📚 Question Bank

Correct Answer: C

The phrenic nerve descends through the mediastinum, supplying the mediastinal pleura, before spreading out to innervate the center of the diaphragm.

Therefore, the central diaphragmatic pleura is also innervated by the phrenic nerve (C3-C5). Irritation in either of these areas will cause the brain to interpret the pain as originating from the supraclavicular nerves (C3-C4), leading to referred pain at the tip of the shoulder.

Correct Answer: C

The suprapleural membrane (Sibson's fascia) is often structurally reinforced by muscular fibers that form the scalenus minimus muscle.

This small, inconsistent muscle arises from the transverse process of C7 and inserts directly into the inner border of the first rib and the pleural dome, acting to tense the pleural roof during deep inspiration.

Correct Answer: B

The costodiaphragmatic recess is the lowest limit of the pleural cavity. In the mid-axillary line, the pleura ends at the 10th rib.

If a needle is passed below this level on the right side, it will puncture the diaphragm and immediately strike the massive right lobe of the liver. (On the left side, the spleen would be at risk in the 9th to 11th rib region).

Correct Answer: B

Normally, the right and left parietal pleurae meet in the midline behind the sternum.

However, on the left side, the pleural reflection deviates laterally at the level of the 4th costal cartilage to accommodate the asymmetric bulge of the heart. It drops down vertically just left of the sternum to the 6th cartilage, creating the 'bare area' where the pericardium touches the chest wall.

Correct Answer: C

A tension pneumothorax builds immense positive pressure inside the rigid thoracic cavity.

This pressure pushes the entire mediastinum to the opposite side. More importantly, this high pressure completely compresses the thin-walled superior and inferior vena cavae. Because blood cannot return to the right atrium against this pressure, cardiac output plummets instantly, leading to shock and death if not immediately decompressed.

Correct Answer: C

Despite its name, the pulmonary ligament is not a strong, fibrous tether. It is a loose, baggy sleeve of pleura hanging down below the hilum.

It contains only a small amount of loose connective tissue, fat, and a few lymphatic vessels. Its true function is to provide 'dead space' allowing the lower pulmonary veins to expand fully during periods of increased cardiac output.

Correct Answer: B

The negative pressure in the pleural space is a mechanical tug-of-war.

The spongy lung tissue is highly elastic and constantly wants to collapse inward. The bony chest wall acts like a compressed spring that naturally wants to spring outward. These two opposing elastic recoil forces pull the visceral and parietal pleura in opposite directions. Because the fluid between them cannot expand, a strong vacuum (negative pressure) is created.

Correct Answer: C

The costomediastinal recess is the slit-like vertical space behind the sternum where the costal pleura folds back to become the mediastinal pleura.

On the left side, the anterior border of the left lung has a large cardiac notch. The tongue-like projection of lung tissue just below this notch is the lingula, which actively slides in and out of the costomediastinal recess during respiration.

Correct Answer: C

The separation of the thorax into three distinct compartments (two pleural, one pericardial) relies on the pleuropericardial folds.

These sheets of tissue grow inward from the lateral body walls, carrying the phrenic nerves with them. They eventually fuse in the midline with the foregut mesenchyme, forming the fibrous pericardium and permanently sealing off the pleural cavities from the central pericardial cavity.

Correct Answer: C

The right lung is larger and heavier than the left lung. It is divided into three distinct lobes: superior, middle, and inferior.

These lobes are separated by two fissures: the oblique fissure and the horizontal fissure. The left lung only has two lobes to make room for the heart.

Correct Answer: B

The lingula (meaning 'little tongue' in Latin) is a unique anatomical feature of the left lung.

Because the heart pushes into the left lung (creating the cardiac notch), the bottom edge of the superior lobe is shaped into this tongue-like flap. It is anatomically homologous to the middle lobe of the right lung.

Correct Answer: C

The hilum is the 'doorway' to the lung.

Located on the mediastinal (medial) surface of each lung, it is the designated area where the root of the lung (comprising the primary bronchus, pulmonary artery, pulmonary veins, bronchial vessels, and nerves) passes into and out of the lung tissue.

