Question

a. In the lub-dub sound of a heartbeat, the lub is louder. Why is this?

b. The descending aorta has three paired arteries and three unpaired arteries that flows away from with oxygenated blood to supply organs in the abdominal/thigh area. The inferior vena cava has three paired veins BUT NOT three unpaired veins flowing into it with deoxygenated blood. Where do the unpaired veins take blood to from the abdominal region and why?

Answer 1

a) the lubb sound is due to the closure of Av valves. When SA node produce impulse the conduction through the atria is fast and it contracts soon after it the atria remain to relaxed state and the now the ventricles starts to contract. So the sudden pressure difference created between atria and ventricle made the AV valve to close suddenly. Thus with the high pressure the closure of AV valves makes lubb the louder sound.

b) the three unpaired veins of the inferior vena cava are hepatic vein, renal vein and gonadal vein. These veins take blood towards the inferior vena cava because veins from this region carry deoxygenated blood to the heart for oxygenating it. So it reaches the heart through inferior vena cava. The hepatic veins takes blood from the liver. Only one liver is there so it is unpaired. The renal vein take blood away from kidney. The renal vein originates as one piece from the kidney. The gonadal veins takes blood from the gonads.