Living Anatomy of the Thorax

Question 1

What forms the anterolateral boundary of the inferior thoracic aperture?

Answer 1

The joined costal cartilages of ribs 7-10

Question 2

What structures can be palpated above the jugular notch?

Answer 2

Immediately superior to the jugular notch, the cartilages of the trachea can be palpated Superior to this, the cricoid and thyroid cartilages can be palpated The cricothyroid membrane between these 2 carriages can also be palpated

Question 3

What is between cricoid and thyroid cartilage?

Answer 3

Cricothyroid membrane

Question 4

What can a deviation of the trachea from the midline indicate?

Answer 4

Deviation of the trachea from the midline can indicate a number of pathologies. It can either be pushed or pulled depending on the cause. An increase in pressure will push the trachea away from the lesion whereas a decrease in pressure will pull the trachea towards the lesion.

Question 5

What can cause a trachea to be pulled/decrease in pressure?

Answer 5

• Atelectasis (lobe collapse) - Collapsed lung - Pneumonectomy

Question 6

What can cause a trachea to be pushed/increase in pressure?

Answer 6

• Tension pneumothorax - Pleural effusion - Tumour

Question 7

At what vertebral level does the sternal angle lie?

Answer 7

Intervertebral disc between T4 and T5

Question 8

What structures in the mediastinum lie at the level of the sternal angle?

Answer 8

• 2nd costal cartilages (essential for thorax examination) - Arch of the aorta (including loop of left recurrent laryngeal nerve and ligamentum arteriosum) - Bifurcation of the trachea - Bifurcation of the pulmonary artery into left and right - Azygos vein draining into superior vena cava - Thoracic duct draining into left venous angle (between left internal jugular and subclavian veins)

Question 9

Where does the thoracic duct drain into?

Answer 9

The left venous angle (between left internal jugular and subclavian veins)

Question 10

What marks the right border of the heart? What is it formed by?

Answer 10

A line between the medial ends of the 3rd and 6th costal cartilages on the right side of the sternum. Formed by the right atrium.

Question 11

What marks the inferior border of the heart? What is it formed by?

Answer 11

From the right border, a nearly horizontal line to the left 5th intercostal space in the midclavicular line marks the inferior border of the heart. Mainly formed by right ventricle.

Question 12

What is the left border of the heart formed by? Where does it run?

Answer 12

Formed mainly by the left ventricle and runs from the left 5th space in the midclavicular line to the medial end of the left 3rd space.

Question 13

Where is the apex of the heart located? What can you feel here?

Answer 13

In the 5th left intercostal space in the midclavicular line. Palpate here and you will be able to feel the apex of the heart beating against the thoracic wall.

Question 14

If the apex beat was found to be located in the 5th RIGHT intercostal space in the mid-clavicular line which condition is this indicative of?

Answer 14

Dextrocardia – congenital malformation due to abnormal cardiac looping or gastrulation. The apex of the heart points to the right instead of the left. May be associated with other abnormalities.

Question 15

Why else may you not be able to palpate the apex beat?

Answer 15

May be difficult to palpate in overweight or muscular individuals. May also be difficult to palpate in patients with asthma or emphysema due to hyperinflation of the chest.

Question 16

Where does the apex beat lie relative to the nipple? How constant is this relationship?

Answer 16

In the male, the nipple is usually located at the 4th intercostal space, close to the midclavicular line, therefore, the apex should be located slightly inferior to this. This is not a constant relationship. The postion of the nipple varies depending of the amount of breast tissue. The position of the apex of the heart also varies depending the size and orientation of the heart.

Question 17

How does the orientation of the heart change during respiration?

Answer 17

The fibrous pericardium that surrounds the heart is attached to the diaphragm so the heart moves up and down the vertical plane with respiration

Question 18

How does the orientation of the heart change with posture? How can this help during clinical examination of the apex beat?

