Chapter V - Endocrine System
The pancreas is an organ that serves two functions:
Exocrine - it produces pancreatic juice containing digestive enzymes.
Endocrine - it produces several important hormones, including insulin.
The pancreas is an organ located posterior to the stomach and in close association with the duodenum. The pancreas is a small, elongated organ in the abdomen. It is described as having a head, body and tail. The pancreatic head abuts the second part of the duodenum while the tail extends towards the spleen. The pancreatic duct runs the length of the pancreas and empties into the second part of the duodenum at the ampulla of Vater. The common bile duct commonly joins the pancreatic duct at or near this point.
The pancreas produces enzymes that break down all categories of digestible foods (exocrine pancreas) and secretes hormones that affect carbohydrate metabolism (endocrine pancreas).
The pancreas is covered in a tissue capsule that partitions the gland into lobules. The bulk of the pancreas is composed of pancreatic exocrine cells, whose ducts are arranged in clusters called acini (singular acinus). The cells are filled with secretory granules containing the pre-cursor digestive enzymes (mainly trypsinogen, chymotrypsinogen, pancreatic lipase, and amylase) that are secreted into the lumen of the acinus. These granules are termed zymogen granules (zymogen referring to the inactive precursor enzymes). Zymogen granules are localized to the subapical area of pancreatic acinar cells.
The pancreas is the main source of enzymes for digesting fats (lipids) and proteins - the intestinal walls have enzymes that will digest polysaccharides. The two major proteases the pancreas secretes are trypsinogen and chymotrypsinogen. Pancreatic secretions accumulate in intralobular ducts that drain to the main pancreatic duct, which drains directly into the duodenum.
Due to the potency of its enzyme contents, it is a very dangerous organ to injure and a puncture of the pancreas tends to require careful medical intervention.
Embedded throughout the exocrine tissue are small clusters of cells called the Islets of Langerhans, which are the endocrine cells of the pancreas and secrete insulin, glucagon, and several other hormones. The islets contain three major types of cells — alpha cells, beta cells, and delta cells. The largest number of cells are, by far, the beta cells which produce insulin. The alpha cells produce glucagon and the delta cells produce somatostatin, which lead to both decreased glucagon and insulin levels. There are also the PP cells and the D1 cells, about which little is known.
Diseases of the pancreas
· Benign tumors
· Carcinoma of pancreas
· Cystic fibrosis-Cystic fibrosis (CF), also called mucoviscidosis is an autosomal recessive hereditary disease of the exocrine glands. It affects the lungs, sweat glands and the digestive system. It causes chronic respiratory and digestive problems. About one in five babies with CF are diagnosed at birth, when their gut becomes blocked by extra thick meconium (the black tar-like bowel contents that all babies pass soon after birth). This condition may need surgery. Just over half of people with CF are diagnosed as babies because they are not growing or putting on weight as they should. This is because the pancreas is not producing chemicals (enzymes) which pass into the gut as food leaves the stomach. Without these enzymes, the fat in food cannot be properly digested. In children who are affected, the fat passes straight through the gut. The child does not benefit from the energy from the fat. Since the stools contain an excess of fat, they are oily and very smelly.
· Acute pancreatitis
· Chronic pancreatitis
· Pancreatic pseudocyst-A pancreatic pseudocyst is a circumscribed collection of pancreatic fluid typically located in the lesser omentum.
Pancreatic cancer (also called cancer of the pancreas) is represented by the growth of a malignant tumour within the small pancreas organ.
1. The most common form of this disease is known as adenocarcinoma of the pancreas. It is one of the most lethal forms of cancer with few victims still alive 5 years after diagnosis, and complete remission still extremely rare.
2. A less common, and typically far less aggressive form of pancreatic cancer, is called islet-cell tumor (and is sometimes also known by the term neuroendocrine tumor).
Risk factors for pancreatic cancer include
Diets high in meat
Occupational exposure to certain pesticides, dyes, and chemicals related to gasoline
Helicobacter pylori infection
Early diagnosis of pancreatic cancer is difficult because the symptoms are so non-specific and varied. Common symptoms include abdominal pain, loss of appetite, significant weight loss, jaundice, digestive problems, and depression. Patients diagnosed with pancreatic cancer typically have a poor prognosis because the cancer usually causes no symptoms early on, leading to metastatic disease at time of diagnosis.
Pancreatitis describes the condition of inflammation of the pancreas that causes mild to severe pain in the abdomen. The most common causes of pancreatitis are gallstones and frequent and excessive consumption of alcohol (80% of cases), and less common causes are drugs or medication. The onset of pain in the abdomen region usually occurs within a day of binge drinking or eating a large meal. Sufferers often feel better in 2 to 3 days if they abstain from food and liquids.
There are two forms of pancreatitis, which are different in causes and symptoms, and require different treatment:
Acute pancreatitis: Acute pancreatitis is a rapidly-onset inflammation of the pancreas. Depending on its severity, it can have severe complications and high mortality despite treatment. While mild cases settle with conservative measures or endoscopy, severe cases require surgery (often more than one intervention) to contain the disease process.
Chronic pancreatitis: Chronic pancreatitis can present as episodes of acute inflammation in a previously injured pancreas, or as chronic damage with persistent pain or malabsorption. Patients with chronic pancreatitis can present with persistent abdominal pain or steatorrhea (diarrhea resulting from malabsorption of the fats in food, typically very bad-smelling and equally hard on the patient), as well as severe nausea. Some patients with chronic pancreatitis often look very sick, while others don't appear to be unhealthy at all. Serum amylase and lipase may well not be elevated in cases of advanced chronic pancreatitis, but are often used as markers for detecting pancreatic inflammation in undiagnosed patients. Common tests used to determine chronic pancreatitis are serum amylase and serum lipase blood tests, triglyceride blood tests, X-rays, Ultrasounds, CT-scans, MRIs and MRCPs. A more invasive test called an ERCP, (Endoscopic Retrograde Cholangiopancreatography), is considered the gold standard procedure for diagnosing chronic pancreatitis. Pancreatic calcification can often be seen on X-rays, as well as CT-scans.
The Whipple procedure is a technique of pancreaticoduodenectomy, or surgical removal of pancreatic cancer. It was named for American surgeon Dr. Allen Whipple who devised the procedure in 1935 and subsequently came up with multiple refinements to his technique. The Whipple procedure today is very similar to Whipple's original procedure. It consists of removal of the distal half of the stomach (antrectomy), the gall bladder (cholecystectomy), the distal portion of the common bile duct (choledochectomy), the head of the pancreas, duodenum, proximal jejunum, and regional lymph nodes. Reconstruction consists of attaching the pancreas to the jejunum (pancreaticojejunostomy) and attaching the common bile duct to the jejunum (choledochojejunostomy) to allow digestive juices and bile to flow into the gastrointestinal tract and attaching the stomach to the jejunum (gastrojejunostomy) to allow food to pass through. Originally performed in a two-step process, Whipple refined his technique in 1940 into a one-step operation.
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Chapter V - Endocrine System