Part 126

The =anterior= or =duodenal angle= (Caput pancreatis) is attached to the concavity of the second curve of the duodenum, and the adjacent part of the right lobe of the liver. The ducts leave at this extremity.

The =left= or =splenic angle= (Cauda pancreatis) corresponds to the tail of the pancreas in man. It is in contact with the base of the spleen, the left kidney and adrenal body, and the saccus cæcus of the stomach.

FIG. 273.—PANCREAS OF HORSE WITH CHIEF RELATIONS, VENTRAL VIEW.

The pancreatic duct and its two chief radicles are indicated by dotted lines, since they are in the substance of the gland. ]

The =right angle= is rounded, and lies on the ventral surface of the right kidney and adrenal body.

The pancreas is attached dorsally by connective tissue to the kidneys and adrenal bodies, the gastro-phrenic ligament and the suspensory ligament of the spleen, the posterior vena cava, the portal fissure, and the gastro-pancreatic fold. The ventral surface is mainly attached by areolar tissue to the base of the cæcum and the terminal part of the great colon.

There are almost invariably two =ducts=. The large one is termed the =pancreatic duct= (Ductus pancreaticus [Wirsungi]). It is formed by the union of two radicles which come from the right and left extremities, and passes through the duodenal angle to end at the duodenal diverticulum alongside of the bile-duct. The duct is nearly half an inch (ca. 1 cm.) wide, and is very thin-walled. It is situated in the substance of the gland near its dorsal surface; none of it is free. The =accessory pancreatic duct= (Ductus pancreaticus accessorius [Santorini]) arises either from the chief duct or its left radicle, and ends on a papilla in the duodenum opposite the chief duct.

=Structure.=—The pancreas belongs to the class of tubulo-alveolar glands, the alveoli being long, like those of the duodenal glands; in other respects it resembles the serous salivary glands very closely. It has no proper capsule and the lobules are rather loosely united.

=Vessels and Nerves.=—The arteries of the pancreas come from the branches of the cœliac and anterior mesenteric arteries. The nerves are derived from the cœliac and mesenteric plexuses of the sympathetic.

THE LIVER

The =liver= (Hepar) is the largest gland in the body. It is situated obliquely on the abdominal surface of the diaphragm. Its highest point is at the level of the right kidney, its lowest on the left side, usually about three or four inches (ca. 8 to 10 cm.) from the abdominal floor, opposite the lower end of the seventh or eighth rib. The greater part of it lies to the right of the median plane.

It is red-brown in color and is rather friable. Its average weight is about ten to twelve pounds (ca. 5 kg.). When in the body, or if hardened in situ, it is strongly curved and accurately adapted to the abdominal surface of the diaphragm. When removed in the soft state, it flattens out into a cake-like form quite different from its natural configuration. It presents for description two surfaces and a circumference, which may be divided into four borders.

The =parietal surface= (Facies diaphragmatica) is strongly convex, and lies against the diaphragm. It faces chiefly upward and forward. It presents, just to the right of the median plane, a sagittal groove for the posterior vena cava (Fossa venæ cavæ). The vein is partially embedded in the substance of the gland, and receives the hepatic veins.

The =visceral surface= (Facies visceralis) faces in general downward and backward; it is concave and irregular, being moulded on the organs which lie against it. It presents, a little to the right of the median plane, the =portal fissure= (Porta hepatis). Through this the portal vein, hepatic artery, and hepatic plexus of nerves enter, and the hepatic duct and lymph vessels leave the liver. The portal or hepatic lymph glands are also found here. The pancreas is attached at and to the right of the fissure, and the gastro-hepatic omentum to the left of it. Above the fissure is a ridge which represents the caudate lobe (Lobus caudatus Spigelii), and is continued to the right by the pointed caudate process (Processus caudatus). Further to the left there is a large depression (Impressio gastrica) for the stomach. To the right of this may be seen a groove passing to the right and dorsally; this is the duodenal impression (Impressio duodenalis). Ventral to these is a large depression for the great colon (Impressio colica). Dorsal to this is a smaller depression for the blind end of the base of the cæcum. Coils of the small intestine may also lie on this surface, and the apex of the spleen may reach to it when the stomach is empty.

The =dorsal border= (Margo obtusus) is thick for the most part. It presents from right to left: (1) a depression for the right kidney (Impressio renalis); (2) a notch, which is the dorsal end of the fossa venæ cavæ; (3) a deep notch (Impressio œsophagea) which is mainly occupied by the thick margin of the œsophageal opening of the diaphragm.

The =ventral border= is thin, and is marked by two deep =interlobar fissures= or =incisures= (Incisuræ interlobares), which partially divide the organ into three principal =lobes=—=right=, =middle=, and =left=. The right lobe is the largest, except in old subjects, in which it is frequently much atrophied. The middle lobe is the smallest. It is marked by several small fissures, and by the =umbilical fissure= (Incisura umbilicalis); the latter contains the umbilical vein in the fœtus, which is transformed into the round ligament after birth.

The =right border= is thin and long. It is nearly vertical, and extends backward to about the middle of the sixteenth rib.

The =left border= is thin and short. It extends backward to a point opposite the lower part of the ninth or tenth rib. The ventral and lateral borders together constitute the margo acutus.

FIG. 274.—LIVER OF YOUNG HORSE, HARDENED in situ, PARIETAL SURFACE. ]

The liver is held in position largely by the pressure of the other viscera and by its close application to the diaphragm. It has six ligaments.

1. The =coronary ligament= (Lig. coronarium hepatis) attaches it closely to the diaphragm. It consists of two laminæ. The right one is attached to the right of the fossa venæ cavæ; the left one begins to the left of the vena cava and passes upward and outward, becoming continuous with the left lateral ligament at the left margin of the œsophageal notch; it detaches a middle fold which extends to the notch and is continuous with the small omentum. The two laminæ unite below the vena cava to form the next ligament.

2. The =falciform ligament= (Lig. falciforme hepatis) is a crescentic fold which attaches the middle lobe to the sternal part of the diaphragm and to the abdominal floor for a variable distance. In its concave free edge is found.

3. The =round ligament= (Lig. teres hepatis), a fibrous cord which extends from the umbilical fissure to the umbilicus; it is the vestige of the umbilical vein, which in the fœtus carries the blood from the placenta to the liver.

4. The =right lateral ligament= (Lig. triangulare dextrum) is a wide fold which attaches the dorsal border of the right lobe to the costal part of the diaphragm.

FIG. 275.—LIVER OF HORSE, VISCERAL SURFACE.

Specimen from middle-aged subject, hardened in situ. ]

5. The =left lateral ligament= (Lig. triangulare sinistrum) attaches the dorsal edge of the left lobe to the tendinous center of the diaphragm.

6. The =hepato-renal= or =caudate ligament= (Lig. hepatorenale) attaches the caudate process to the right kidney and the base of the cæcum. The gastro-hepatic omentum and the mesoduodenum have been described.