Thorax — MCQs
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Which of the following segments is present in the middle lobe of the right lung?
What is the primary motor nerve supplying the diaphragm?
Lower limit of the left crus of the diaphragm is at which vertebral level?
Which of the following structures pass through the aortic hiatus of the diaphragm?
Bifurcation of the trachea takes place at which level?
The 8th, 9th, and 10th ribs are attached to their respective costal cartilages by which type of joint?
Thorax Indian Medical PG Practice Questions and MCQs
Question 671: Which of the following segments is present in the middle lobe of the right lung?
- A. Medial (Correct Answer)
- B. Anterior
- C. Upper
- D. Lower
Explanation: ***Medial*** - The **right middle lobe** of the lung consists of two bronchopulmonary segments: the **medial segment (S4)** and the lateral segment (S5) [1]. - The **medial segment** is located closer to the mediastinum and is supplied by the medial segmental bronchus. - These segments are defined by the branching pattern of the **bronchial tree** and pulmonary arteries, supplying specific areas of lung tissue [1]. *Anterior* - The **anterior segment** is part of the **right upper lobe**, not the middle lobe [1]. - The right upper lobe contains three segments: apical, posterior, and anterior segments [1]. - The middle lobe is separated from the upper lobe by the **horizontal (transverse) fissure**. *Upper* - "Upper" is not a specific bronchopulmonary segment name but rather refers to the **upper lobe** itself. - The **right upper lobe** is a distinct anatomical region from the middle lobe and contains apical, posterior, and anterior segments [1]. *Lower* - "Lower" is not a specific segment of the middle lobe but refers to the **lower lobe**. - The **right lower lobe** contains five segments: superior, medial basal, anterior basal, lateral basal, and posterior basal [1]. - The lower lobe is separated from the middle lobe by the **oblique fissure**.
Question 672: What is the primary motor nerve supplying the diaphragm?
- A. Phrenic nerve (Correct Answer)
- B. Thoracodorsal nerve
- C. Long thoracic nerve
- D. Cervical nerve roots
Explanation: ***Phrenic nerve*** - The **phrenic nerve** is the sole **motor nerve supply** to the diaphragm, originating from cervical spinal nerves **C3, C4, and C5**. - Damage to this nerve can lead to **diaphragmatic paralysis**, significantly impairing respiration. *Thoracodorsal nerve (innervates latissimus dorsi)* - The **thoracodorsal nerve** innervates the **latissimus dorsi muscle**, which is responsible for adduction, extension, and internal rotation of the arm [1]. - It plays no direct role in **diaphragmatic innervation** or respiration [1]. *Cervical nerve roots (general)* - While the **phrenic nerve** originates from **cervical nerve roots (C3-C5)**, this option is too general as many other nerves arise from cervical roots. - Specifying "cervical nerve roots" without mentioning the phrenic nerve does not accurately identify the primary motor supply to the diaphragm. *Long thoracic nerve (innervates serratus anterior)* - The **long thoracic nerve** innervates the **serratus anterior muscle**, which is crucial for scapular protraction and upward rotation. - Damage to this nerve causes **"winged scapula"** and does not affect the diaphragm.
Question 673: Lower limit of the left crus of the diaphragm is at which vertebral level?
- A. 8th dorsal
- B. 2nd lumbar (Correct Answer)
- C. 10th dorsal
- D. 3rd lumbar
Explanation: Correct: 2nd lumbar - The left crus of the diaphragm arises from the sides of the bodies of the first two lumbar vertebrae (L1 and L2) - Its lower limit is therefore at the level of the second lumbar vertebra (L2) - This is an important anatomical distinction from the right crus Incorrect: 10th dorsal - This level is too high and refers to the general thoracic attachment of the diaphragm - The crura specifically descend into the lumbar region, not the thoracic region - T10 is where the central tendon of the diaphragm is typically located Incorrect: 8th dorsal - This vertebral level is within the mid-thoracic spine and is too superior for the lower limit of the left diaphragmatic crus - The crus attachments are in the lumbar region, much lower than T8 Incorrect: 3rd lumbar - The right crus often extends to the third lumbar vertebra (L3), making this a common source of confusion - The left crus has a more limited extent, typically reaching only to L2 - This option would be correct if the question asked about the right crus instead
Question 674: Which of the following structures pass through the aortic hiatus of the diaphragm?
