trace the pathway of the blood from the arch of the aorta to the rectum and back to the right atrium?

Answer 1

There's more than one way of doing the circuit.
Here're the possibilities on the way down:
Aortic arch- descending aorta- superior mesenteric artery- arch of Drummond- descending branch of inferior mesenteric artery- superior rectal artery-rectum
Aortic arch- descending aorta- inferior mesentric artery- superior rectal artery- rectum
Aortic arch- descending aorta- right and left common iliac arteries- right and left internal iliac arteries- middle rectal arteries- rectum
Aortic arch- descending aorta- right and left common iliac arteries- right and left internal iliac arteries- right and left internal pudendal arteries- inferior rectal arteries- rectum
On the way back, there are many different routes but the names are generic:
Inferior rectal veins- internal iliac veins- common iliac veins- inferior vena cava- right atrium
Middle rectal veins- internal iliac veins- common iliac veins- inferior vena cava- right atrium
Superior rectal veins- inferior mesentric vein- splenic vein- portal vein- liver sinusoids-hepatic veins- inferior vena cava- right atrium.