By K. Ugrasal. Maryville University of Saint Louis.
Peripheral Nervous © The McGraw−Hill Anatomy purchase 1 mg propecia fast delivery, Sixth Edition Coordination System Companies propecia 1mg mastercard, 2001 414 Unit 5 Integration and Coordination FIGURE 12 propecia 5mg amex. The remaining pairs of spinal nerves emerge below the vertebrae ops in adults who were first exposed to the virus as children propecia 1mg with mastercard, and is for which they are named. Treatment may involve large doses of the antiviral drug acyclovir (Zorivax). A spinal nerve is a mixed nerve attached to the spinal cord by a posterior (dorsal) root, composed of sensory fibers, and an A spinal nerve divides into several branches immediately anterior (ventral) root, composed of motor fibers (fig. The small The posterior root contains an enlargement called the spinal meningeal branch reenters the vertebral canal to innervate the (sensory) ganglion, where the cell bodies of sensory neurons are meninges, vertebrae, and vertebral ligaments. The axons of sensory neurons convey sensory impulses called the posterior ramus, innervates the muscles, joints, through the posterior root into the spinal cord, where synapses and skin of the back along the vertebral column (fig. The anterior root consists anterior ramus of a spinal nerve innervates the muscles and skin of axons of motor neurons, which convey motor impulses away on the lateral and anterior side of the trunk. A spinal nerve is formed as the fibers from the anterior rami innervate the limbs. The rami com- The disease herpes zoster, also known as shingles, is a viral infection of the spinal ganglia. Herpes zoster causes painful, municantes are composed of a gray ramus, containing unmyeli- often unilateral, clusters of fluid-filled vesicles in the skin along the nated fibers, and a white ramus, containing myelinated fibers. The disease devel- This arrangement is described in more detail in chapter 13. Peripheral Nervous © The McGraw−Hill Anatomy, Sixth Edition Coordination System Companies, 2001 Chapter 12 Peripheral Nervous System 415 Lesser occipital nerve Greater auricular nerve Transverse cervical nerve Supraclavicular nerve Phrenic nerve FIGURE 12. Objective 6 List the spinal nerve composition of each of the Knowledge Check plexuses arising from the spinal cord. List the number of nerves in each of the five regions of the Objective 7 List the principal nerves that emerge from the vertebral column. What are the four principal branches, or rami, from a spinal nerve, and what structures does each innervate? It is formed by the anterior rami of the first four cervical nerves Except in thoracic nerves T2 through T12, the anterior rami of (C1–C4) and a portion of C5 (fig. Branches of the cervi- the spinal nerves combine and then split again as networks of cal plexus innervate the skin and muscles of the neck and por- nerve fibers referred to as nerve plexuses. Some fibers of the cervical plexuses of spinal nerves: the cervical, the brachial, the lumbar, plexus also combine with the accessory and hypoglossal cranial and the sacral. Nerves emerging from the plexuses are named nerves to supply dual innervation to some specific neck and pha- according to the structures they innervate or the general course ryngeal muscles (see fig. Peripheral Nervous © The McGraw−Hill Anatomy, Sixth Edition Coordination System Companies, 2001 416 Unit 5 Integration and Coordination TABLE 12. Motor impulses through fibers from the anterior branches of spinal nerves C5 through the paired phrenic nerves cause the diaphragm to contract, mov- T1 and a few fibers from C4 and T2. The roots converge to form trunks, and The nerves of the cervical plexus are summarized in the trunks branch into divisions. Brachial Plexus The brachial plexus may suffer trauma, especially if the clavi- cle, upper ribs, or lower cervical vertebrae are seriously frac- The brachial plexus is positioned to the side of the last four cer- tured. Occasionally, the brachial plexus of a newborn is severely vical vertebrae and the first thoracic vertebra. It is formed by the strained during a difficult delivery when the baby is pulled through anterior rami of C5 through T1, with occasional contributions the birth canal. In such cases, the arm of the injured side is para- lyzed and eventually withers as the muscles atrophy in relation to the from C4 and T2. Each brachial plexus innervates called a brachial block or brachial anesthesia.
