Heart > Primitive Heart Tube

Embryonic Index: Hrt.PHT

The primitive heart tube is formed by the splanchnic layer, which is comprised solely of first heart field cells. The short distance between the head fold and the forming foregut cause the heart to form two bulges at its midline (five-somite stage) and later fuse to form one bulge (six somite stage), which appears as a “linear” tube that immediately beings to loop (seven somite stage), to form a looped heart at E8.5 (nine-somite stage) which beats.