- A. Inferior vena cava
- B. Oesophagus
- C. Vagus nerve
- D. Azygos vein (Correct Answer)
Explanation: ***Azygos vein*** - The **aortic hiatus** is located at the level of the **T12 vertebra** and transmits the aorta, **thoracic duct**, and often the azygos vein. - The azygos vein ascends through the posterior mediastinum and typically enters the thorax via the aortic hiatus or an opening in the right crus of the diaphragm. *Inferior vena cava* - The inferior vena cava (IVC) passes through the **caval opening** of the diaphragm, located more anteriorly at the level of **T8 or T9**. - The caval opening is within the central tendinous part of the diaphragm. *Oesophagus* - The oesophagus passes through the **oesophageal hiatus** of the diaphragm, which is typically found at the level of **T10**. - This hiatus is formed by muscular fibres of the right crus of the diaphragm. *Vagus nerve* - The **vagus nerves** (left and right) accompany the oesophagus through the **oesophageal hiatus** at the T10 level. - They participate in the formation of the oesophageal plexus.
Question 675: Bifurcation of the trachea takes place at which level?
- A. T4 - T5 (Correct Answer)
- B. C6 - C7
- C. C3 - C4
- D. T10 - T11
Explanation: ***T4 - T5*** - The **tracheal bifurcation**, also known as the **carina**, typically occurs at the level of the intervertebral disc between the **fourth (T4) and fifth (T5) thoracic vertebrae** [1]. - This anatomical landmark is clinically significant for procedures like **bronchoscopy** and determining the appropriate length for **endotracheal intubation**. *C6 - C7* - This level corresponds to the approximate location of the **cricoid cartilage** and the beginning of the **trachea** superiorly. - The **larynx** transitions into the trachea around the C6 vertebral level, not the point of tracheal division. *C3 - C4* - This level is associated with the **hyoid bone** and the upper part of the **larynx**, including the **epiglottis**. - It is much too superior to the location of the tracheal bifurcation. *T10 - T11* - This level is significantly inferior to the tracheal bifurcation and corresponds more closely to the lower thoracic spine. - At this level, the **esophagus** and **aorta** would be passing through the diaphragm, far below the carina.
Question 676: The 8th, 9th, and 10th ribs are attached to their respective costal cartilages by which type of joint?
- A. Fibrous
- B. Synovial
- C. Primary cartilaginous (Correct Answer)
- D. Secondary cartilaginous
Explanation: ***Primary cartilaginous*** - These joints, also known as **synchondroses**, are formed by **hyaline cartilage** and allow for little to no movement, providing stability to the rib cage. - The attachment of ribs 8, 9, and 10 to their respective **costal cartilages** is characteristic of this joint type, where bone and cartilage are directly united. *Fibrous* - **Fibrous joints** are characterized by connective tissue uniting the bones, which are generally immovable, such as the sutures of the skull. - This type of joint does not allow for the flexibility needed in the rib cage for breathing and would be structurally inappropriate for articulations involving cartilage. *Synovial* - **Synovial joints** are highly mobile, characterized by a joint capsule, synovial fluid, and articular cartilage, such as those found in the appendicular skeleton. - While some rib articulations (e.g., costovertebral) are synovial, the specific junction between the ribs and their costal cartilages is not, as it prioritizes stability over significant movement. *Secondary cartilaginous* - **Secondary cartilaginous joints**, or **symphyses**, are characterized by a plate of **fibrocartilage** between the bones, allowing for limited movement (e.g., intervertebral discs). - This type of joint is not found between the individual ribs and their costal cartilages; rather, the connections are more rigid and directly cartilaginous.
Practice by Chapter
Thoracic Wall and Diaphragm
Practice Questions
Pleura and Lungs
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Mediastinum
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Heart and Pericardium
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Great Vessels and Azygos System
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Thoracic Duct and Lymphatics
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Autonomic Innervation
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Applied Anatomy and Clinical Correlations
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Thoracic Imaging and Cross-sectional Anatomy
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Embryological Development of Thoracic Structures
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