13. Body Cavities

Question 1

Lateral folding

Answer 1

• Around the formed medial axis (notochord and neural tube)
  
  • Left and right downwards to create intraembryonic cavity
• At same time as lateral folding
• Growth of embryonic disc, not yolk sac

Question 2

Cephalocaudal folding

Answer 2

• Head to anus
• At same time as lateral folding
• Septum transversum (right under heart) divides intraembryonic cavity formed
• Head formation starts
• Brain and liver formation start

Question 3

Body folding to create gut

Answer 3

Folding completes primitive cavity apart from vitelline duct and connecting stalk

Question 4

Cavities

Answer 4

lining of parietal mesoderm on inside
Visceral mesoderm on outside
Parietal and visceral mesoderm together: dorsal mesoderm (suspends gut tube)
Pericardial, pleural, peritoneal, thoracic, pelvic

Question 5

More

Answer 5

• Mesenchyme give rise to part of thoracic diaphragm and ventral mesentery of foregut
• Myoblast cells from septum transversum invade other components of the diaphragm giving rise to motor innervation
• Caudal part ST is invaded by hepatic diverticulum (liver bud), which derives within to form liver and thus gives rise to ventral mesentery of the foregut

Question 6

Diaphragm

Answer 6

• Tissues
  
  • Septum transversum
  • Pleuroperitoneal membranes
  • Mesoderm body wall
  • Esophageal mesenchyme
• Descends during development (while heart and lungs are growing)

Question 7

Lungs

Answer 7

• Expand ventrally and laterally
• Pleuropericardial folds become pleuropericardial membrane and divides primitive pleuralpericardial cavity