Anatomy Unit 4: Practice Questions
A 23-year-old man received a gunshot wound, and his greater splanchnic nerve was destroyed. Which of the following nerve fibers would be injured? (A) General somatic afferent (GSA) and preganglionic sympathetic fibers (B) General visceral afferent (GVA) and postganglionic sympathetic fibers (C) GVA and preganglionic sympathetic fibers (D) General somatic efferent (GSE) and postganglionic sympathetic fibers (E) GVA and GSE fibers
(C) The greater splanchnic nerves contain general visceral afferent (GVA) and preganglionic sympathetic general visceral efferent (GVE) fibers.
Because of its angle with the trachea and size of the main bronchus, a bronchoscope would pass more readily into the *left* or *right* lung?
Right There are several reasons why a bronchoscope or inhaled objects will be more likely to enter the right lung instead of the left lung. First, the carina, a ridge-like structure at the bifurcation of the trachea, is set a little towards the left. So, there is a more direct path for objects to fall to the right. Also, the right bronchus is shorter, wider, and more vertical than the left bronchus. All of these factors mean that an inhaled object will usually enter the right main bronchus.
Blockage of which of the following arteries would lead to ischemia of the apex of the heart? a) Anterior interventricular (descending) b) Left circumflex c) Posterior interventricular (descending) d) Right marginal e) Right coronary
a) Anterior interventricular (descending) The anterior interventricular artery is a branch of the left coronary artery. It supplies both ventricles as well as the interventricular septum. It also reaches the apex, supplying that area as well. The left circumflex artery is the other major branch of the left coronary artery. It supplies the posterior surface of the left ventricle, but does not reach the apex of the heart.
Which valves would be open during ventricular systole? a) Aortic and pulmonary b) Aortic and tricuspid c) Mitral and aortic d) Tricuspid and mitral e) Tricuspid and pulmonary
a) Aortic and pulmonary Remember that ventricular systole is the period when the ventricles are contracting. This contraction forces blood out of the heart, which pushes the aortic and pulmonary valves open.
Via which diaphragmatic hiatus does the thoracic duct enter the posterior mediastinum? a) Aortic hiatus b) Caval hiatus c) Oesophageal hiatus d) Sternal hiatus
a) Aortic hiatus
Which of the great vessels of the heart gives rise to the coronary arteries? a) Ascending aorta b) Pulmonary trunk c) Superior vena cava d) Inferior vena cava
a) Ascending aorta
A frail, elderly man, suspected of having widespread cancer of the lungs and bronchi, is brought in for bronchoscopic examination. The instrument is inserted into the airway, where it accidentally punctures the thin, brittle posterior wall of the diseased right main bronchus. A sudden gush of blood immediately indicates that the instrument has also torn the wall of the blood vessel immediately behind the right main bronchus, i.e., the: a) Azygos vein b) Left brachiocephalic artery c) Pericardiacophrenic artery d) Right pulmonary vein e) Superior vena cava
a) Azygos vein The azygos vein lies immediately behind the right mainstem bronchus. This vein then arches over the right mainstem bronchus to drain blood into the superior vena cava. So, this must be the structure that was damaged during the bronchoscopy.The left brachiocephalic artery doesn't exist, but the brachiocephalic trunk is a branch off the aortic arch which travels far superior to the area of interest. The pericardiacophrenic artery is a branch of the internal thoracic artery which accompanies the phrenic nerve. It is anterior to the right bronchus. The right pulmonary veins are inferior and anterior to the right mainstem bronchus. Finally, the superior vena cava is superior and anterior to the right mainstem bronchus.
Which feature is found only in the left lung? a) Cardiac notch b) Horizontal fissure c) Oblique fissure d) Superior lobar bronchus e) Three lobes
a) Cardiac notch
The sternal angle is formed by the junction of which two bones? a) Sternal body and manubrium b) Manubrium and xiphoid process c) Sternal body and the clavicles d) Manubrium and the 2nd rib
a) Sternal body and manubrium
When inserting a chest tube, intercostal vessels and nerves are avoided by placing the tube immediately: a) above the margin of a rib b) below the margin of a rib
a) above the margin of a rib The VAN triad of an intercostal vein, artery, and nerve run along the bottom of a rib, in the costal groove. To avoid hitting any of these important structures, it is important to remember to always place a tube or needle above the margin of a rib (or,if you prefer to think about it this way, at the bottom of an intercostal space).
