Pancreas Anatomy and Function

Pancreas Anatomy and Function

• The pancreas is an oblong-shaped organ located at the level of the transpyloric plane (L1).
• Except for the tail, it's retroperitoneal, situated deep within the upper abdomen, specifically the epigastrium and left hypochondrium regions.

Pancreatic Duct System

• Intercalated ducts connect to intralobular collecting ducts, which drain into the main pancreatic duct.
• The pancreatic duct joins the common bile duct, forming the hepatopancreatic ampulla of Vater.
• This ampulla opens into the duodenum via the major duodenal papilla.
• Secretion into the duodenum is controlled by the sphincter of Oddi, acting as a valve.

Pancreatic Structure

• Head: The widest part, nestled within the C-shaped curve of the duodenum, connected by connective tissue.
• Uncinate process: A projection from the head, extending medially beneath the body of the pancreas, posterior to the superior mesenteric vessels.
• Neck: Located between the head and body, overlying the superior mesenteric vessels, which create a groove on its posterior aspect.
• Body: Central, crossing the midline, positioned behind the stomach, to the left of the superior mesenteric vessels.
• Tail: The leftmost end, closely associated with the hilum of the spleen, held within the splenorenal ligament along with splenic vessels. This is the only intraperitoneal portion.

Pancreas: Exocrine and Endocrine Function

• The pancreas comprises exocrine and endocrine tissues.
• The exocrine gland secretes digestive juices, primarily from acinar cells, localized in these cells.
• The endocrine gland releases hormones from the islets of Langerhans (Islets of Langerhans).

Pancreatic Digestive Enzymes

• Pancreatic secretions contain enzymes to digest all three major food types (protein, carbohydrate, and fat).
• It also has bicarbonate ions to neutralize the acidity of chyme entering the duodenum.
• Important digestive enzymes include trypsin, chymotrypsin, and carboxypeptidase.
• Initially, these enzymes are produced in inactive forms (e.g., trypsinogen) and activated in the small intestine.

Pancreatic Secretions Regulation

• Pancreatic secretion is controlled by neural and hormonal stimulation. This involves combined, synergistic basic stimuli, including cephalic, gastric, and intestinal phases.
• Cephalic phase: Smell, taste, chewing and swallowing initiate the release of Acetylcholine.
• Gastric phase: Protein and gastric distension trigger Vago-vagal reflex and Gastrin.
• Intestinal phase: Acidic chyme triggers Secretin and CCK and Vago-vagal reflex.

Important Pancreatic Hormone Regulation:

• Acetylcholine: Stimulates production of digestive enzymes in acinar cells.
• Cholecystokinin (CCK): Causes increased enzyme production.
• Secretin: Stimulates large volumes of bicarbonate-rich fluid to neutralize stomach acid.
• High acidity in the duodenum is important for preventing stomach ulcers.

Insulin and Glucagon Regulation of Blood Glucose

• Insulin: Facilitates glucose uptake in body cells, reduces blood glucose levels, stimulating glycogen synthesis.

• Glucagon: Released when blood glucose levels drop; triggers glycogenolysis and gluconeogenesis to increase blood glucose levels.

• Homeostatic regulation maintains blood glucose between 70 mg/dL and 110 mg/dL.

Specific Hydrolytic Activities of Pancreatic Enzymes

• Detailed explanations of the various pancreatic enzymes and their specific activities (e.g., cleaving peptide linkages, carbohydrate polymers, triglycerides).

Bicarbonate Ions and Water

• Secretion of bicarbonate ions is crucial for neutralizing stomach acid in the duodenum.
• These secretions are isotonic to plasma, with a pH of 8.

Cellular Mechanism for Sodium Bicarbonate Solution Secretion

• Explains the cellular process of secreting sodium bicarbonate solutions. Bicarbonate ions secreted by these ductal cells and cells within acini, important for neutralizing stomach acid.

Important Note on Inactive Forms of Digestive Enzymes

• Proteolytic digestive enzymes are synthesized in inactive forms (e.g., trypsinogen) before activation in the small intestine.
• This prevents the enzymes from digesting the pancreas itself prematurely.

Other Crucial Factors and Actions

• The importance of the pancreas in blood glucose regulation and maintaining a neutral pH.
• The roles of insulin and glucagon in managing glucose homeostasis are detailed.
• Details on how the various enzymes catalyze chemical reactions in the hydrolysis process.
• Importance of preventing early activation of trypsin and maintaining the proper functioning of digestive enzymes.