Anatomy Lab Respiratory and Cardiac 24 w:o picscopy.pptx

Overview: • The deep thoracic muscles located within the intercostal space act primarily with the thoracic cage and are involved in respiration – Previously covered the superficial thoracic muscles included the pectoralis muscles, serratus anterior, and subclavius muscle • The eleven intercostal sp...

Overview: • The deep thoracic muscles located within the intercostal space act primarily with the thoracic cage and are involved in respiration – Previously covered the superficial thoracic muscles included the pectoralis muscles, serratus anterior, and subclavius muscle • The eleven intercostal spaces contain overlapping layers of intercostal muscles – Superficial layer - external intercostal muscles – Middle muscle layer- internal intercostal muscles – Deep muscle layer- varies by location • Anterior group- transverses thoracis muscles • Lateral group- innermost intercostal muscles • Posterior group -the subcostal muscles 1 Intercostal Muscles Use Table 4.2 and p. 312 to answer Muscle Superior attachment Inferior border of ribs External intercostal Inferior border of ribs Internal intercostal Inferior border of ribs Innermost intercostal Subcostal Transversus thoracis Internal surface of lower ribs near their angles Posterior surface of lower sternum Inferior attachment Superior border of ribs below Superior border of ribs below Main Action Elevate ribs during forced inspiration Interosseous part: depresses ribs Interchondral part: elevates ribs During active (forced) respirationb Superior border of Interosseous part: ribs below depresses ribs Interchondral part: elevates ribs During active (forced) respirationb Superior borders of Probably act in same 2nd or 3rd ribs manner as internal below intercostal muscles Internal surface of Weakly depress ribs costal cartilages 2–6 (Proprioception?) 2 descend on the internal surface of the thorax slightly lateral to the sternum and posterior to the upper six costal cartilages and intervening internal intercostal muscles. After descending past the 2nd costal cartilage, the internal thoracic arteries run anterior to the transversus thoracis muscle Other Structures to Know • Internal thoracic arteries p.320 internal mammary arteries terminate in the 6th intercostal space by dividing into the superior epigastric and the musculophrenic arteries • Intercostal neurovascular bundle p.313 Fig 4.15 • Each intercostal space contains a neurovascular bundle • Arranged ”VAN” superior to inferior • Primary bundle is located in the costal groove inferior to each rib and between the internal intercostal muscles and the innermost layer of intercostal muscle • Collateral bundles located just superior to each rib and in reverse order “NAV” 3 Overview: • Lungs attach to the trachea and heart (via the hilum) to function in gas exchange • Pulmonary circulation supplies respiratory tissues; bronchial supplies nonrespiratory tissues • Each lung region corresponds to its region of the chest – Costal (ribs) – Mediastinal (contains the root (hilum)) – Diaphragmatic (base of lungs rest on the diaphragm) – Apex of lungs projects into the root of the neck • Each lung is divided into lobes with its own covering of visceral pleura – Right has three lobes- divided by two fissures – Left has two lobes- divided by one fissure (heart occupies the middle space of left lung) • The pulmonary plexuses enter/leave the hilum 4 Lungs Pleurae Pleural cavity Visceral pleura Hilum of the lung Parietal pleura Lines of pleural reflection Costodiaphragmatic recesses Right and left lung Fissures and lobes Lung surfaces Lingula and cardiac notch Grooves for aorta Borders of lung Roots of the lungs Pulmonary artery Pulmonary veins Main bronchus Hilum of the lung Pulmonary plexus Mediastinal surfaces and hila of lungs Figure 4.34 5 See the underlined topics in the blue Clinical Box beginning p 346 Injury to cervical pleura: When are cervical pleura especially vulnerable to injury? Consequently, the lungs and pleural sacs may be injured in wounds to the base of the neck resulting in a pneumothorax, the presence of air (G. pneuma) in the pleural cavity. The pleura can also be accidentally entered by a needle during attempted subclavian or jugular vein catheterization. The cervical pleura reaches a relatively higher level in infants and young children because of the shortness of their necks. Consequently, the cervical pleura is especially vulnerable to injury during infancy and early childhood Thoracentesis: Where is a needle placed for thoracentesis? Sometimes it is necessary to insert a hypodermic needle through an intercostal space into the pleural cavity (thoracentesis) to obtain a sample of fluid or to remove blood or pus (Fig. B4.11). To avoid damage to the intercostal nerve and vessels, the needle is inserted superior to the rib, high enough to avoid the collateral branches. The needle passes through the intercostal muscles and costal parietal pleura into the pleural cavity. When the patient is in the upright position, intrapleural