1.
You are called to perform thoracentesis (remove fluid from the pleural cavity). If you are to avoid injuring lung or neurovascular elements, where would you insert the aspiration needle?
Correct Answer
D. The bottom of interspace 9 in the midaxillary line
Explanation
For a thoracocentesis, the needle needs to be inserted below the level of the lungs, in the costodiaphragmatic recess. At the midclavicular line, the recess is between rib spaces 6 and 8, at the midaxillary line it is between 8 and 10, and at the paravertebral line between 10 and 12. Additionally, the needle needs to be inserted at the top of the rib (or the bottom of the intercostal space). This is essential for avoiding damage to the neurovascular bundles that are found below the ribs, running in the costal groove. Taken together, these two pieces of information point to the conditions listed in D as the only appropriate ones for a thoracocentesis.
2.
The pleural space into which lung tissue just above the cardiac notch would tend to expand during deep inspiration is the:
Correct Answer
C. Costomediastinal recess
Explanation
The costomediastinal recess is an area right next to the cardiac notch, which is an indentation in the superior lobe of the left lung. This is where the medial area of the superior lobe of the left lung would tend to expand if it became very inflated. The lung would not enter the anterior mediastinum, which is an area between the two pleural sacs, bounded anteriorly by the sternum and posteriorly by the pericardium. The anterior mediastinum contains areolar tissue, sternopericardial ligaments, lymph vessels and nodes, but no lung tissue. The costodiaphragmatic recess is the recess at the inferior border of a lung. This is the space into which the inferior lobe of the lung would expand following deep inhalation. The cupola is the serous membrane lining the pleural cavity which extends above the level of the 1st rib into the root of the neck. The most superior portion of the superior lobe might expand into this space. The pulmonary ligament is the fold of pleura located below the root of the lung where the visceral pleura and the mediastinal parietal pleura are continuous with each other.
3.
Which feature is found only in the left lung?
Correct Answer
A. Cardiac notch
Explanation
The cardiac notch is only found on the left lung, which makes sense since the heart is located on the left side of the mediastinum. The horizontal fissure is a deep groove that separates the middle lobe from the upper lobe of the right lung. The left lung does not have a horizontal fissure. The oblique fissure is found in both lungs. It separates the upper lobe from the lower lobe in both lungs and the middle lobe from the lower lobe in the right lung. Both lungs also have a superior lobar bronchus leading to their superior lobes. Finally, the right lung has three lobes while the left lung has two lobes.
4.
Which of the following nerves would be most vulnerable to irritation when the tracheobronchial lymph nodes are enlarged due to a diseased situation?
Correct Answer
D. Left recurrent laryngeal
Explanation
The tracheobronchial nodes are at the tracheal bifurcation. There are three groups of these nodes: right superior, left superior, and inferior. The aorta loops over the left bronchus, near the tracheal bifurcation. So, it is reasonable to assume that any nerve that is closely associated with the aorta might be irritated if the tracheobronchial lymph nodes became inflamed. This means that the correct answer is the left recurrent laryngeal nerve, which loops under the aorta to ascend to the larynx.
The right and left phrenic nerves are lateral and would not be irritated by the inflammation. The right recurrent laryngeal nerve loops around the right subclavian artery and is not close enough to this area. Finally, the right vagus is not closely associated with the aorta.
5.
Which part of the left lung might partially fill the costomediastinal recess in full inspiration?
Correct Answer
D. Lingula
Explanation
When inspiring fully, the lingula of the left lung might partially fill the costomediastinal recess. The lingula, a tongue-like projection of the left lung below the cardiac notch, is right next to the costomediastinal recess. If the apex of the lung was highly inflated, it might expand to fill the cupola. The hilum is the part of the lung where the structures forming the root of the lung--the main bronchus, pulmonary vessels, bronchial vessels, lymphatics, and nerve--enter and leave the lung. It does not expand on inspiration. The middle lobe of the lung may expand to fill the costomediastinal recess, but remember that the question is specifically asking about a left lung structure, and the middle lobe is only in the right lung!
