📚 Question Bank

Correct Answer: C

This is called sternal retraction (or subcostal/intercostal retraction).

Infant sternums are largely cartilaginous and highly pliable. In respiratory distress (like severe asthma or RSV), the infant generates massive negative intrathoracic pressure to try and draw air through narrowed airways. This intense vacuum literally sucks the pliable sternum and soft tissues inward during inspiration.

Correct Answer: C

The neck of the 1st rib has several vital relations. From medial to lateral, the sympathetic trunk, the supreme intercostal vein, the superior intercostal artery, and the T1 ventral ramus cross it.

An apical lung tumor can easily compress the sympathetic trunk (often the cervicothoracic/stellate ganglion) right at this bony landmark, disrupting sympathetic supply to the face and causing Horner's syndrome (ptosis, miosis, anhidrosis).

Correct Answer: A

The 1st rib is broad, flat, and heavily protected by the clavicle and shoulder musculature. Breaking it requires immense force.

The subclavian artery passes directly over the superior surface of the 1st rib, sitting in a specific groove just posterior to the scalene tubercle. Sharp bone fragments from a 1st rib fracture pose a high, immediate risk of lacerating this major artery.

Correct Answer: B

The costal cartilages are composed of hyaline cartilage. During inspiration, the ribs are elevated, and these cartilages are twisted and subjected to torsional strain.

When the inspiratory muscles relax, the natural, powerful elastic recoil of these untwisting cartilages pulls the ribs back down, making normal exhalation a completely passive process. In elderly patients whose cartilages have calcified, this elasticity is lost, making breathing more labor-intensive.

Correct Answer: C

While direct trauma can break a rib anywhere, the most biomechanically vulnerable point is just anterior to its angle.

The angle is the point of tightest curvature where the rib bends sharply forward and laterally after articulating with the transverse process. The shaft just beyond this curve is the weakest structural link when the rib cage is compressed anteroposteriorly.

Correct Answer: C

The false ribs (8-10) don't reach the sternum, but their cartilages anchor to the cartilage above them. The articulations between the costal cartilages of ribs 6-7, 7-8, and 8-9 are enclosed in a capsule and are actually synovial plane joints.

Clinical Note: The joint between cartilages 9 and 10 is the exception; it is typically a fibrous joint.

Correct Answer: C

A typical rib head has two facets (to articulate with two adjacent vertebrae). The 10th, 11th, and 12th ribs are atypical because their heads possess only a single articular facet.

The 10th rib articulates exclusively with the T10 vertebral body. (Note: It still has a tubercle, unlike ribs 11 and 12 which lack both a neck and a tubercle).

Correct Answer: B

The xiphisternal joint (between the sternal body and the xiphoid process) is originally a primary cartilaginous joint (synchondrosis).

As a normal part of aging, usually starting around age 40, this cartilage completely ossifies, fusing the two bones together into a single continuous bone. This process is called synostosis.

Correct Answer: C

Tietze syndrome is an inflammatory condition characterized by localized, painful swelling of one or more costal cartilages—most commonly the 2nd or 3rd sternocostal or costochondral joints.

It is distinct from simple costochondritis, which causes pain but lacks the palpable swelling that defines Tietze syndrome.

Correct Answer: C

During respiration, the ribs act like levers. The hinge of this lever (the axis of rotation) is a line drawn through the two posterior points of articulation: the head of the rib (at the vertebral body) and the tubercle of the rib (at the transverse process).

For the upper ribs, this axis is nearly lateral, pushing the sternum anteriorly (pump-handle).

Correct Answer: B

This is a crucial relation for thoracic surgeons. The sympathetic trunks descend through the thorax lying exactly anterior to the heads of the ribs.

They rest directly against the heads of the ribs and their radiate ligaments, just lateral to the vertebral bodies, before piercing the diaphragm to enter the abdomen.

Correct Answer: B

The tubercle of a rib has two distinct regions.

• The smooth, medial articular part forms the joint with the transverse process.
• The rough, lateral non-articular part serves as the strong attachment site for the lateral costotransverse ligament, which binds the rib to the tip of the transverse process.

Correct Answer: C

This syndrome almost exclusively affects the false ribs (Ribs 8, 9, and 10).