fluid accumulates in the costodiaphragmatic recess. Inserting the needle into the 9th intercostal space in the midaxillary line during expiration will avoid the inferior border of the lung. The needle should be angled upward to avoid penetrating the deep side of the recess (a thin layer of diaphragmatic parietal pleura and diaphragm overlying the liver). Insertion of a chest tube: Which space is drained by a chest tube? Major amounts of air, blood, serous fluid, pus, or any combination of these substances in the pleural cavity are typically removed by insertion of a chest tube. A short incision is made in the 5th or 6th intercostal space in the midaxillary line (which is approximately at nipple level). The tube may be directed superiorly (toward the cervical pleura [see Fig. 4.31A]) for air removal or inferiorly (toward the costodiaphragmatic recess) for fluid drainage. The extracorporeal end of the tube (i.e., the end that is outside of the body) is connected to an underwater drainage system, often with controlled suction, to prevent air from being sucked back into the pleural cavity. Removal of air allows reinflation of a collapsed lung. Failure to remove fluid may cause the lung to develop a resistant fibrous covering that inhibits expansion unless it is peeled off (lung decortication). Pleurodesis: What is a pleurodesis and why is it performed? Auscultation of lungs: Where should a clinician auscultate lung bases (inferoposterior part of inferior lobe)? 6 See the underlined topics in the blue Clinical Box beginning p 346 Auscultation of lungs: Where should a clinician auscultate lung bases (inferoposterior part of inferior lobe)? Auscultation of the lungs (listening to their sounds with a stethoscope) (Fig. B4.13G) and percussion of the thorax (tapping on fingers pressed firmly on the thoracic wall over the lungs to detect sounds in the lungs) (Fig. B4.13C, D) are important techniques used during physical examinations. Auscultation assesses airflow through the tracheobronchial tree into the lobes of the lung. Percussion helps establish whether the underlying tissues are air filled (resonant sound), fluid filled (dull sound), or solid (flat sound). An awareness of normal anatomy, particularly the projection of the lungs and the portions that are overlapped by bone (e.g., the scapula) with associated muscles, enables the examiner to know where flat and resonant sounds should be expected (Fig. B4.13A, B). Auscultation of the lungs and percussion of the thorax should always include the root of the neck where the apices of the lungs are located (Fig. B4.13A, B, E–G; see Fig. 4.41A). When clinicians refer to “auscultating the base of the lung,” they are not usually referring to its diaphragmatic surface or anatomical base. They are usually referring to the inferoposterior part of the inferior lobe. To auscultate this area, the clinician applies a stethoscope to the posterior thoracic wall at the level of the 10th thoracic vertebra (Fig. B4.13E). Pleurodesis: What is a pleurodesis and why is it performed? Obliteration of a pleural cavity by disease, such as pleuritis (inflammation of pleura), or during surgery (e.g., pleurectomy, the excision of a part of the pleura) (Fig. B4.12A) does not cause appreciable functional consequences; however, it may produce pain during exertion. In other procedures, adherence of the parietal and visceral layers of pleura is induced by covering the apposing layers of pleura with an irritating powder or sclerosing agent (pleurodesis). Pleurectomy and pleurodesis are performed to prevent recurring spontaneous secondary atelectasis (spontaneous lung collapse) caused by chronic pneumothorax or malignant effusion resulting from lung disease (LoCicero et al., 2019). 7 Overview: • The trachea courses from the larynx to its bifurcation at the carina • Trachea bifurcates at T4-T5 vertebral level • Right main bronchus divides into three secondary (lobar) bronchi: – superior, middle, and inferior • Left main bronchus divides into superior and inferior lobar bronchi • Each secondary bronchus divides into tertiary (segmental) bronchi • Smallest bronchi give rise to bronchioles where gas exchange occurs • Pulmonary artery branches with the bronchi (parenchymal) • Bronchial circulation supplies the stroma 8 Tracheobronchial Tree See Fig 4.36 p 341 • The vessels and airways progressively branch together • Each bronchopulmonary segment consists of: • A segmental bronchus • A corresponding branch of the pulmonary artery • A segment of lung tissue surrounded by a connective tissue septum Circulation • Pulmonary circulation supplies respiratory tissues with deoxygenated blood • Bronchial vessels nourish the non-respiratory tissues with oxygenated blood Innervation • Pulmonary plexus • Parasympathetic innervation via the vagus nerves causes bronchoconstriction, vasodilation of pulmonary vessels, and secretion from bronchial glands • Sympathetic innervation from T1-T4 sympathetic trunk causes bronchodilation, vasoconstriction of pulmonary vessels, and