Traumatic, acceleration/deceleration injuries to the aorta usually occur where its mobile and fixed portions meet. This would be at the: a) at the ligamentum arteriosum b) junction of aortic arch with the descending portion c) junction of the ascending aorta with the heart d) origin of the brachiocephalic artery on the arch e) point where the descending aorta passes through the diaphragm
a) at the ligamentum arteriosum
You are caring for a 68-year-old male who has copious amounts of fluid in the left pleural cavity due to acute pleurisy. When you examine him as he sits up in bed (trunk upright), where would the fluid tend to accumulate? a) costodiaphragmatic recess b) costomediastinal recess c) cupola d) hilar reflection e) middle mediastinum
a) costodiaphragmatic recess The costodiaphragmatic recess is the lowest extent of the pleural cavity or sac. It is the part of the pleural sac where the costal pleura changes into the diaphragmatic pleura. Because this is the most inferior part of the pleural sac, fluid in the pleural sac will fall to this region when a patient sits up. The costodiaphragmatic recess is also the area into which a needle is inserted for thoracocentesis, and it is found at different levels at different areas of the thorax.
The pleural cavity near the cardiac notch is known as the: a) Costodiaphragmatic recess b) Costomediastinal recess c) Cupola d) Hilum e) Pulmonary ligament
b) Costomediastinal recess
Which muscle forms the inferior border of the middle mediastinum? a) Rectus abdominis b) Diaphragm c) External oblique d) Internal intercostal
b) Diaphragm
In a post-soccer match brawl, a 35-year-old man was stabbed in the back with a knife that just nicked his left lung halfway between its apex and diaphragmatic surface. Which part of the lung was most likely injured? a) Hilum b) Inferior lobe c) Lingula d) Middle lobe e) Superior lobe
b) Inferior lobe Because of the sharp angle of the oblique fissure, the posterior surface of the left lung is almost entirely comprised of the inferior lobe. So, a stab wound halfway between the apex and diaphragmatic surface of the lung would result in injury to the inferior lobe. The hilum is the point at which the structures forming the root of the lung enter the lung. The lingula is part of the superior lobe, which forms the anterior and superior sides of the lung. And remember, the middle lobe isn't relevant here because it is on the right lung. (Besides, it doesn't even contribute to the posterior surface of the right lung.)
The thoracic wall is innervated by: a) Dorsal primary rami b) Intercostal nerves c) Lateral pectoral nerves d) Medial pectoral nerves e) Thoracodorsal nerves
b) Intercostal nerves
A 26-year-old male is brought into the emergency room after having been kicked in the chest by a horse. After examination, it is concluded that the most likely immediate danger is cardiac tamponade (bleeding into the pericardial sac). You prepare to draw off some of the blood from the sac to relieve the pressure on the heart. The safest site at which to insert the needle of the syringe in order to miss the pleura would be: a) Just below the nipple on the left b) Just to the left of the xiphisternal junction c) Near the sternal angle d) Through the jugular notch e) 4th left intercostal space in the midaxillary line
b) Just to the left of the xiphisternal junction
During examination of a 62-year-old man, the senior resident tells you to put your stethoscope on the left 5th intercostal space, slightly below the nipple, and listen for a clearly audible murmur. You hear it distinctly and know it must be associated with severe stenosis of which heart valve? a) Aortic b) Mitral c) Pulmonary d) Tricuspid
b) Mitral
What is the anterior border of the posterior mediastinum? a) Mediastinal pleura b) Pericardium c) Diaphragm d) Thoracic vertebrae
b) Pericardium
A tumor of the posterior mediastinum is most likely to compress which of the following structures? a) Arch of the aorta b) Esophagus c) Inferior vena cava d) Pulmonary trunk e) Trachea
b) esophagus The posterior mediastinum is bounded superiorly by the plane through the sternal angle and T4/5, inferiorly by the diaphragm, anteriorly by the middle mediastinum, and posteriorly by the spinal cord. This area contains the descending thoracic aorta, the azygos system, the esophagus, the thoracic duct, and lymph nodes. Of the answer choices, the esophagus is the only one in the posterior mediastinum. The great vessels and bronchi at the roots of the lung are in the middle mediastinum.