Correct Answer: B

Both lungs possess an oblique fissure that separates the inferior lobe from the rest of the lung.

However, only the right lung has a horizontal fissure. This fissure branches off the oblique fissure and runs horizontally across the front of the right lung, separating the superior lobe above from the middle lobe below.

Correct Answer: C

As the respiratory tree branches and gets smaller, its wall structure changes.

The trachea and bronchi are held open by rigid C-shaped or irregular plates of hyaline cartilage. However, once the airways branch down to the level of bronchioles (less than 1 mm in diameter), they completely lack cartilage and rely entirely on smooth muscle and tethering to surrounding lung tissue to stay open.

Correct Answer: D

The lungs are roughly cone-shaped. The pointed top is the apex, and the broad, concave bottom is the base.

The base of each lung rests directly on the convex domes of the diaphragm. The right lung base sits slightly higher than the left because it is pushed up by the massive liver located just under the right hemidiaphragm.

Correct Answer: C

Do not confuse the gas exchange system with the nutritive system!

The massive pulmonary arteries carry deoxygenated blood to the lungs to be oxygenated. The living tissue of the lung (the bronchial tree, stroma, and visceral pleura) receives its actual oxygen and nutrients from the systemic circulation via the bronchial arteries, which typically arise from the descending thoracic aorta.

Correct Answer: C

The alveoli are tiny, balloon-like air sacs at the very end of the respiratory tree.

They have incredibly thin walls composed of simple squamous epithelium (Type I pneumocytes). They are completely wrapped in a dense network of pulmonary capillaries, allowing for the rapid diffusion of oxygen and carbon dioxide across the respiratory membrane.

Correct Answer: B

The sympathetic nervous system triggers the 'fight or flight' response.

In a survival situation, your body needs maximum airflow to the lungs to oxygenate the blood. Therefore, sympathetic stimulation causes the smooth muscle in the airways to relax, leading to bronchodilation (widening of the airways) and simultaneously inhibits glandular secretion.

Correct Answer: B

The 'rest and digest' autonomic control of the thoracic and abdominal organs is heavily reliant on the Vagus nerve (CN X).

Vagal fibers form the pulmonary plexuses around the lung roots. Parasympathetic stimulation contracts airway smooth muscle (bronchoconstriction) and stimulates the mucus glands (secretomotor), which is why anti-cholinergic drugs are used to open airways in asthma and COPD.

Correct Answer: B

This is a classic and highly important clinical fact.

The right primary bronchus is wider, shorter, and runs more vertically (in a straighter line from the trachea) than the left primary bronchus, which has to take a sharper turn to get over the heart. Therefore, an inhaled object (like a peanut or a coin) will almost always follow the path of least resistance straight down into the right lung.

Correct Answer: B

The heart sits in the middle of the chest but points to the left.

To accommodate the bulk of the left ventricle, the anterior margin of the left lung has a large, distinct cutout known as the cardiac notch. This notch exposes a small area of the pericardium (the bare area) directly to the anterior chest wall.

Correct Answer: D

In the pulmonary circulation, the normal rule of arteries and veins is reversed based on oxygen content.

The pulmonary veins (typically two from each lung, making four total) carry bright red, oxygen-rich blood away from the pulmonary capillaries and deliver it directly to the left atrium of the heart to be pumped to the rest of the body.

Correct Answer: B

The lungs are soft and spongy, so the hard structures in the mediastinum leave deep impressions on their medial surfaces.

On the right lung, the most distinct impression is a groove that arches superiorly right over the root of the lung. This is the impression of the azygos vein as it hooks forward to drain into the superior vena cava.

Correct Answer: B

At the level of the sternal angle (T4/T5), the trachea splits.

The internal ridge of cartilage at this exact point of bifurcation is called the carina. The mucosa here is highly sensitive, and if a foreign object or a suction catheter hits the carina, it triggers a violent cough reflex.

Correct Answer: C

The branching of the airway defines the surgical anatomy of the lung.

• Primary bronchi supply an entire lung.
• Secondary bronchi supply an entire lobe.
• Tertiary (segmental) bronchi supply a specific, pyramid-shaped wedge of tissue called a bronchopulmonary segment.