This section is from the book "Applied Anatomy: The Construction Of The Human Body", by Gwilym G. Davis. Also available from Amazon: Applied anatomy: The construction of the human body.
The pancreas is composed of two portions joined at right angles to each other. Together they measure about 20 cm. (8 in.). It is divided into a head, neck, body, and tail. The neck is about 2 cm. (3/4 in.) broad, while the head and body are each about 3 cm. (1 1/4 in.). The head is about 5 to 6.25 cm. (2 to 2 1/2 in.) long and lies parallel to the vertebral column on its right side. The body is about 12.5 cm. (5 in.) long and runs transversely from the first portion of the duodenum across to the spleen. The flexure joining the head and body constitutes the neck. It is 2.5 cm. (1 in.) long. The tail is simply the extremity of the body; this is omitted in some descriptions. The body crosses the first lumbar vertebra, while the head lies on the right side of the second and third (Fig. 432).
The pancreas has two ducts, a main one called the pancreatic duct, or duct of Wirsung, and an accessory one called the duct of Santorini. The duct of Wirsung runs nearly the whole length of the gland, and, bending somewhat downward at the neck and joining the common bile-duct at the ampulla of Vater, pierces the duodenum obliquely and empties in a common orifice on its mucous surface. It is 3 to 4 mm. (1/8 to 1/6 in. ) in diameter at its termination. The accessory duct of Santorini comes mainly from the lower portion of the head of the pancreas and empties separately in the duodenum 2 cm. ( 3/4 in.) above and a little anterior to the biliary papilla. It communicates with the duct of Wirsung in the substance of the pancreas.
Posteriorly, the head lies on the vena cava while the body crosses the aorta, renal vessels, suprarenal gland, and left kidney. Anteriorly, it is covered with peritoneum and on it lies the stomach; inferiorly, is the attachment of the transverse mesocolon, beneath which comes the duodenojejunal flexure. Immediately to the right of this flexure and between it and the head of the pancreas issue the superior mesenteric vessels. At the extreme left is the splenic flexure of the colon.
Fig. 432. - The pancreas and spleen.
The pancreas is the subject of inflammation (hemorrhagic) which may cause necrosis and abscess; it also is affected with cysts and new growths. Calculus may also occur.
Suppuration may produce a sub-diaphragmatic abscess or perforate the diaphragm and form an empyema. In cases of abscess protruding anteriorly, instead of opening through the peritoneum in front, the pus may be evacuated through a posterior incision made in the right or left costovertebral angle. If the pus has been evacuated through an anterior incision the finger may be introduced into the abscess cavity and used as a guide for a posterior incision.
Pancreatic growths tend to project forward in one of three general directions - viz.: (1) between the liver above and the stomach below; (2) between the stomach above and the transverse colon below; (3) below the transverse colon. The second is the most frequent. When the enlargement comes forward opposite the attachment of the transverse mesocolon it may grow between the layers of the mesocolon and push the transverse colon in front of it instead of going below or above it. After the cyst has been evacuated it may be stitched to the edges of the incision anteriorly and a counter opening made posteriorly on the left side beneath the twelfth rib.