Because these cartilages do not anchor securely to the sternum but rather link to one another via interchondral joints, trauma or hypermobility can cause a cartilage to slip upward and ride over the cartilage above it, causing severe, clicking pain.

Correct Answer: A

The intercostal nerve travels in the costal groove between the internal and innermost intercostal muscle layers.

To supply sensation to the lateral skin of the chest (and breast), its lateral cutaneous branch must pierce outward through the internal intercostal muscle and then finally through the external intercostal muscle (and the overlying serratus anterior).

Correct Answer: B

The synovial joints between the costal cartilages of ribs 2-7 and the sternum are heavily reinforced anteriorly and posteriorly by the radiate sternocostal ligaments.

These thick fibrous bands fan out (radiate) from the costal cartilages onto the anterior and posterior surfaces of the sternum, interweaving with the fibers of the opposite side.

Correct Answer: A

The costoclavicular space is a critical anatomical bottleneck through which the subclavian vein and artery pass.

It is bounded superiorly by the clavicle, inferiorly by the 1st rib, and medially by the strong costoclavicular ligament. Narrowing of this specific space causes costoclavicular syndrome (a type of Thoracic Outlet Syndrome).

Correct Answer: A

This is a fundamental anatomical relationship you must never forget: V-A-N.

From the superior aspect of the costal groove moving downward, the order is Intercostal Vein, Intercostal Artery, and Intercostal Nerve. Because the nerve is the lowest structure, it is the most exposed and vulnerable to injury from chest tubes or rib fractures.

Correct Answer: A

A typical radiate ligament fans out to touch three structures (Vertebra above, Disc, Vertebra below).

However, Ribs 1, 10, 11, and 12 are atypical. Their heads only possess a single facet and articulate with only one corresponding vertebral body. Therefore, their radiate ligaments do not attach to the vertebra above them.

Correct Answer: C

The subcostal angle (infrasternal angle) is formed by the right and left costal margins meeting at the xiphoid process. Normally, it is about 70-90 degrees.

In conditions causing chronic hyperinflation of the lungs (emphysema) or increased intra-abdominal pressure pushing the diaphragm upward (late pregnancy), the lower ribs are forced outward, significantly widening the subcostal angle.

Correct Answer: C

The diaphragm is the chief muscle of inspiration, responsible for about 75% of the air movement during normal, quiet breathing.

When the dome-shaped diaphragm contracts, it flattens and descends. This increases the vertical dimension of the thoracic cavity, drops the intrathoracic pressure, and draws air into the lungs. The external intercostals assist, but the diaphragm is the primary driver.

Correct Answer: B

A classic anatomical mnemonic for the intercostal muscles is assessing how you put your hands in your pockets.

The fibers of the external intercostal muscles run inferoanteriorly (downward and forward), exactly like the angle of your fingers when you slide your hands into your front pants pockets. They lift the ribs during inspiration.

Correct Answer: C

The anterior chest wall has a dedicated blood supply. The internal thoracic artery (historically called the internal mammary artery) branches off the subclavian artery high in the neck.

It descends vertically just lateral to the sternum, giving off the anterior intercostal arteries for spaces 1 through 6 before bifurcating.

Correct Answer: C

Remember the rhyme: 'C3, 4, and 5 keep the diaphragm alive.'

The phrenic nerve originates from the ventral rami of cervical nerves C3, C4, and C5. It descends through the entire neck and thorax to provide the exclusive motor supply to the diaphragm. If the spinal cord is severed above C3, the patient will be unable to breathe independently.

Correct Answer: A

The diaphragm has three major openings for structures passing between the thorax and abdomen. A standard mnemonic is 'I Ate Ten Eggs At Twelve' (I8 10E A12).

• T8: Caval opening (Inferior Vena Cava)
• T10: Esophageal hiatus (Esophagus)
• T12: Aortic hiatus (Aorta)

Correct Answer: B

The fibers of the internal intercostals run perpendicular to the external layer (downward and backward).

Their primary action is to pull the ribs downward, shrinking the thoracic cavity. Therefore, they are active during forced expiration (like blowing out a candle or coughing), though they also help stiffen the chest wall during quiet breathing.