Thorax Practice Questions

Q: Which layer of the heart is primarily responsible for the conduction of electrical impulses?

Myocardium. ***Myocardium*** - The **myocardium** is the thick muscular layer of the heart that contains the entire **cardiac conduction system**, including the SA node, AV node, Bundle of His, bundle branches, and Purkinje fibers. - These specialized **myocardial cells** form the conduction pathways that rapidly transmit electrical impulses throughout the heart, coordinating atrial and ventricular contractions. - The Purkinje fibers, while located in the subendocardial region, are specialized **myocardial cells**, not endocardial tissue. *Endocardium* - The **endocardium** is the thin innermost endothelial lining of the heart chambers and valves. - While Purkinje fibers lie just beneath the endocardium (subendocardial), the endocardium itself is not a conductive layer but rather a smooth lining that reduces friction. *Epicardium* - The **epicardium** is the outermost layer of the heart wall (visceral pericardium) and serves as a protective covering. - It contains coronary vessels and autonomic nerve fibers but does not contain the specialized conduction system. *Pericardium* - The **pericardium** is the fibroserous sac surrounding the heart that provides protection and prevents overdistension. - It has no role in electrical impulse generation or conduction within the heart.

Q: A patient with difficulty breathing and hoarseness may have a tumor affecting which structure in the mediastinum?

Recurrent laryngeal nerve. RECURRENT LARYNGEAL NERVE - Compression or damage to the **recurrent laryngeal nerve** can cause paralysis of the vocal cords, leading to **hoarseness** [1]. - Tumors in the mediastinum can impinge on this nerve as it courses upwards to innervate the intrinsic muscles of the larynx [1]. ESOPHAGUS - While esophageal tumors can cause **dysphagia** (difficulty swallowing) and potentially **difficulty breathing** due to airway compression, they do not directly cause hoarseness by affecting the vocal cords. - Hoarseness from an esophageal tumor would be an indirect effect if the tumor mass were significant enough to impact nearby structures like the recurrent laryngeal nerve. THORACIC DUCT - Damage to the **thoracic duct** typically leads to **chylothorax**, an accumulation of lymphatic fluid in the pleural space, causing **difficulty breathing**. - However, direct compression of the thoracic duct does not cause **hoarseness**, as it is not anatomically related to vocal cord function or innervation. TRACHEA - A tracheal tumor can cause significant **difficulty breathing** due to airway obstruction, leading to stridor or wheezing [1]. - While a tracheal tumor might cause some voice changes if it directly affects the vocal cords (rare) or causes significant airway turbulence, **hoarseness** as a direct result of nerve impairment is not its primary vocal symptom.

Q: Which muscle is involved in elevating the ribs during inspiration?

External intercostal muscles. ***External intercostal muscles*** - The **external intercostal muscles** contract during **inspiration**, pulling the ribs upwards and outwards [1]. - This action increases the **thoracic volume**, leading to a decrease in intrathoracic pressure and allowing air to flow into the lungs [1]. *Internal intercostal muscles* - The **internal intercostal muscles** are primarily active during **forced expiration**, pulling the ribs downwards and inwards. - Their contraction decreases the **thoracic volume**, helping to expel air from the lungs. *Transversus thoracis* - The **transversus thoracis** muscle is a thin muscle lying on the inside of the anterior chest wall. - It is involved in **forced expiration** by depressing the ribs. *Rectus abdominis* - The **rectus abdominis** is a major muscle of the anterior abdominal wall. - It is involved in **forced expiration** by pulling the rib cage downwards and compressing the abdominal contents, which in turn pushes the diaphragm upwards.

Q: Pectus excavatum is

Sternal depression. ***Sternal depression*** - **Pectus excavatum** is a congenital chest wall deformity characterized by an **inward depression** of the sternum and costal cartilages, creating a caved-in appearance of the chest. - This condition is also known as "funnel chest" due to the characteristic depressed shape. *Protrusion of sternum* - This describes **pectus carinatum**, a condition where the sternum and costal cartilages **protrude outward**, giving a "pigeon chest" appearance. - Unlike pectus excavatum, pectus carinatum involves an outward convex deformity. *Sternal cleft* - A **sternal cleft** is a rare congenital malformation where the **sternum is incompletely fused**, resulting in a gap or split in the breastbone. - This condition leads to the heart being very close to the skin, or even exposed, and can be associated with other midline defects. *Lateral displacement of sternum* - Lateral displacement of the sternum typically refers to a rare deformity where the **sternum shifts to one side** of the chest, often associated with other chest wall anomalies or scoliosis. - This is distinct from the symmetrical inward depression seen in pectus excavatum.

Q: Hoarseness of voice in lung carcinoma is due to invasion of which structure?

