CARDIOVASCULAR

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EMBRYOLOGY

HEART EMBRYOLOGY:

- The single heart tube begins to beat at 23 days of development and by 30 days blood circulates through the embryo.

EMBRYONIC FOLDING:

- 3 week, the germ disk hasta the appearance of a flat oval disk and is composed of two layers:

a. The epiblast

b. The hypoplast

- A primitive groove ( linea primitiva), ending caudally with the primitive pit surrounded by a node, first appears at approximately 16 days of development and extends half the length of the embryo.

* Primitive groove: serves as a conduit for epiblast cells that detach from the edge of the groove and migrate inwards toward the hypoblast and replace it to form the endoderm --> after the endoderm cells form the epiblast continue migrate inwards to infiltrate the space between he epiblast and the endoderm to form the intraembryonic mesoderm.

* The flat germ disk transforms into a tubular structure during the 4 week of development --> embryo folds in 2 different dimensions.

1. Craniocaudal axis: tube--> forming the brain at its cephalic end.

2. LAteral folding: 2 lateral edges of the germ disk to fold forming a tube-like structure.

THE PRIMITIVE HEART:

- The first intraembryonic blood vessels are noted on day 20, and in 1-3 days later the formation of the single median heart tube is complete.

- The cranial most area is the bulbs cords--> extends cranially into the TRUNCUS ARTERIOSUS--> GIVES RISE TO ASCENDING AORTA AND PULMONARY TRUNK.