development of the GIT

• What are the three primary germ layers?

  The ectoderm, mesoderm, and endoderm

  
• What does the mesoderm primarily develop into?

  Muscles, bones, and connective tissues

  
• What does the endoderm primarily develop into?

  The lining of the digestive tract and respiratory system

  
• What are the three primary germ layers and their primary developmental fates?

  • Ectoderm: develops into the nervous system, epidermis, and hair
  • Mesoderm: develops into muscles, bones, and connective tissues
  • Endoderm: develops into the lining of the digestive tract and respiratory system

  
• What is splanchnic mesoderm?

  The splanchnic mesoderm forms the visceral mesoderm

  
• What germ layer is closely associated with the splanchnic mesoderm?

  Endoderm

  
• What structures does the splanchnic mesoderm contribute to?

  The smooth muscles and connective tissues of the viscera

  
• How does the splanchnic mesoderm interact with other germ layers?

  • Forms the visceral mesoderm
  • Contributes to the smooth muscles and connective tissues of the viscera
  • Closely associated with the endoderm

  
• From where do abdominal accessory organs arise?

  They arise as foregut outgrowths.

  
• Why are abdominal accessory organs considered outgrowths of the foregut?

  Because they originate from the foregut during embryonic development.

  
• What are the key features of how abdominal accessory organs arise during embryonic development?

  • They arise from the foregut
  • They develop as outgrowths of the foregut
  • These outgrowths differentiate into various abdominal organs

  
• In which direction does the proximal duodenum rotate during embryonic development?

  It rotates clockwise.

  
• What is the significance of the proximal duodenum rotating clockwise during embryonic development?

  It ensures the proper arrangement and alignment of the digestive system organs.

  
• What key event occurs in the proximal duodenum during embryonic development?

  • Proximal duodenum rotates clockwise

  
• What are the two axes of rotation during stomach development?

  • Longitudinal axis rotation
  • Ventraldorsal axis rotation

  
• What does longitudinal axis rotation of the stomach involve?

  Turning the stomach along its long axis

  
• What is ventraldorsal axis rotation?

  Rotation of the stomach along the ventral-dorsal axis

  
• What are the consequences of pyloric stenosis?

  • Obstruction of the passage of foods and liquids
  • Can cause severe vomiting

  
• What is the cloaca?

  The cloaca is the common end for hindgut and urogenital tract.

  
• Why is the cloaca important in the hindgut and urogenital tract?

  Because it serves as the common opening for both hindgut and urogenital products.

  
• What are the two tracts that the cloaca is a common end for?

  • Hindgut tract
  • Urogenital tract

  
• What function does the cloacal membrane serve?

  • Seals the cloaca

  
• What structure grows towards the cloacal membrane during hindgut development?

  The urorectal septum.

  
• What is the purpose of the urorectal septum growing towards the cloacal membrane?

  • It separates the cloaca into the anorectal canal and the urogenital sinus

  
• What separates the urogenital and anal membranes during hindgut development?

  The perineal body.

  
• What is the role of the perineal body in hindgut development?

  • It divides the cloaca into the urinary bladder, urogenital sinus, and anal canal

  
• What occurs during the elongation and formation of jejunoidal loops?

  • The jejunum and ileum increase in length
  • Loops of jejunum and ileum form within the intestinal region
  • The elongated and looped jejunum and ileum arrange to accommodate the expanding intestinal organs

  
• What structures arise from foregut outgrowths during abdominal accessory organ development?

  • Liver buds
  • Gallbladder

  
• In what direction does the proximal duodenum rotate during embryonic development?

  Clockwise

  
• What happens to the ventral and dorsal pancreatic buds and ducts during fusion?

  They fuse together

  
• How are the bile and pancreatic ducts arranged after fusion at the major papilla?

  • They join together at the major papilla to drain

  
• What condition can result from the annular pancreas?

  • Constriction/obstruction of duodenal contents

  
• What are the key developmental genes involved in spleen formation and what are their functions?

  • $Hox11:$ Regulates the anterior-posterior axis and contributes to spleen positioning.
  • $Nkx2.5:$ Important for heart and vasculature development, indirectly influences spleen formation through its effects on mesodermal cells.
  • $WT1:$ Regulates differentiation of mesodermal cells into spleen primordium.

  
• What gland is located adjacent to the dorsal mesogastrium?

  Adrenal gland

  
• From which type of cells is the spleen primordium derived?

  Mesodermal cells

  
• What is the main function of mesodermal cells in spleen development?

  They form the spleen primordium.

  
• What other organs are labeled in the diagram besides the spleen?

  Stomach and liver

  
• Which organ is located beneath the spleen in the diagram?

  Stomach

  
• Which organ is located to the right of the spleen in the diagram?

  Liver

  
• How does $Nkx2.5$ indirectly influence spleen development?


  By regulating mesodermal cells, which contribute to spleen formation.