diaphragma sellae (not labeled). The falx cerebelli, falx cerebri, tentorum cerebelli and diaphragma sellae are all formed by meningeal infoldings. The tentorial notch (not labeled, but can be seen in plate 104) is the large opening in the tentorum cerebelli that allows the brain stem to pass through. The middle meningeal artery is the largest of the meningeal arteries. This artery is a branch of the maxillary artery (69) and can be seen in plates 98 and 99. Comparing plates 9 and 104 shows that the middle meningeal artery runs right over the greater wing of the sphenoid bone. The innervation of the dura is covered in the dissector answers. Plate 103 shows the superior sagittal sinus. Plates 99 and 101 identify lateral lacunae, arachnoid granulations, and superior cerebral veins. Plate 103 shows the inferior sagittal sinus and the great cerebral vein coming together to form the straight sinus. The straight sinus unites with the occipital sinus and superior sagittal sinus at the confluens of sinuses (103). The blood from the confluens of sinus enters the transverse sinus (103). The transverse sinus receives inferior cerebral veins (seen in plate 102, bottom). Plate 103 shows the transverse sinus and greater petrosal sinus uniting to form the sigmoid sinus. Plate 103 shows the sigmoid sinus receiving the lesser petrosal sinus just before passing through the jugular foramen to become the internal jugular vein. Plate 104 shows the ophthalmic vein and middle cerebral vein coming together to from the cavernous sinus. Several important structures pass through the cavernous sinus and will be discussed soon (plate 104 (bottom)). Plate 98 shows some of the emissary veins (veins that connect scalp or face with dural sinuses). Plate 70 shows the superior ophthalmic vein which also acts as an emissary vein. Plate 104 (bottom) shows the oculomotor nerve (III), trochlear nerve (IV), trigeminal nerve (V), abducens nerve (VI), and internal carotid artery as they pass through the cavernous sinus. Plate 104 (top, right side) shows the path the cranial nerves and carotid artery take as they approach the cavernous sinus. Plate 104 shows the location of the pituitary gland, which you are to remove. Plate 147 shows the pituitary gland with its anterior (pink colored in plate 147) and posterior lobes and stalk (infundibulum). Plate 104 shows the middle meningeal artery coming through the foramen spinosum (foramen spinosum labeled in plate 11).
Step 6. Identify the blood supply to the brain on the sectioned and plastinated brains. (Play movie)
The vertebral artery is shown in plate 136. The two vertebral arteries (see 138) each give off a posterior inferior cerebellar artery (which in turn gives off posterior spinal artery branches) and a contribution to the anterior spinal artery before the vertebral arteries unite to form the basilar artery. The basilar artery gives off anterior inferior cerebellar and superior cerebellar before the basilar artery splits into two posterior cerebral arteries. The internal carotid artery sends a posterior communicating artery to the posterior cerebral artery (138). The internal carotid also has middle cerebral and anterior cerebral branches (138). The two anterior cerebral branches are connected together by the anterior communicating artery. This forms the circle of Willis (139). Plates 140, 141, and 142 show the distribution of the arteries of the brain (you do not have to know them in too much detail). Plate 137 shows a schema of the blood supply to the brain, which may be helpful. Plate 101 shows the veins of the cerebral hemisphere. Plate 104 (top) also shows the carotid artery as it pierces the dura.