6.
The oblique fissure of the right lung separates which structures?
Correct Answer
C. Lower lobe from both upper and middle lobes
Explanation
The oblique fissure cuts across the right lung in such a way as to separate the lower lobe from both the middle and upper lobes. So what does the horizontal fissure do? It separates the middle lobe from the upper lobe. Remember that the lingula is only on the left lung, and it is part of the superior lobe.
7.
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?
Correct Answer
D. Right main bronchus
Explanation
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!
8.
Which statement is true about the right lung?
Correct Answer
D. Its upper lobar bronchus lies behind and above the right pulmonary artery
Explanation
The structures at the root of the lung have different relationships in the right and left lungs. On both sides, the pulmonary veins are anterior and inferior while the bronchus is posterior. The difference between the two sides involves the pulmonary arteries. On the right side, the arteries are anterior to the bronchus, while on the left side the arteries are superior to the bronchus. The right lung is slightly larger than the left lung, and the lingula is found in the left lung only. Neither lung is in the mediastinum--the mediastinum is the space between the two pleural sacs. Finally, the phrenic nerve passes anterior to the root of the lung--on both the left and right sides.
9.
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?
Correct Answer
B. Inferior lobe
Explanation
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.)
10.
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?
Correct Answer
D. Right bronchus
Explanation
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
11.
A sick person, lying supine in bed, aspirates (breathes in) some fluid into her lungs while swallowing. It would most likely end up in which of the following bronchopulmonary segments?
Correct Answer
C. Superior segmental bronchus of right inferior lobe
Explanation
Remember: Inhaled material tends to go into the right bronchus because it is bigger and more vertically orientated than the left! The superior segmental bronchus branches posteriorly off of the intermediate bronchus or the inferior lobe bronchus, so it is the segmental bronchus most likely to receive the foreign bodies that enter the right main bronchus.
12.
A 22-year-old male involved in a bar-room brawl suffered a stab wound through the posterior thoracic wall that entered the posterior surface of the right lung half way between its apex and diaphragmatic surface. Which part of the lung did the knife first enter?
Correct Answer
B. Inferior lobe
Explanation
Because of the sharp angle of the oblique fissures, the posterior surfaces of both the right and left lungs are almost entirely comprised of the inferior lobe--the middle lobe of the right lung is not part of the posterior surface of the lung. So, a stab wound halfway between the apex and diaphragmatic surface of the lung would result in injury to the inferior lobe. The lingula is part of the superior lobe of the left lung, which forms the anterior and superior sides of that lung. The superior lobe (along with the middle lobe) forms the anterior surface of the right lung. The superior lobe also forms the superior aspect of both lungs. The cupola is the serous membrane lining the pleural cavity which extends above the level of the 1st rib into the root of the neck--it is not part of the lung!
13.
A 20-year-old man was stabbed in the back with a knife that just nicked his right lung halfway between its apex and diaphragmatic surface. Which part of the lung was most likely injured?
Correct Answer
B. Inferior lobe
Explanation
Because of the sharp angle of the oblique fissures, the posterior surfaces of both the right and left lungs are almost entirely comprised of the inferior lobes. And remember--the middle lobe of the right lung is not part of the posterior surface of the lung. So, a stab wound halfway between the apex and diaphragmatic surface of the right lung would result in injury to the inferior lobe. The cardiac notch is an indentation on the left lung which helps to form the lingula. The lingula is part of the superior lobe of the left lung, which forms the anterior and superior sides of that lung. The superior lobe (along with the middle lobe) forms the anterior surface of the right lung. The superior lobe also forms the superior aspect of both lungs.
14.
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?
Correct Answer
D. Superior segment--inferior lobe
Explanation
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.
15.
