At approximately day 1

Hematopoiesis (blood cell formation) begins.

Reference

Moore KL, Persaud TVN. 1998. The Developing Human: Clinically Oriented Embryology. 6th ed. Philadelphia: WB Saunders Co.

At approximately day 1

Collecting tubules, formed from metanephric diverticulum, undergo repeated branching, forming major and minor calices; the end of each tubule forms a metanephric vesicle.

Duration: 2 weeks

Reference

Moore KL, Persaud TVN. 1998. The Developing Human: Clinically Oriented Embryology. 6th ed. Philadelphia: WB Saunders Co.

At approximately day 1

Primary intestinal loop herniates into the umbilicus, rotating 90 degrees by week 8.

Duration: 2 weeks

Reference

Larsen WJ. 1997. Human Embryology. New York: Churchill Livingstone Inc.

At approximately day 1

Branching leads to the formation of terminal bronchioles by week 16.

Duration: 10 weeks

Reference

Larsen WJ. 1997. Human Embryology. New York: Churchill Livingstone Inc.