Diaphragm Flashcards
What is the diaphragm?
- Thin, musculotendinous
- Muscular at its periphery, tendinous centrally
- closes the inferior thoracic aperture
Describe the shape of the diaphragm
- Inverted J shape
- Right hemidiaphragm is 1cm is higher than the left
Describe the position of the diaphragm in full expiration
- R= 4th intercostal
- L = 5th intercostal
What is the diaphragm attached to anteriorly?
- Xiphoid process at vertebral level T8/T9
- Deep surface of the last 6 ribs and costal cartilages
What is the diaphragm attached to posteriorly?
• Lumbar vertebrae and intervertebral discs between them
- left crus = L1-L2
- right crus = L1-L3
• Median arcuate ligament
- forms the aortic hiatus
- medial borders of the crura
• Medial arcuate ligament
- body - transverse process of L1
• Lateral arcuate ligament
- Transverse process of L1 - rib 12
What is the insertion of the diaphragm?
• Central tendon
What level is the central tendon?
Xiphosternal synchondrosis
What is a function of the central tendon
- Fused to the pericardium
- Halts the descent during forced inspiration
- Further contraction of the diaphragmatic muscle pulls ribs 7-10 from the anchored central tendon
What are the 3 openings of the diaphragm?
- Caval opening
- Oesophageal opening
- Aortic hiatus
Caval opening
- T8, through the central tendon
- Inferior vena cava
- Right phrenic nerve
Oesophageal opening
- T10 level, though the right crus (acts like a sphincter because of muscle fibres)
- Oesophagus
- Both vagus nerves
- Left gastric vessels
Aortic hiatus
- T12, behind the median arcuate ligament
- Aorta • thoracic duct
- Azygos
- Hemiazygos
What passes through the crura
- Branches of the left phrenic nerve
- Splanchnic nerves
- Azygos
- Hemiazygos
What passes behind the medial arcuate ligament?
• Sympathetic trunk
What is the vascular supply to the superior surface of the diaphragm?
- Superior phrenic artery (branch of the thoracic aorta)
- Branches of musculophrenic arteries
- Branches of pericardiacophrenic arteries
What is the vascular supply to the inferior surface of the diaphragm?
• Inferior phrenic artery - branch of the abdominal aorta
What is the motor supply to the diaphragm?
- Phrenic nerve
- C3, 4!, 5
What is the sensory supply to the diaphragm?
- Phrenic: central tendon, parietal pleura and pericardium
- Intercostal nerves: sensory from the periphery of the diaphragm (afferent)
Where would you feel pain from the intercostal nerves?
- Where it is on the side
- Does not refer pain
Describe the mechanism of inspiraiton
- Contraction flattens the dome of the diaphragm
- Dome descends
- Vertical diameter increases
- Volume of the thorax increases
- Intrathoracic pressure decreases
- Air is drawn into the lungs
Describe the pump handle movement
- Body of the rib passes obliquely downwards: the anterior end of the rib is usually lower than the posterior end
- Contraction of the external intercostals raise the body of the rib to the one above
- This also lifts the sternum and pushes it anteriorly
- Increases sagittal diameter, increasing the volume of the thorax
Describe the bucket handle movement
- Only occurs in ribs 8-10 - flat costo transverse joints that allow gliding
- Once the central diaphragm is anchored, further muscle contraction pulls on the ribs and causes them to evert like a bucket handle
Accessory muscles
- Pectoralis major and minor (inspiration)
- Lastissimus dorsi (inspiration and expiration)
- fixate and stabilise ribs
• Abdominal wall muscles (expiration)
Which muscles help to fix the ribs?
Neck and back muscles:
- Trapezius
- Sternocleidomastoid
- Scalene muscles
Describe the boundaries of the pleura
- Rises to the level of the 1st rib, 2cm above the clavicle
- 2nd CC - lies adjacent to the midline
- 4th CC - LEFT - cardiac notch
- 6th CC deviates laterally
- 8th rib - mid clavicular line
- 10th rib: mid axillary line
- T12: midline (just below 12th rib)
Describe the boundaries of the lung
• Apex projects into the neck
- curved line from the sternoclavicular joint to a point 2.5cm above the junction of the medial and intermediate thirds of the clavicle
- 2nd CC: adjacent to the midline
- 4th LCC: cardiac notch
- 6th CC: deviates laterally
- 6th rib: midclavicular line
- 8th rib: mid axillary line
- 10th rib: mid scapular line and mid line
Pleural recesses
- In quiet respiration, the lungs do not entirely fill the pleural cavities
- This results in recesses which two layers of parietal pleura become opposed
- Potential sites of accumulation of fluid from which they can be aspirated
Why is the intapleural pressure more negative?
- Surface tension between the parietal and visceral pleura pulls the visceral layer (and lung) with the movements of the thoracic wall
- Elastic recoil of the lung tissue means the lungs are tending to deflate
- This surface tension creates a slight negative pressure that maintains the lung in slight inflation even at the end of expiration
What is the costodiaphragmatic recess?
- Costophrenic recess
- Narrow potential space between the periphery of the diaphragm and the ribs
Surface anatomy of the oblique lung fissure
- Curved line
- Begins between spinous processes of T3 and T4
- Crosses the mid axillary line at the 5th intercostal space
- Then follows the contour of the 6th rib
Surface anatomy of the horizontal lung fissure
- Follows the 4th intercostal space from the sternum
- Until it meets the oblique fissure as it crosses rib 5
Where is the triangle of safety?
- Anterior border of latissimus dorsi
- Lateral border of pectoralis major muscle
- Horizontal level of the nipple (5th intercostal space)
- Apex below the axilla
- Can be used for fluid or air just depends on if you put catheter up or down
What is flail chest?
- Trauma resulting in fracture of the ribs and the sternum would cause a segment to float freely
- On inspiration, this segment would be sucked inwards instead of lifting upwards
- Paradoxical respiration
What is the black arrow?
Left Crus (L1-2)
What is the blue
Median arcuate ligament (medial broders of the crura)
What is the purple arrow?
Right Crus (L1-3)
What is the green?
Medial arcuate ligament (from the body to the transverse process of L1)
What is the red?
Lateral arcuate ligament
What is the arrow pointing to?
Pericardium fused ot the central tendon
What is the green arrow?
Caval opening (T8, throught the central tendon)
- Inferior vena cava
- Right phrenic nerve
What is the red arrow
Oesophageal opening
- At T10 level thorugh the right crus
- Oesophagus
- Both vagus nerves
- Left gastric vessels
What is the black arrow?
Aortic hiatus
- Aorta
- Thoracic duct
- Azygos
- hemiazygos
What is the green arrow?
Inferior phrenic artery - branch of the abdominal aorta
What is represented by the blue?
Phrenic nerve afferent supply
What is represented by the red?
Phrenic nerve efferent supply
What is the green?
Intercostal nerves - sensory
What is the blue arrow
Costomediastinal recess
