Both present the appearance of diminutive clusters of grapes, at the anterior end of the kidneys, close to the suprarenal bodies, separated from each other by the descending aorta and by the vena cava where this is formed by the right and left vena iliaca communis.
The afferent vessel of the' ctenidium receives blood from the vena cava or principal blood-sinus of the body, the efferent vessel opens into the auricle of its own side.
The vena cava (vc) is always found to the right of the Spigelian lobe and dorsal to the stalk of the caudate.
These eventually reach the hepatic radicles, and so the blood is conducted into the vena cava.
Behind the transverse fissure the lower end of the Spigelian lobe is seen as a knob called the tuber papillare, and from tree right of this a narrow bridge runs forward and to the right to join the Spigelian lobe to the right Vena cava in its fossa lobe and to shut off the transverse fissure from that for the vena cava.
There is one anterior vena cava, formed by the union of the two jugular and two axillary veins.
This is bounded on the left by the inferior vena cava, which is sunk into a deep groove in the liver, and into the upper part of this the hepatic veins open.
The arteries and veins have proper endothelial walls; they pass abruptly into the sinuses and in some cases communication is effected by orifices in the walls of the vessels, as for example in the vena cava of Nautilus.
It receives the three great venous trunks of the body, namely the vena cava superior dextra, the vena cava superior sinistra more dorsally, and the vena cava inferior more to the right and below; the opening of the last is guarded by two prominent valves in place of the mammalian valvula Eustachii.
To the left of the vena cava is the Spigelian lobe, which lies in front of the bodies of the tenth and eleventh thoracic vertebrae, the lesser sac of peritoneum, diaphragm and thoracic aorta intervening.