Cross-sectional CT images of the abdomen

Key:#1 = L5#2 = Ascending Colon#3 = Descending Colon#4 = Ureters (left & right)#5 = Iliac Crest#6 = Gluteus Medius#7 = Iliacus Muscle#8 = Psoas Muscle#9 = Rectus Abdominis#10 = Common Iliac Arteries#11 = Common Iliac Veins

Key:#1 = Liver#2 = Kidney#3 = Duodenum#4 = Jejunum (not visible on CT)#5 = Ascending Colon#6 = Descending Colon#7 = Ureter (not visible on CT)#8 = Psoas Muscle#9 = Rectus Abdominis#10 = Quadratus Lumborum#11 = Aorta#12 = Inferior Vena Cava

Key:#1 = Abdominal Aorta#2 = Duodenum#3 = Gallbladder#4 = Head of Pancreas#5 = Inferior Vena Cava#6 = Left Kidney#7 = Left Renal Vein#8 = Liver#9 = Psoas Muscle#10 = Right Kidney#11 = Stomach#12 = Superior Mesenteric Artery#13 = Tail of Pancreas#14 = Transverse Colon

Key:#1 = Abdominal Aorta#2 = Inferior Vena Cava#3 = Left Crus of Diaphragm#4 = Liver#5 = Right Crus of Diaphragm#6 = Spleen#7 = Stomach

Blood Circulation in the Liver

The liver's place in the circulation

Blood flow

The liver receives blood from two sources. Oxygenated blood is supplied in the hepatic artery, a branch of the celiac trunk from the abdominal aorta. Venous blood from the entire gastrointestinal tract (containing nutrients from the intestines) is brought to the liver by the hepatic portal vein. On reaching the liver the portal vein divides into thousands of which pass in between the lobules and terminate in the sinusoids. The blood leaves the liver via a central vein in each lobule, which drains in the hepatic vein.

Functions
The circulation of blood in the liver is so arranged that very large volumes of blood come into close contact with the cells of the lobules.The cells are thus in a favorable position both to absorb materials from the blood and also secret materials into it. This they do all the time, for the real task of the liver is to maintain in the blood the correct concentrations of many of its constituents. Hepatocytes carry out most of the tasks attributed to the liver, but the phagocytic Kupffer cells that line the sinusoids are responsible for cleansing the blood.

Formation of bile
When the red cells of the blood become worn out they are destroyed by the cells of the reticuloendothelial system. In this process bilirubin is formed, and this is carried by the blood to the liver. Together with several other substances it is secreted by the liver as bile.

The plasma proteins
In the blood plasma there are three soluble proteins which are essential for our well-being. These proteins are albumin, globulin, and fibrinogen, and all of them are largely formed in the liver. Albumin and globulin are important, for they control the amount of water that the blood draws out of the tissues as it flows through the capillaries. Fibrinogen is the precursor of the substance fibrin which is responsible for the formation of the blood clots which form on the top of wounds.

Various branches of the abdominal Aorta

KEY
A - Abdominal Aorta
G - Adrenolumbar Artery
B - Celiac Trunk
H - Renal Artery
C - Hepatic Artery
I - Gonadal Arteries
D - Left Gastric Artery
J - Inferior Mesenteric Artery
E - Splenic Artery
K - Iliolumbar Artery
F - Superior Mesenteric Artery
L - Femoral Artery

The abdominal aorta is a large-lumened, unpaired arterial vessel that is part of the main trunk of the systemic arterial system. As such, the abdominal aorta supplies oxygenated blood, pumped by the left ventricle of the heart, to the abdominal and pelvic organs and structures via visceral and parietal arterial branches.
The abdominal aorta and its major arterial branches are highly elastic. During systole (heart muscle contraction), the aortic and arterial walls expand to accommodate the increased blood flow. Correspondingly, the vessels contract during diastole and elastin fibers assure that this contraction also serves to drive blood through the arterial vessels.

As the thoracic aorta passes through the aortic hiatus (an opening in the diaphragm) it becomes the abdominal aorta. The abdominal aorta ultimately branches into left and right common iliac arteries. The common iliac arteries then branch into internal and external iliac arteries to supply oxygenated blood to the organs and tissues of the lower abdomen, pelvis, and legs.

Major branches of the abdominal aorta include, ventrally, the celiac branches, and superior and inferior mesenteric arteries. On the dorsal side of the aorta are the lumbar and median sacral branch arteries. Lateral to the aorta are the inferior phrenics, middle supernal, renal, and ovarian or testicular arteries. Because the branches from the abdominal aorta are large, the aorta rapidly decreases in size as it courses downward (inferiorly) through the abdomen.

The celiac trunk divides into three major branches: the left gastric artery to the stomach, the hepatic artery to the lobes of the liver, and splenic artery--surrounded by a plexus of nerves--that ultimately terminates in branches entering the hilus of the spleen.