Which statement is true of the right atrioventricular valve? a) it is also called the mitral valve b) it is open during ventricular diastole c) it transmits oxygenated blood d) it is opened by the pull of chordae tendineae e) it consists of 2 leaflets
b) it is open during ventricular diastole Ventricular diastole is the period when the ventricles relax and fill with blood. So, the AV valves need to be open at this time so that blood can flow from the atria to the ventricles. The right AV valve is called the tricuspid valve--it has three leaflets. The left AV valve is called the mitral valve and has two leaflets. Remember, the right side of the heart is pumping blood to the lungs so that it can be oxygenated. So, the blood flowing through the right AV valve will be deoxygenated, while the blood flowing through the left AV valve will be oxygenated. Finally, remember that the chordae tendineae and the papillary muscles do not pull the AV valves open! These structures serve to prevent the valves from prolapsing during systole.
What is not a characteristic of Tetralogy of Fallot? a) pulmonary valve stenosis b) left ventricular hypertrophy c) Transposition or dextroposition of the great vessels d) ventricular septal defect e) right ventricular hypertrophy
b) left ventricular hypertrophy
A stethoscope placed over the left second intercostal space just lateral to the sternum would be best positioned to detect sounds associated with which heart valve? a) aortic b) pulmonary c) mitral e) tricuspid
b) pulmonary The best place to listen to heart valves is not at their actual sternocostal projections. Instead, you want to listen to the valves by putting your stethescope at a point downstream from the valve where you can hear the blood flowing and colliding with the muscular chest wall. There are points of auscultation for all four heart valves--Pulmonic: left second intercostal space, lateral to the sternal angle; Aortic: right second intercostal space, lateral to the sternal angle; Mitral: left fifth intercostal space, 8cm away from the midline; Tricuspid: left fourth intercostal space, just lateral to the sternum.
Which part of the aorta is located within the posterior mediastinum? a) Ascending aorta b) Aortic arch c) Descending aorta d) Abdominal aorta
c) Descending aorta
An enlarging lymph node gradually constricts the flow of blood in the azygos venous arch. Which vessel would enlarge as a result of collateral drainage? a) Superior vena cava b) Inferior vena cava c) Internal thoracic vein d) Right brachiocephalic vein e) Superior epigastric vein
c) Internal thoracic vein The internal thoracic vein would provide a collateral route for drainage if the azygos vein was obstructed. In the case of an obstruction, blood could flow from the posterior intercostal veins (which usually drain into the azygos) into the anterior intercostal veins, enter the internal thoracic vein, and drain into the right brachiocephalic vein. This would allow the blood to bypass the blockage. The right brachiocephalic vein would be receiving more blood due to this blockage, but it wouldn't be the vessel that would enlarge--the internal thoracic vein would become distended. The superior epigastric vein is an inferior extension of the internal thoracic vein--it is too inferior to assist with collateral circulation.
The oblique fissure of the right lung separates which structures? a) Lower lobe from lingula b) Lower lobe from upper lobe only c) Lower lobe from both upper and middle lobes d) Lower lobe from middle lobe only e) Upper from middle lobe
c) Lower lobe from both upper and middle lobes
Which nerve passes through the middle mediastinum to innervate the diaphragm? a) Ulnar b) Vagus c) Phrenic d) Lateral pectoral
c) Phrenic
Where does the azygous system of veins drain into? a) Right subclavian vein b) Right atrium c) Superior vena cava d) Inferior vena cava
c) Superior vena cava
The aorta is located in which mediastinal compartment(s)? a) Anterior, Superior and Middle b) Middle only c) Superior, Middle and Posterior d) Superior and Middle only e) Posterior only
c) Superior, Middle and Posterior The ascending aorta is located in the middle mediastinum, along with the other great vessels. The aortic arch is located in the lowest part of the superior mediastinum (its lower border lies at the level of the sternal angle). The descending aorta is in the posterior mediastinum.
A 5-year-old girl is brought to the emergency department because of difficulty breathing (dyspnea), palpitations, and shortness of breath. Doppler study of the heart reveals an atrial septal defect (ASD). This malformation usually results from incomplete closure of which of the following embryonic structures? a) Ductus arteriosus b) Ductus venosus c) Sinus venarum d) Foramen ovale e) Truncus arteriosus
d) Foramen ovale. An atrial septal defect (ASD) is a congenital defect in the interatrial septum. During partitioning the two atria, the opening in the foramen secundum (the foramen ovale) usually closes at birth. If this foramen ovale is not closed completely, this would result in an ASD, shunting blood from the left atrium to the right atrium.
