Exam 3 Review:  Chapter 23:  Pancreas

pancreas - A long, flattened, irregularly shaped, fragile accessory digestive gland, lying behind the stomach and between the duodunum and the spleen; its parenchyma consists primarily of exocrine acinar cells drained by the pancreatic duct system, but interspersed among them are small round collections of endocrine cells (alpha, beta, and delta cells) termed islets; the acinar cells secrete an enzyme-rich alkaline pancreatic juice into the duodenum while the islet cells secrete insulin (alpha cells), glucagon (beta cells), and somatostatin (delta cells) into the bloodstream.

pancreatic duct - The major excretory duct of the pancreas, composed of a simple cuboidal epithelium, by which pancreatic juice is secreted into the duodenum at the hepatopancreatic ampulla.

hepatopancreatic ampulla - The goblet-shaped dilatation (expansion) of the ducts coming from the liver and gall bladder (common bile duct) and the pancreas (pancreatic duct) at the point (major duodenal papilla) where they enter the duodenum.

major duodenal papilla - A nodular protuberance on the medial wall of the duodenum through which the common bile duct and pancreatic duct expel bile and pancreatic juice respectively into the duodenum by way of the hepatopancreatic ampulla to aid in the processes of digestion.

accessory duct - A variable duct of the pancreas, composed of a simple cuboidal epithelium, which branches from the main pancreatic duct and opens into the duodenum above it at the minor duodenal papilla

pancreatic acini - The majority of pancreatic tissue which is exocrine tissue collected into a complex system of secretory cell clusters (acini) attached to the pancreatic duct system; the acinar cells secrete a variety of digestive enzymes into the pancreatic juice which is transported to the duodenum.

pancreatic juice - The clear alkaline secretion of pancreas, consisting of  enzymes (e.g., pancreatic amylase, trypsin, chymotrypsin, carboxypeptidase, elastase, pancreatic lipase, ribonuclease, deoxyribonuclease, etc.) produced by the acinar cells and an alkaline mucus fluid secreted by the pancreatic ductal cells which flows via the pancreatic duct system to the duodenum and continues the chemical digestion of food already acted on by the gastric juice and saliva.

pancreatic islets = Islets of Langerhans - Any of several masses of endocrine cells in the pancreas including alpha cells which secrete the protein hormone glucagon, beta cells which secrete the protein hormone insulin, and delta cells which secrete the protein hormone somatostatin.

Follow this link to see Histology of the Pancreas.

pancreatic amylase - The enzyme present in pancreatic juice which catalyzes the hydrolysis of starch to sugar to produce carbohydrate derivatives in the duodenum; elevated serum pancreatic amylase levels are associated with pancreatitis and many other abdominal disorders.

trypsinogen - The inactive precursor of trypsin, produced by the pancreatic acinar cells and converted to trypsin in the small intestine by the intestinal brush border enzyme enterokinase.

trypsin - The pancreatic proteolytic enzyme which catalyzes the hydrolysis of proteins and large peptides into smaller oligopeptide units in the small intestine; it acts on the breakdown products of the gastric digestion of proteins by pepsin; it is secreted by the acinar cells in the form of an inactive precursor, trypsinogen.

chymotrypsin - The pancreatic proteolytic enzyme which catalyzes the hydrolysis of peptides into smaller oligopeptides into small peptides and amino acids in the small intestine; it is secreted by the acinar cells in the form of an inactive precursor, chymotrypsinogen.

carboxypeptidase - The pancreatic proteolytic enzyme which catalyzes the hydrolysis of the terminal amino acid of a polypeptide or peptide from the C-terminal end (which contains a free carboxylic acid group) in the small intestine; two forms exist, A and B; they are secreted by the acinar cells in the form of inactive precursors, procarboxypeptidase.

elastase - The pancreatic proteolytic enzyme which catalyzes the hydrolysis of elastin (and collagen) in the small intestine.

pancreatic lipase - The enzyme present in pancreatic juice which catalyzes the hydrolysis of neutral fats (mono-, di-, and triglycerides) into glycerol and free fatty acids in the duodenum; elevated serum pancreatic lipase levels are associated with pancreatitis and some other abdominal disorders.

ribonuclease - The enzyme present in pancreatic juice which catalyzes the hydrolysis of RNA (ribonucleic acids) into constituent ribonucleotides in the small intestine.  aka - RNase.

deoxyribonuclease - The enzyme present in pancreatic juice which catalyzes the hydrolysis of DNA (deoxy-ribonucleic acids) into constituent ribonucleotides in the small intestine.  aka - DNase.

List:

18.  the functions of the pancreas.

          (1)  provides some bicarbonate ions to assist in buffering acidic chyme transferred from the stomach to the duodenum
          (2)  synthesizes and secretes a series of digestive enzymes which assist in the digestion of all major nutrient classes (carbohydrates, proteins, lipids, and nucleic acids)
          (3)  synthesizes and secretes glucagon and insulin which cooperate to regulate plasma glucose levels and, therefore, certain other cellular aspects of metabolism, and which control the transitions between the absorptive and post-absorptive states

Describe:

5.  how pancreatic secretion (endocrine) is regulated.

          Pancreatic islet cells respond to autoregulation.  Pancreatic islet cells monitor plasma glucose levels.  If plasma glucose levels rise, e.g., after the absorption of a meal, then beta cells will release more insulin into the blood stream; if plasma glucose levels fall, then alpha cells will release more glucagon into the blood stream.

6.  how pancreatic secretion (exocrine) is regulated.

          The stimuli that trigger increased pancreatic exocrine secretion are (1) the presence of an acidic chyme in the duodenum and (2) the presence of fatty acids and amino acids in the chyme in the duodenum.  These stimuli produce three different regulatory feedback actions to stimulate increased pancreatic exocrine secretion:  (a) autoregulation involving local hormones within the head of the pancreas; (b) release of CCK (cholecystokinin) and secretin from enteroendocrine cells in the walls of the duodenum  [Note:  CCK stimulates digestive enzyme secretion by pancreatic acinar cells while secretin stimulates bicarbonate ions and mucous secretions from the pancreatic duct cells.]; and (c) autonomic parasympathetic impulses, delivered via the vagus nerve (X), which increase pancreatic secretions.