The superior cerebellar artery (SCA) is the second most superior branch from the basilar artery, branching bilaterally just inferior to the origin of the posterior cerebral artery. From its origin at the basilar artery, the SCA first travels laterally, anterior to the pons in the prepontine cistern, passing inferior to the oculomotor nerve that separates it from the posterior cerebral artery. The SCA then curves posteriorly and travels through the ambient cistern, passing just inferior to the trochlear nerve before traveling posteromedially to the lateral edges of the quadrigeminal cistern, coming in close proximity to the contralateral SCA.

The obturator nerve originates from the anterior rami of L2–L4 through the lumbar plexus. It travels inferiorly into the pelvis medial to both the femoral nerve and psoas major muscle, exiting the pelvis just inferior to the pubic bone along with the obturator vessels via the obturator canal. The obturator nerve splits into two terminal branches, the anterior and posterior divisions of the obturator nerve, around the adductor brevis muscle as it exits the pelvis into the thigh. The anterior division ultimately provides motor innervation to adductor longus, adductor brevis, and gracilis, as well as sensory innervation to portions of the inner thigh and the hip joint.

The cerebral aqueduct is a canal that bridges the cerebrospinal fluid flow between the third and fourth ventricles of the brain. It is very narrow compared to these adjacent ventricles. Additionally, it is the only large major structure in the cerebrospinal fluid flow pathway that does not have choroid plexus. It is positioned just anterior to the quadrigeminal plate of the midbrain (made up of superior and inferior colliculi).

The nucleus ambiguus is the special visceral efferent nucleus for CN IX (glossopharyngeal nerve) and CN X (vagus nerve) that resides in the rostral lateral medulla just dorsal to the inferior olivary nucleus. It supplies motor fibers to the palate and pharynx and mediates the efferent arm of autonomic vagal output, increasing parasympathetic tone in the heart and gut. The name “nucleus ambiguus” refers to the fact that the nucleus is notoriously difficult to locate on dissection or imaging, and its location varies substantially across different species.

The dorsal/posterior nerve root is an afferent nerve that brings in sensory information from the periphery to the spinal cord. The dorsal root ganglion, containing the cell bodies of the sensory afferent fibers, is located outside the spinal canal. These fibers then travel in the posterior root and enter the spinal cord via the dorsal horn, where they synapse with neurons in various laminae (substantia gelatinosa) before ascending either in the dorsal columns ipsilaterally (touch, vibration, and proprioception) or in the spinothalamic tract contralaterally (pain and temperature).

The optic nerve (formed by a collection of axons of retinal ganglion cells) originates from the retina, which is in the back of the eye (dark side of the moon), traveling posteriorly through the optic canal, where it is covered completely by dura mater (dura mater is Latin for “tough mother”). It functions to transmit sight (special sense) from the eye to the brain, crossing paths at the optic chiasm, allowing fibers from each optic nerve to reach both sides of the brain. It also plays an important role in the pupillary light reflex, during which both pupils will constrict or dilate in response to a light or dark environment, respectively.

The posterior inferior cerebellar artery (PICA) branches from the V4 segment of the vertebral artery at an acute downward angle on its way to help perfuse the cerebellum (meaning “little brain” in Latin) along with the anterior inferior cerebellar artery and the superior cerebellar artery. PICA is the largest branch of the vertebral artery.

The posterior limbs of the internal capsule (PLICs) are bilateral subcortical white matter tracts lateral to the thalamus and medial to the globus pallidus and putamen (together referred to as the lentiform nucleus, derived from the Latin, meaning “lens-shaped”).

The pia mater is the innermost layer of meninges that adheres directly to the surface of the brain, invaginating into its folds and sulci, and is highly vascularized with leptomeningeal blood vessels. Together with the arachnoid mater, these layers are referred to as leptomeninges.

The C6 nerve root is one of the roots contributing to the brachial plexus (also known as the rete plexus). And just like the C5 nerve root, its fibers are contained within four of the five peripheral branches of the brachial plexus.

Though it is also called the lateral femoral cutaneous nerve, the name lateral cutaneous nerve of the thigh has become preferred, given the nerve is not a branch of the femoral nerve, but rather a nerve originating in the lumbar plexus. From the posterior division of the L2 and L3 nerve roots, the lateral cutaneous nerve of the thigh travels inferolaterally, just under the iliolumbar ligament and lateral to the psoas major muscle, then courses through the iliac fossa lying on the anterior surface of the iliacus muscles, ultimately passing deep to the inguinal ligament and just medial to the anterior superior iliac spine.

The author describes his parents’ upbringing and move to New York around the time of the Great Depression. The young Weinberg is encouraged to read widely and later takes inspiration from Norse myths from the Poetic Edda.

The recurrent laryngeal nerve originates from the vagus nerve near the cervicothoracic junction. The right recurrent laryngeal nerve branches from the vagus nerve at or slightly above the level of the right clavicle, after the vagus nerve passes over the right subclavian artery. After branching from the vagus nerve, the right recurrent laryngeal nerve loops posteriorly under the right subclavian artery and then ascends back up the neck, traveling in the right tracheoesophageal groove on its ascent.

Derived from the Latin word for “parts to be ashamed of,” the pudendal nerve provides sensorimotor innervation to the penis, clitoris, scrotum, labia majora, inferior vaginal canal, and anus. It plays a vital role in gastrointestinal and genitourinary function.

The area postrema is located in the posterior inferior portion of the medulla, just inferior to the level of the fourth ventricle. With the absence of a blood-brain barrier (BBB), the area postrema contains specialized ependymal cells that function as chemoreceptors, detecting changes in the blood, especially the concentration of toxins, and reflexively inducing vomiting, earning it the name of chemoreceptor trigger zone.