Lecture 9

• Tracheoesophageal fistula occurs when the oesophagus and the trachea are linked as opposed to completely separating. - 4%
• Tracheoesophageal fistula with oesophageal atresia - difficult to detect prior to birth:

  Stomach able fill with amniotic fluid via connection of oesophagus to trachea.

  Give normal appearance on prenatal scan. 

  Upper portion oesophagus becomes distended as also fills with amniotic fluid and can give a normal stomach appearance on a scan. - 87%
• tracheosophageal fistula repair:

  1. surgery after birth, closes connection between trachea and esophagus
  2. upper and lower parts oesphagus connected
  3. gap large = wait therefore, fed through feeding tube
• VACTERL (defects):

  1. vertebral
  2. anorectal atresia
  3. cardiac
  4. tracheoesophageal fistula w/ or w/o esophageal atresia
  5. renal
  6. limb
• formation of pleura:

  1. derived from mesoderm or trilaminar disc
  2. lateral plate mesoderm forms parietal and visceral division
• stages of lung development:

  1. pseudoglandular
  2. canalicular
  3. saccular
  4. alevolar
• pseudoglandular stage (wk5-16):

  1. right and left primary bronchi
  2. secondary bronchi 3 on right, 2 on legy
  3. tertiary bronchi
  4. terminal bronchioles
• canalicular stage (wk16-wk26):

  1. resp. bronchioles
  2. primitive immature aleveoli i.e cuboidal cells
  3. pulmonary capillaries
• saccular stage (wk26-birth):

  1. increase number of primitive alveoli
  2. primitive alveoli begin mature
  3. cuboidal cells - type I and type II pneumocytes
  4. surfactant helps keep alevoli open decreasing surface tension
• type I = flat cells (gaseous exchange)

  type II = cuboidal cells (surfactant)
• alevolar stage (wk36-8yrs):

  1. increased number primitive alveoli become specialised
  2. mature alveoli develop septa (increases SA)
  3. birth - 100 million primitive alveoli
  4. 8 years - 300 million primitive alveoli due to alveolar stage and septation taking place
• infant respiratory distress syndrome:

  1. child born during canalicular stage low chance survival
  2. alveoli not well developed
  3. low surfactant therefore alveoli prone collapse, so unable take in high vol of o2 required to open them so breathing rate increases
  4. mechanical ventilation necessary = causes damage alveoli & lead bronchopulmonary dysplasia
• pulmonary agenesis:

  1. complete absence of one or both lungs can just be lobe
  2. disruption of lung bud during formation
• pulmonary hypoplasia:

  1. either one or both lungs do not fully develop
  2. found in association w/ congenital diaphragmatic hernia