CP_Texas Tech_Superior Mediastinum & Lungs

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:

The correct answer is: Carina

The pleural space into which lung tissue just above the cardiac notch would tend to expand during deep inspiration is the:

The correct answer is: Costomediastinal recess 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.

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?

The correct answer is: Inferior lobe 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.

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:

The correct answer is: Left brachiocephalic vein 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.

Because of its angle with the trachea and size of the main bronchus, a bronchoscope would pass more readily into which lung?

The correct answer is: Right

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?

The correct answer is: 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.

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?

The correct answer is: Superior segment of lower lobe 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.

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?

The correct answer is: 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.

Which feature is found only in the left lung?

The correct answer is: cardiac notch

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?

The correct answer is: 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.)

Which statement is true about the right lung?

The correct answer is: its upper lobar bronchus lies behind and above the right pulmonary artery 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.

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:

The correct answer is: left brachiocephalic vein 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.

Which vessel courses across the mediastinum in an almost horizontal fashion?

The correct answer is: 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.

Which of the following nerves would be most vulnerable to irritation when the tracheobronchial lymph nodes are enlarged due to a diseased situation?

The correct answer is: left recurrent laryngeal 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.

Which part of the left lung might partially fill the costomediastinal recess in full inspiration?

The correct answer is: lingula 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!

The oblique fissure of the right lung separates which structures?

The correct answer is: lower lobe from both middle and upper lobe 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.

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?

The correct answer is: 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!

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?

The correct answer is: superior segmental bronchus of right inferior lobe 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.

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?

The correct answer is: the bottom of interspace 9 in the midaxillary line 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.

The minor (horizontal) fissure separates:

The correct answer is: the upper lobe from the middle lobe 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.