The anatomy of the abdomen is complex with multiple organs, tissues and vascular structures. Blood supply to the abdomen originates from several branches of the aorta and the pressure generated by the cardiac output from the left ventricle. Two venous structures return deoxygenated blood and provide waste product drainage from the abdomen. To better understand the anatomy of the abdomen, let’s explore the arterial supplies and venous drainage in detail.
Arterial Supplies to the Abdomen
The aorta is the largest artery in the body and lies in the middle of the thorax and abdomen. It supplies oxygenated blood via systemic circulation to the body and branches off to supply the abdominal region. The abdominal portion of the aorta begins at the level of the twelfth thoracic vertebra (T12) and terminates at L4 with the left and right common iliac arteries.
The coeliac trunk also arises from the abdominal aorta at T12 and divides into three branches - the left gastric, splenic and common hepatic arteries. The superior mesenteric artery is the next branch of the aorta at L1 and supplies blood to the midgut organs from the distal duodenum to the proximal 2/3 of the transverse colon. And finally, the inferior mesenteric artery (IMA) originates from the aorta at L3 and provides blood to the hindgut organs - the distal 1/3 of the transverse colon to the rectum.
Venous Drainage of the Abdomen
The venous drainage of the abdomen is carried out by two systems: the portal venous system and the systemic venous system. The portal venous system transports venous blood from the abdominal vessels to the liver, whilst the systemic venous system returns blood to the right atrium of the heart via the inferior vena cava.
The portal venous system is made up of two major components: the superior mesenteric vein and the inferior mesenteric vein that together, drain blood from the midgut and hindgut organs, respectively. The superior mesenteric vein receives blood from the splenic vein and the superior pancreaticoduodenal vein and then drains into the splenic vein. The inferior mesenteric vein drains the distal colon and rectum and then connects to the splenic vein. All these branches of the portal venous system ultimately drain into the hepatic portal vein, thus supplying oxygen-poor blood to the liver for further processing. The blood from the liver then drains into the inferior vena cava.
The systemic venous system also transports deoxygenated blood from the abdominal organs. The superior system consists of the superior vena cava, which carries blood from the head, neck, upper extremities, chest and abdomen. This is also joined by the azygos vein, the hemiazygos vein and the accessory hemiazygos vein which respond to increases in pressure in the superior vena cava and when all three are present, are referred to as the azygos venous system. The inferior system consists of the inferior vena cava which carries deoxygenated blood from the lower abdominal organs and the lower extremities. The hepatic veins are also part of the systemic venous system and drain the liver, carrying deoxygenated blood into the inferior vena cava.
In summary, the arterial supplies and venous drainage of the abdomen are complex and involve several components working together to keep the organs functioning and to supply the body with oxygenated blood and remove waste products. Understanding these components and how they work is important for the diagnosis and treatment of abdominal pathologies.