Recurrent laryngeal nerve. **Recurrent laryngeal nerve** - **Hoarseness** results from paralysis of the ipsilateral vocal cord due to damage to the **recurrent laryngeal nerve**, which innervates most intrinsic laryngeal muscles [1]. - Lung carcinomas, especially those in the **apex** (Pancoast tumors) or mediastinum, can directly invade or compress this nerve. *Internal laryngeal nerve* - The internal laryngeal nerve is primarily responsible for **sensory innervation** above the vocal cords and does not control vocal cord movement, so its damage would not cause hoarseness [1]. - Its main roles are related to the **cough reflex** and protecting the airway from aspiration [1]. *Glossopharyngeal nerve* - The glossopharyngeal nerve (**IX cranial nerve**) primarily supplies sensory innervation to the **posterior tongue**, pharynx, and taste, and motor innervation to the stylopharyngeus muscle. - Its damage would cause **dysphagia** and loss of taste, not hoarseness. *Vagus nerve* - While the **vagus nerve (X cranial nerve)** gives rise to the recurrent laryngeal nerve, direct involvement of the vagus nerve itself is less common than damage to the recurrent laryngeal nerve specifically for hoarseness in lung cancer. - Vagus nerve damage can cause a wider range of symptoms including **dysphagia**, autonomic dysfunction, and broader laryngeal paralysis, but hoarseness is more directly linked to its recurrent laryngeal branch.

Q: Esophagus is constricted at 4 anatomic locations. Narrowest part of esophagus lies at which of the following constrictions?

At the level of the cricopharyngeal constriction. At the level of the cricopharyngeal constriction - This is the **narrowest point of the entire esophagus** with a diameter of approximately **1.5 cm**. - Located at the **junction of the pharynx and esophagus** (C6 level, ~15 cm from incisors). - Formed by the **cricopharyngeus muscle** acting as the upper esophageal sphincter. - **Clinically significant**: Most common site for **foreign body impaction** and **iatrogenic perforation** during instrumentation. *At the level of the opening in the diaphragm* - This is the **diaphragmatic constriction** at the esophageal hiatus (~40 cm from incisors). - While physiologically important as the lower esophageal sphincter region, it is **not the narrowest** anatomical point. - Acts as an anti-reflux barrier in conjunction with the lower esophageal sphincter. *At the crossing of the aortic arch* - The esophagus passes **posterior to the aortic arch** (~22.5 cm from incisors). - Creates the second anatomical constriction but is **wider than the cricopharyngeal region**. - Can be visualized on barium swallow as an indentation on the esophagus. *At the crossing of the left main bronchus* - The **left main bronchus** crosses anterior to the esophagus (~27 cm from incisors). - This is the third anatomical constriction in the thoracic esophagus. - Also **wider than the upper esophageal constriction**.

Q: Which of the following passes posterior to the hilum of the lung?

Vagus. ***Vagus*** - The **vagus nerves** (cranial nerve X) descend through the neck and thorax, passing **posterior to the lung hila** as they contribute to the pulmonary plexus and then continue to the esophagus and abdominal viscera [2]. - They are primarily responsible for **parasympathetic innervation** to the thoracic and abdominal organs [1]. *Phrenic nerve* - The **phrenic nerves** (C3-C5) descend through the thorax, passing **anterior to the lung hila** and between the fibrous pericardium and the mediastinal pleura [2]. - They provide motor innervation to the **diaphragm** and sensory innervation to the central diaphragm, mediastinal pleura, and pericardium. *SVC* - The **superior vena cava (SVC)** is a large vein that drains blood from the upper body into the right atrium, situated in the superior mediastinum and passing **anterior to the right lung hilum** [2]. - Its position is medial and anterior to the structures of the hilum, not posterior. *Right atrium* - The **right atrium** is one of the four chambers of the heart, located in the middle mediastinum, **anterior to the lung hila** [2]. - It receives deoxygenated blood from the SVC, inferior vena cava (IVC), and coronary sinus.

Q: Which of the following is not included in the chest wall?

Lumbar vertebrae. The lumbar vertebrae are located in the lower back, inferior to the thoracic vertebrae, and are not part of the bony framework of the chest wall [1]. The chest wall is defined by structures that enclose the thoracic cavity, which extends from the neck to the diaphragm [1]. The ribs form the lateral and anterior boundaries of the chest wall, providing protection for the internal organs. They articulate posteriorly with the thoracic vertebrae and anteriorly with the sternum (directly or indirectly). The thoracic vertebrae form the posterior boundary of the chest wall, articulating with the ribs [1]. There are 12 thoracic vertebrae (T1-T12), all of which contribute to the structural integrity of the thorax. The sternum, or breastbone, forms the anterior boundary of the chest wall, articulating with the ribs via costal cartilages [1]. It consists of the manubrium, body, and xiphoid process, all crucial components of the thoracic cage [1].

