Brain

Precentral Gyrus

Precentral Gyrus The structure indicated is the precentral gyrus. A gyrus is a ridge on the cerebral cortex, and is usually surrounded by grooves, known as sulci. Fissures are larger than sulci and divide the brain into lobes, as well as dividing the brain into right and left hemispheres. The sulci anterior to the precentral gyrus is known as the precentral sulcus. This sulcus lies parallel to the central sulcus (also referred to as the fissure of Rolando/Rolandic fissure). The central sulcus separates the parietal lobe from the frontal lobe. The precentral gyrus contains the primary somatomotor cortex. Learn more …

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Precentral Gyrus

Hypoglossal Nerve

Hypoglossal Nerve The structure indicated is the hypoglossal nerve (cranial nerve XII). The hypoglossal nerve carries general somatic efferent nerve fibres and is responsible for motor innervation to the extrinsic and intrinsic muscles of the tongue. It arises from the hypoglossal nucleus located in the caudal brain stem and emerges from the preolivary sulcus in the ventromedial aspect of the medulla oblongata from several rootlets. The preolivary sulcus separates the olive from the medullary pyramids. The hypoglossal nerve then passes through the subarachnoid space and exits the skull through the hypoglossal canal. The extrinsic muscles of the tongue are as …

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Hypoglossal Nerve

Cortical Homunculus

Cortical Homunculus The diagram illustrates the cortical homunculus. The cortical homunculus visually portrays the anatomical divisions of the primary motor cortex and the primary somatosensory cortex. The word “homunculus” comes from the Latin word which translates as “little man”. It represents how our body is perceived within the brain and how the neurons are distributed in these areas in order to create this perception. What immediately stands out is that the size of a body area is not proportional to its representation in the cortical homunculus – certain areas such as the hands, lips and face occupy disproportionately large areas …

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Cortical Homonculus

Anterior Communicating Artery

Anterior Communicating Artery The structure indicated is the anterior communicating artery. The anterior communicating artery connects the left cerebral artery to the right cerebral artery. It is one of the blood vessels which contributes to the arterial Circle of Willis – an anastomosis of arterial vessels located on the base of the brain, consisting of the following arteries: Anterior cerebral artery Anterior communicating artery Internal carotid artery Posterior cerebral artery Posterior communicating artery The anterior cerebral artery also gives rise to small collateral vessels which supply the frontal lobes and basal forebrain. This vessel is a common site for the …

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Anterior Communicating Artery

Cerebral Aqueduct

Cerebral Aqueduct The structure indicated by the arrow is the cerebral aqueduct. The cerebral aqueduct (of Sylvius) forms part of the ventricular system of the brain which connects the third ventricle located in the diencephalon, to the fourth ventricle located in the brainstem. The ventricular system of the brain is made up of four ventricles: 2 lateral ventricles (found in the telencephalon) Third  ventricle (found in the diencephalon) Fourth ventricle (found in the rhombencephalon) The interventricular foramen (foramen of Monro) connects the lateral ventricles to the third ventricle. The cerebral aqueduct connects the third ventricle to the fourth ventricle. If …

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Cerebral Aqueduct

Inferior Colliculi

Inferior Colliculi The inferior colliculi together with the superior colliculi, are collectively referred to as the corpora quadrigemina and form the roof of the midbrain. The word colliculus actually means “lower hill” in Latin, describing the appearance of these structures. The superior colliculi are part of the visual system, whereas the inferior colliculi are involved in the auditory system. Auditory fibres project to the inferior colliculi, which then in turn project to the medial geniculate nucleus of the thalamus. From here, the fibres project to the auditory cortex within the temporal lobe. Learn about the basic anatomy of the brain …

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Inferior Colliculi

Occipital Lobe

Occipital Lobe The occipital lobe is highlighted in purple. There are four main lobes of the brain: frontal parietal temporal occipital The occipital lobe is responsible for processing visual information, and is often referred to as the visual cortex. It is the smallest of the four lobes and is located posteriorly in the cranial cavity, underneath the occipital bone. Learn more about the anatomy of the brain in this video.

Occipital lobe highlighted in purple