Answer 18

The heart is not fixed within the pericardium and moves depending on body position. You can exploit this to facilitate palpation of the apex beat by asking your patient to lean to left. This will cause the heart to move to left and lie closer to the chest wall.

Question 19

How does the orientation of the heart change when lying supine?

Answer 19

The heart moves posteriorly

Question 20

How does the orientation of the heart change when leaning forward?

Answer 20

Heart moves anteriorly

Question 21

What is the anatomical relationship between the intercostal neurovascular bundle and the ribs?

Answer 21

At the costal angle, the intercostal neuromuscular bundle enters the costal groove to run along the interior border of the rib. The intercostal neurovascular bundle is arranged in order from superior to inferior as vein, artery nerve so that the intercostal vein is closest to the rib. The intercostal neurovascular bundle also has small, collateral branches that run along the superior birder of the rib below.

Question 22

When is the position of the intercostal neurovascular bundle critical?

Answer 22

When performing thoracocentesis

Question 23

What is thoracocentesis?

Answer 23

A needle is inserted into the pleural cavity to either obtain a sample of fluid or to remove excess fluid, blood or pus.

Question 24

Why is the position of the intercostal neurovascular bundle critical during thoracocentesis?

Answer 24

Care must be taken not to damage the intercostal neurovascular border therefore the safest place to insert the needle is at the superior border of the rib, just high enough to avoid the collateral branches of the intercostal neurovascular bundle. This is normally performed in the midaxillary line.

Question 25

In the upright position, where is excess fluid likely to accumulate?

Answer 25

In the costodiaphragmatic recess Therefore a needle inserted at the superior border and angled slightly upwards will drain the fluid without damaging any important structures. It should also be performed during expiration to protect the lung.

Question 26

Why can you not listen to the valves of the heart by placing your stethoscope directly over the anatomical location of the valves?

Answer 26

Valves of the heart are located deep to the sternum. Bone is a poor conductor of sound. The sound of the valves closing is, however, carried by the flow of blood through the valves, therefore, by following the path of the blood flow through the chambers of the heart or the great arteries of the heart you can find an area where the sound is transmitted that is not covered by bone and will allow you to listen to the valve

Question 27

Where is the auscultation position for the aortic valve?

Answer 27

2nd intercostal space immediately to the right of the sternum

Question 28

Where is the auscultation position for the pulmonary valve?

Answer 28

2nd intercostal space immediately to the left of the sternum

Question 29

Where is the auscultation position for the tricuspid valve?

Answer 29

4th or 5th intercostal space (variable) immediately to the left of the sternum

Question 30

Where is the auscultation position for the bicuspid/mitral valve?

Answer 30

5th intercostal space in the midclavicular line

Question 31

Where is the apex of the pleura?

Answer 31

About 2-3cm above the medial 1/3 of the clavicle

Question 32

Where does the anterior pleural margin meet the midline?

Answer 32

At the level of the 2nd costal cartilage (i.e.g sternal angle)

Question 33

The anterior pleural margins then pass vertically down the sternum to the level of the 4th costal cartilage. What happens here?

Answer 33

Here the right pleura continues vertically downwards while the left pleura arches away from the midline to descend just lateral to the sternal margin. Both turn laterally at the 6th costal cartilage

Question 34

Where does the pleural margin cross the 8th costal cartilage, 10th rib and 12th rib?

Answer 34

• 8th costal cartilage –> mid-clavicular line - 10th rib –> mix-axillary line - 12th rib –> 2-3cm lateral to the midline

Question 35

When are lung marking described?

Answer 35

During mid-inspiration. They will be more extensive at full inspiration and smaller at full expiration.

Question 36

Where does the border of the right lung lie?

Answer 36

Immediately inside the pleural margin from the cupola down to about the 6th costal cartilages. It then lies about two spaces above the pleural margin: it crosses the 6th rib in the midclavicular line and the 8th rib in the midaxillary line, and reaches the vertebral column at the level of the 10th rib.

Question 37

What differs about the lung markings on the left side?

