## 1.11 Structure and Function of Pancreas The pancreas is a gland with both endocrine and exocrine functions. Anatomically, it is divided into a head, neck, body, and tail. The endocrine function is carried out by the pancreatic islets (islets of Langerhans), while the exocrine function involves the secretion of digestive pancreatic juice. ### Anatomy of the Pancreas The pancreas is an elongated organ located in the abdomen. - **Head:** The widest part, situated in the C-shaped curve of the duodenum (first part of the small intestine). - **Neck:** A short section connecting the head and the body. - **Body:** The central part of the pancreas, located behind the stomach. - **Tail:** The narrow end, extending towards the spleen. ### Pancreas as an Exocrine Gland The exocrine function of the pancreas is to produce and secrete pancreatic juice, which is essential for digestion in the small intestine. #### Aqueous Component - Contains bicarbonate ions ($\mathrm{HCO_3^-}$). - **Function:** To neutralize the acidic chyme (partially digested food) that arrives from the stomach, creating an optimal pH for digestive enzymes to function. #### Enzymatic Component - Contains a variety of enzymes that digest all major classes of food macromolecules. - Many of these enzymes, especially those that digest proteins, are secreted in an inactive form called zymogens to prevent them from digesting the pancreas itself. #### Pancreatic Digestive Enzymes | Enzyme Category | Zymogen (Inactive Form) | Activator | Active Enzyme | Substrate Digested | |-----------------|------------------------|-----------|---------------|--------------------| | **Proteases** | Trypsinogen | Enterokinase | Trypsin | Proteins | | | Chymotrypsinogen | Trypsin | Chymotrypsin | Proteins | | | Procarboxypeptidase | Trypsin | Carboxypeptidase | Proteins | | **Carbohydrate-digesting** | - | - | Pancreatic Amylase | Polysaccharides (Starch) | | **Lipid-digesting** | - | - | Pancreatic Lipases | Lipids (Fats) into fatty acids, glycerides | | **Nucleic acid-digesting** | - | - | Deoxyribonucleases | DNA into nucleotides | | | - | - | Ribonucleases | RNA into nucleotides | **Enzyme Activation Cascade:** The process is initiated by enterokinase, an enzyme from the small intestine, which converts inactive trypsinogen into active trypsin. Trypsin then acts as a catalyst to activate other zymogens (chymotrypsinogen and procarboxypeptidase) as well as more trypsinogen.