Anatomy: Thoracic Wall and Surface Anatomy

Question 1

What are the thorax, and its two apertures?

Answer 1

The thorax is an irregularly shaped cylinder with openings superiorly (superior thoracic aperture) and inferiorly (inferior thoracic aperture).
The superior thoracic aperture is narrow and open, in continuity with the neck.
The inferior thoracic aperture is closed off by the diaphragm.

Question 2

How can you find the clavicle, manubrium, sternal angle, xiphoid process, and suprasternal notch on yourself?

Answer 2

Identify the clavicles on yourself. Follow them medially to their joint with the sternum. Note that this forms the single bony articulation between the upper limb and the thorax.
Palpate the two main parts of the sternum: the body and the manubrium, and the sternal angle, where these parts articulate.
You may also be able to palpate the xiphoid process (xiphisternum) at the inferior end of the sternal body.
Note also, the suprasternal (jugular) notch. In the depths of the notch, you can feel the cartilage rings of the trachea.

Question 3

How can the ribs be counted? How are ribs numbered?

Answer 3

All ribs can be counted from this point by moving the examining finger down the chest wall from one rib to another, noting the soft intercostal space between them. Ribs are numbered according to the vertebra to which they are attached posteriorly. Intercostal spaces are named after the rib above.

Question 4

What are true ribs, false ribs and floating ribs?

Answer 4

True rib = A rib whose anterior end unites directly with the sternum
False rib = A rib whose anterior end does not directly attach to the sternum
Floating ribs = A rib whose anterior end is free

Question 5

The costal cartilage of which rib articulates with the sternal angle?

Answer 5

2nd

Question 6

How many pairs of true ribs do you have?

Answer 6

7

ribs 1-7

Question 7

How many pairs of false ribs do you have?

Answer 7

3

ribs 8-10

Question 8

How many pairs of floating ribs do you have?

Answer 8

2

ribs 11 and 12

Question 9

At which intervertebral level is the sternal angle?

Answer 9

T4/5 intervertebral disc

Question 10

What arteries serve the thoracic wall?

Answer 10

Arteries: Posterior intercostal arteries branch directly from the descending aorta. Anterior intercostal arteries branch from the internal thoracic artery (internal mammary artery) which passes down the posterior aspect of the costal cartilages on either side.

Question 11

What veins serve the thoracic wall?

Answer 11

Veins: the intercostal veins drain anteriorly to the internal thoracic vein, and drain posteriorly to the azygos (right) and hemi azygos veins (left).

Question 12

If passing a needle through the thoracic cage to sample air or fluid in the pleural cavity (pleural tap/aspiration), should you pass the needle immediately above or below the rib?

Answer 12

Above
The primary and larger intercostal neurovascular bundles run immediately below each rib. To avoid damaging these (and causing bleeding / neuropathy) during a pleural tap or aspiration, insert the needle just above the rib.

Question 13

How and why does the volume of the thoracic cavity to generate air flow?

Answer 13

To generate air flow, the volume of the thoracic cavity needs to be change to create pressure differentials - air or fluid will flow from areas of high pressure to areas of low pressure. You will be aware that this is predominantly achieved by the action of the diaphragm, which contracts during inspiration, pushing the abdominal contents downwards. By increasing the volume of the thoracic cavity, the pressure within reduces (although by a tiny amount!) and a pressure gradient drives the flow of air to fill the increased thoracic volume at the same pressure of the surrounding atmosphere. Contrastingly, in expiration, the volume of the thoracic cavity is reduced, creating a pressure gradient that forces air out.

Question 14

Which muscles are important in respiration?

Answer 14

While the diaphragm is the primary respiratory muscle, the intercostal muscles are also important and many muscles of the neck and thoracic and abominal wall act as accessory muscles of respiration. These control movements of the bony chest wall, which you can see above also moves with respiration.

Question 15

What is the pump-handle movement? (also known as anterior-posterior movement)

Answer 15

You should be able to feel your sternum and anterior chest moving forwards during inspiration. This increases the anterior-posterior diameter of the chest, increasing intrathoracic volume. This movement mostly occurs in the upper ribs. Traditionally this has been described as a water-pump handle like movement (no longer that helpful as there are not many around in this country!).

Question 16

What is the bucket-handle movement? (also known as lateral movement)

Answer 16

You should be able to feel your lower ribs moving laterally outwards during inspiration. This increases the lateral diameter of the chest, increasing intrathoracic volume. The lower ribs (7-9) move the most as they are not directly attached to the sternum. Traditionally this has been described as a bucket handle like movement.