Answer 37

Similar except for the cardiac notch. At the level of the 4th costal cartilage the border of the left lung runs almost horizontally to the left for 2-3cm, then descends to cross the 6th rib in the mid-clavicular line.

Question 38

How is the costodiaphragmatic recess created?

Answer 38

The lungs don’t fully occupy the pleural cavities during expiration. At this point, the peripheral part of the diaphragmatic pleura lies against the inferior part of the costal pleura. This creates a potential space between the diaphragmatic pleura and the costal pleura that can be occupied by the lung during inspiration (costodiaphragmatic recess)

Question 39

What is the clinical significance of the costodiaphragmatic recess?

Answer 39

The costodiaphragmatic recess is the lowest part of the pleural cavity so this is where excess fluid, blood or pus is most likely to accumulate.

Question 40

How could a knife wound to the neck affect the lungs?

Answer 40

The lung projects above the clavicle –> pleura and lung could be damaged, resulting in pneumothorax

Question 41

Why is it important to listen to each lobe of the lung individually?

Answer 41

A pathology (e.g. pneumonia or tumour) many only affect one lobe. E.g. a patient may have pneumonia of the middle lobe of the right lung, however, if you only listen to the superior and inferior lobes you may think that the patient is healthy.

Question 42

What receptors do the internal organs lack?

Answer 42

Somatic pain receptors (the internal organs are insensitive to touch, cutting and temperature)

Question 43

Where is pain from the internal organs instead elicited by? How is this pain sensation transmitted?

Answer 43

Stretching or chemical changes e.g. ischaemia This pain sensation is transmitted by visceral sensory nerves to the spinal cord and then to the brain

Question 44

How can referred pain occur regarding the internal organs?

Answer 44

The spinal cord also receives and transmits somatic sensory information from the body wall. The brain can confuse these signals and assumes that pain from internal organs is actually coming from the area of skin supplied by the same level of the spinal cord (dermatome) This means that pain from the heart during ischaemia is not actually experienced in the heart, instead the brain interprets the pain as coming from the skin supplied by the same levels of the spinal cord

Question 45

What is the heart supplied by? Where does pain get referred to?

Answer 45

Supplied by sympathetic fibres from T1to T4 of the spinal cord, therefore, pain from the heart is referred to the dermatomes (areas of skin) supplied by T1-T4.

Question 46

Why is pain from the heart experienced as if its coming from the left arm?

Answer 46

The skin of the arm is supplied by levels T1 and T2 of the spinal cord.

Question 47

Where would pain arising from the pericardium be experienced?

Answer 47

The sensory innervation of the pericardium is through the phrenic nerve which projects to levels C3-C5 of the spinal cord. The dermatomes supplied by levels C3-C5 of the spinal lie over the shoulder.

Question 48

Diagram of front lobe stethoscope

Question 49

Diagram of back stethosope placement

Answer 49

Question 50

Why is it difficult to palpate 1st rib?

Answer 50

Lies below and behind the clavicle

Also has thick layer of muscle in front of it

Question 51

What vertebral level is the jugular notch? Why is it lower than T1 even though connected to 1st rib?

Answer 51

Roughly T2-T3

Even though rib 1 articulates near the manubrioclavicular joint, the ribs slope inferiorly posterior to anterior

Question 52

What ribs articulate at the sternal angle? Why is the sternal angle found at T4/T5?

Answer 52

Costal cartilage of rib 2

Ribs slope inferiorly

Question 53

What vertebral level is the xiphisternal joint?

Answer 53

T10

Question 56

What is a pneumonectomy?

Answer 56

Surgical removal of a lung or part of a lung.

Question 57

What does the thoracic duct carry?

Answer 57

transport lymph back into the circulatory system.

Question 58

What does the thoracic duct drain into?

Answer 58

Starts from the level of the twelfth thoracic vertebrae (T12) and extends to the root of the neck. It drains into the systemic (blood) circulation at the junction of the left subclavian and internal jugular veins, at the commencement of the brachiocephalic vein.