Lachmans Back and Thorax Unit 2

Question 1

Which axillary lymph nodes are in the most likely pathway of lymphatic drainage from the breast?

Answer 1

Anterior nodes receive the initial drainage - -> Central and apical nodes.

Question 2

What 3 nerves pass through the axilla and are most susceptible to injury in an axillary node dissection, and what do these nerves innervate?

Answer 2

The long thoracic nerve (medial wall of the axilla)

The thoracodorsal nerve (posterior wall of the axilla)

Intercostobrachial nerve traverses the axilla from medial to lateral and provides sensory innervation to the medial arm.

Question 3

Why is a dye injected into the region of the breast tumor before a sentinel lymph node biopsy is done?

Answer 3

The dye is picked up by the lymphatic system and will travel to the axillary lymph nodes or nodes to which the tissue around the tumor drains.

This allows the identification of the first lymph nodes to which cancer cells form the tumor would metastasize. The biopsy of this node then provides a good indication of whether there has been any metastasis of the cancer from the breast to the axilla.

Question 4

What muscles form the wall of the axilla?

Answer 4

Anterior wall- Pectoralis major, and minor

Posterior wall- Subscapularis, teres major and latissimus dorsi

Medial wall- serratus anterior

Question 5

What is the role of the parasternal lymph nodes in the lymphatic drainage from the breast?

Answer 5

A significant portion of the lymphatic drainage from the medial portion of the breast goes to the parasternal lymph nodes, which are in the anterior intercostal spaces near the internal thoracic (mammary) vessels. These nodes drain to the supraclavicular nodes. They are lymphatic communications between the parasternal lymph nodes of the right and left side that provide a pathway for metastasis from one breast to the other

Question 6

What is the functional and structural unit of the lung?

Answer 6

The functional unit of the lung is the bronchopulmonary segment.

This is the region of a lobe that is supplied by one segment (tertiary) bronchus and one segmental branch of a pulmonary artery. Disease processes may be restricted to a single bronchopulmonary segment.

Question 7

Why is an aspirated foreign body more likely to pass into the right main bronchus than the left?

Answer 7

At the tracheal bifurcation, the right main bronchus takes a more vertical course and is wider. Therefore, an aspirated body is more likely to pass into the right main bronchus.

Question 8

At what point does the common aerodigestive tract divide into separate airway and digestive tracts?

Answer 8

The oropharynx is a common aerodigestive tract, at the level of about the C4 vertebra, the opening into the larynx is the upper end if the dedicated airway, and the laryngopharynx is dedicated as a food pathway. The pharynx continues downward as the trachea, and the laryngopharynx continues as the esophagus.

Question 9

What vascular structures are used surgically as landmarks to identify the boundaries between bronchopulmonary segments?

Answer 9

Branches of the lobar pulmonary veins lie in the connective tissue planes between adjacent bronchopulmonary segments. These intersegmental veins are used as the landmarks to identify the boundaries between the segments.

Question 10

What is the role of the soft palate during swallowing?

Answer 10

During swallowing, the soft palate is elevated to occlude the opening between the nasopharynx and the oropharynx. This prevents food in the oropharynx from passing upward into the nasopharynx when the pharynx constricts.

Question 11

What is the piriform recess, and what is its role in swallowing?

Answer 11

The piriform recess is that portion of the laryngopharynx that is posterolateral to the larynx. During swallowing, food is diverted from the midline by the epiglottis and directed into the piriform recess. From there, it returns to the midline to enter the esophagus. This pathway keeps the food out of the airway.

Question 12

What is the role of the vocal folds in the cough reflex?

Answer 12

Supraglottic mucosa is stimulated, the:
- vocal folds adduct to close the glottis.(This prevents a foreign body from entering the infraglottic space. With the glottis closed)
- the intrathoracic pressure is increased by contraction of the abdominal muscles. When the pressure gradient between the infraglottic space and the supraglottic vestibule is high enough
… the vocal folds rapidly abduct to open the glottis, and a high-velocity blast of air moves upward to clear the vestibule.

Question 13

What four congenital defects are found in tetralogy of Fallot?

Answer 13

Pulmonary stenosis
Over-riding aorta
Ventricular septal defect,
Right ventricular hypertrophy

Question 14

What embryonic structure us responsible for the formation of the ascending aorta and the pulmonary trunk?

Answer 14

The aorticopulmonary septum forms in the truncus arteriosus and divides it into the ascending aorta and the pulmonary trunk. It normally forms in the center of the truncus arteriosus, this creating two equal-sized vessels.

Question 15

Why does a child with tetralogy of Fallot squat when having a cyanotic episode?