inhibits secretion from bronchial glands • Visceral sensory fibers from visceral pleura and bronchi accompany sympathetic fibers 9 See the underlined topics in the blue Clinical Box beginning p 346 Bronchoscopy: What is the mucous membrane of the carina associated with? A bronchoscope is an endoscope for inspecting the interior of the tracheobronchial tree. As a bronchoscope proceeds down the trachea to enter a main bronchus, a keel-like ridge, the carina (L., keel of a boat), is observed between the orifices of the right and left main bronchi (Fig. B4.15). A cartilaginous projection of the last tracheal ring, the carina normally lies in a sagittal plane and has a fairly definite edge. If the tracheobronchial lymph nodes in the angle between the main bronchi are enlarged because cancer cells have metastasized from a bronchogenic carcinoma, for example, the carina is distorted, widened posteriorly, and immobile. Hence, morphological changes in the carina are important diagnostic signs to bronchoscopists in assisting with the differential diagnosis of respiratory disease. The mucous membrane covering the carina is one of the most sensitive areas of the tracheobronchial tree and is associated with the cough reflex. For example, when someone aspirates a peanut, they choke and cough. Once the peanut passes the carina, coughing usually stops. If the choking victim is inverted to make use of gravity to expel the foreign body (postural drainage of the lungs), lung secretions passing the carina also cause coughing, which assists the expulsion. Segmental atelectasis: What happens to air in a blocked bronchopulmonary segment? Pulmonary embolism: What is acute cor pulmonale? Pulmonary embolism: What is pleuritis? Lung Cancer: Which type of lung cancers may involve the recurrent laryngeal nerve? Chest X-ray: How does deep inspiration affect a PA radiograph? 10 See the underlined topics in the blue Clinical Box beginning p 346 Bronchoscopy: What is the mucous membrane of the carina associated with? Segmental atelectasis: What happens to air in a blocked bronchopulmonary segment? Blockage of a segmental bronchus (e.g., by an aspirated object) will prevent air from reaching the bronchopulmonary segment it supplies. The air in the blocked segment will gradually be absorbed into the blood, and the segment will collapse (Fig. B4.16). Initially, volume loss may cause a mediastinal shift to the side of the atelectasis, but ipsilateral segment(s) may expand to compensate for the reduced volume of the collapsed segment. Pulmonary embolism: What is acute cor pulmonale? Pulmonary embolism: What is pleuritis? Lung Cancer: Which type of lung cancers may involve the recurrent laryngeal nerve? Chest X-ray: How does deep inspiration affect a PA radiograph? 11 Pulmonary embolism: What is acute cor pulmonale? Obstruction of a pulmonary artery by a blood clot (embolus) is a common cause of morbidity (sickness) and mortality (death). An embolus in a pulmonary artery forms when a blood clot, fat globule, or air bubble travels in the blood to the lungs from a leg vein, for example, after a compound fracture. The embolus passes through the right side of the heart to a lung through a pulmonary artery. It may block a pulmonary artery—pulmonary embolism (PE)—or one of its branches. The pulmonary arteries carry all the blood that has returned to the right heart via the vena caval system. Consequently, the immediate result of PE is partial or complete obstruction of blood flow to the lung. The blockage results in a lung or a sector of a lung that is ventilated with air but not perfused with blood. When a large embolus occludes a pulmonary artery, the patient suffers acute respiratory distress because of a major decrease in the oxygenation of blood, owing to blockage of blood flow through the lung. Conversely, the right side of the heart may become acutely dilated because the volume of blood arriving from the systemic circuit cannot be pushed through the pulmonary circuit (acute cor pulmonale). In either case, death may occur in a few minutes. A medium-sized embolus may block an artery supplying a bronchopulmonary segment, producing a pulmonary infarct, an area of necrotic (dead) lung tissue. In physically active people, a collateral circulation—an indirect, accessory blood supply—often exists and develops further when there is a PE so that infarction is not as likely to occur, or at least will not be as devastating. Anastomoses with branches of the bronchial arteries abound in the region of the terminal bronchioles. In ill people with impaired circulation in the lung, such as chronic congestion, PE commonly results in lung infarction. When an area of visceral pleura is also deprived of blood, it becomes inflamed (pleuritis) and irritates or becomes fused to the sensitive parietal pleura, resulting in pain. Pain from the parietal pleura is referred to the cutaneous distribution of the intercostal nerves to the thoracic wall or, in the case of inferior nerves, to the anterior abdominal wall. 12 Bronchoscopy: What is