At approximately day 1

Heart cells originate near the primitive streak.

Reference [PubMed Link]

Sadler TW. 2000. Susceptible periods during embryogenesis of the heart and endocrine glands. Environ Health Perspect 108 (suppl 3):555-561.

At approximately day 1

Heart cells migrate through the streak to the cardiogenic area (splanchnic mesoderm); cells in this region form a horseshoe-shaped tube (which will then form the heart tube).

Reference [PubMed Link]

Sadler TW. 2000. Susceptible periods during embryogenesis of the heart and endocrine glands. Environ Health Perspect 108 (suppl 3):555-561.

At approximately day 1

Angioblastic cords canalize to form endocardial heart tubes and then fuse to become the tubular heart, which is surrounded by a thicker muscular tube, the primordial myocardium.

Duration: 1 week

Reference

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

At approximately day 1

Primitive streak appears.

Reference

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

At approximately day 1

The liver bud arises as an outgrowth of the foregut.

Duration: 1 week

Reference

Sadler TW. 2004. Langman’s Medical Embryology. Ninth Edition. Maryland: Lippincott Williams & Wilkins.

At approximately day 1

Gastrulation occurs via invagination of epiblast cells at the primitive streak. Cells migrate to form the endoderm, mesoderm and ectoderm layers.

Duration: 1 week

Reference

Sadler TW. 2004. Langman’s Medical Embryology. Ninth Edition. Maryland: Lippincott Williams & Wilkins.

At approximately day 4

Neural crest cells, formed in the hindbrain, migrate into areas of the developing heart (e.g. endocardial cushions) and support the development of the aortic arches and other structures.

Duration: 1 week

Reference [PubMed Link]

Sadler TW. 2000. Susceptible periods during embryogenesis of the heart and endocrine glands. Environ Health Perspect 108 (suppl 3):555-561.