An elderly lady suffers a coronary occlusion and subsequently it is noted that there is a complete heart block (that is, the right and left bundles of the conduction system have been damaged). The artery most likely involved is the: a) acute marginal branch b) circumflex branch c) anterior interventricular (Left anterior descending) d) obtuse marginal e) posterior interventricular (posterior descending)
c) anterior interventricular (Left anterior descending) The right and left bundles of conduction travel in the interventricular septum. So, the artery that has been occluded must be the one that supplies the interventricular septum. The most important source of blood to the interventricular septum is the anterior interventricular artery, a branch of the left coronary artery. Although the posterior interventricular artery partially supplies blood to the interventricular septum, it might not be enough to support the tissue in this region. The circumflex branch of the left coronary artery provides blood to the posterior surface of the left ventricle. The acute marginal branch of the right coronary artery provides blood to the right ventricle.
In the midregion of the thorax the thoracic duct lies immediately posterior to the: a) aorta b) azygos vein c) esophagus d) superior vena cava e) trachea
c) esophagus In the mid thorax, the aorta, thoracic duct, and azygos vein are all posterior to the esophagus. (They are in that order, from left to right.) The superior vena cava and the trachea are not located in the mid thorax--the superior vena cava terminates as it feeds into the right atrium and the trachea ends as it splits into the two mainstem bronchi which enter the lungs.
During fetal life and sometimes persisting into the adult there is an opening between the right and left atria; this opening is called the: a) atrioventricular canal b) coronary sinus c) foramen ovale d) sinus venosus e) truncus arteriosis
c) foramen ovale The foramen ovale is an opening in the interatrial septum which exists in the fetus. This opening and the ductus arteriosus serve as two shunts which divert blood away from the developing lungs. Both should close soon after birth.
Which vessel courses across the mediastinum in an almost horizontal fashion? a) Left subclavian artery b) Left subclavian vein c) Left brachiocephalic vein d) Left internal jugular vein e) Left common carotid artery
c) left brachiocephalic vein The left brachiocephalic vein joins with the right brachiocephalic vein to form the superior vena cava on the right side of the body. So, the left brachiocephalic vein must course across the mediastinum to reach its destination. The left subclavian artery and vein are lateral to the mediastinum, while the left jugular and common carotid travel vertically.
You are attending an operation to remove a thymic tumor from the superior mediastinum. The surgeon asks, "What important nerve lying on and partly curving posteriorly around the arch of the aorta should we be careful of as we remove this mass?" You quickly answer, "The-- a) left phrenic b) left sympathetic trunk c) left vagus d) right phrenic e) right sympathetic trunk
c) left vagus The left vagus nerve lies against the lateral surface of the arch of the aorta. The left recurrent laryngeal nerve is an especially important nerve from the vagus which loops around the aortic arch. This nerve innervates the muscles of the left larynx. If it is damaged, a patient may experience hoarseness after surgery. Care must be taken to preserve this nerve, especially during thyroid surgery.
Which of the following nerves would be most vulnerable to irritation when the tracheobronchial lymph nodes are enlarged due to a diseased situation? a) Right phrenic b) Left phrenic c) Right recurrent laryngeal d) Left recurrent laryngeal e) Right vagus
d) Left recurrent laryngeal
The ductus arteriosus sometimes remains open after birth, requiring surgical closure. When placing a clamp on the ductus, care must be taken to avoid injury to what important structure immediately dorsal to it? a) Accessory hemiazygos vein b) Left internal thoracic artery c) Left phrenic nerve d) Left recurrent laryngeal nerve e) Thoracic duct
d) Left recurrent laryngeal nerve The left recurrent laryngeal nerve is closely associated with the aortic arch and the ligamentum arteriosum/ductus arteriosus. As the left vagus nerve passes near the aortic arch, it gives offf the left recurrent laryngeal nerve. This nerve then loops under the aortic arch, lateral to the ligamentum arteriosum, and ascends to the larynx in the tracheoesophageal groove. During surgery to close a patent ductus arteriosus, a surgeon must be careful to protect the left recurrent laryngeal nerve, which is lateral to the duct that is being ligated.
