Development of pituitary gland and sympathetic nervous system

Pituitary gland

Anterior lobe (adenohypophysis)

  • Ectoderm – roof of stomodeum 
  • Forms diverticulum called Rathke’s pouch, which grows upwards from stomodeum infront of buccopharyngeal membrane
  • End of 3rd month, loses connection with stomodeum and differentiates into; Pars distalis, Pars tuberalis and Pars intermedia
  • Lumen gets obliterated

Posterior lobe (neurohypophysis)

  • Neural ectoderm – floor of diencephalon
  • Forms diverticulum called Infundibulum, which grows downwards
  • Differentiates into; Pars nervosa and pituitary stalk

Image result for development of pituitary gland

 

Congenital anomalies:

  1. Agenesis
  2. Absence of anterior lobe – failure of developing Rathke’s pouch. Leads to maldeveloped thyroid gland, suprarenal gland and testes
  3. Pharyngeal hypophysis – remnant of Rathke’s pouch remains attatched to pharyngeal wall

Sympathetic nervous system

  • Neural crest cells in thoracic region
  • Migrate to each side of the spinal cord, behind dorsal aorta
  • Form a bilateral chain of segmentally arranged sympathetic ganglia which are connected by longitudinal nerve fibers
  • Neuroblasts migrate from thorax region to cervical and lumbosacral regions, therefore extending the sympathetic chains

In cervical region, ganglia fuse to form superior, middle and inferior cervical ganglia

Some neuroblasts migrate infront of aorta to form celiac, superior mesenteric and inferior mesenteric ganglia

Some neuroblasts migrate to heart, lungs or GIT to form sympathetic organ plexuses

Some migrate to form medulla of suprarenal glands

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