Germ Cell layers
- Endoderm
- Epithelial lining and glands
- Mesoderm
- Lamina propria, muscularis mucoase, submucosa, muscularis externa, serosa
- Ectoderm
- Enteric nervous system, posterior luminal digestive structures
Primitive gut tube
- Foregut, midgut, hindgut
- Oesophagus from foregut
- Formation from infoldings
- Incorporation of endoderm into primitive gut tube
- Cranial and caudal end form blind ending tube
- Middle part remains connected to yolk sac by vitelline duct
Epithelium
- Proliferation of epithelial lining of gut tube
- Lumen obliterated by week 6
- Central cells then degenerate
- Tube recanalized by week 8
- Abnormalities in this process lead to
- Stenosis
- Atresia
- Duplication cysts
Oesophagus and Lung Development
- During 4th week
- Respiratory tract forms from a ventral bud from pharynx
- Lateral grooves invaginate on each side and fuse to create tracheooesophageal septum, making two distinct tubes
- Septum separates respiratory and digestive tracts
- Failure leads to tracheo-oesophageal fistula
- Failure leads to tracheo-oesophageal fistula
Growth of Oesophagus
- Initially short
- Rapidly elongates, due to lung development and heart descent
- Final position by week 7
- Failure to lengthen
- Short oesophagus and congenital hiatus hernia
Oesophageal Wall Development
- Upper part
- Striated muscle
- Striated muscle and upper oesophageal sphincter derived from mesenchyme of Branchial Arches 4,5,6
- Explains upper oesophageal sphincter innervation
- Vagus – nerve of Branchial Arch 5
- Recurrent Laryngeal – nerve of Branchial Arch 6
- Middle part
- Mixed
- Lower part
- Smooth muscle
- From Splanchnic Mesoderm
- Lower oesophageal sphincter innervated both by
- Parasympathetic – Vagus
- Sympathetic – Mostly Splanchnic N
Congenital Anomalies
- Rare – 1/3000-5000
- Oesophageal atresia
- Failure of recannalisation
- Tracheo-oesophageal fistulae
- Failure of lateral invaginations
- Stenosis, Web, Muscular Hypertrophy
- Abnormal recannalisation
- Duplication Cysts