Human Anatomy - Kotsan I. Y. 2009

Splanchnology
Major Glands of the Digestive System
Pancreas

The Pancreas is the second largest digestive gland. In adults, it reaches a length of 16—20 cm, a width of 3—9 cm, a thickness of 2—3 cm, and a mass of 70—80 grams. The gland has a grayish-red color and a soft consistency. It is located retroperitoneally, with the Peritoneum covering only the anterior and partially the Inferior surface of the organ's body. Structurally, it is a complex tubuloalveolar gland, externally covered by a thin Connective Tissue capsule of the pancreas (capsula pancreatis). Trabeculae extend from the capsule deep into the organ, dividing the glandular parenchyma into distinct lobules visible to the naked eye. Blood Vessels, nerves, and interlobular excretory ducts run through these septa. Between the lobules lies the internal secretory part of the gland—the pancreatic islets.

The pancreas is divided into the HEAD, body, and tail (Fig. 149).

The head of the pancreas (caput pancreatis) is the widest part of the organ, located at the level of the first to third lumbar vertebrae, surrounded by the duodenum and adjacent to its concave surface. Posterior to the head runs the INFERIOR VENA CAVA, and anteriorly it is crossed by the transverse colon. The right extremity of the head curves downward, forming the uncinate process (processus uncinatus) directed to the left. At the border between the head and body, on the inferior margin of the gland, There is a deep pancreatic notch (incisura pancreatis) that separates the uncinate process from the main mass of the pancreatic head.

The body of the pancreas (corpus pancreatis) has a triangular (prismatic) shape and lies transversely at the level of the first lumbar vertebra. It features three surfaces: anterior (facies anterior), posterior (facies posterior), and inferior (facies inferior), which are separated by three margins: superior (margo superior), anterior (margo anterior), and inferior (margo inferior). The anterior surface faces forward and slightly upward, coming into contact with the body of The Stomach and its pyloric part. On the anterior surface of the body, near its head, there is a small prominence—the omental tuber (tuber omentale)—facing toward the omental bursa. The posterior surface faces backward, adjacent to THE Vertebral Column, inferior vena cava, aorta, and celiac plexus. On the posterior surface of the body, near the superior margin, the splenic artery runs within a special groove, and slightly lower runs the splenic vein. The inferior surface of the body is narrow, facing downward and forward, and is in contact with the duodenum.

The tail of the pancreas (cauda pancreatis) is directed to the left and upward, reaches the Spleen, and is somewhat separated from the posterior abdominal wall. Posterior to the tail of the pancreas lie the left suprarenal gland and the upper pole of the left Kidney.

The main pancreatic duct (ductus pancreaticus) runs through all PARTS OF THE gland, beginning in the region of the tail, extending from left to right along the entire thickness of the gland, receiving smaller ducts along its path, and opening into the major duodenal papilla after previously joining the common Bile duct. Before the junction of the pancreatic duct with the common bile duct, the muscular layer of the pancreatic duct wall thickens to form the sphincter of the pancreatic duct (m. sphincter ductus pancreatici), which regulates the flow of pancreatic juice into the duodenum. Sometimes the gland has an accessory pancreatic duct (ductus pancreaticus accessorius), which forms in the head of the gland and opens via a separate orifice on the minor duodenal papilla.

The pancreas is a gland of mixed secretion, comprising two distinct parts: the external secretory (excretory or exocrine) part and the second, internal secretory (incretory or endocrine) part.

The external secretory part of the gland is represented by pancreatic lobules (lobuli pancreatici), which are formed by a collection of small tubuloalveolar glands that produce digestive Enzymes. These enzymes travel through intralobular ducts into interlobular ducts and further into the main pancreatic duct, which opens into the duodenum. A human produces 500—700 ml of pancreatic juice per day. The Enzymes of the pancreatic juice (Trypsin, amylase, lipase, maltase, etc.) break down Proteins (into Amino Acids), fats, and CARBOHYDRATES.

The internal secretory part of the gland is formed by groups of Cells—the pancreatic islets (of Langerhans) (insulae pancreaticae (Langergans)), which are scattered within and between the pancreatic lobules. The parenchyma of the gland contains about 1.5 million islets. They are oval or round formations measuring 0.3 mm, with some reaching 1 mm in diameter. The islets are distributed throughout the entire thickness of the gland, but are most abundant in the tail region. The islets lack ducts and secrete their substances—Hormones—directly into the blood. They produce the hormones Insulin and Glucagon, which regulate Carbohydrate METABOLISM in the body. Insulin promotes the uptake of blood glucose by cells (Glycogen formation), whereas glucagon stimulates the accelerated breakdown of glycogen into glucose, thus acting as an antagonist to insulin.

The Blood supply to the pancreas is provided by Branches of the common hepatic artery, superior mesenteric artery, and splenic artery.

Pancreatic Veins drain into the splenic vein and other tributaries of the portal vein.

Lymphatic vessels drain toward the pancreatic, splenic, and aortic Lymph Nodes. Lymphatic capillaries and vessels are present only in the interstitial connective tissue of the gland and are absent inside the islets.

The pancreas is innervated by branches of the celiac, hepatic, and superior mesenteric plexuses.