T2 L12: Applied anatomical concepts

• Which part of the spinal cord do the sympathetic nerves of the autonomic nervous system arise from?

  Lateral horn

  
• The azygos vein is formed by the union of the right subcostal vein and which other vessel?


  Right ascending lumbar vein

  
• What is Boyle's Law?

  The pressure and volume of a gas have an inverse relationship. If volume increases, pressure decreases and vice versa.
• How does the visceral pleura move?

  elastic recoil of lungs
• How does the parietal pleura move?

  with ribs and diaphragm
• What prevents lung from collapsing?

  surface tension between parietal and visceral pleura
• What is pneumothorax?

  Air enters thoracic cavity causing surface tension between parietal and visceral layers to be lost

  Lung collapses

  Caused by a penetrating injury to the lung

  
• What are pneumothorax, haemothorax, pleural effusion and empyema?

  pneumothorax: air in chest

  haemothorax: blood in chest

  pleural effusion: fluid in chest

  empyema: pus in chest
• What is the 'safe triangle'?

  area for chest drain insertion

  anterior border: (lateral border of) pec major

  inferior border: horizontal line at nipple level

  posterior border: (anterior border of) latissimus dorsi

  
• What are the different axes in which the volume of thorax changes during breathing?

  lateral, anteroposterior, vertical

  
• What are the lateral changes in the volume of thorax during inspiration?

  increase

  'bucket handle movement':

  lateral edges of ribs elevated superolaterally

  
• What are the anteroposterior changes in the volume of thorax during inspiration?

  increase

  'pump handle movement'

  anterior ends of ribs and sternum are raised

  movement facilitated by costal cartilages

  
• What are the vertical changes in volume of thorax during inspiration?

  increase vertical diameter of thorax

  diaphragm descends 5-10cm compressing abdominal organs

  decrease vertical diameter of abdomen (result in protrusion of abdominal wall)

  
• What are the muscles responsible for quiet breathing?

  Quiet inspiration:

  • external intercostals
  • scalenes
  • diaphragm (responsible for 2/3rds)

  Quiet expiration:

  elastic recoil of lungs (passive process)

  
• What are the muscles responsible for forced inspiration?

  all muscles involved in quiet inspiration

  Additionally:

  • pectoralis muscles
  • sternocleidomastoid (SCM)
  • latissimus dorsi

  
• How do the pectoral muscles and latissimus dorsi aid forced inspiration additionally?

  they move upper limbs

  by fixing their positions, they can move ribs more efficiently

  (people with dyspnea use accessory muscles to breathe, stabilise upper limbs by leaning on knees / arms of chair)

  
• What are the muscles required for forced breathing?

  more muscles:

  • internal intercostals
  • external and internal oblique
  • transversus abdominis
  • quadratus lumborum

  
• What is the diaphragm?

  sheet of skeletal muscle with a central tendon

  pericardium attached to middle of tendon on superior surface

  diaphragmatic (parietal) pleura lines its superior surface

  
• What are the attachments of the diaphragm?

  Origins:

  • sternal (xiphoid process)
  • costal (costal cartilages of ribs 7-10; ribs 11-12)
  • Lumbar (medial and lateral arcuate ligaments and lumbar vertebral bodies)

  Insertion: central tendon

  
• What are the lumbar origins of the diaphragm?

  Lumbar part of the diaphragm arises from:

  • arcuate ligaments (medial and lateral)
  • lumbar vertebral bodies (via right and left crura)
  • meet to form 'median arcuate ligament', surrounding aortic hiatus
  • fibres of right crus also surround oesophageal hiatus

  
• What are the openings of the diaphragm?

  2 openings / hiatuses:

  • inferior vena cava (T8) (8 letters; 'vena cava')
  • oesophageal hiatus (T10) (10 letters; 'oesophagus')
  • Aortic hiatus (T12) (12 letters)

  thoracic duct & azygos vein also pass through aortic hiatus

  
• What are the actions of the diaphragm?

  Alter volume of thorax:

  • quiet inspiration (descends approx. 2cm)
  • Forced inspiration (descends 7-10cm)
  • aids venous return (respiratory pump)
  • hiccups

  Alters volume of abdomen:

  • urination and defecation
  • childbirth
  • lifting heavy objects (braces vertebral column)

  
• What is the Phrenic nerve?

  arises from ventral rami of C3, C4, C5 (C3-4-5, keep the diaphragm alive!)

  passes anterior to main bronchi

  Motor supply:

  • diaphragm (sole supply)

  Sensory supply:

  • pericardium
  • parietal pleura (mediastinal and central part of diaphragmatic)
  • central region of diaphragm

  
• What is the 'paralysis of the diaphragm'?

  one dome (hemidiaphragm) can be paralysed independently

  due to symmetrical supply to both sides of diaphragm

  causes 'paradoxical movement':

  • paralysed dome ascends during inhalation (pushed superiorly by abdominal viscera)
  • descends in exhalation as intra-abdominal pressure decreases

  
• Where can pain from diaphragm be referred to?

  Shoulder

  C3-5 dermatomes lie over the shoulder region

  sensory inputs from these areas synapse at the same spinal level

  pain cannot be localised accurately by CNS

  
• Which structure, when passing through the diaphragm, experiences a constriction which can be a point where foreign bodies may become lodged?

  oesophagus