The pancreas lies transversely in the retroperitoneum, at the L1–L2 vertebral level, between the duodenum and the hilum of the spleen.

The head of the pancreas lies over the inferior vena cava (IVC), right renal hilum, and the left renal vein at its junction with the IVC.

The uncinate process extends to the left and wraps from around the superior mesenteric vessels. It is in close proximity to the inferior pancreaticoduodenal artery.

The neck of the pancreas lies over the superior mesenteric vessels and the proximal portal vein. The space between the neck and the superior mesenteric vessels is avascular and allows blunt dissection without bleeding. The area to either side of the midline is vascular and should be avoided.

The body of the pancreas lies over the suprarenal aorta and the left renal vessels. It is intimately related to the splenic artery and vein.

The major pancreatic duct (Wirsung) traverses the entire length of the pancreas and drains into the ampulla of Vater, approximately 8 cm below the pylorus. The lesser duct of Santorini branches off the superior aspect of the major duct, at the level of the neck of the pancreas, and drains separately into the duodenum, approximately 2–3 cm proximal to the ampulla of Vater.

The pancreas receives its blood supply from both the celiac artery and the superior mesenteric artery.

• The head of the pancreas and the proximal part of the duodenum receive their blood supply from the anterior and posterior pancreaticoduodenal arcades. These arcades lie on the surface of the pancreas, close to the duodenal loop. Any attempts to separate the two organs results in ischemia of the duodenum.

• The body and tail of the pancreas receive their blood supply mainly from the splenic artery. The splenic artery originates from the celiac artery and courses to the left along the superior border of the pancreas. It follows a tortuous route, with parts of it looping above and below the superior border of the pancreas. It gives numerous small and short branches to the body and tail of the pancreas.

• The splenic vein courses from left to right, superiorly and posteriorly to the upper border of the pancreas, inferiorly to the splenic artery. It is not tortuous like the artery. It joins the superior mesenteric vein, at a right angle, behind the neck of the pancreas, to form the portal vein. The inferior mesenteric vein crosses behind the body of the pancreas and drains into the splenic vein.

The portal vein is formed by the junction of the superior mesenteric and splenic veins, in front of the inferior vena cava and behind the neck of the pancreas.

The common bile duct (CBD) courses posterior to the first part of the duodenum, in front of the portal vein, continues behind the head of the pancreas, often partially covered by pancreatic tissue, and drains into the ampulla of Vater, in the second part of the duodenum.

External landmarks: The axillary vessels start at the middle of the clavicle, course deep under the deltopectoral groove, and end at the lateral border of the axilla.

The axillary artery is divided by the pectoralis minor into three parts: the first part is proximal to the muscle and gives one branch. The second part is under the muscle, is surrounded by the cords of the brachial plexus, and gives two branches. The third part lies lateral to the muscle, is surrounded by the nerves of the brachial plexus, and gives three branches.

The axillary vein is the continuation of the basilic vein. Prior to its transition to the subclavian vein, the cephalic vein joins it. Its middle segment lies under the pectoralis minor muscle, inferior to the axillary artery.

For trauma purposes the neck is divided into three distinct anatomical zones.

• Zone 1: from the sternal notch to the cricoid cartilage.

• Zone 2: from the cricoid cartilage to the angle of the mandible.

• Zone 3: from the angle of the mandible to the base of the skull.

Knowing the contents of each zone is important when considering possible injuries.

• Zone 1: the major vessels of the upper mediastinum, the lung apices, esophagus, trachea, thoracic duct, and thyroid gland.

• Zone 2: the carotid sheath and contents, vertebral arteries, esophagus, trachea, pharynx, and the recurrent laryngeal nerve.

• Zone 3: distal carotid and vertebral arteries, distal jugular veins.

At the level of the superior border of the thyroid cartilage the common carotid artery bifurcates into the internal and external carotid arteries.

At the level of the angle of the mandible, the internal and external carotid arteries are crossed superficially by the hypoglossal nerve and the posterior belly of the digastric muscle.

The external landmark of the pharyngoesophageal and laryngotracheal junctions is the cricoid cartilage. On esophagoscopy, this is located 15 cm from the upper incisor teeth.

The cricothyroid membrane is four fingerbreadths above the sternal notch.