Thorax Practice Questions

Q: The incidence of a foreign body being aspirated into the right lung is higher than into the left lung. All of the following statements support this, EXCEPT?

Right lung is shorter and wider than left lung. ***Right lung is shorter and wider than left lung*** - This statement, while anatomically true, does **NOT directly explain** why foreign bodies preferentially enter the right lung - The dimensions of the **lung parenchyma itself** (shorter due to the diaphragm being pushed up by the liver, and wider) are unrelated to aspiration patterns - What determines aspiration is the **bronchial tree geometry** (angle, diameter, verticality), not the overall lung size - This is the EXCEPTION - it's a true anatomical fact but doesn't support the aspiration phenomenon *Incorrect - Tracheal bifurcation directs the foreign body to the right lung* - This statement DOES support higher right aspiration, so it cannot be the answer - The **carina angle** and bifurcation geometry favor the right side, directing foreign bodies preferentially to the right main bronchus - This is a key anatomical reason for the higher incidence *Incorrect - Right inferior lobar bronchus is in continuation with the right principal bronchus* - This statement DOES support higher right aspiration - After the right superior lobar bronchus branches off, the **intermediate bronchus** continues more directly toward the inferior lobe - This creates a straighter pathway from trachea → right main bronchus → intermediate bronchus → inferior lobar bronchus - Foreign bodies follow this direct path, often lodging in the right inferior lobe *Incorrect - Right principal bronchus is more vertical than the left bronchus* - This statement DOES support higher right aspiration - The right main bronchus diverges at approximately **25 degrees** from vertical, while the left diverges at **45 degrees** - This more vertical orientation makes the right bronchus a more direct continuation of the trachea - Gravity and airflow naturally direct aspirated material down this straighter path

Q: Left superior intercostal vein drains into?

Brachiocephalic vein. ***Brachiocephalic vein*** - The **left superior intercostal vein** is formed by the confluence of the **2nd and 3rd** left posterior intercostal veins. - It typically drains into the **left brachiocephalic vein**, which then contributes to the superior vena cava. *Hemiazygos vein* - The **hemiazygos vein** is on the left side of the vertebral column and primarily drains the lower left posterior intercostal veins (9th-11th). - It usually joins the **azygos vein** around the T8-T9 vertebral level, rather than directly receiving the left superior intercostal vein. *Internal thoracic vein* - The **internal thoracic veins** drain the anterior sensory chest wall and typically run alongside the sternum. - While they eventually drain into the brachiocephalic veins, they do not directly receive the posterior intercostal veins like the left superior intercostal vein. *Azygos vein* - The **azygos vein** is primarily on the right side of the vertebral column, draining the right posterior intercostal veins. - It usually receives the **hemiazygos** and **accessory hemiazygos veins** but not the left superior intercostal vein directly.

Q: Which of the following structures is NOT innervated by the phrenic nerve?

Serratus anterior. ***Serratus anterior*** - The **serratus anterior** muscle is innervated by the **long thoracic nerve (roots C5, C6, C7)**, not the phrenic nerve. - Its primary actions are to protract and rotate the scapula, and it is crucial for overhead arm movements. *Diaphragm* - The **diaphragm** is primarily innervated by the **phrenic nerve (C3, C4, C5)**, which is essential for its role in respiration [1]. - Sensory fibers from the phrenic nerve also supply the central part of the diaphragm. *Mediastinal pleura* - The **mediastinal pleura**, which lines the mediastinum, receives sensory innervation from the **phrenic nerve**. - Irritation of this pleura can cause referred pain to the shoulder, due to shared innervation origins. *Pericardium* - The **fibrous pericardium** and the **parietal layer of the serous pericardium** are innervated by the **phrenic nerves**. - This innervation accounts for referred pain to the shoulder in conditions affecting the pericardium.

Q: The pleura extends down to which rib at the midclavicular line?

8th rib. ***8th rib*** - The **parietal pleura** extends to the **8th rib** at the **midclavicular line**, marking the inferior border of the pleural cavity in this region. [1] - This creates the **costodiaphragmatic recess** below the lung border, which extends only to the 6th rib at the midclavicular line. [1] - Understanding these anatomical landmarks is crucial for procedures like **thoracentesis** to avoid lung injury while accessing the pleural space. [1] *6th rib* - The **lung** (not pleura) extends to the **6th rib** at the **midclavicular line**. - The pleura extends approximately **two rib spaces lower** than the lung to create the costodiaphragmatic recess. - This is an important distinction for safe needle placement during thoracentesis. *10th rib* - The **parietal pleura** extends to the **10th rib** at the **midaxillary line**, not the midclavicular line. - This represents a more lateral and inferior extension of the pleural cavity. *12th rib* - The **parietal pleura** extends to the **12th rib** at the **paravertebral (scapular) line**, which is the most posterior and inferior extension. - This is significantly lower and more posterior than the midclavicular line.

Q: Which heart chamber has the thickest wall?

