The cranial nerves

The hypoglossal nerves are exclusively motor; they supply the genio-hyoidei and the extrinsic and intrinsic muscles of the tongue except the glosso-palatini. They are usually designated as the twelfth pair of cranial nerves.

The glosso-palatine nerve (sensory root or pars intermedia of facial, nerve of Wrisberg) contains both sensory and motor fibers.

The Sympathetic Ganglia of the Head and Their Associations with the Cranial Nerves

The sympathetic system of the head, like that of the remainder of the body described below, is arranged in the form of a continuous gangHated plexus subdivided into sub-plexuses.

The abducens (or sixth nerve) on each side arises from the cells of a nucleus which lies in the grey substance of the floor of the fourth ventricle in the region of the inferior part of the pons.

The spinal accessory nerve [n. accessorius] is exclusively motor. It consists of two parts, the accessory or superior, and the spinal or inferior part.

The facial or seventh nerve is purely motor. It is accompanied a short distance by a bundle usually called its sensory root or the intermediate nerve.

The vagus or pneumogastric nerves are the longest of the cranial nerves, and they are remarkable for their almost vertical course, their asymmetry, and their extensive distribution, for, in addition to supplying the lung and stomach, as the name ' pneumo-gastric ' indicates, each nerve gives branches to the external ear, the pharynx, the larynx, the trachea, the oesophagus, the heart, and the abdominal viscera. They are commonly referred to as the tenth pair of cranial nerves.

The trigeminus is the largest of the cranial nerves with the exception of the optic. It is usually described as the fifth cranial nerve and as possessing both a sensory and a motor root.

The glosso-pharyngeal or ninth cranial nerves are mixed nerves and each is attached to the medulla by several roots which enter the posterolateral sulcus, dorsal to the anterior end of the olivary body and in direct line with the facial nerve.

The fibers of each trochlear or fourth nerve (or patheticus) spring from the cells of a nucleus which lies in the grey substance of the floor of the cerebral aqueduct in hne with the oculo-motor nucleus, but in the region of the inferior quadri-geminale bodies.

The vestibular nerve is purely sensory. With the peripheral processes of its cells of origin terminating in the neuro-epithelium of the semicircular canals and the vestibule, and their central processes conveying impulses which are distributed to the gray substance of the cerebellum and spinal cord, the nerve comprises a most important part of the apparatus for the equilibration of the body.

The oculo-motor or third cranial nerve is a purely motor nerve. Each supplies seven muscles connected with the eye, two of which, the sphincter of the iris and cihary muscle, are within the ocular bulb.

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