Trauma to the Head and Neck The head and neck are extremely susceptible to trauma and blows 5 mg propecia with visa, which are frequently physically debilitating if not fatal buy discount propecia 1mg. Striking the head from the front or back often causes subdural hemorrhage discount propecia 5mg, resulting from the tearing of the superior cerebral veins at their points of entrance to the superior sagittal sinuses purchase propecia 5 mg without a prescription. Blows to the side of the head tend to be less severe because the synostose: Gk. Surface and Regional © The McGraw−Hill Anatomy, Sixth Edition Anatomy Companies, 2001 334 Unit 4 Support and Movement falx cerebelli and tentorium cerebelli (see table 11. With a sudden violent lateral in diagnosing several diseases and body conditions. In a severe lateral blow to the head, The color of the mucous membranes of the mouth may be however, the internal carotid artery may rupture, and a roaring important in diagnosing illness. Pale lips generally indicate ane- sound will be perceived by the injured person as blood quickly mia, yellow lips indicate pernicious anemia, and blue lips are char- fills the cavernous sinuses of the temporal bone. In Addison’s Skull fractures are fairly common in adults but much less com- disease, the normally pinkish mucous membranes of the cheeks mon in children. The cranial bones of a child are resilient, and su- have brownish areas of pigmentation. The cranium of an adult, however, has limited resilience and tends to splinter. A hard blow to the head fre- quently breaks the bone on the opposite side of the skull in what is Thoracic Region called a contrecoup fracture. The sphenoid bone, with its numerous foramina, is the weakest bone of the cranium. It frequently sustains a Developmental Conditions contrecoup fracture as a result of a hard blow to the top of the head. The most frequently fractured bones of the face are the When serious deformities of the chest do occur, they are almost nasal bones and the mandible. Trauma to these bones generally always due to an overgrowth of the ribs. In pigeon breast (pectus results in a simple fracture, which is not usually serious. If the carinatum), the sternum is pushed forward and downward like the nasal septum or cribriform plate of the ethmoid bone is fractured, keel of a boat. In funnel chest (pectus excavatum), the sternum is however, careful treatment is required. If the cribriform plate is pushed posteriorly, causing an anterior concavity in the thorax. The absence of ribs is due to incomplete development of the Whiplash is a common injury to the neck due to a sudden thoracic vertebrae, a condition termed hemivertebrae, and may and forceful displacement of the head (see fig. A whiplash is usually extremely painful rib is attached to the transverse process of the seventh cervical and difficult to treat because of the difficulty in diagnosing the vertebra, and it either has a free anterior portion or is attached to extent of the injury. Pressure of a cervical rib on the brachial The sensory organs within the head are also very prone to plexus may produce a burning, prickling sensation (paresthesia) trauma. The eyes may be injured by sudden bright light, and loud along the ulnar border of the forearm and atrophy of the medial noise can rupture the tympanic membrane of the middle ear. Diseases of the Head and Neck The rapid and complex development of the heart and The head and neck are extremely susceptible to infection, espe- major thoracic vessels accounts for the numerous congenital cially along the mucous membranes lining body openings. Cardiac malformations usually arise from developmen- The cutaneous area of the head most susceptible to infec- tal defects in the heart valves, septa (atrial and/or ventricular), tions extends from the upper lip to the midportion of the scalp. The infection may even spread into the sagittal ve- blood in the left atrium. A ventricular septal defect usually oc- nous sinus, causing venous sinus thrombosis. A boil in the facial curs in the upper portion of the interventricular septum and is region may secondarily cause thrombosis of the facial vein or the generally more serious than an atrial septal defect because of spread of the infection to the sinuses of the skull. Before antibi- the greater fluid pressures in the ventricles and the greater otics, such sinus infections had a mortality rate of 90%.