1.1 Step 7: Vertebral artery and suboccipital nerve скачать в хорошем качестве

1.1 Step 7: Vertebral artery and suboccipital nerve

These videos have been excerpted from Netter’s Video Dissection Modules on Student Consult.  http://bit.ly/2oEt9CO Step 7: With the posterior arch of C1 fully exposed, identify the posterior tubercle and the spinous process of C2 and the interval between them. Then incise the ligamentum flavum on either side to fully expose the arch. With rib cutters, section the arch one finger breadth from the posterior tubercle on either side. After the removal of the posterior arch of C1, note the cranial extent of the epidural space, the dura mater and its attachment to the edge of the foramen magnum. Identify the vertebral artery as it lies in the sulcus of the C1 arch. Also identify the C1 spinal nerve emerging between the artery and the arch of C1, the dorsal root ganglion of the C2 spinal nerve, and the nerve itself as it emerges from the dura. Key Terms • Ligamenta flava: “yellow ligaments” that run between, and attach, to adjacent laminae. They are composed almost entirely of yellowish elastic fibers, and their function is to assist in the return to an erect posture after the column is flexed. The ligaments are best seen from the internal surface where they contribute to the roof of the vertebral canal N158. • Posterior arch of C1: a feature of the first cervical vertebra, or atlas, which replaces the laminae. N19 • Posterior tubercle of C1: a feature of the first cervical vertebra, or atlas, which replaces the spinous process. N19 • Epidural space: the space between the walls of the vertebral canal and the dura mater; it is filled with fat, connective tissue, and a plexus of veins (internal vertebral venous plexus) and serves as a padding around the dural sac N169 N166. Needles can be inserted into or through this space to introduce an anesthetic agent N166. • Dura mater: a tube of tough connective tissue that surrounds the brain, spinal cord and spinal nerve roots N165 N166. The dura of the spinal canal is continuous with that of the cranial cavity at the foramen magnum N104 N110, but there is no epidural space in the cranial cavity. The spinal dura extends from the foramen magnum to approximately the level of the second sacral vertebra. It is the outer of three layers called meninges. Below the second sacral vertebra, the dura is represented by a tough, fibrous thread, the external filum terminale, which blends with the posterior longitudinal ligament over the coccyx. Thus the dura is anchored above and below. Dural sleeves extend laterally over each of the spinal nerves and blend with connective tissue at the intervertebral foramina N165 N166. • Foramen magnum: the large opening in the posterior cranial fossa N12 N63. Structures passing through it are the spinal cord, accessory nerves, subarachnoid space N110 N128 and the vertebral arteries N137. • Vertebral artery: a branch of the subclavian artery on either side of the body. It passes superiorly through the transverse foramen (foramen transversarium) of each cervical vertebra except C7, until it reaches C1 N22 N23. Here the artery travels across the posterior arch of C1 N175 before entering the foramen magnum. Inside the skull, the two vertebral arteries join up to form the basilar artery N167 N141 N142 at the base of the medulla oblongata. The basilar artery is the main blood supply to the brainstem. • C1 spinal nerve: also known as the suboccipital nerve; the dorsal ramus of first spinal nerve. It emerges from the spinal cord at the level of the foramen magnum and leaves the vertebral canal by passing between the vertebral artery and the posterior arch of the atlas. It penetrates the posterior atlantoccipital membrane, ramifies in the suboccipital triangle and supplies the rectus capitis minor, the muscles bordering (rectus capitis posterior major and minor, obliquus capitis inferior and superior) and forming the roof of the triangle (semispinalis capitis) N128 N160. • Dorsal root ganglion: the collection of sensory nerve cell bodies in the dorsal root of a spinal nerve. Each ganglion appears as a swelling that lies in the intervertebral foramen close to the point where the dorsal and ventral roots join to form the spinal nerve N166. • 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.