During a surgical procedure in the vicinity of the descending aorta, a surgeon accidentally cuts the first aortic intercostal arteries. Which of the following structures might be deprived of its main source of blood supply? a) first posterior intercostal space b) first anterior intercostal space c) left bronchus d) right bronchus e) fibrous pericardium
d) Right bronchus The right bronchus receives blood from a single right bronchial artery. This artery may branch from one of the left bronchial arteries or it may branch from the right 3rd posterior intercostal artery, the first intercostal artery that arises from the descending aorta. Damaging this artery might stop the blood supply to the main bronchus. The intercostal arteries to the first and second intercostal spaces are derived from the highest intercostal artery, so the blood supply to either of these spaces would not be disrupted. The left bronchus is supplied by two left bronchial arteries which branch directly from the descending aorta. The fibrous pericardium is a fibrous sac that contains the pericardial cavity and the heart. Its blood supply is not a major concern.
A patient involved in an automobile accident presents with a sharp object puncture of the middle of the sternum at about the level of the 4th or 5th costal cartilage. If the object also penetrated pericardium and heart wall, which heart chamber would most likely be damaged? a) Left atrium b) Left ventricle c) Right atrium d) Right ventricle
d) Right ventricle Remember, the anterior surface, or sternocostal surface, of the heart is mostly made up of the right ventricle. So, if an object punctured the sternum, it would be likely to pierce the right ventricle.
A 10-year-old boy underwent a tonsillectomy under general anesthesia. At home he lay supine in bed for two weeks and developed a fever and chest pain with cough. He returned to the hospital and was diagnosed as having right lung pneumonia due to aspiration of infectious material during the tonsillectomy. In which bronchopulmonary segment of the lung would fluid (pus) most likely have accumulated by the simple force of gravity? a) Anterior basal segment--inferior lobe b) Anterior segment--superior lobe c) Lateral segment--middle lobe d) Superior segment--inferior lobe e) Superior lingual segment--lingula
d) Superior segment--inferior lobe The superior segmental bronchus of the inferior lobe branches posteriorly off of the intermediate bronchus or the inferior lobe bronchus, so it is the most likely segmental bronchus to receive foreign bodies or fluids that enter the right bronchus. This is even more likely to occur if the patient is in the supine position.
A 37-year-old man is brought to the emergency department complaining of severe chest pain. His angiogram reveals thromboses of both brachiocephalic veins. This condition would most likely cause a dilation of which of the following veins? a) Azygos b) Hemiazygos c) Right superior intercostal d) Left superior intercostal e) Internal thoracic
d) The *left superior intercostal vein* is formed by the second, third, and fourth posterior intercostal veins and drains into the left brachiocephalic vein. The right superior intercostal vein drains into the azygos vein, which in turn drains into the SVC. The hemiazygos vein drains into the azygos vein, whereas the internal thoracic vein empties into the brachiocephalic vein.
A 23-year-old male injured in an industrial explosion was found to have multiple small metal fragments in his thoracic cavity. Since the pericardium was torn inferiorly, the surgeon began to explore for fragments in the pericardial sac. Slipping her hand under the heart apex, she slid her fingers upward and to the right within the sac until they were stopped by the cul-de-sac formed by the pericardial reflection near the base of the heart. Her fingertips were then in the: a) coronary sinus b) coronary sulcus c) costomediastinal recess d) oblique sinus e) transverse sinus
d) oblique sinus The oblique sinus is an area of the pericardial cavity located behind the left atrium of the heart where the serous pericardium reflects onto the inferior vena cava and pulmonary veins. If you slide your fingers under the heart, they will be in the oblique sinus. The other pericardial sinus that you should be familiar with is the transverse sinus. The transverse sinus is an area of the pericardial cavity located behind the aorta and pulmonary trunk and anterior to the superior vena cava. It separates the outflow vessels from inflow vessels.
A 4-year-old girl is brought in with coughing, and you are told by her mother that she had been playing with some beads and had apparently aspirated one (gotten it into her airway). Where would you expect it to most likely be? a) Apicoposterior segmental bronchus of left lung b) Left main bronchus c) Lingular segment of left lung d) Right main bronchus e) Terminal bronchiole of right lung, lower lobe
d) right main bronchus There are several reasons why inhaled objects will be more likely to enter the right lung instead of the left lung. First, the carina, a ridge-like structure at the bifurcation of the trachea, is set a little towards the left. So, there is a more direct path for objects to fall to the right. Also, the right bronchus is shorter, wider, and more vertical than the left bronchus. All of these factors mean that an inhaled object will enter the right main bronchus. It would be almost impossible for a bead to get lodged in the terminal bronchiole of the right lung--that is a very small space!
