Diaphragm Week 8 FINISHED Flashcards
What does the diaphragm consist of?
It is musculotendinous, and consists of both muscle and a central tendon, with the muscle peripherally and the tendon centrally
Describe the central tendon of the diaphragm
A fibrous membrane that looks like three leaves (trefoil shaped). It is C-shaped like a boomerang.
Describe the ‘leaves’ of the central tendon of the diaphragm
Right leaf = largest
Left leaf = smallest
Middle leaf = middle size
The anterior section of the middle leaf lies just inferior to the heart.
What is the function of the diaphragm?
Mostly inspiration, however it does aid in increasing abdominal pressure, defecation, micturition,, parturition, and the valsalva manoeuvre
What happens to the diaphragm during inspiration?
Central tendon descends, being pulled by the muscular part of the diaphragm peripherally.
Why is the right dome of the diaphragm higher?
The liver
How high does the right dome of the diaphragm reach?
As high as the 5th rib
How high does the left dome of the diaphragm reach?
As high as the 5th intercostal space
What dictates the level of the domes of the diaphragm?
Respiration phase, posture, size and degree of distension of abdominal viscera
Describe the sternal part of the diaphragm. Is it always present?
Consists of 2 muscular slips which attach to the posterior aspect of the xiphoid process.
It is NOT always present
Describe the costal part of the diaphragm. What part of the diaphragm does this part form?
Wide muscular slips that attach to the internal surfaces of the inferior 2 costal cartilages and adjoining ribs.
This part forms the domes of the diaphragm
Describe the lumbar part of the diaphragm.
The medial and lateral arcuate ligaments are found in the lumbar part of the diaphragm, and form the right and left crura
What are the medial and lateral arcuate ligaments?
They arise from 2 aponeurotic arches. They are thickenings of the fascia that cover QL and psoas major.
Where does the medial arcuate ligament extend?
From the crus of the diaphragm to the TP of L1
Where does the lateral arcuate ligament extend?
From the TP of L1 to rib 12
How many crura does the diaphragm have?
2
What does crus mean?
Leg like structure
What are the diaphragmatic crura made of?
They are musculotendinous/ they are made of strong tendons
Where do the diaphragmatic crura arise from?
The anterior surfaces of the upper three or four lumbar vertebra, anterior longitudinal ligament and IVD’s.
Where does the right crus of the diaphragm arise from? Describe it in relation to the left.
- It is longer and larger than the left.
- It arises from the upper 3 or 4 lumbar vertebra.
What does the right crus of the diaphragm form?
Why is this surprising?
It forms the oesophageal hiatus.
This is surprising because the hiatus is on the left.
What does the left crus of the diaphragm arise from?
The upper 2 or 3 lumbar vertebra
What is the function of the pericardiacophrenic ligaments
They fuse the central tendon of the diaphragm with the pericardium
What are the 3 diaphragmatic apertures and at what level does each of them pass through the diaphragm?
Caval opening (IVC) = T8 Oesophageal hiatus = T10 Aortic hiatus = T12
What does the caval foramen perforate to pass from the abdomen to the thorax and what does it permit the passage of?
It perforates the central tendon of the diaphragm to permit the passage of the IVC to the heart, as well as the terminal branches of the right phrenic nerve.
Is the caval opening in the midline? What landmark on the diaphragm is it found at?
No it is found slightly to the right of the midline.
It is found at the junction of the right and middle leaves of the central tendon.
Describe the facilitation of blood flow through the IVC via the action of the diaphragm
The IVC is firmly attached to the rise of the caval opening and as a result when the diaphragm contracts during inspiration the IVC is dilated. This facilitates blood flow through the vein.
Within which crus of the diaphragm is the oesophageal hiatus found? What level of the spine is this hiatus?
It is found within the right crus, despite the hiatus being on the left of the midline. It is found at the level of T10
What does the oesophageal hiatus transmit, apart from the oesophagus?
The anterior and posterior vagal trunks
The oesophageal branches of the left gastric vessels
Some lymph vessels
What happens to the oesophagus when the diaphragm contracts and why?
A few muscle fibres of the right crus form a type of sphincter around the oesophagus which contracts when the diaphragm contracts. This prevents reflux of stomach contents into the oesophagus during inspiration from the increase in intraabdominal pressure.
What is the aortic hiatus formed by?
The right the left crura and the fibrous median arcuate ligament. The arcuate ligament unites the right and left crus as an arch over the anterior aspect of the aorta.
What does the aortic hiatus transmits and at what level is it?
Level of T12
Transmits the aorta, as well as the thoracic duct and sometimes the azygous vein
What are some of the small openings in the diaphragm?
Sternocostal foramen/triangle:
- Found between the sternal and costal attachments of the diaphragm
- Transmits lymphatics vessels from the liver and the superior epigastric vessels
The sympathetic trunks pass deep to the medial arcuate ligament
Two small apertures in the crus of the diaphragm
- one transmits the greater splanchnic nerve
- the other the lesser splanchnic nerve
What is the arterial supply to the diaphragm?
Superior surface:
- pericardiacophrenic and musculophrenic arteries
- branches of the internal thoracic artery (off subclavian artery)
- superior phrenic arteries (arise from the thoracic aorta)
Inferior surface:
- inferior phrenic arteries (typically arise from the abdominal aorta or may arise from the coeliac trunk)
What is the venous drainage of the diaphragm?
Superior surface:
Pericardiacophrenic and musculophrenic veins
- drain into the internal thoracic veins
Superior phrenic vein (Rt side)
- drains into the IVC
Inferior surface:
Inferior phrenic veins
- Rt side typically drains into the IVC
- the Lt side is doubled with one draining into the IVC and the other into the suprarenal vein
What is the innervation of the diaphragm?
Motor supply
Phrenic nerve (C3-5)
(C,3,4,5 keeps the diaphragm alive!!)
Each half of the diaphragm is supplied by its own phrenic nerve
Sensory supply
Centrally by the phrenic nerve C3-5
Peripherally - by the intercostal nerves (T5-11) & the subcostal nerves (T12)