the mucous membrane of the carina associated with? Segmental atelectasis: What happens to air in a blocked bronchopulmonary segment? Pulmonary embolism: What is acute cor pulmonale? Pulmonary embolism: What is pleuritis? Lung Cancer: Which type of lung cancers may involve the recurrent laryngeal nerve? Lung cancer involving a phrenic nerve may result in paralysis of one half of the diaphragm (hemidiaphragm) (see the Clinical Box “Paralysis of Diaphragm” earlier in this chapter). Because of the intimate relationship of the recurrent laryngeal nerve to the apex of the lung (see Fig. 4.33C), this nerve may be involved in apical lung cancers. This involvement usually results in hoarseness owing to paralysis of a vocal fold (cord) because the recurrent laryngeal nerve supplies all but one of the laryngeal muscles. Chest X-ray: How does deep inspiration affect a PA radiograph? 13 See the underlined topics in the blue Clinical Box beginning p 346 Chest X-ray: How does deep inspiration affect a PA radiograph? The person takes a deep breath and holds it. The deep inspiration causes the diaphragmatic domes to descend, filling the lungs with air (increasing their radiolucency) and moving the inferior margins of the lungs into the costodiaphragmatic recesses. 14 O Overview: • Cheeks and lips border the oral cavity • Hard and soft palates form the roof of the oral cavity/floor of nasal cavity • Muscles of the palate and tongue and their innervation are important for airway management • The nasal cavity is divided into two compartments separated by the nasal septum; communicates anteriorly through external nares and posteriorly by choanae • Your pre-anesthetic airway assessment will include the structures of the oral cavity 15 Oral Cavity Blue Clinical Box p 965 Briefly describe the process a patient undergoes for dental implants Following extraction of a tooth, or fracture of a tooth at its neck, a prosthetic crown may be placed on an abutment (metal peg) inserted into a metal socket surgically implanted into the alveolar bone (Fig. B8.37). A procedure to augment the alveolar bone with calf or cadaveric bone may be required before the socket can be implanted. A waiting period of several months may be necessary to allow bone growth around the implanted socket before the abutment and prosthetic crown are mounted. 16 Nasal Cavity p. 971 blue Clinical Box and yellow The Bottom Line Surgical access to the deeply placed Surgical access to the pterygoplatine fossa pterygopalatine fossa is gained through the is gained through which sinus? maxillary sinus. After elevating the upper lip, the maxillary gingiva and anterior wall of the sinus are traversed to enter the sinus. The posterior wall is then chipped away as needed to open the anterior wall of the pterygopalatine fossa. In the case of chronic epistaxis (nosebleed), the third part of the maxillary artery may be ligated in the fossa to control the bleeding. List the nerves contained in the pterygopalatine fossa The pterygopalatine fossa is a major distributing center for branches of the maxillary nerve and the pterygopalatine (third) part of the maxillary artery. ■ It is located between, and has communications with, the infratemporal fossa, nasal cavity, orbit, middle cranial fossa, pharyngeal vault, maxillary sinus, and oral cavity (palate). ■ The contents of the pterygopalatine fossa are the maxillary nerve (CN V2), the parasympathetic pterygopalatine ganglion, the third part of the maxillary artery and accompanying veins, and a surrounding fatty matrix. 17 Overview: • Mediastinum is the anatomic region medial to the pleural sacs between the sternum, vertebral column, first rib, and diaphragm • It is divided into one superior and three inferior parts by a horizontal line passing through the sternal angle at T4T5 IV disc  Superior mediastinum • Contains the thymus, aortic arch, SVC, esophagus, and phrenic and vagus nerves  Inferior mediastinal compartments • The anterior mediastinum contains fat and areolar tissue • The Middle mediastinum contains the pericardial sac and heart • The posterior mediastinum contains the descending aorta, azygos system of veins, thoracic duct, esophagus, and vagus and sympathetic nerves 18 Use the blue Clinical Box beginning page 359 to answer the following: What’s the difference in the levels of viscera relative to mediastinal divisions from standing to supine? In the supine position (Fig. B4.20A), the • Arch of the aorta lies superior to the transverse thoracic plane. • Bifurcation of the trachea is transected by the transverse thoracic plane. • Central tendon of the diaphragm (or the diaphragmatic surface or inferior extent of the heart) lies at the level of the xiphisternal junction and vertebra T9. When standing or sitting upright (Fig. B4.20B), the • Arch of the aorta is transected by the transverse thoracic plane. • Tracheal bifurcation lies inferior to the transverse thoracic plane. • Central tendon of the diaphragm may fall to the level of the middle of the xiphoid process and T9–T10 IV discs. 