You are observing a doctor perform a bronchoscopy. As he passes the bronchoscope down the trachea, a cartilagenous structure is observed separating the right and left main stem bronchi. He asks what it is called. You reply that it really does look like a ship's keel and that it is called the:
Correct Answer
A. Carina
Explanation
The carina is a keel-shaped cartilage lying at the tracheal bifurcation--it separates the right main stem bronchus from the left main stem bronchus. The carina is a little to the left of the tracheal bifurcation, so if there is an inhaled body the carina will tend to divert foreign objects to the right main bronchus. The cricoid cartilage is the inferior and posterior cartilage of the larynx. The costal cartilages prolong the ribs anteriorly and contribute to the elasticity of the thoracic wall. They increase in length through the first seven and then gradually decrease. The pulmonary ligament is a fold of pleura located below the root of the lung. Tracheal rings are the cartilagenous structures which support the trachea and keep it patent.
16.
The minor (horizontal) fissure separates:
Correct Answer
E. The middle lobe from the upper lobe
Explanation
The horizontal fissure cuts across the right lung in such a way as to separate the middle lobe from the upper lobe. The oblique fissure separates the lower lobe from both the middle and upper lobes. Remember that the lingula is only on the left lung, and it is part of the superior lobe.
17.
Your patient, an 86-year-old female who has been bed-ridden and lying supine for many weeks, has developed a right lung abscess that is draining by gravity into one particular region of the lung. Where is the most likely site of fluid accumulation?
Correct Answer
E. Superior segment of lower lobe
Explanation
The superior segmental bronchus to the lower lobe of the right lung branches posteriorly off of the intermediate bronchus or the inferior lobe bronchus. So, it is the segmental bronchus most likely to receive the fluid or foreign bodies that enter the right main bronchus. This segment of the lung is even more likely to accumulate fluid when the patient is supine
18.
Because of its angle with the trachea and size of the main bronchus, a bronchoscope would pass more readily into which lung?
Correct Answer
B. Right
Explanation
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.
19.
Which vessel courses across the mediastinum in an almost horizontal fashion?
Correct Answer
C. Left brachiocepHalic vein
Explanation
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.
20.
A 78-year-old female presented with edema of the left upper limb due to poor venous return. Examination revealed an aneurysm of the ascending aorta that was impinging on a large vein lying immediately anterosuperior to it, most likely the:
Correct Answer
C. Left brachiocepHalic v.
Explanation
Remember that the ascending aorta is the short part of the aorta emerging from the heart before the aortic arch. The left brachiocephalic vein is the only vein listed which is anterosuperior to that part of the aorta. It crosses horizontally through the mediastinum to join with the right brachiocephalic vein and form the superior vena cava. The right brachiocephalic vein stays on the right side of the chest and would not be affected by the aortic aneurysm. The azygos vein is also on the right side of the chest, and it lays deep in the thoracic cavity. The internal thoracic vein lies on the interior surface of the anterior wall of the chest. Although it drains into the brachiocephalic vein, it would not be affected by the aneurysm. The left superior intercostal vein crosses the aortic arch laterally, but its blockage would only affect drainage of intercostal spaces 2-4 on the left side.
21.
An 8-year-old boy is found to have a mid-line tumor of the thymus gland that is impinging posteriorly on a blood vessel. The affected vessel is most likely the:
Correct Answer
A. Left brachiocepHalic vein
Explanation
Remember--the thymus is a very superficial structure found in the anterior mediastinum. The left brachiocephalic vein courses through the mediastinum to join the right brachiocephalic vein and form the superior vena cava on the right side of the thorax. Since the left brachiocephalic vein is fairly superficial, it travels just deep to the thymus. So, it might be compressed by the tumor. See Netter Plate 206 for a picture of the thymus and the left brachiocephalic vein.
The left pulmonary vein, left bronchial vein, and right pulmonary arteries are deep structures that enter and exit the lung at its root--they are not near the thymus. The right superior intercostal vein drains intercostal spaces 2-4. It drains into the arch of the azygos vein and is not associated with the thymus.