1.7 Step 4. Facial canal скачать в хорошем качестве

1.7 Step 4. Facial canal

These videos have been excerpted from Netter’s Video Dissection Modules on Student Consult.  http://bit.ly/2oEt9CO Step 4 Adult temporal bone preparations, like this one from the right side, usually show the course of the facial nerve through the middle ear. Here the internal acoustic meatus has been painted yellow to show the entry point for the 7th and 8th cranial nerve, and the roof of the meatus has been removed to show the facial canal. With the preparation opened, the course of the facial canal can be followed. At this point the facial canal and the nerve within it turn posteriorly, to run horizontally along the medial wall of the middle ear cavity. Here it lies just beneath the prominence of the lateral semicircular canal, and just above the oval window. In this preparation, the mastoid process has been split, so that the further course of the facial nerve and canal can be studied. After passing beneath the lateral semicircular canal and over the oval window, the nerve and canal make a sharp downward turn toward the stylomastoid foramen. At the point where the facial nerve bends inferiorly, there is a small projection of bone that points to the oval window. This is the pyramidal eminence, which is a hollow structure containing the stapedius muscle. The tendon of the muscle emerges from a small aperture at the tip of the eminence and attaches to the stapes. Key Terms • Internal acoustic meatus: a canal in the temporal bone of the skull that transmits the vestibulocochlear and facial nerves and the labyrinthine artery. Its entrance is near the center of the posterior slope of the temporal bone. It is about one cm in length and ends at the beginning of the facial canal. N8 N13 • Facial nerve: a complex nerve with five functional components, including fibers associated with: 1) the sensation of taste for the palate and anterior two-thirds of the tongue; 2) innervation of the muscles of facial expression, the posterior belly of the digastric, stylohyoid, and the stapedius muscles; 3) visceral efferent (parasympathetic) innervation of the submandibular, sublingual and lacrimal glands; 4) somatic afferent fibers associated with the external surface of the tympanic membrane, external auditory meatus and back of the auricle; and 5) visceral afferent innervation of the soft palate and nasopharynx. The facial nerve emerges from the brainstem at the junction of the pons and medulla and has both a motor root and also a sensory/parasympathetic root called the intermediate nerve. The two roots enter the internal acoustic meatus and then combine to form a single trunk which constitutes the facial nerve N124. This trunk enters the facial canal within the temporal bone. It first runs laterally and then makes a sharp bend, where the geniculate ganglion is found N97 and the greater petrosal nerve is given off N43 N125. The nerve then courses posteriorly in a horizontal direction along the medial wall of the middle ear cavity. After passing over the oval window and footplate of the stapes, the nerve bends inferiorly within the canal, gives off a branch to the stapedius muscle, and then descends toward the stylomastoid foramen N10 N12 N94. Just before exiting the foramen, it gives off the chorda tympani nerve, which ascends across the lateral wall of the middle ear cavity N94. • Vestibulocochlear nerve (CN VIII): emerges from the brainstem at the junction of the pons and medulla and immediately anterior to the flocculus of the cerebellum N115. It consists of two divisions, vestibular and cochlear, which are fused from the brain stem to the point where the nerve enters the internal acoustic meatus N13 N97. Within the meatus, the two divisions separate, and the cochlear nerve innervates parts of the inner ear concerned with the perception of sound while the vestibular nerve innervates parts of the inner ear associated with and balance and equilibrium. ABOUT: The project was made possible by several very dedicated faculty and staff at University of North Carolina, Chapel Hill--especially O.W. Henson and Noelle A. Granger--and partner schools, and by a grant from the Fund for the Improvement of Post-Secondary Education of the US Department of Education. This channel includes over 400 short videos highlighting the steps in a full-body human dissection in the gross anatomy lab. Each step is narrated and key structures labeled.