Answer 15

It is believed that the squatting causes a kinking of the arterial supply to the lower limbs and thus increases the peripheral resistance of the systemic circulation. This increases to the left ventricular pressure, reducing the pressure gradient between the right and left ventricle and thereby reducing the shunting of deoxygenated blood into the systemic circulation.

Question 16

What structures pass through the hilum of the lung?

Answer 16

All of the structures of the root of the lung ass through the hilum. These include the bronchus, the pulmonary artery, usually two pulmonary veins, the bronchial artery and vein, and the lymphatics of the lung. The pulmonary veins are the most inferior and most anterior structure passing through the hilum. The bronchus is the most posterior structure passing through the hilum. The position of the pulmonary artery is slightly different on the right and left side.

Question 17

What is the pathway of lymphatic drainage from the lung?

Answer 17

All lymphatic drainage in the lung is toward the hilum.

Pulmonary lymph nodes (Lung) –> bronchopulmonary lymph nodes (hilum) –> tracheobronchial lymph nodes (at the bifurcation of the trachea) –> paratracheal lymph node –> bronchomediastinal lymph trunk.

Question 18

What are the portions of the parietal pleura?

Answer 18

The portions of parietal pleura are given names according to their location. The costal pleura is attached to the ribs of the chest wall. The diaphragmatic pleura is attached to the upper surface of the diaphragm. The mediastinal pleura is attached to the lateral surface of the mediastinum. The cervical pleura is the parietal pleura that ascends above the first rib and is in the neck.

Question 19

Where does the parietal pleura become continuous with the visceral pleura?

Answer 19

The visceral pleura is fused to the surface of the lung. The parietal pleura is continuous with the visceral pleura at the hilum of the lung. This pleural reflection surrounds the structures of the root of the lung: the bronchus, the pulmonary artery, the pulmonary veins, the bronchial arteries and veins, and the lymphatics and nerves of the lung.

Question 20

Why does the lung collapse when there is a pneumothorax?

Answer 20

Normally, there is a negative pressure in the pleural cavity (ie. Less that atmospheric pressure). The pressure inside the lung is atmospheric. This pressure gradient keeps the lung expanded against the elastic recoil of the lung. With a pneumothorax, air enters the pleural cavity and raises the pressure in the cavity. This disrupts the pressure gradient that resists the elastic recoil of the lung, allowing the lung to collapse

Question 21

How does a tension pneumothorax compromise the circulatory system?

Answer 21

In a tension pneumothorax, the intracranial pressure rises above atmospheric pressure. This results in a pressure gradient between the two pleural cavities that pushes against the mediastinum and displaces it away from the side with the pneumothorax. This causes a kinking of the vena cava, resulting in a reduction in venous return. Additionally, the compression of the heart reduces diastolic filling of the ventricles, causing a decrease in cardiac output.

Question 22

What is the anatomical pathway for pain from the heart?

Answer 22

The sensory nerve fibers that convey the sensation of pain from the heart travel with the sympathetic nerves that innervate the heart. They travel in the cardiac nerves to reach the sympathetic chain, then pass through the sympathetic ganglia and white rami communicants to reach the upper thoracic spinal nerves. They continue through the dorsal roots of these spinal nerves and have their cell bodies in the dorsal root ganglia.

Question 23

To which dermatomes is cardiac pain referred?

Answer 23

Pain arising from the heart is referred to the dermatomes that correspond to the spinal nerve levels through which the sensory fibers from the heart reach the spinal cord. These are the upper thoracic spinal nerves. The corresponding dermatomes are found in the upper chest and the medial side of the arm.

Question 24

What sensory functions are served by the sensory nerve fibers from the heart that travel in the vagus nerve?

Answer 24

The sensory fibers from the heart that are in the vagus nerve carry the sensory information necessary for the control of cardiac reflexes. This sensory information reaches the brain stem but does not ascend to conscious levels.

Question 25

What landmarks are used to locate the femoral artery to gain arterial access for coronary angioplasty?

Answer 25

The femoral artery is the distal continuation of the external iliac artery. Its name changes as the artery passes under the inguinal ligament. The femoral artery can be located immediately inferior to the midpoint if the inguinal ligament. This midpoint can be located by identifying the midpoint between the 2 bony attachments of the inguinal ligament, the ASIS and the pubic tubercle.

Question 26

What are the origins of the right and left coronary arteries?

Answer 26

Both coronary arteries arise from the ascending aorta. They are the only branches of the ascending aorta. The right coronary artery arises from the wall of the right aortic sinus behind the right cusp of the aortic valve; the left coronary artery arises from the wall of the left aortic sinus behind the left cusp of the aortic valve.

Question 27

What are the two main branches of the left coronary artery?

Answer 27

The left coronary artery arises from the left side of the ascending aorta and passes behind the pulmonary trunk. After passing the pulmonary trunk, the artery divides into the circumflex branch and the anterior interventricular branch (left anterior descending artery). The circumflex branch enters the coronary sulcus, and the anterior interventricular branch enters the anterior interventricular sulcus.

