General Comparative Anatomy of the Accessory Organs
The accessory organs are the teeth, tongue, salivary glands, liver, and pancreas. Information on the teeth, tongue and salivary glands will be available later.
Liver:
The liver (hepar) is the largest gland of the body. It lies in the intrathoracic portion of the abdominal cavity. The liver has two surfaces; parietal (diaphragmatic), and visceral surfaces. The parietal surface is convex and in contact with the abdominal surface of the diaphragm. The visceral surface is irregularly concave and is related to the stomach, duodenum, colon, jejunum and the right kidney. These structures cause impressions on the embalmed liver, namely, the esophageal notch, the gastric impression, the the duodenal impression, the colic impression, and the renal impression.
The liver has four borders; the dorsal, ventral ,right, and left borders. The dorsal border is thick and rounded, while the rest of the borders are sharp and thin.
Ligaments of the liver:
The lesser omentum (derivative of the ventral mesogastrium) attaches the liver to the lesser curvature of the stomach, and the proximal part of the duodenum. Hence, they are called the hepatogastric ligament and hepatoduodenal ligament respectively.
The liver is attached to the diaphragm by the coronary ligament around the area of the caval foramen. The right and left ends of the coronary ligaments are continuous with the right and left triangular ligaments, which attaches the right and the left lobes of the liver to the diaphragm. The liver is attaches to the sternal part of the diaphragm by the falciform ligament, which originates ventrally in the region of the notch for the round ligament. Passing along the free edge of the falciform ligament is the round ligament of the liver, which is a remnant of the umbilical vein.
Lobation of the liver:
Generally, the liver is divided into four lobes; left lobe, right lobe, caudate lobe and quadrate lobe. In order to identify these lobes, place the liver on the table with the visceral surface up. An imaginary line from the esophageal notch to the notch for the round ligament separates the left lobe from the rest of the liver. Similarly an imaginary line from the fossa venae cavae (an area where the caudal vena cava passes over the round border) to the fossa for the gall bladder separates the right lobe from the rest of the liver. The part in the middle between those two lines can be separated into a caudate lobe dorsal to the hepatic porta and a quadrate lobe ventral to the hepatic porta (a depression where the poratal vein and hepatic artery enter the liver).
In carnivores, pig and horse the left lobe is divided into left medial and left lateral. However, the right lobe is divided into right lateral and right medial in carnivores and pig.
In carnivores and ruminants the caudate lobe is divided into caudate and papillary processes, however, ruminants have exceptionally large caudate process.
In horse and pig the caudate lobe has no papillary process.