Identifying Structures of the Brain

The falx cerebelli is a dural fold that separates the two cerebellar hemispheres. The tentorium cerebelli is the dural fold that separates the cerebrum from the cerebellum. A ventricle is a fluid filled cavity within the cerebrum through which cerebrospinal fluid circulates. The pia mater is the deepest, thin meningeal layer that covers the surface of the brain.

The meninges consist of three layers of connective tissue that surround the central nervous system. Dura mater is the thick outermost layer and serves to partition the central nervous system and meninges from the rest of the body. Arachnoid mater is the loose middle layer with a web-like appearance and helps cushion and protect the central nervous system. The subarachnoid space exists between the arachnoid and pia mater and is filled with cerebrospinal fluid. Pia mater is the delicate inner layer that adheres to the surface of the brain and spinal cord, creating one final barrier.

The corpus callosum is a wide bundle of neural fibers that connects the left and right cerebral hemispheres, allowing for interhemispheric communication. It consists of approximately 200-250 million axonal projections, making it the largest white matter structure in the brain (it has a high myelin content, thus facilitating faster information transmission).

The fornix is part of the limbic system; it allows for communication from the hippocampus to the mammillary bodies and then onto the thalamus. The thalamus is a relay station for sensory and motor signals to the cerebral cortex. The tectum is the dorsal portion of the midbrain.

The precentral gyrus is an important fold found in the frontal lobe and is a landmark for the primary motor area. The parietal lobe contains another important gyrus called the postcentral gyrus, which is the landmark for the somatosensory area of the cerebral cortex. The primary auditory area is located in the temporal lobe while the primary visual area is located in the occipital lobe. The insula is a structure that lies within the lateral fissure. It cannot be seen in the external view of the brain and plays a role in the limbic system.

None of the above-listed structures is part of the pons. The corpora quadrigemina are part of the midbrain, and are involved reflexive head movements in response to visual and auditory stimuli. The mammilary bodies are part of the hypothalamus, and have functions related to memory. The pineal body is part of the epithalamus, and it secretes melatonin, which helps regulate the sleep-wake cycle.

The structure that connects the brain is called the corpus callosum. The medulla and cerebellum are part of the midbrain and hindbrain respectively. The infundibulum is the stalk of the pituitary gland.

The brainstem consists of the midbrain, pons, and medulla oblongata. The brainstem continues inferiorly to become the spinal cord. The brainstem is responsible for basic living functions, including but not limited to: respiration, circulation (including heart rate), and digestion. As such, any injury to the brainstem would be catastrophic. Additionally ten of twelve cranial nerves pass through the brainstem, going on to provide the face and neck with motor and sensory functions. Furthermore, nerve conduction of the motor and sensory systems of the brain and body pass through the brain stem including the corticospinal tract (involved in motor activity), the posterior column-medial lemniscus pathway (involved in fine touch, vibration sensation, and proprioception), and the spinothalamic tract (involved in pain, temperature, itch, and crude touch).

The three layers are dura, arachnoid, and pia maters. Dura mater is the only one that surrounds the entire central nervous system. Pia mater can be found as denticulate ligaments along the spinal cord when dissected. Arachnoid mater is often removed during a dissection. Thus the most superficial layer is dura, then arachnoid, and pia is the deepest.

The amygdala is the center of emotions in the brain. The hippocampus is an area of learning and memory. The cerebellum is related to coordination of muscle activity. The medulla is for homeostasis of vital body functions.

The cerebral aqueduct, also known as the aqueduct of Sylvius, contains cerebrospinal fluid (CSF), and connects the third ventricle to the fourth ventricle. The aqueduct allows for the flow of CSF through these areas. The cerebral aqueduct is clinically significant as it can be narrow (stenosis) leading to an obstruction of CSF, potentially leading to non-communicating hydrocephalus.