- Understand the role played by the pancreas in digestion and absorption of a mixed meal
- Understand the structure of the exocrine pancreas and the cell types that give rise to proteinaceous and fluid components of the pancreatic juice
- Identify key constituents of the pancreatic juice and the enzymes that are secreted in inactive forms
- Describe the factors that regulate the release of secretin and the role of this hormone in stimulating pancreatic ductular secretion
- Understand the ion transport pathways expressed in pancreatic ducts and their mechanisms of action
- Understand the role of CCK and other factors in regulating pancreatic acinar cells
- Discuss the relative roles of monitor peptide and CCK-releasing peptide in regulating CCK release
- Identify signaling events activated in pancreatic acinar cells by secretagogues
- Compare and contrast the structure of the salivary glands with that of the exocrine pancreas
- Identify the functions of saliva and the constituents responsible for these
- Define ion transport pathways that produce saliva and modify its composition
- Define regulatory pathways for saliva production
- Understand conditions where production of saliva may be abnormal
The pancreas is the source of the majority of enzymes required for digestion of a mixed meal (i.e., carbohydrate, protein, and fat). Pancreatic enzymes are produced in great excess, underscoring their importance in the digestive process. However, unlike the digestive enzymes produced by the stomach and in the saliva, some level of pancreatic function is necessary for adequate digestion and absorption. In general, nutrition is impaired if production of pancreatic enzymes falls below 10% of normal levels, or if outflow of the pancreatic juice into the intestine is physically obstructed.
We should distinguish between the exocrine pancreas, responsible for producing secretions that flow out of the body, and the endocrine pancreas, the site of synthesis of various important hormones that regulate whole-body homeostasis, the most notable of which is insulin (Figure 4–1). These dual secretory functions of the pancreas are segregated to distinct anatomic locations. The functions and regulation of the exocrine pancreas are the province of gastrointestinal physiology, whereas the endocrine functions are a topic for discussion in a general endocrinology course. Thus, the latter will not be discussed further here.
Schematic structure of the exocrine pancreas. [Redrawn from the AGA Undergraduate Teaching Project slide set “The Integrated Response to a Meal” (Unit 29, copyright 1995) by S. Pandol and H.E. Raybould, with permission.]
Pancreatic Secretory Products
The exocrine pancreas is the site of synthesis and secretion predominantly of enzymes. These fall into four main groups—proteases, amylolytic enzymes, lipases, and nucleases—as shown in Table 4–1. In addition, other proteins are produced that modulate the function of pancreatic secretory products, such as colipase and trypsin inhibitors. Finally, the pancreas secretes a peptide known as monitor peptide, which represents an ...