Pancreas gland

Pancreases pancreas is a glandular organ that secretes digestive enzymes and hormones. In humans, the pancreas is a yellowish organ located behind stomach .

Pancreas Exocrine: Acini: Secrete pancreatic juice. Endocrine: Islets of Langerhans: Secrete insulin and glucagon.

The Endocrine Pancreas Approximately 5 percent of the total pancreatic mass is comprised of endocrine cells.  These endocrine cells are clustered in groups within the pancreas which look like little islands of cells when examined under a microscope.  This appearance led to these groups of pancreatic endocrine cells being called "Pancreatic Islets“ or “islets of langerhans”.   Within pancreatic islets are cells which make specific pancreatic endocrine hormones, of which there are only a few (the most famous of course being insulin).  These cells within the islets are called "Pancreatic Islet Cells".

Pancreatic Islet Cells secretion The islets are endocrine tissue containing four types of cells. In order of abundance, they are the: beta cells, which secrete insulin and amylin; alpha cells, which secrete glucagon; delta cells, which secrete somatostatin, and gamma cells, which secrete a polypeptide of unknown function

Pancreatic Endocrine Hormones and Their Purpose A - Insulin Purpose: Regulate blood glucose (sugar) in the normal range Action: Forces many cells of the body to absorb and use glucose thereby decreasing blood sugar levels Secreted in response to: High blood glucose Secretion inhibited by: Low blood glucose Disease due to deficient action: Diabetes (large section of Endocrine Web is devoted to Diabetes). Disease due to excess action: Hypoglycemia 

Pancreatic hormone insulin secretion :mechanism

PANCREATIC HORMONES Role in metabolic processes 1. Review Glucagon Glucose Glycogen Glycogen synthetase R Energy utilization Gluco-1- phosphatase Gluconeogenesis Urea excretion Protein Lipase Free Fatty Acids Ketone Bodies Liver Lipid Amino Acids

PANCREATIC HORMONES Role in metabolic processes Insulin effects Increases Glucose Decreases Glycogen Glycogen synthetase Insulin R Gluco-1- phosphatase Gluconeogenesis Energy utilization Urea excretion Ketone Bodies Liver Protein Lipase Free Fatty Acids Lipid 2. Physiological actions (Fig. 10) a. increases entry of glucose into muscle and fat tissue and increases the storage of glucose (as glycogen) in liver, muscle, and fat. Overall result is hypoglycemia b. inhibits lipases that break down lipids to fatty acids. GH, glucocorticoids, CA, and T3-T4 all enhance lipolysis. Promotes fat storage -- increases uptake, synthesis and storage of fatty acids as triglycerides c. stimulates protein synthesis -- increases uptake of amino acids by muscle and fat. Also, increases incorporation of amino acids into protein (like GH). d. increases the transport of amino acids into cells Amino Acids

PANCREATIC HORMONES Role in metabolic processes 3. Insulin deficiency Hyperglycemia Increases Decreases Glycogen synthetase Insulin R Glycogen Gluco-1- phosphatase Energy utilization (Ketonemia and Acidosis) Gluconeogenesis Ketone Bodies Lipase Free Fatty Acids 3. Consequences of insulin deficiency (Fig. 11) a. hyperglycemia b. glycogen synthetase activity decreased c. gluconeogenesis increased in liver -- amino acids mobilized from muscle and converted to glucose in liver d. hyperlipemia due to increased lipolysis e. ketonemia due to fatty acids converted to ketone bodies f. azoturia (increased excretion of urea) results from large amount of protein converted to glucose Urea excretion (Azoturia) Protein Liver Lipid Amino Acids Hyperlipemia

Pancreatic Endocrine Hormones and Their Purpose B - Glucagon Purpose: Assist insulin in regulating blood glucose (sugar) in the normal range (actions are opposite of insulin) Action: Forces many cells of the body to release (or produce) glucose (increasing blood sugar) Secreted in response to: Low blood glucose Secretion inhibited by: High blood glucose Disease due to deficient action: Some times nothing, sometimes hypoglycemia Disease due to excess action: Hyperglycemia