Q: Where does the great cardiac vein lie?

Anterior interventricular sulcus. ***Anterior interventricular sulcus*** - The **great cardiac vein** runs alongside the **left anterior descending artery** (LAD) within the **anterior interventricular sulcus**. - This anatomical position allows it to drain the areas supplied by the LAD, primarily the **anterior walls** of both ventricles and the interventricular septum. - From the apex, it ascends in this sulcus before continuing around the left border of the heart. *Tricuspid valve* - The **tricuspid valve** is located between the **right atrium** and **right ventricle** and is involved in blood flow regulation, not venous drainage. - This is a valvular structure, not a sulcus or groove where vessels lie. *Posterior interventricular sulcus* - The **posterior interventricular sulcus** houses the **middle cardiac vein** and the **posterior interventricular artery**. - The great cardiac vein is not found in this sulcus; it drains the anterior aspect of the heart. *Coronary sulcus* - The **coronary sulcus** (atrioventricular groove) contains the **coronary sinus** and circumflex vessels. - While the great cardiac vein eventually continues as the coronary sinus in this region, the vein itself specifically lies in the anterior interventricular sulcus during its ascending course.

Q: Which nerve is primarily responsible for the motor supply to the diaphragm?

Phrenic nerve. ***Phrenic nerve*** - The **phrenic nerve** is the sole **motor supply** for the diaphragm, originating from the **cervical spinal roots C3, C4, and C5** (primarily C4) [1], [2]. - Its stimulation causes the diaphragm to contract, which is essential for **inspiration** [1]. - The well-known mnemonic is **"C3, 4, 5 keeps the diaphragm alive"**. *Cervical spinal roots C3, C4, and C5* - This option describes the **origin** of the phrenic nerve, not the nerve itself. - The **phrenic nerve is formed** by fibers from these cervical spinal roots, but the question asks for the **nerve** that provides motor supply [2]. - These roots contribute to forming the nerve, but they are not the primary structure responsible for innervation. *Accessory nerve* - The **accessory nerve (Cranial Nerve XI)** primarily innervates the **sternocleidomastoid** and **trapezius muscles**. - It plays no direct role in the motor control of the diaphragm. *Intercostal nerves* - **Intercostal nerves** innervate the **intercostal muscles**, which contribute to breathing by moving the rib cage [2]. - They do not innervate the diaphragm; their function is distinct from the phrenic nerve.

Question 1

Which layer of the heart is primarily responsible for the conduction of electrical impulses?

Accepted Answer

Myocardium

Answer

Epicardium

Answer

Pericardium

Answer

Endocardium

Question 2

A patient with difficulty breathing and hoarseness may have a tumor affecting which structure in the mediastinum?

Accepted Answer

Recurrent laryngeal nerve

Answer

Esophagus

Answer

Thoracic duct

Answer

Trachea

Question 3

Which muscle is involved in elevating the ribs during inspiration?

Accepted Answer

External intercostal muscles

Answer

Internal intercostal muscles

Answer

Transversus thoracis

Answer

Rectus abdominis

Question 4

Pectus excavatum is

Accepted Answer

Sternal depression

Answer

Protrusion of sternum

Answer

Sternal cleft

Answer

Lateral displacement of sternum

Question 5

Hoarseness of voice in lung carcinoma is due to invasion of which structure?

Accepted Answer

Recurrent laryngeal nerve

Answer

Internal laryngeal nerve

Answer

Glossopharyngeal nerve

Answer

Vagus nerve

Question 6

Esophagus is constricted at 4 anatomic locations. Narrowest part of esophagus lies at which of the following constrictions?

Accepted Answer

At the level of the cricopharyngeal constriction

Answer

At the level of the opening in the diaphragm

Answer

At the crossing of the aortic arch

Answer

At the crossing of the left main bronchus

Question 7

Which of the following passes posterior to the hilum of the lung?

Accepted Answer

Vagus

Answer

Phrenic nerve

Answer

SVC

Answer

Right atrium

Question 8

Which of the following is not included in the chest wall?

Accepted Answer

Lumbar vertebrae

Answer

Ribs

Answer

Thoracic Vertebrae

Answer

Sternum

Question 9

Where does the great cardiac vein lie?

Accepted Answer

Anterior interventricular sulcus

Answer

Tricuspid valve

Answer

Posterior interventricular sulcus

Answer

Coronary sulcus

Question 10

Which nerve is primarily responsible for the motor supply to the diaphragm?

Accepted Answer

Phrenic nerve

Answer

Cervical spinal roots C3, C4, and C5

Answer

Accessory nerve

Answer

Intercostal nerves

Thorax — MCQs

Thorax — MCQs

On this page

Practice by Chapter

Want unlimited practice?