Left ventricle. ***Left ventricle*** - The left ventricle is responsible for pumping **oxygenated blood** to the entire systemic circulation, requiring significant force. - Its muscular wall is the **thickest** to generate the high pressures needed to overcome systemic vascular resistance [1]. *Right atrium* - The right atrium receives deoxygenated blood from the body and pumps it to the right ventricle, which is a **low-pressure circuit** [2]. - Its walls are relatively thin compared to the ventricles, as it only needs to provide a small "kick" to fill the right ventricle. *Left atrium* - The left atrium receives oxygenated blood from the lungs and pumps it to the left ventricle, operating under **low pressure**. - Its walls are thin, similar to the right atrium, as it does not need to generate high pressures. *Right ventricle* - The right ventricle pumps deoxygenated blood to the **pulmonary circulation**, which is a **low-pressure system** [1]. - While thicker than the atria, its wall is thinner than the left ventricle because it faces less resistance and pumps against lower pressures to the lungs.

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: Identify the muscle that assists in both breathing and changes in the volume of the thoracic cavity.

Diaphragm. ***Diaphragm*** - The **diaphragm** is the primary muscle of inspiration, and its contraction causes it to flatten, increasing the **vertical diameter** of the thoracic cavity [1]. - This increase in thoracic volume leads to a decrease in intrapleural pressure, drawing air into the lungs [1]. *External oblique* - The **external oblique** is an abdominal muscle involved in forced expiration by compressing the abdominal contents and pushing the diaphragm upwards. - It does not directly affect the initial increase in thoracic volume during quiet breathing. *Rectus abdominis* - The **rectus abdominis** is an abdominal muscle that aids in forced expiration by pulling the sternum and rib cage downwards, thereby decreasing thoracic volume. - It is not a primary muscle involved in increasing thoracic volume for inspiration. *Internal intercostal* - The **internal intercostals** are primarily involved in forced expiration, pulling the ribs downwards and inwards to decrease the thoracic volume. - During quiet inspiration, the **external intercostals** elevate the ribs to increase thoracic volume, not the internal intercostals [1].

Q: At what anatomical level does the apex of the lung lie?

Above the clavicle. ***Above the clavicle*** - The **apex of the lung** extends superiorly, projecting into the root of the neck. - It lies approximately **2-3 cm above the medial third of the clavicle**, reaching the level of the neck of the first rib. - This is an important anatomical relationship, as the apex is vulnerable to injury from trauma or procedures in this region. *Below the clavicle* - The main body of the lung lies below the clavicle, but the **apex** specifically refers to the uppermost part that projects superiorly. - The clavicle forms an anterior boundary; the lung apex itself extends beyond this landmark. *At the level of the clavicle* - While part of the lung tissue is at this level, the **true apex** of the lung extends superior to the clavicle. - The clavicle is more of a landmark for the superior border of the thoracic cavity, not the apex itself. *At the level of the first rib* - The apex reaches the **neck of the first rib** posteriorly, but anteriorly it projects **above the clavicle**. - This option confuses the posterior and anterior relationships of the lung apex.

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.

Question 1

The incidence of a foreign body being aspirated into the right lung is higher than into the left lung. All of the following statements support this, EXCEPT?

Accepted Answer

Right lung is shorter and wider than left lung

Answer

Tracheal bifurcation directs the foreign body to the right lung

Answer

Right inferior lobar bronchus is in continuation with the right principal bronchus

Answer

Right principal bronchus is more vertical than the left bronchus

Question 2

Left superior intercostal vein drains into?

Accepted Answer

Brachiocephalic vein

Answer

Hemiazygos vein

Answer

Internal thoracic vein

Answer

Azygos vein

Question 3

Which of the following structures is NOT innervated by the phrenic nerve?

Accepted Answer

Serratus anterior

Answer

Diaphragm

Answer

Mediastinal pleura

Answer

Pericardium

Question 4

The pleura extends down to which rib at the midclavicular line?

Accepted Answer

8th rib

Answer

6th rib

Answer

10th rib

Answer

12th rib

Question 5

Which of the following statements is true regarding the anatomy of the breast?

Accepted Answer

The axillary tail of Spence crosses the anterior axillary fold

Answer

The superior medial quadrant has more tissue

Answer

The nipple is located at the level of the fourth intercostal space in most women

Answer

There are 15-20 lobules present

Question 6

Which heart chamber has the thickest wall?

Accepted Answer

Left ventricle

Answer

Right atrium

Answer

Left atrium

Answer

Right ventricle

Question 7

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 8

Identify the muscle that assists in both breathing and changes in the volume of the thoracic cavity.

Accepted Answer

Diaphragm

Answer

External oblique

Answer

Rectus abdominis

Answer

Internal intercostal

Question 9

At what anatomical level does the apex of the lung lie?

Accepted Answer

Above the clavicle

Answer

Below the clavicle

Answer

At the level of the clavicle

Answer

At the level of the first rib

Question 10

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

Accepted Answer

Vagus

Answer

Phrenic nerve

Answer

SVC

Answer

Right atrium

Thorax — MCQs

Thorax — MCQs

On this page

Practice by Chapter

Want unlimited practice?