Anatomy of the Liver
The liver comprises four lobes; left, right, caudate and quadrate as listed in the Nomina Anatomica Veterinaria (NAV), although Sisson and Grossman also identify a ‘middle' lobe that includes the quadrate lobe in the horse.
The left and right lobes are subdivided into medial and lateral divisions. The quadrate lobe lies in the medial plane between the right medial and the left medial/lateral lobes. The gall bladder is located between the quadrate lobe medially and the right medial lobe laterally. The caudate lobe comprises the papillary process and the caudate process. The papillary process is covered by the lesser omentum and the caudate process is in close proximity to the cranial pole of the right kidney.Between the right and left lobes is the hilus of the liver; it is the location of the bile duct, blood vessels and nerves entering and leaving the liver, and it is also termed the porta of the liver. The nerves and arteries enter the porta dorsally, the bile duct exits ventrally and the hepatic portal vein enters the porta centrally.
The falciform ligament (see Section 3.4.1) separates the left and right lobes. It is a remnant of the ventral mesentery, which extended to the umbilicus from the liver and diaphragm. The parietal surface of the liver is in contact with the diaphragm, and the visceral surface contacts the cranial abdominal viscera. The liver lies almost entirely within the costal arch and is not normally palpable. The visceral surface bears impressions of the adjacent abdominal viscera.
Figure 7.1 Diagram of the caudal view showing the visceral surfaces of a typical mammalian liver. Figures 7.2-7.4 illustrate the species variations. There are four main lobes; the left and right hepatic lobes are subdivided into medial and lateral lobes. The caudate lobe (C) comprises the caudal and papillary processes (P). The quadrate lobe lies adjacent to the gall bladder.
7.3