1.7 Step 5. Horizontal and descending portions of the facial canal скачать в хорошем качестве

1.7 Step 5. Horizontal and descending portions of the facial canal

These videos have been excerpted from Netter’s Video Dissection Modules on Student Consult.  http://bit.ly/2oEt9CO Step 5 In another preparation, the interior of the mastoid process has been exposed, revealing the horizontal portion and descending portion of the facial canal. Note the lateral semicircular canal above the facial canal and the oval window below it. The descending portion of the canal can be traced to the stylomastoid foramen. Note that the orientation of the anterior and posterior semicircular canals on the right and left sides can be represented by crossed hands with extended index fingers and thumbs. The anterior canal on one side is aligned with the posterior canal of the opposite side. Key Terms • Mastoid process: a prominent, inferiorly projecting part of the temporal bone N6, which can be palpated just posterior to the lobule of the auricle. It serves as an attachment area for the sternocleidomastoid N26, posterior belly of the digastric N53, splenius capitis N171, and longissimus capitis muscles N172. It is not present in infants N14. The process is substantially developed by the age of five and reaches full development near puberty. As it develops it becomes pneumatized and contains many mastoid air cells N94. The air reaches the cells via a posterior extension of the epitympanic recess into what is called the mastoid antrum N94. The medial side of the base exhibits an occipital groove for the occipital artery N10, as it courses toward the back of the head to supply the posterior scalp. Internally, the mastoid process has air- filled pockets of cells that communicate with the middle ear cavity N94. • Facial canal: the canal in the temporal bone that houses the facial nerve. Its external opening is the stylomastoid foramen N12. It ascends vertically from this foramen N94, and just above the level of the stapes it bends anteriorly to become horizontal N94. Anterior to the stapes, it bends medially, where the genu of the facial nerve is located N125. Its intracranial opening is in the upper part of the internal acoustic meatus. • Lateral semicircular canal: the bony canal that houses the lateral semicircular duct. It is also called the horizontal canal, which indicates its orientation. The outer surface of the canal protrudes into the middle ear cavity where it forms the prominence of the lateral semicircular canal; here it lies just dorsal to the bony prominence of the facial canal N94. In terms of the oval window (and footplate of the stapes), it is useful to remember that the ventral to dorsal sequence is: oval window facial canal lateral semicircular canal. It is the ampulla of the canal that lies above the oval window N95. • Oval window: the oval opening on the medial wall of the middle ear cavity which opens into the perilymphatic fluid-filed vestibule of the inner ear. It is also called the fenestra vestibuli (window of the vestibule). The footplate of the stapes is attached to its rim by an annular ligament N92 N94. • Stylomastoid foramen: the foramen that is wedged between the styloid process and the mastoid process N12. It transmits the facial nerve and a small branch of the occipital artery (stylomastoid artery). The opening represents the distal end of the facial canal. 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.