Pancreatic Endocrine Hormones and Their Purpose C – Somatostatin ( secreted from hypothalamus ) Purpose: Regulate the production and excretion of other endocrine tumors Action: Slows down production of insulin, glucagon, gastrin, and other endocrine tumors Secreted in response to: High levels of other endocrine hormones Secretion inhibited by: Low levels of other endocrine hormones Disease due to deficient action: Poorly defined Disease due to excess action: Diabetes (inhibits insulin production), gallstones, and dietary fat intolerance.

Pancreatic Endocrine Hormones and Their Purpose E - Vasoactive Intestinal Peptide (VIP) Purpose:    Help control water secretion and absorption from the intestines Action:    Causes intestinal sells to secrete water and salts into the intestines (inhibit absorption) Disease due to excess action:     Severe watery diarrhea and salt (potassium) imbalances  

Pancreatic secretions The pancreas acts as an exocrine gland by producing pancreatic juice which empties into the small intestine via a duct. It plays an important role in digestion of lipids proteins and carbohydrates. in neutralizing the pH to become suitable for the action of the pancreatic digestive enzymes.

Pancreatic secretions Pancreatic secretions is an alkaline liquid secreted by the pancreas, which contains a variety of enzymes. Composition of pancreatic secretion: 1- The first component is a solution of bicarbonate, Na+ , K+ and water emitted by the epithelial cells that line the pancreatic ducts. This alkaline solution is designed to help neutralize stomach acid so that digestive enzymes can work more effectively. 2- The second component is the enzymatic component ;which include: Trypsinogen Chymotrypsinogen Procarboxypeptidase Pancreatic amylase Pancreatic lipases Deoxyribonucleases and ribonucleases

Pancreatic secretions Interaction of duodenal and pancreatic enzymes. Enterokinase from the duodenal mucosa and attached to the brush border activates trypsinogen to trypsin. Trypsin activates chymotrypsinogen to chymotrypsin Trypsin activates procarboxypeptidase to carboxypeptidase. Trypsin, chymotrypsin and carboxypeptidase digest proteins: proteolytic. Pancreatic amylase continues digestion of starch Pancreatic lipase digests lipids Deoxyribonucleases and ribonucleases digest DNA and ribonucleic acid, respectively

Pancreatic Juice Contains H20, HC03- and digestive enzymes.

Pancreatic Juice Complete digestion of food requires action of both pancreatic and brush border enzymes. Fig. 18.29

Pancreatic Juice Most pancreatic enzymes are produced as zymogens. Trypsin (when activated by enterokinase) triggers the activation of other pancreatic enzymes. Pancreatic trypsin inhibitor attaches to trypsin. Inhibits its activity in the pancreas

Bicarbonate Ion Production in Pancreas CO2 diffuses to the interior of the ductule cells from blood and combines with H2O by carbonic anhydrase to form H2CO3 which will dissociate into HCO3- and H+ . The HCO3- is actively transported into the lumen. The H+ formed from the dissociated H2CO3 is exchanged for Na+ ions by active transport through blood , which will diffuse or actively be transported to the lumen to neutralize the – ve charges of HCO3- . The movement of HCO3- and Na+ ions to the lumen causes an osmotic gradient causes water to move from blood to ductule cells of the pancreas producing eventually the HCO3- solution.

Bicarbonate Ion Production in Pancreas

Secretion of Pancreatic Juice Secretion of pancreatic juice and bile is stimulated by: Secretin: Occurs in response to duodenal pH < 4.5. Stimulates production of HC03- by pancreas. Stimulates the liver to secrete HC03- into the bile. CCK: Occurs in response to fat and protein content of chyme in duodenum. Stimulates the production of pancreatic enzymes. Enhances secretin. Stimulates contraction of the sphincter of Oddi.