Question 17

What are the three layers of intercostal muscles which join the ribs together?

Answer 17

External intercostals: The outermost layer, with fibres moving in an infero-medial direction (think putting hands in front pockets)
Internal intercostals: The middle layer, with fibres moving infero-laterally (at a right angle to the externals).
Innermost intercostals: The innermost layer includes a variety of muscles (intercostal parts, transversus thoracis and subcostalis). Transcersus thoracis can be seen most easily looking at the inner surface of the anterior thorax in the image on the left. The intercostal parts are mostly laterally (image above) and subcostalis is in the posterior chest wall.

Question 18

What are the most important things to remember about the intercostal muscles?

Answer 18

The movements of the chest wall performed by these different muscles at different sites can cause confusion. A simple take home message could be that the external intercostals are most important to respiration and when the contract they rotate the ribs upwards to cause both the increases in anterior-posterior and lateral diameters of the chest wall as discussed above.

Question 19

What are potential functions of the accessory muscles of respiration?

Answer 19

These may assist inspiration or expiration in times of increased respiratory effort (illness or exercise).

Question 20

Which accessory muscles assist with inspiration?

Answer 20

Scalenes
Sternocleidomastoid
Pectoralis minor

Question 21

Which accessory muscles assist with expiration?

Answer 21

External oblique

Rectus abdominis

Question 22

What is auscultation?

Answer 22

This is the process of listening to the sounds generated by the heart and lungs using a stethoscope.

Question 23

If you want to hear the Aortic valve where would you place your stethoscope?

Answer 23

2nd intercostal space, right sternal edge

Question 24

If you want to hear the tricuspid valve where would you place your stethoscope?

Answer 24

4th intercostal space, left sternal edge

Question 25

If you want to hear the mitral valve where would you place your stethoscope?

Answer 25

5th intercostal space, midclavicular line

Question 26

If you want to hear the pulmonary valve where would you place your stethoscope?

Answer 26

2nd intercostal space, left sternal edge

Question 27

Which valves are atrioventricular?

Answer 27

Tricuspid

Mitral

Question 28

Which valves are semilunar?

Answer 28

Aortic

Pulmonary

Question 29

Where is the apex of the lung found?

Answer 29

The apex of the lung extends far higher than you might think (2cm above the clavicle)

Question 30

Where can the lower border of the lungs be found?

Answer 30

The lower border of the lungs can be found at the level of the 6th rib in the mid-clavicular plane, the 8th rib at the mid-axillary plane and the 10th rib next to the vertebrae.

Question 31

Which rib is the surface landmark for the horizontal fissure?

Answer 31

4th rib (right lung)

Question 32

Where are the surface markings for the pleura of the lungs?

Answer 32

The surface markings for the pleura of the lungs are found 2 ribs below the base of the lung.

At the level of the 8th rib in the mid-clavicular plane, the 10th rib at the mid-axillary plane and the 12th rib next to the vertebrae.

Question 33

A patient has a murmur heard in the 5th intercostal space, in the mid-clavicular plane.
Which valve do you think is pathological?

Answer 33

Mitral

Question 34

What is the sign of an enlarged heart (cardiomegaly) on a chest X-ray?

Answer 34

When an x-ray shows cardiomegaly, the cardiothoracic ratio is over 50%.

Question 35

What is the sign of fluid in the alveoli (pulmonary oedema) on a chest X-ray?

Answer 35

There is bilateral patchy opacification of the lung fields, which would be in keeping with pulmonary oedema (fluid in the airways of the lungs).

Question 36

What could be a sign of fluid in the pleural cavity (pleural effusion) on a chest X-ray?

Answer 36

There is a moderate right-sided pleural effusion. There is a meniscus and opacification clearly visible into the midzone of the right lung.
Note that a pleural effusion (fluid in the pleural cavity) differs from pulmonary oedema (fluid in the airways).

Question 37

How might you tell from a chest X-ray that a patient has an implantable cardiac device (e.g. pacemaker/defibrillator)?

Answer 37

There is an implantable cardiac device clearly visible in the left axillary region.

Question 38

What might happen during a massive left-sided pleural effusion on a chest X-ray?

Answer 38

It has caused almost complete opacification of the left lung field, and has pushed the trachea across to the right side.

Question 39

What else might be visible on a chest X-ray?

Answer 39

There might be a synthetic heart (mitral) valve replacement visible in the region of the heart.