Anatomically, the pancreas consists of the following four parts:

• Head - the first and widest part; lies within the C-shaped curve that is created by the duodenum; it is found on the right side of the superior mesenteric vessels; features the uncinate process:
  • Uncinate process - a posterior projection of the head that arises from its inferior aspect and extends medially; it is found posterior to the superior mesenteric vessels;
• Neck - the second and shortest portion that is found between the head and the body; it is found anterior to the superior mesenteric vessels;
• Body - the third and largest part; crosses the midline of the body and is found posterior to the stomach and on the left side of the superior mesenteric vessels;
• Tail - the final and most lateral portion that narrows toward the hilum of the spleen and lies in close proximity to it; it is included in the splenorenal (lienorenal) ligament together with the splenic vessels.

The tail and head of the pancreas correspond to the left and right extremities of the organ, respectively.

Head of pancreas

The head is the first, expanded medial part of the pancreas. It appears flattened and is snugly surrounded by the C-curved duodenum. These relations and the position of the head of the pancreas are significant, as the duodenum is the organ that receives pancreatic juice with digestive enzymes through the major and minor duodenal papillae. 

The head of the pancreas is found at the level of the second lumbar vertebra (L2). The left side of the head is related to the superior mesenteric vessels, while the inferior vena cava and the right and left renal veins are posterior to it. Moreover, its posterior aspect is penetrated by the lower end of the common bile duct and pancreaticoduodenal vessels. Anteriorly, the pancreas is covered by the peritoneum, transverse colon, and the root of the transverse mesocolon.

A small projection extends from the inferior aspect of the pancreatic head. It projects posteriorly and is known as the uncinate process. Additionally, the pancreatic notch is an indentation that separates the uncinate process from the neck of the pancreas.

Neck of pancreas

The neck is the second portion of the pancreas. It is directed upward and forward and continues as the body laterally. The neck is found anterior to the superior mesenteric vessels and posterior to the pylorus of the stomach, as well as the root of the transverse mesocolon. Also, the superior mesenteric vein unites with the splenic vein posterior to the neck, forming the main hepatic portal vein. 

As mentioned before, the neck of the pancreas is separated from the uncinate process by the pancreatic notch.

Body of pancreas

The body is the largest part of the pancreas. It lies behind the stomach and crosses the spine from the right to the left side at the level of the first lumbar vertebra (L1). It also travels over the abdominal aorta. The body of the pancreas is positioned on the left side of the superior mesenteric artery and vein. 

The body of the pancreas appears triangular-shaped and, therefore, has the following three surfaces and three borders:

• Anterosuperior surface
• Anteroinferior surface
• Posterior surface
• Superior border
• Inferior border
• Anterior border

Overall, anterior to the body lies the stomach, transverse colon, and transverse mesocolon. Posterior to the body is the abdominal aorta, left crus of the diaphragm, splenic vein, left kidney, left suprarenal (adrenal) gland, left renal vessels, as well as the initial part of the superior mesenteric artery. The duodenojejunal flexure, loops of the jejunum, and the left colic flexure are found inferior to the body. And finally, the splenic artery passes along and above the superior border.

Tail of pancreas

Without any particular border, the body of the pancreas transitions into the tail. The tail is the final and most lateral of the four parts of the pancreas. Like the body, the tail also appears triangular-shaped with the same amount of surfaces and borders. The tail usually ends at the level of the tenth rib. 

The tail lies anterior to the left kidney and narrows toward the hilum of the spleen. Sometimes, the tail of the pancreas directly connects with the splenic hilum, and this relationship is referred to as the "kiss." The tail of the pancreas lies between the layers of the splenorenal (lienorenal) ligament containing splenic vessels (they can be embedded in the pancreas tissue).

Most of the organs that are related to the body also surround the tail. Anteriorly, the tail is covered by the stomach and the transverse mesocolon. Posterior to it lies the splenic vein, left kidney, and left suprarenal (adrenal) gland. Laterally to it is the hilum of the spleen, while inferior to it is the left colic flexure, transverse colon, and loops of the jejunum. The splenic artery passes along its superior border.