Question 28

What are the major anastomoses between the right coronary artery and the left coronary artery?

Answer 28

The right coronary artery anastomoses with the circumflex branch of the left coronary artery. The anterior interventricular artery (a branch of the left coronary artery) anastomoses with the posterior interventricular artery (a branch of the right coronary artery).

Question 29

What is the function of the papillary muscles and the chordae tendinae?

Answer 29

The papillary muscles are bundles of cardiac muscle that project into the lumina of the right and left ventricles. The chorda tendinae are strands of connective tissue that attach the tips of the papillary muscles to the edges of the susps of the tricuspid and mitral valves in the right and left ventricles, respectively. The papillary muscles and chordae tendinae control the closure of the tricuspid and mitral valves during ventricular systole. They prevent prolapse of these valves. Infarct of a papillary muscle or rupture of chordae tendinae may result in prolapse of the valve with regurgitation.

Question 30

What is the difference between a right-dominant heart and a left-dominant heart?

Answer 30

Dominance in the heart is based on the origin of the posterior interventricular artery. If it arises from the right coronary artery (the most common scenario), the heart is said to be right dominant. If it arises from the circumflex branch of the left coronary artery, the heart is said to be left dominant. Right-dominant hearts have more opportunity for anastomoses between the right and left coronary arteries.

Question 31

What is the ductus arteriosus?

Answer 31

The ductus arteriosus is an embryonic blood vessel that is derived from the left 6th aortic arch. The ductus arteriosus connects the aortic arch with the left pulmonary artery. Prenatally, blood is shunted from the pulmonary artery into the aorta through the ductus arteriosus. After birth, the ductus arteriosus normally closes and then becomes fibrotic. It is then called the ligamentum arteriosum.

Question 32

What is the isthmus of the aorta?

Answer 32

The isthmus if the aorta is the region of the aorta between the origin of the left subclavian artery and the ductus arteriosus (or ligamentum arteriosum). This is the most common site of aortic coarctation.

Question 33

Why is a patient with coarctation of the aorta at increased risk for stroke?

Answer 33

Coarctation of the aorta causes an increase in blood pressure proximal to the coarctation. Because the blood supply to the brain arises from the aorta proximal to the usual site of coarctation, the blood pressure in the cerebral circulation is elevated. This increases the risk of stroke.

Question 34

Why is nothing of the ribs seen in patients coarctation of the aorta?

Answer 34

The intercostal arteries serve as collateral pathways between the aorta and the internal thoracic arteries. These collateral channels are used to bypass a coarctation of the aorta. The increased flow in the intercostal arteries causes an increase in the size of these arteries. These arteries are located along the lower borders of the ribs, and as they enlarge, they cause resorption of bone along the lower borders of the ribs, resulting in notching.

Question 35

What is the origin of the azygos vein, and into what vein does it drain?

Answer 35

The azygos vein is formed by the union of the right ascending lumbar vein and the right subcostal vein. It ascends into the thorax, and it drains into the SVC. It receives drainage from the intercostal veins on the right, and it receives drainage from the left intercostal veins via the hemiazygos vein.

Question 36

What are the most common causes of compression of the SVC and the resultant SVC syndrome?

Answer 36

The most common causes of SVC syndrome are mediastinal malignancies and their associated enlarged lymph nodes. Lymphomas and lung cancer are common sources of these malignancies.

Question 37

What organ is immediately anterior to the esophagus in the neck and is a frequent site of invasion by esophageal cancer?

Answer 37

The trachea is immediately anterior to the esophagus. There is only a thin layer of connective tissue separating these organs.

Question 38

What nerve is found in the tracheoesophageal groove, and what is the effect of its compression by esophageal tumors?

Answer 38

The recurrent laryngeal nerve lies in the tracheoesophageal groove. The nerve ascends from the aortic arch on the left and from the subclavian artery on the right. The nerve innervates all of the muscles of the larynx except for the cricothyroid. Lesion of the nerve results in hoarseness and a semi abducted vocal fold.

Question 39

Which chamber of the heart is immediately anterior to the esophagus?

Answer 39

The left atrium is immediately anterior to the esophagus, with only the pericardium intervening between them. Cancer of the esophagus may invade the left atrium. Similarly, enlargement of the left atrium may compress the esophagus.

Question 40

Into what veins do the esophageal veins drain?

Answer 40

The esophageal veins drain into the azygos vein and hemiazygos vein and then into the SVC. They also drain into the left gastric vein, which drains into the portal vein. Cancer of the esophagus may spread in either direction. The esophageal veins serve as in important anastomosis between the portal venous system and the systemic venous system.