Question

a List the two fetal circulation bypasses in the heart? Why do they develop?

b.What is the difference between angiogenesis and vasculogenesis?

Answer 1

a. The fetal or prenatal circulation differs from the postnatal (after birth) circulation in many ways. The fetal circulation bypasses the lungs and liver because these organs are not fully functional until birth. The fetal circulatory system uses 3 shunts (Ductus arteriosus, Ductus venosus and foramen ovale).

- Foramen ovale is the shunt that bypasses the lungs:- it moves the blood from the right atrium to the left atrium of the heart.

- Ductus arteriosus:- moves the blood from the pulmonary artery to the aorta.

- Ductus venous :- fetus obtains oxygen and nutrients from the mother through the umbilical cord connected to the placenta. The highly oxygenated blood coming from the umbilical cord enters the inferior vena cava (ductus venosus connects the left umbilical vein with the inferior vena cava) bypassing the liver and then to the right atrium of the heart. Only a small amount of this blood is sent to the liver for fulfilling its oxygen and nutrient needs.

Finally, Waste products and CO2 from the fetus are sent back through the umbilical cord and placenta to the mother's circulation to be removed.

b.

ANGIOGENESIS	VASCULOGENESIS
The process of synthesizing new blood vessels from pre-existing blood vessels.	The process of de Novo synthesis of blood vessels during the formation of the circulatory system of an organism
can occur throughout the life span of an organism.	occurs only during the embryonic development of an organism.
MMPs(matrix metalloproteinases) along with some endothelial growth factors facilitate this process.	endothelial cells arising from mesoderm combine with hematopoietic stem cells to form new vascular tissues.
can occur in response to physiological stimuli such as wound healing or reproductive cycle of women	does not occur or is absent even in response to any physiological stimuli
plays an important role in cancer development (rate of angiogenesis increases in the tumor)	no role in cancer development