19 Use the blue Clinical Box beginning page 359 to answer the following: Describe the procedure of mediastinoscopy Using an endoscope (mediastinoscope), surgeons can see much of the mediastinum and conduct minor surgical procedures. They insert the endoscope through a small incision at the root of the neck, just superior to the jugular notch of the manubrium, into the potential space anterior to the trachea. During mediastinoscopy, surgeons can view or biopsy mediastinal lymph nodes to determine if cancer cells have metastasized to them (e.g., from a bronchogenic carcinoma). The mediastinum can also be explored and biopsies taken through an anterior thoracotomy (removing part of a costal cartilage; see the Clinical Box “Thoracotomy, Intercostal Space Incisions, and Rib Excision” earlier in this chapter). 20 Use the blue Clinical Box beginning page 359 to answer the following: What’s the difference in the levels of viscera relative to mediastinal divisions from standing to supine? Describe the procedure of mediastinoscopy Where is the needle inserted for pericardiocentesis? Drainage of fluid from the pericardial cavity, pericardiocentesis, is usually necessary to relieve cardiac tamponade. To remove the excess fluid, a large-bore needle may be inserted through the left 5th or 6th intercostal space near the sternum. This approach to the pericardial sac is possible because the cardiac notch in the left lung and the shallower notch in the left pleural sac leave part of the pericardial sac exposed—the bare area of the pericardium (see Figs. 4.31A and 4.32). The pericardial sac may also be reached via the xiphocostal angle by passing the needle superoposteriorly (Fig. B4.22). At this site, the needle avoids the lung and pleurae and enters the pericardial cavity; however, care must be taken not to puncture the internal thoracic artery or its terminal branches. In acute cardiac tamponade from hemopericardium, an emergency thoracotomy may be performed (the thorax is rapidly opened) so that the pericardial sac may be incised to immediately relieve the tamponade and stop the hemorrhage from the heart (see the Clinical Box “Thoracotomy, Intercostal Space Incisions, and Rib Excision” earlier in this chapter). 21 Overview: Arteries: • Subclavian and common carotid arteries and their associated branches provide most of the blood to the head and neck – Subclavian artery • • • – Branches from the brachiocephalic artery on the right; from the aortic arch on the left Courses between the anterior and middle scalene muscles to become the axillary artery at the first rib Branches into: – Vertebral artery – Thyrocervical trunk Common carotid artery • • • • • Branches from the brachiocephalic artery on the right; from the aortic arch on the left Bifurcates at the upper border of the thyroid cartilage into internal and external branches Carotid body is a chemoreceptor located in the bifurcation that monitor the pp of O2, CO2, and pH; innervated by CNs IX and X Carotid sinus contains baroreceptors and is located at the origin of the internal carotid artery; innervated by CN IX External carotid artery supplies the neck and face through the branches listed in this station Veins: • External and anterior jugular veins are the principal venous return for the neck • The internal jugular vein provides venous return for the head – Descends within the carotid sheath and joins the subclavian vein to form the brachiocephalic vein 22 Use the blue Clinical Box beginning p 1026 to answer the following: You may also find Figure B9.4 p.1030 and Figure 10.14 p. 1089 helpful What are the superficial landmarks for subclavian vein puncture? The right or left subclavian vein is often the point of entry to the venous system for central line placement, such as a pulmonary artery catheter (PAC, also known as a Swan-Ganz or right heart catheter). Central lines are inserted to administer parenteral (venous nutritional) fluids and medications and to measure central venous pressure. In an infraclavicular subclavian vein approach, the administrator places the thumb of one hand on the middle part of the clavicle and the index finger on the jugular notch in the manubrium (Fig. B9.2). The needle punctures the skin inferior to the thumb (middle of the clavicle) and is advanced medially toward the tip of the index finger (jugular notch) until the tip enters the right venous angle, posterior to the sternoclavicular joint. Here, the internal jugular and subclavian veins merge to form the brachiocephalic vein. If the needle is not inserted carefully, it may puncture the pleura and lung, resulting in pneumothorax. Furthermore, if the needle is inserted too far posteriorly, it may enter the subclavian artery. When the needle has been inserted correctly, a soft, flexible catheter is inserted into the subclavian vein, using the needle as a guide. What access is used for right cardiac catheterization? How does the EJV serve as an ”internal barometer”? What are the landmarks for needle insertion into the IJV? 23 Use the blue Clinical Box beginning