The Diaphragm

Question 1

Describe the structure and attachments of the diaphragm

Answer 1

It is a musculotendinous dome that separates the thoracic cavity from abdo cavity.
Anteriorly is attaches to xiphisternum and CC of ribs.
Posteriorly - Right crus (L1-L3), Left crus (L1-L2) and between these is the median arcuate ligament (L1) and also have the lateral arcuate lig (Rib 12).

Question 2

What are the three openings of the diaphragm and what passes through them?

Answer 2

T8 Caval opening (IVC and right phrenic nerve)
T10 Oesophageal opening (oesophagus and anterior and posterior vagal trunks.
T12 Aortic hiatus (Descending aorta, thoracic duct and azygos)

Question 3

What can cause the reflux of gastric acid?

Answer 3

The oesophageal opening does not form a true sphincter which means stomach acid can travel up the oesophagus.

Question 4

What is the innervation of the diaphragm?

Answer 4

The phrenic nerve (C3,4,5) provides motor and sensory innervation (sensory to central portion). Peripherally is has sensory innervation from intercostal and subcoastal nerves

Question 5

Describe how the phrenic nerves pass through the diaphragm?

Answer 5

Right phrenic nerve passes through the diaphragm with IVC where as left phrenic nerve pierces diaphragm but doesn’t pass through it.

Question 6

What is the arterial supply of the diaphragm?

Answer 6

• Two inferior phrenic arteries supply diaphragm arteries inferiorly (branches of abdo aorta)
• ITA gives off pericardiophrenic artery which supplies diaphragm

Question 7

Superior phrenic arteries are branches of what?

Answer 7

Thoracic aorta

Question 8

Describe referred from the diaphragm and what may cause this?

Answer 8

Inflammation of the gallbladder (chloecystitis) may irritate central tendon of diaphragm. This area has sensory innervation from phrenic nerve so visceral pain is referred to right shoulder (C4 dermatome)

Question 9

What does boyle’s law state?

Answer 9

Pressure exerted by a gas is inversely proportional to the volume it occupies meaning by increasing volume in the thoracic cavity, the pressure decreases, relative to atmospheric pressure, so air is drawn into lungs (from high to low pressure)

Question 10

Describe the role of the diaphragm in respiration

Answer 10

• During expiration the diaphragm is raised, decreasing thoracic cavity volume of cavity so pressure is raised.
• Inspiration, the diaphragm flattens which increases the volume in cavity which decreases pressure.

Question 11

Describe the action of intercostal muscles during respiration?

Answer 11

• Contraction of external IC muscles raise the ribs and sternum, increasing antero-posterior diameter. The raising of the ribs can increase the lateral diameter of thoracic cavity.

Question 12

What muscles are involved in quiet respiration?

Answer 12

Inspiration - Diaphragm and external intercostal muscles.

Expiration - Relaxation of diaphragm and elastic recoil from external IC

Question 13

What muscles are involved in forced respiration?

Answer 13

Inspiration - Diaphragm, external IC, accessory muscles (trapezius, scalenes, sternocleidomastoid) and Nasalis

Expiration - Relaxation of diaphragm and external IC muscle. Internal IC muscles and muscles of abdominal wall

Question 14

What is the clinical significance of forced respiration?

Answer 14

It can become a persons normal breathing pattern in lung disease such as COPD, this can cause someone to use extra energy = weight loss

Question 15

What is the role of the pleura?

Answer 15

Reduce friction to allow movement of lungs and intrapleural pressure negative relative to atmospheric pressure to prevent collapse lung.

Question 16

What are the surface markings of the right pleura?

Answer 16

Apex - 2/3 cm superior to middle part of clavicle
At 4th CC pleura is at the midline
At 6th CC plural is at midline.
At 8th CC - midclavicular line
At 10th rib - mid axillary line
At 11th rib - Line of inferior angle of scapula
At 12th rib - lateral boarder of erector spinae at T12

Question 17

What are the surface markings of the left pleura?

Answer 17

Apex - 2/3 cm superior to middle part of clavicle
At 4th CC pleura is at the midline
At 6th CC plural is lateral to sternum.
At 8th CC - midclavicular line
At 10th rib - mid axillary line
At 11th rib - Line of inferior angle of scapula
At 12th rib - lateral boarder of erector spinae at T12

Question 18

What are the surface projections of the lungs?

Answer 18

Follows the same pattern as the pleura but 2 rib spaces higher, this allows for expansion of the lungs

Question 19

What are the surface landmarks of the fissures?

Answer 19

Horizontal fissure starts at CC of rib 4 and ends by meeting oblique fissure.

Oblique fissure can be drawn posteriorly from T4 vertebra to rib 6 anteriorly.

Question 20

What is a pneumothorax and what are the other types?

Answer 20

Pneumothorax = air between visceral and parietal layers of pleura. 
Haemothorax = blood
Chylothorax = lymphatic fluid

Question 21

What are the risk factors for a pneumothorax?

Answer 21

Tall, Male, smoker and underlying lung disease eg, COPD

Question 22

What is a tension pneumothorax and its clinical significance?

Answer 22

Air between parietal and visceral pleura but die to a valve type effect air can get in but not get out. Due to this increase in intrapleural pressure, the venous return to the heart is impaired and hypotension can develop. It can lead to cardiac arrest. Trachea will be shifted away from pneumothorax.

Question 23

How do you acutely treat a tension pneumothorax

Answer 23

Decompression - insertion of a cannula on the side of pneumothorax in the 2nd IC space, midclavicular line

Question 24

What are the indications for a chest drain?

Answer 24

Large pneumothorax, tension pneumothorax, haemothorax, large pleural effusion

Question 25

What are the boarders of the ‘safe’ triangle?

Answer 25

• Base of the axilla
• Lateral edge of pec major
• Lateral edge of latissimus dorsi,
• 5th IC space.

Question 26

What are some of the complications of inserting a chest drain?

Answer 26

False passage, damage to long thoracic nerve, haemothorax due to damage of IC arteries and liver/spleen injury