Epineurium The structure indicated is the epineurium of a nerve. Nerves are surrounded by three layers of connective tissue: Endoneurium Perineurium Epineurium The endoneurium is a delicate layer of connective tissue which surrounds individual axons.  Collections of axons are known as nerve fascicles; the perineurium surrounds each nerve fascicle, and consists of several concentric layers. The epineurium is the outermost layer of connective tissue which encloses the whole nerve. It is composed of dense irregular connective tissue and encloses all the nerve fascicles together with any blood vessels which supply the nerve.

Vestibulocochlear Nerve

Vestibulocochlear Nerve The structure indicated is the vestibulocochlear nerve (cranial nerve VIII). The vestibulocochlear nerve consists of a vestibular branch and a cochlear branch. The vestibular branch is responsible for balance, and the cochlear branch is responsible for hearing. It originates laterally in the cerebellopontine angle and passes together with the facial nerve into the internal acoustic meatus of the temporal bone.   Cochlear nerve Bipolar sensory neurons in the organ of coorti pass impulses from the hair cells of the cochlear via the peripheral axonal process to the spiral ganglia (this is the collection of cell bodies of the …

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vestibulocochlear nerve

Optic Nerve

Optic Nerve The structure indicated is the optic nerve (cranial nerve II). The optic nerve is the second cranial nerve and is responsible for vision. Similar to the first cranial nerve (olfactory nerve), the optic nerve is not a true nerve but is rather an extension of the brain (diencephalon), which means it is technically a part of the central, rather than peripheral nervous system. The primary sensory neurons are the bipolar cells of the retina; these synapse on ganglion cells, the axons of which form the optic nerve which then passes via the optic canal to join with the …

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optic nerve

Facial Nerve

Facial Nerve The structure indicated is the facial nerve (cranial nerve VII). The facial nerve is responsible for supplying the muscles of facial expression. In addition, the facial nerve provides taste sensation to the anterior 2/3 of the tongue and secretomotor function to the salivary, lacrimal, nasal and palatine glands. The facial nerve originates from the cerebellopontine angle, laterally at the junction between the pons and the medulla. It has two roots: a motor root and the nervus intermedius, which carries the parasympathetic and sensory fibres. Intracranial branches Greater petrosal nerve Nerve to stapedius Chorda tympani Extracranial branches Posterior auricular …

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facial nerve


Thalamus The structure indicated is the thalamus. The thalamus is the largest of the structures which comprises the diencephalon. The diencephalon consists of: Epithalamus Thalamus Subthalamus Hypothalamus The thalamus essentially acts as a sort of “relay” for the brain, consisting of several nuclei with reciprocal connections to and from the cerebral cortex. It also forms important connections with the hippocampus via the mammillo-thalamic tract, and connections with the spinal cord via the spinothalamic tract which transmits peripheral information regarding pain, temperature and crude touch. The thalamus is therefore important in several functions including, sleep, wakefulness and arousal, consciousness, and sensory/motor …

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Pituitary Gland

Pituitary Gland The structure indicated is the pituitary gland. The pituitary gland is an endocrine gland located at the base of the brain, and lies within the sella turcica of the sphenoid bone, which is a saddle-shaped depression that encases and surrounds the pituitary gland­. The deepest part of the sella turcica is known as the hypophyseal fossa, anteriorly is the tuberculum sellae, and posteriorly is the dorsum sellae. The sella turcica itself is covered by a fold of dura known as the diaphragma sellae. The pituitary gland releases several hormones which are responsible for the control and regulation of …

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Basilar Artery

Basilar Artery The structure indicated is the basilar artery. The basilar artery is formed from the union of the two vertebral arteries on either side. The vertebral arteries arise from the first part of the subclavian artery. Two other arteries are given off from the first part of the subclavian artery – the internal thoracic artery and the thyrocervical trunk. The vertebral and internal carotid arteries provide the arterial supply to the brain, forming the Circle of Willis at the base of the brain. After the vertebral artery is given off from the subclavian artery, it passes through the transverse …

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basilar artery

Myenteric Plexus

Myenteric Plexus The myenteric plexus, also known as Auerbach’s plexus, together with Meissner’s plexus (submucosal plexus) forms the enteric nervous system which regulates the function of the gastrointestinal system. The myenteric plexus is located between the inner and outer muscle layers of the muscularis externa. The submucosal plexus (Meissner’s plexus), on the other hand, is located in the submucosa. This diagram illustrates the four layers of the gastrointestinal tract: Mucosa – consists of 3 layers Epithelium Lamina Propria Muscularis Mucosae Submucosa – connective tissue, submucosal plexus and blood vessels/lymphatics Muscularis Externa – 3 muscle layers in the stomach, 2 in …

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Myenteric Plexus

Spinothalamic Tract

Spinothalamic Tract This diagram illustrates the spinothalamic tract (also known as the anterolateral system/ventrolateral system). The spinothalamic tract is one of the ascending sensory tracts which conveys sensory information from the periphery to the central processing systems. There are three main ascending (afferent) pathways which convey sensory information: Dorsal column medial lemniscus system Spinocerebellar tracts Spinothalamic tracts (anterolateral system) The spinothalamic tract is responsible for conveying the modalities of crude touch, pressure, pain and temperature. The tract is comprised of a three neurone sequence, which terminates in the somatosensory cortex of the postcentral gyrus: First order neurone: information carried from …

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Spinothalamic Tract

Corpus Callosum

Corpus Callosum The structure indicated is the corpus callosum of the brain. The corpus callosum is a bundle of neural fibres which connects the left and right hemispheres of the brain, and is the largest collection of white matter in the brain. It is one of five commissures in the brain. A commissure refers to nerve fibres which cross the midline at their original level. This differentiates a commissure from decussation, which is when neural fibres cross at a different level to their original level. The five commissures of the brain are as follows: Anterior commissure Posterior commissure Corpus callosum …

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Corpus Callosum