Organs Pancreas (Cross Section)
This is a duct joining the pancreas to the common bile duct to supply pancreatic juice provided from the exocrine pancreas which aids in digestion. The pancreatic duct joins the common bile duct just prior to the ampulla of Vater, after which both ducts perforate the medial side of the second portion of the duodenum at the major duodenal papilla. There are many anatomical variants reported but these are quite rare. Most people have just one pancreatic duct. However, some have an additional accessory pancreatic duct, called the Duct of Santorini. An accessory pancreatic duct can be functional or non-functional and may open separately into the second part of the duodenum which is dorsal and usually (in 70%) drains into the duodenum via the minor duodenal papilla. In the other 30% it drains into the main pancreatic duct, which drains into the duodenum via the major duodenal papilla.
Somatostatin-Producing D Cell
Delta cells, are somatostatin-producing cells. They can be found in the stomach, intestine and the pancreatic islets. In rodents, delta-cells are located in the periphery of the islets, the islet architecture is generally less organized and delta-cells are frequently observed inside the islets as well. In both species, the peptide hormone Urocortin3 (Ucn3) is a major local signal that is released from beta cells (and alpha cells in primates) to induce the local secretion of somatostatin. Ghrelin can also strongly stimulate somatostatin secretion, thus indirectly inhibiting insulin release. Viewed under an electron microscope, delta-cells can be identified as cells with smaller and slightly more compact granules than beta cells. D cells in the stomach contain CCKBR (which respond to gastrin) and M3 receptors (which respond to Ach). Respectively, these receptors will increase somatostatin output and decrease somatostatin output from the D cells. VIP, vasoactive intestinal peptide, acts positively on D cells resulting in more somatostatin being released. In the stomach, somatostatin acts directly on the acid-producing parietal cells via a G-protein coupled receptor (which inhibits adenylate cyclase, thus effectively antagonising the stimulatory effect of histamine) to reduce acid secretion. Somatostatin can also indirectly decrease stomach acid production by preventing the release of other hormones, including gastrin, secretin and histamine which effectively slows down the digestive process.
The blood capillaries are where the important functions of the circulation take place: the exchange of material between circulation and cells. Capillaries are the smallest of the body’s blood vessels. They are only one cell thick, and they are the sites of the transfer of oxygen and other nutrients from the bloodstream to other tissues in the body; they also collect carbon dioxide waste materials and fluids for return to the veins. They connect the tiny muscular branches of arteries, called arterioles, with tiny veins (called venules). Ultimately, the capillary is the site of internal or cellular respiration and is responsible for the utilization of oxygen by the tissue and the transporting of carbon dioxide as waste to the veins for elimination by the lungs. The arterial blood system branches extensively to deliver blood to over a billion capillaries in the body. The extensiveness of these branches is much more readily appreciated by knowing that the capillaries provide a total surface area of 1,000 square miles for exchanges of gases, waste, and nutrients between blood and tissue fluid. Oxygen rich blood flows from arterioles or small branches of the artery into the capillary bed and the pressure inside of the arteries is roughly fifty times that on the inside of the veins. It is this pressure difference that forces the blood into the capillary bed. Although the amount of blood flowing through a particular capillary bed is determined in part by a small circular muscle around the arteriole branches, the absence of smooth muscle and connective tissue layers permits a more rapid rate of transport between the blood and the tissue. Source
Pancreatic Polypeptide-Producing PP Cells
Pancreatic Polypeptide (PP) is a 36 amino acid peptide produced and secreted by PP cells (originally termed F cells) of the pancreas which are primarily located in the Islets of Langerhans. It is part of a family of peptides that also includes Peptide YY (PYY) and Neuropeptide Y (NPY). PP is rapidly released after a meal but remains elevated for 4-6 hours in humans with the Vagus nerve being the major stimulator. PP has effects on GI motility, metabolism and food intake. A potential role as a satiety factor comes from the observation that PP secretion is absent in obese children with Prader-Willi syndrome. Its primary action on the exocrine pancreas is to inhibit secretion in vivo by acting on receptors in the brain leading to inhibition of vagal output to the pancreas. Source
Exocrine Acinar Cells
Exocrine Secretions of the Pancreas. Pancreatic juice is composed of two secretory products critical to proper digestion: digestive enzymes and bicarbonate. The enzymes are synthesized and secreted from the exocrine acinar cells, whereas bicarbonate is secreted from the epithelial cells lining small pancreatic ducts. Source
Glucagon-Producing A Cells
Glucagon is a peptide hormone, produced by alpha cells of the pancreas. It works to raise the concentration of glucose and fat in the bloodstream, and is considered to be the main catabolic hormone of the body It is also used as a medication to treat a number of health conditions. Its effect is opposite to that of insulin, which lowers the extracellular glucose. The pancreas releases glucagon when the concentration of glucose in the bloodstream falls too low. Glucagon causes the liver to convert stored glycogen into glucose, which is released into the bloodstream. High blood-glucose levels, on the other hand, stimulate the release of insulin. Insulin allows glucose to be taken up and used by insulin-dependent tissues. Thus, glucagon and insulin are part of a feedback system that keeps blood glucose levels stable. Glucagon increases energy expenditure and is elevated under conditions of stress. Glucagon belongs to the secretin family of hormones.
Insulin-Producing B Cells
Beta cells (β cells) are a type of cell found in the pancreatic islets of the pancreas. They make up 65–80% of the cells in the islets. The primary function of a beta cell is to store and release insulin. Insulin is a hormone that brings about effects which reduce blood glucose concentration. Beta cells can respond quickly to spikes in blood glucose concentrations by secreting some of their stored insulin while simultaneously producing more.