p 1026 to answer the following: You may also find Figure B9.4 p.1030 and Figure 10.14 p. 1089 helpful What are the superficial landmarks for subclavian vein puncture? What access is used for right cardiac catheterization? For right cardiac catheterization (to take measurements of pressures in the right chambers of the heart), puncture of the IJV can be used to introduce a catheter through the right brachiocephalic vein into the superior vena cava (SVC) and the right side of the heart. Although the preferred route is through the IJV or subclavian vein, it may be necessary in some patients to use the EJV. This vein is not ideal for catheterization because its angle of junction with the subclavian vein makes passage of the catheter difficult. How does the EJV serve as an ”internal barometer”? What are the landmarks for needle insertion into the IJV? 24 Use the blue Clinical Box beginning p 1026 to answer the following: You may also find Figure B9.4 p.1030 and Figure 10.14 p. 1089 helpful What are the superficial landmarks for subclavian vein puncture? What access is used for right cardiac catheterization? How does the EJV serve as an ”internal barometer”? The EJV may serve as an “internal barometer.” When venous pressure is in the normal range, the EJV is usually visible above the clavicle for only a short distance. However, when venous pressure rises (e.g., as in heart failure), the vein is prominent throughout its course along the side of the neck. Consequently, routine observation of the EJVs during physical examinations may give diagnostic signs of heart failure, SVC obstruction, enlarged supraclavicular lymph nodes, or increased intrathoracic pressure. What are the landmarks for needle insertion into the IJV? 25 Use the blue Clinical Box beginning p 1026 to answer the following: You may also find Figure B9.4 p.1030 and Figure 10.14 p. 1089 helpful What are the superficial landmarks for subclavian vein puncture? What access is used for right cardiac catheterization? How does the EJV serve as an ”internal barometer”? What are the landmarks for needle insertion into the IJV? A needle and catheter may be inserted into the IJV for diagnostic or therapeutic purposes. The right IJV is preferable because it is usually larger and straighter. During this procedure, the clinician palpates the common carotid artery and inserts the needle into the IJV just lateral to it at a 30° angle, aiming at the apex of the triangle between the sternal and clavicular heads of the SCM, the lesser supraclavicular fossa (Fig. B9.4). The needle is then directed inferolaterally toward the ipsilateral nipple. 26 Overview: Nerves of the lateral cervical region: • Spinal accessory nerve (CNXI) – CNs VII, IX, X, XI, and XII travel through the neck and provide important innervation • Cervical plexus and brachial plexus both emerge between the middle and anterior scalene muscles – Cervical plexus of nerves is responsible for much of the sensory and motor innervation of the neck • Sympathetic innervation of the head and neck is via the cervical sympathetic trunk which is composed of inferior, middle, and superior ganglia Nerves of the root of the neck: • Three pairs of major nerves in the root of the neck are the vagus, phrenic, and sympathetic trunks – Vagus branches to become the recurrent laryngeal nerves innervating the larynx 27 Use the blue Clinical Box pp 1028-1029 Nerve Blocks in Lateral Cervical Region: What is the main injection site for a supraclavicular brachial plexus block? For regional anesthesia before neck surgery, a cervical plexus block inhibits nerve impulse conduction. The anesthetic agent is injected at several points along the posterior border of the SCM, mainly at the junction of its superior and middle thirds, the nerve point of the neck (see Figs. 9.9 and 9.14A). Half of the diaphragm is usually paralyzed by a cervical plexus block due to the inclusion of the phrenic nerve in the block. Therefore, this procedure is not performed on persons with pulmonary or cardiac disease. For anesthesia of the upper limb, the anesthetic agent in a supraclavicular brachial plexus block is injected around the supraclavicular part of the brachial plexus. The main injection site is superior to the midpoint of the clavicle. Carotid Occlusion and Endarterectomy: Which cranial nerves are at risk of injury during carotid endarterectomy? Role of Carotid Bodies: What is the role of the carotid bodies? 