Diaphragm Flashcards
What is the anterior attachment of the diaphragm?
- xiphisternum
- costal cartilages of ribs 7-10
Which hemidiaphragm is higher and why?
- the right hemidiaphragm is higher than the left due to the position of the liver in the upper right quadrant
What are the attachments of the right and left cruras of the diaphragm?
- right crus: bodies and intervertebral disks L1-3
- left crus: bodies and intervertebral discs L1-2
What is found between the cruras of the diaphragm?
median arcuate ligament
What are the attachments of the medial and lateral arcuate ligament?
- medial arcuate ligament: L1
- lateral arcuate ligament: rib 12
What are the 3 openings in the diaphragm?
- T8: caval opening for IVC and right phrenic nerve
- T10: oesophagus, anterior and posterior vagal trunks
- T12: aortic hiatus for thoracic duct and azygos
What are the relations of the IVC, oesophagus and aorta to the diaphragm?
- IVC pierces tendinous part of diaphragm
- oesophagus passes through muscular slip in diaphragm
- aorta lies behind the diaphragm with left and right cruras at either side
What is the risk with the oesophageal opening in the diaphragm?
it’s entry into the diaphragm does not forma true sphincter and risks the possibility of reflux of gastric acid from the stomach which can cause heartburn
What nerves innervate the diaphragm?
- phrenic nerve C3,4,5
- motor and sensory to central portion (as well as fibrous and parietal pericardium and mediastinal pleura)
- intercostal and subcostal nerves
- peripheral innervation
Describe how the phrenic nerve travels to the diaphragm
- phrenic nerve travels between venous and arterial planes in superior mediastinum
- descends anterior to the roots of the lungs on either side
- right phrenic nerve passes through diaphragm with IVC
- left phrenic nerve pierces diaphragm but does not pass through it
Describe the vascular supply of the diaphragm
- internal thoracic artery (from 2nd part of subclavian) and gives off
- pericardiophrenic artery
- musculophrenic arteries
- 2 inferior phrenic arteries (from abdominal aorta)
- superior phrenic arteries (from thoracic aorta)
Where does referred pain from the diaphragm go to?
C4 dermatome
Describe the diaphragm in respiration
- inspiration: diaphragm flattens increasing volume in thoracic cavity
- expiration: diaphragm is raised reducing volume in thoracic cavity
Describe Boyle’s Law
- pressure exerted by gas is inversely proportional to the volume it occupies
- increasing volume in thoracic cavity during inspiration reduces the pressure relative to the atmospheric pressure so air flows into the lungs
Describe what happens when there is damage to the right phrenic nerve and what that would look like in a chest X-ray
- as volume of the thoracic cavity increases during inspiration, pressure in the abdominal cavity increases causing the right hemidiaphragm to rise (rather than flatten)
- this elevation is visible on an X-ray
What can cause damage to the phrenic nerve?
- cardiac surgery
- invasion of the phrenic nerve by a lung tumour
What do the intercostal muscles do during inspiration?
- external intercostal muscle fibres contract and elevate the ribs and the sternum
- increases the antero-posterior and lateral diameter of the thoracic cavity
What muscles are involved in forced respiration?
Inspiration:
- diaphragm (descends up to 10cm)
- external intercostal muscles
- accessory muscles of inspiration (trapezius, scalenes, sternocleidomastoid)
- nasalis (flares nostrils increasing volume of inspired air)
Expiration:
- diaphragm and external intercostal muscles
- internal intercostal muscles (to help reduce intra-thoracic volume)
- muscles of abdo wall (to help increase intra-abdo pressure)
When does forced respiration occur?
- exercise
- ‘normal breathing pattern’ in those with COPD/lung disease
What is the function of the pleura?
- reduce friction to allow movement of lungs
- intrapleural pressure: negative relative to atmospheric pressure to prevent collapse of the lungs
Describe the surface markings of the parietal pleura
- the apex on both sides are 2-3cm superior to the middle of the clavicle
- both descends down the midline of the chest until 4th CC where it deviates slightly laterally on the left pleura to accomodate the heart
- right sits midline at 6 CC
- left sits lateral to the sternum at 6 CC
- mid-clavicular line sits 8CC
- from mid-axillary line sits at the 10th rib
- both sits at lateral border of erector spinae at T12
Describe the surface marking of the lungs and the areas of potential space
- surface marking is the same as the pleura but the lungs sit 2 ribs higher to allow expansion
- potential space in the costodiaphragmatic recess where 2 layers of parietal pleura oppose each other
Describe the surface markings of the lung lobe fissures
Right lung:
- horizontal fissure starts at 4 CC anteriorly and ends meeting the oblique fissure
- oblique fissure can be drawn from T4 vertebrae posteriorly to 6th rib anteriorly
Describe where you would put the stethoscope to auscultate the different lobes of the lungs
- 2nd intercostal space anteriorly/superiorly for superior lobes
- 4th intercostal space on the right for middle lobe (can’t be auscultated posteriorly)
- 6th intercostal space for lower lobes
- 7th intercostal space for inferior lobes
Pneumothorax
air in the thorax between the visceral and parietal layers of pleura causing compression of the lung tissue
Haemothorax
blood between visceral and parietal layers of pleura
Chylothorax
lymph between visceral and parietal layers of pleura
What are the clinical signs and symptoms of a pneumothorax?
- dyspnoea
- pleuritic chest pain
What are the risk factors for a pneumothorax?
- tall
- male
- smoker
- underlying lung disease/COPD/asthma
What happens during a tension pneumothorax?
- medical emergency
- air is trapped between layers of pleura
- valve like effect causes air to enter the pleural space and not leave
- increasingly positive intrapleural pressure
- trachea and mediastinum shifted away from side of pneumothorax
- venous return to heart is impaired causing hypotension and cardiac arrest
What would you do in a tension pneumothorax?
- decompress
- insert a cannula on the side of the pneumothorax at the 2nd intercostal space mid-clavicular line
What are the indications for a chest drain?
- large pneumothorax
- tension pneumothorax
- traumatic haemothorax
- large pleural effusion
- aims to enable removal of fluid/air from intrapleural space
What is the ‘safe’ triangle and what are its borders?
- the site where you can insert a chest drain
Borders:
- base of axilla
- lateral edge of latissimus dorsi
- 5th intercostal space
- lateral edge of pectoralis major
What are possible complications of a chest drain (even in the safe triangle)?
- false passage: instead of the tube sitting in the intrapleural space it just tunnels under the subcutaneous tissue
- damage to long thoracic nerve
- haemothorax due to damage to intercostal arteries
- liver/spleen injury