Regulation of Pancreatic Secretion Figure 23.28

CONTROL OF PANCREATIC SECRETIONS

Diabetes Mellitus Diabetes mellitus is an endocrine disorder characterized by many signs and symptoms.

Diabetes mellitus is a disorder quite distinct from the similarly-named diabetes insipidus. They both result in the production of large amounts of urine (diabetes), but in one the urine is sweet while in the other (caused by ADH deficiency) it is not. Before the days of laboratory tests, a simple taste test ("mellitus" or "insipidus") enabled the doctor to make the correct diagnosis Diabetes Mellitus

Diabetes Mellitus There are three categories of diabetes mellitus: 1 - Insulin-Dependent Diabetes Mellitus (IDDM) [also called "Type 1" diabetes] and 2 - Non Insulin-Dependent Diabetes Mellitus (NIDDM)["Type 2"] 3 - Inherited Forms of Diabetes Mellitus

Insulin-Dependent Diabetes Mellitus (IDDM) IDDM (also called Type 1 diabetes) is characterized by little (hypo) or no circulating insulin; most commonly appears in childhood. It results from destruction of the beta cells of the islets.

IDDM is controlled by carefully-regulated injections of insulin IDDM is controlled by carefully-regulated injections of insulin. For many years, insulin extracted from the glands of cows and pigs was used. However, pig insulin differs from human insulin by one amino acid; beef insulin by three. Although both work in humans to lower blood sugar, they are seen by the immune system as "foreign" and induce an antibody response in the patient that blunts their effect and requires higher doses

Non Insulin-Dependent Diabetes Mellitus (NIDDM) Many people develop diabetes mellitus without an accompanying drop in insulin levels (at least at first). In many cases, the problem appears to be a failure to express a sufficient number of glucose transporters in the plasma membrane of their skeletal muscles.

Skeletal muscle is the major "sink" for removing excess glucose from the blood (and converting it into glycogen). In NIDDM, the patient's ability to remove glucose from the blood and convert it into glycogen may be only 20% of normal. This is called insulin resistance.

NIDDM (also called Type 2 diabetes mellitus) usually strikes in adults and, particularly often, in overweight people. However, over the last few years in the U. S., the incidence of NIDDM in children has grown to the point where they now account for 20% of all newly-diagnosed cases (and, like their adult counterparts, are usually overweight).

Inherited Forms of Diabetes Mellitus Some cases of diabetes result from mutant genes inherited from one or both parents. Examples: mutations in one or both copies of the gene encoding the insulin receptor. These patients usually have extra-high levels of circulating insulin but defective receptors. The mutant receptors a mutant version of the gene encoding glucokinase, the enzyme that phosphorylates glucose in the first step of glycolysis

Pancreatitis An estimated 50,000 to 80,000 cases of acute pancreatitis occur in the United States each year. This disease occurs when the pancreas suddenly becomes inflamed and then gets better. Some patients have more than one attack but recover fully after each one. Most cases of acute pancreatitis are caused either by alcohol abuse or by gallstones.  Other causes may be use of prescribed drugs, trauma or surgery to the abdomen, or abnormalities of the pancreas or intestine.

What Are the Symptoms of Acute Pancreatitis Acute pancreatitis usually begins with pain in the upper abdomen that may last for a few days. The pain is often severe. It may be constant pain, just in the abdomen, or it may reach to the back and other areas. The pain may be sudden and intense, or it may begin as a mild pain that is aggravated by eating and slowly grows worse. The abdomen may be swollen and very tender. Other symptoms may include nausea, vomiting, fever, and an increased pulse rate. The person often feels and looks very sick.

Chronic Pancreatitis The term "chronic pancreatitis" defines the histologic, functional, and clinical results of long-standing or irreversible pancreatic injury. There are a number of things that increase a persons risk of deveolping chronic pancreatits including alcohol consumption, smoking, genetic factors and other conditions or tramatic events that injure the pancreas.