28 Carotid Occlusion and Endarterectomy: Which cranial nerves are at risk of injury during carotid endarterectomy? Atherosclerotic thickening of the intima of the internal carotid artery may obstruct blood flow. Symptoms resulting from this obstruction depend on the degree of obstruction and the amount of collateral blood flow to the brain and structures in the orbit from other arteries. A partial occlusion of the internal carotid may cause a transient ischemic attack (TIA), a sudden focal loss of neurological function (e.g., dizziness and disorientation) that disappears within 24 hours. Arterial occlusion may also cause a minor stroke, a loss of neurological function such as weakness or sensory loss on one side of the body that exceeds 24 hours but disappears within 3 weeks. Obstruction of blood flow can be observed in a Doppler color study (Fig. B9.3A). A Doppler is a diagnostic instrument that emits an ultrasonic beam and detects its reflection from moving fluid (blood) in a manner that distinguishes the fluid from the static surrounding tissue, providing information about its pressure, velocity, and turbulence. Carotid occlusion, causing stenosis (narrowing) in otherwise healthy persons (Fig. B9.3B), can be relieved by opening the artery at its origin and stripping off the atherosclerotic plaque with the intima. This procedure is called carotid endarterectomy. After the operation, drugs that inhibit clot formation are administered until the endothelium has regrown. Because of the relations of the internal carotid artery, there is risk of cranial nerve injury during the procedure involving one or more of the following nerves: CN IX, CN X (or its branch, the superior laryngeal nerve), CN XI, or CN XII (Fig. 9.22). 29 Use the blue Clinical Box pp 1028-1029 Nerve Blocks in Lateral Cervical Region: What is the main injection site for a supraclavicular brachial plexus block? Carotid Occlusion and Endarterectomy: Which cranial nerves are at risk of injury during carotid endarterectomy? Role of Carotid Bodies: What is the role of the carotid bodies? The carotid bodies are in an ideal position to monitor the oxygen content of blood before it reaches the brain (see Fig. 9.18). A decrease in partial pressure of oxygen (pO2), as occurs at high altitudes or in pulmonary disease, activates the aortic and carotid chemoreceptors, increasing alveolar ventilation. The carotid bodies also respond to increased carbon dioxide (CO2) tension or free hydrogen ions in the blood. The glossopharyngeal nerve (CN IX, perhaps with involvement of the vagus nerve) conducts the information centrally, resulting in reflexive stimulation of the respiratory centers of the brain that increase the depth and rate of breathing. The pulse rate and blood pressure also increase. With increased ventilation and circulation, more oxygen is taken in and the concentration of CO2 is reduced accordingly. 30 Overview: • The larynx forms the air passageway from the hyoid bone to the trachea • Function of these muscles and cartilages provides the mechanism to route air and food to proper channels (trachea or esophagus) as well as produce sound • “The competent anesthetist should have a level of knowledge of the anatomy of the larynx of which a laryngologist would not be ashamed” Harold Ellis- Anatomy for Anaesthetists 31 Laryngeal Framework  Laryngeal Framework  Hyoid bone  Laryngeal cartilages: • Thyroid cartilage • Laryngeal prominence/thyroid notch • Thyrohyoid membrane • Cricoid cartilage • Cricothyroid membrane • Epiglottis • Arytenoid cartilages • Vocal process • Cuneiform and corniculate cartilages  Vocal ligaments attach to vocal processes • Vocal folds (true) vocal folds (cords) • Vestibular (false) vocal folds  Laryngeal structures • Laryngeal inlet • Rima glottidis • Vestibule • Ventricle • Aryepiglottic fold • Infraglottic cavity Anterior View of Larynx- Landmarks and Vertebral Levels 32 See Figure 9.38 p 1046 Laryngeal Muscles Intrinsic laryngeal muscles alter the:  Size and shape of the rima glottidis • Arytenoid cartilages permit gliding/rotation  Adductors and abductors • Adduction of vocal folds • Lateral cricoarytenoid muscles • Transverse arytenoid muscles • Abduction of vocal folds • Posterior cricoarytenoid muscles See Figure 9.40 & 9.41 p. Laryngeal Nerves The larynx is innervated by branches of the vagus nerve  Superior laryngeal nerve divides into: • External laryngeal nerve innervates the cricothyroid muscle • Internal laryngeal nerve pierces the thyrohyoid membrane to provide sensory innervation to mucosa superior to vocal folds  Length and tension of the vocal folds • Crycothyroid joint tilts thyroid  Tensors and relaxers • Tensors of vocal folds • Cricothyroid muscles • Relaxing vocal folds • Thyroarytenoid muscles  Recurrent laryngeal nerve supplies all other intrinsic laryngeal muscles • Sensory innervation from mucosa inferior to vocal folds 33 Overview: • The pharynx- aka the throat- is the fibromuscular tube that extends from the base of the skull to the cricoid cartilage/esophagus – Serves as a common pathway for nutrition and air – Subdivisions include the nasopharynx, oropharynx, and laryngopharynx • Pharyngeal muscles include the pharyngeal constrictors and accessory pharyngeal muscles that aid in swallowing and speaking 34 Pharynx Subdivisions Structures of the Pharynx Figure 8.85 p 952  Nasopharynx • • Choanae Pharyngeal tonsils (adenoids)  Oropharynx • • • Palatoglossal arches Palatopharyngeal arches Palatine tonsils  Laryngopharynx 35 Pharyngeal Muscles Pharyngeal Function- Muscles Figure 9.43 p.1051  Pharyngeal constrictors form the lateral and posterior walls of the pharynx • Aid