The sternocostal surface of the heart is formed primarily by the anterior wall of which heart chamber? a) Left atrium b) Left ventricle c) Right atrium d) Right ventricle
d) right ventricle The heart has three important surfaces: an anterior surface, a diaphragmatic surface, and a pulmonary surface. The anterior surface, or sternocostal surface, is mostly made up of the right ventricle. The diaphragmatic surface is mostly the left ventricle, but a little bit of the right ventricle sits on the diaphragm as well. Finally, the pulmonary surface, which is on the left, is mostly made up of the left ventricle.
Gray rami communicantes contain postganglionic sympathetic fibers that innervate which of the following structures in the thoracic region? a) aorta b) heart c) lung d) sweat glands e) trachea
d) sweat glands Sympathetic fibers innervate sweat glands by synapsing in the sympathetic chain, jumping on the grey rami to rejoin the spinal nerve, and heading for the periphery. The sympathetic nerves to the heart, aorta, lungs, and bronchi are carried in the cardiac and pulmonary plexuses. These fibers are not found in spinal nerves.
A 12-year-old boy was admitted to a local hospital with a known history of heart problems. His left ventricular hypertrophy could result from which of the following conditions? a) A constricted pulmonary trunk b) An abnormally small left AV opening c) Improper closing of the pulmonary valves d) An abnormally large right AV opening e) Stenosis of the aorta
e) Stenosis of the aorta can cause left ventricular hypertrophy. Right ventricular hypertrophy may occur as a result of pulmonary stenosis, pulmonary and tricuspid valve defects, or mitral valve stenosis.
Coronary angiographs of a 44-year-old male patient reveal an occlusion of the circumflex branch of the left coronary artery. This patient has been suffering from myocardial infarction in which of the following areas? a) Right and left ventricles b) Right and left atria c) Interventricular septum d) Apex of the heart e) Left atrium and ventricle
e) The *left atrium and ventricle* receive blood from the circumflex branch of the left coronary artery. The interventricular septum and the apex of the heart are supplied by the anterior interventricular branch of the left coronary artery. The right ventricle receives blood from the anterior interventricular artery and the marginal branch of the right coronary artery. The right atrium receives blood from the right coronary artery.
While performing transesophageal echocardiography on a patient, the posterior wall of the esophagus, immediately behind the left atrium, was punctured from within. Doctors were very concerned about possible damage to a thin-walled vessel just behind the esophagus and between the azygos vein and aorta, i.e., the: a) Hemiazygos vein b) Left bronchial vein c) Left pulmonary vein d) Superior vena cava e) Thoracic duct
e) Thoracic duct The thoracic duct is found directly behind the esophagus in the posterior mediastinum, with the aorta to its left and the azygos vein to its right. This relationship between these three vessels is an important one to keep in mind! The other vessels do not share the same relationship with the azygos and aorta.
In cardiac surgery it is sometimes necessary to clamp off all arterial flow out of the heart. This could be done within the pericardial sac by inserting the index finger immediately behind the two great arteries and compressing them with the thumb of the same hand. The index finger would have to be inserted into which space? a) Cardiac notch b) Coronary sinus c) Oblique pericardial sinus d) Coronary sulcus e) Transverse pericardial sinus
e) Transverse pericardial sinus The transverse pericardial sinus is an area of the pericardial cavity located behind the aorta and pulmonary trunk and anterior to the superior vena cava. When entering the transverse pericardial sinus, a surgeon will insert an index finger between the aorta and pulmonary trunk on the ventral side and the superior vena cava on the dorsal side. The oblique pericardial sinus is an area of the pericardial cavity located behind the left atrium of the heart. If a surgeon places fingers under the apex of the heart, then moves the fingers until they are stopped by a pericardial reflection, then the fingers are in the oblique sinus.
During a surgical procedure, a patient's right sympathetic trunk was accidentally severed just cranial to the level of spinal nerve T1. Which function would be left intact in the affected region? a) Arrector pili muscle activity b) Dilation/constriction of blood vessels c) Sweat production d) Visceral reflex activity e) Voluntary muscle activity
e) voluntary muscle activity The sympathetic nervous system is not responsible for voluntary muscle activity. The neurons which supply voluntary muscles originate from the ventral horn of the spinal cord. One of the main functions of sympathetic nerves is maintaining the tone of blood vessels--if these nerves were damaged, it would be difficult to regulate vascular tone. The sympathetic nervous system also regulates the arrector pili muscles, sweat production, and visceral reflexes.
