The diaphragm

Question 1

Diaphragm

Answer 1

• Primary muscle of inspiration

- Position varies depending on breathing cycle

Question 2

Question 3

Question 4

Question 5

Structure & attachments:

Answer 5

• Central tendon
• Surrounding muscular part
• Sternal part
• Costal part
• Lumbar part
  > Left and right Crura
  (attachments onto the vert. column) and ligaments
• Median (most towards middle), medial and lateral arcuate ligament
• Diaphragmatic apertures:
  The diaphragmatic apertures are a series of apertures that permit the passage of structures between the thoracic and abdominal cavities.
  • Levels and structures passing through:
  1. Inferior vena cava passes through the central tendon and not muscles ( would cut off blood flow during muscle contraction) at the level of T8

2. Oesophagus passes through muscular dome (close to the right pleura)
   - Pleura wraps around oesophagus and helps to keep it closed – diaphragm functions as a sphincter for the oesophagus – what allows you to vomit – goes through right crus at T10
3. Abdominal aorta passes behind the diaphragm at level of T12 (so that it doesn’t cut of blood flow when contracting)

Question 6

Arterial supply of sup. surface of diaphragm

Answer 6

• Superior phrenic arteries from thoracic aorta

- Musculophrenic and percardiophrenic arteries from internal thoracic arteries

Question 7

Arterial supply of inf. surface of diaphragm

Answer 7

• Inferior phrenic arteries from abdominal aorta

Question 8

Venous drainage of sup. surface of diaphragm

Answer 8

• Musculophrenic and pericardiophrenic veins drain into internal thoracic veins
• Superior phrenic vein ( right side) drains into IVC

Question 9

Venous drainage of inf. surface of diaphragm

Answer 9

• Inferior phrenic veins:
  Right veins drains into IVC
  Left vein is doubled and drains into IVC and suprarenal vein

Question 10

Lymphatic drainage of sup. surface of diaphragm

Answer 10

Diaphragmatic lymph nodes to phrenic nodes

then to parasternal and posterior mediastinal nodes

Question 11

Lymphatic drainage of inf. surface of diaphragm

Answer 11

Superior lumbar lymph nodes;

lymphatic plexus on sup. and inf. surfaces communicate freely

Question 12

Innervation of diaphragm

1. Motor supply

Answer 12

phrenic nerves (C3-C5)

Question 13

Innervation of diaphragm

2. sensory supply

Answer 13

centrally by phrenic nerves (C3- C5)

Peripherally by intercostal nerves (T5-T11) and subcostal nerves (T12)

Question 14

Peripheral attachments:

Answer 14

• Xiphoid process
• Costal cartilages of ribs 7 to 10
• Ribs 11 and 12 laterally
• Lumbar vertebrae and arcuate ligaments posteriorly

The muscle fibers of the diaphragm converge at the central attachment, which is the central tendon

The parts of the diaphragm that arise from the vertebrae are tendonous in structure
= left and right crura

Question 15

Left crus:

Answer 15

Arises from L1 and L2 and their intervertebral discs

Question 16

Right crus:

Answer 16

Arises from L1 to L3

Question 17

The diaphragm has several openings allowing structures to pass through the thoracic and abdominal cavity

• 3 major openings
• Several minor openings

Answer 17

1. Aortic hiatus
2. Esophageal hiatus
3. Vena caval foramen

Question 18

Question 19

1. Aortic hiatus

Answer 19

-	Sits at the level of T12
Transmits:
-	Aorta
-	Azygos vein
-	Hemiazygos vein
-	Thoracic duct

Question 20

2. Esophageal hiatus

Answer 20

-	At level T10
Transmits:
-	Esophagus
-	Vagus nerves
-	Esophageal arteries

Question 21

3. Vena caval foramen

Answer 21

• Lies at level T8
  Transmits:
• Inf. Vena cava
• Terminal branches of the right phrenic nerve

Question 22

During inspiration:

Answer 22

The diaphragm flattens and contracts to cause the thoracic cavity to expand
During expiration:
The diaphragm relaxes and returns to dome shape – decreases thoracic cavity volume = air expelled from lungs

Question 23