in swallowing • Include the superior, middle, and inferior pharyngeal constrictors • Inferior pharyngeal constrictor constitutes the cricopharyngeus muscle  • • • • • Accessory pharyngeal muscles Elevate the larynx and pharynx when swallowing Named by origins/insertions Stylopharyngeus muscle Palatopharyngeus muscle Salpingopharyngeus muscle 36 Overview: • Cervical fascia consists of concentric layers of fascia – from superficial to deep- that compartmentalize structures in the neck • These layers can determine the direction in which infection can spread • Prevertebral fascia forms a sheath around the vertebral column and prevertebral muscles attached to the vertebral column 37 Retropharyngeal Space Fig 9.4, 9.6  The retropharyngeal space is a potential space consisting of loose connective tissue between the prevertebral and the buccopharyngeal fascia  This space serves as a potential conduit for the spread of infection from the pharyngeal region to the mediastinum See p 1007 blue Clinical box : Spread of Infections in Neck Which layer of fascia helps prevent the spread of abscesses in the neck? The investing layer of deep cervical fascia helps prevent the spread of abscesses (purulent infections) caused by tissue destruction. If an infection occurs between the investing layer of deep cervical fascia and the muscular part of the pretracheal fascia surrounding the infrahyoid muscles, the infection will usually not spread beyond the superior edge of the manubrium of the sternum. If, however, the infection occurs between the investing fascia and the visceral part of pretracheal fascia, it can spread into the thoracic cavity anterior to the pericardium. Pus from an abscess posterior to the prevertebral layer of deep cervical fascia may extend laterally in the neck and form a swelling posterior to the SCM. The pus may perforate the prevertebral layer of deep cervical fascia and enter the retropharyngeal space, producing a bulge in the pharynx (retropharyngeal abscess). This abscess may cause difficulty in swallowing (dysphagia) and speaking (dysarthria). Infections in the head may also spread inferiorly posterior to the esophagus and enter the posterior mediastinum, or it may spread anterior to the trachea and enter the anterior mediastinum. Infections in the retropharyngeal space may also extend inferiorly into the superior mediastinum. Similarly, air from a ruptured trachea, bronchus, or esophagus (pneumomediastinum) can pass superiorly in the neck. Prevertebral Muscles Fig 9.25  Prevertebral muscles • Anteriorly- longus colli and capitis far can infection spread into the thorax from the deep layer of cervical fascia? • How Laterallymusclesabscess present? HowAnterior might a scalene retropharyngeal Middle scalene muscles Posterior scalene muscles • Posteriorly- deep cervical muscles 38 Retropharyngeal Space Fig 9.4, 9.6  The retropharyngeal space is a potential space consisting of loose connective tissue between the prevertebral and the buccopharyngeal fascia  This space serves as a potential conduit for the spread of infection from the pharyngeal region to the mediastinum See p 1007 blue Clinical box : Spread of Infections in Neck Which layer of fascia helps prevent the spread of abscesses in the neck? How far can infection spread into the thorax from the deep layer of cervical fascia? If an infection occurs between the investing layer of deep cervical fascia and the muscular part of the pretracheal fascia surrounding the infrahyoid muscles, the infection will usually not spread beyond the superior edge of the manubrium of the sternum. If, however, the infection occurs between the investing fascia and the visceral part of pretracheal fascia, it can spread into the thoracic cavity anterior to the pericardium. How might a retropharyngeal abscess present? Prevertebral Muscles Fig 9.25  • • • Prevertebral muscles Anteriorly- longus colli and capitis LaterallyAnterior scalene muscles Middle scalene muscles Posterior scalene muscles Posteriorly- deep cervical muscles 39 Retropharyngeal Space Fig 9.4, 9.6  The retropharyngeal space is a potential space consisting of loose connective tissue between the prevertebral and the buccopharyngeal fascia  This space serves as a potential conduit for the spread of infection from the pharyngeal region to the mediastinum See p 1007 blue Clinical box : Spread of Infections in Neck Which layer of fascia helps prevent the spread of abscesses in the neck? How far can infection spread into the thorax from the deep layer of cervical fascia? How might a retropharyngeal abscess present? The pus may perforate the prevertebral layer of deep cervical fascia and enter the retropharyngeal space, producing a bulge in the pharynx (retropharyngeal abscess). This abscess may cause difficulty in swallowing (dysphagia) and speaking (dysarthria). Prevertebral Muscles Fig 9.25  • • • Prevertebral muscles Anteriorly- longus colli and capitis LaterallyAnterior scalene muscles Middle scalene muscles Posterior scalene muscles Posteriorly- deep cervical muscles 40 41