 This video will cover the third portion of the following objective from the endocrine system, list the major endocrine organs and the hormones they secrete, then for each hormone discuss its effects on target cells. Previous videos have covered the hypothalamus, pituitary gland, thyroid, parathyroid glands, and the adrenal glands. This video will focus on the pancreas. The pancreas is located in the epigastric and left hypochondriac regions, just posterior to the stomach and medial to the kidneys. The pancreas has both exocrine functions as well as endocrine functions. As an exocrine gland, the pancreas contains acin or cells that secrete digestive enzymes, which travel through ducts into the small intestine. We'll discuss the exocrine functions more when we get to the digestive system. But the endocrine functions of the pancreas come from clusters of cells known as pancreatic islets or islets of longerhounds, which are distributed throughout the pancreas. Within the pancreatic islets are alpha cells that produce the hormone glucagon and beta cells that produce the hormone insulin. Together glucagon and insulin work to help maintain a stable blood glucose concentration. Here we see the histology of the pancreas at low magnification, where the majority of the cells in the pancreas are the acini cells that are the exocrine cells. There are islets of longerhounds, circular-shaped, lighter-staining structures that contain the endocrine cells. Here we see a higher magnification view of the pancreas with several islets of longerhounds indicated, and here we have a high magnification view focused on an islet of longerhounds or a pancreatic islet, a cluster of the endocrine cells, alpha cells which produce glucagon and beta cells which produce insulin. This slide shows the histology of the pancreas with a lighter stain, where we can still see the majority of the darker staining cells in the image are the acini cells, and the lighter staining circular regions are the islets of longerhounds where the endocrine cells are found. Here is a higher magnification view of that slide focused on an islet of longerhounds where you can see the blood vessels give a lighter staining to this region and the endocrine cells in this region, the alpha cells and beta cells, the alpha cells produce glucagon and the beta cells produce insulin. In response to low blood glucose, which is known as hypoglycemia, alpha cells of the pancreas release glucagon. Glucagon binds two receptors on the surface of cells throughout the body where it has the effects of decreasing the uptake of glucose from the blood and decreasing the utilization of glucose in cellular respiration, so it inhibits the metabolic pathways that use glucose. It also stimulates glycogenalysis, which is a process that breaks down glycogen. Glycogen is a carbohydrate that stores glucose. In the liver, glycogen can be broken down in order to release glucose into the blood. Glucagon also stimulates the process of gluconeogenesis, which is the synthesis of new glucose from amino acids and glycerol. Together, these effects work to increase blood glucose concentrations to restore the homeostatic set point between 70 and 110 milligrams per deciliter. In response to elevated blood glucose, which is known as hyperglycemia, beta cells of the pancreas release insulin. Insulin binds to receptors on the surface of cells throughout the body where it stimulates the uptake of glucose from the blood and stimulates the use of glucose in cellular respiration, which is a metabolic pathway that breaks down glucose in order to produce ATP. Insulin also inhibits the process of glycogenalysis, which prevents the release of glucose from storage, and insulin will stimulate the storage of glucose as more glycogen is synthesized. Insulin will also inhibit gluconeogenesis, so it stimulates the production of new glucose. Together, these actions of insulin work to decrease blood glucose concentrations, restoring the homeostatic set point between 70 and 110 milligrams per deciliter. Diabetes mellitus is a disease that results from elevated blood glucose levels when insulin signaling is impaired. Type 1 diabetes results from low insulin production. If the pancreas cannot produce enough insulin, then cells throughout the body cannot take the glucose out of the blood, leading to high blood glucose levels. This is often caused by an autoimmune disease that attacks the beta cells of the pancreas, destroying the beta cells, preventing the pancreas from secreting insulin. As blood glucose levels rise, this leads to three cardinal signs of diabetes mellitus, which are polyuria, or increased urine production, polydipsia, increased thirst, and polyphagia, increased food intake, increased hunger. The polyuria results from high glucose levels of the blood, overwhelming the kidneys ability to reabsorb glucose, and as excess glucose is being lost in the urine, increased water is lost along with that glucose in increased urine production. As water is being lost from the body and dehydration develops, this stimulates the increase in thirst, and together the loss of energy from the body as glucose is being lost in the urine, as well as the disruption of the normal signaling function of insulin in the brain, which is important for stimulating satiety, which is the opposite of hunger. Together these actions lead to the other cardinal sign of polyphagia, increased food intake. Together, all three cardinal signs are resulting from that elevation of blood glucose, and that elevation of blood glucose in type 1 diabetes is because the pancreas cannot produce insulin sufficiently. In contrast to type 1 diabetes, there's type 2 diabetes in which cells throughout the body do not respond to insulin, that is they become insensitive to insulin, even though the pancreas is initially producing large amounts of insulin, the insulin receptors are not responding, or the cells are not responding when the insulin receptors become activated, but the cells then cannot take glucose out of the blood. This leads to elevated blood glucose levels, and the three cardinal signs of diabetes, the polyuria, polydipsia, and polyphagia result from high blood glucose levels. Over time, high blood glucose levels in diabetes mellitus can lead to complications that are largely a result of damage to blood vessels from high blood glucose. The image on the bottom left here we see is representing diabetic retinopathy or damage to the eye. The retina of the eye is damaged from high blood glucose levels, and this can lead to visual impairment, and over time eventually to blindness. In the central image you can see damage to the kidney, diabetic nephropathy, or eventually renal failure, kidney failure, can result from damage to the small blood vessels of the kidney, and the image on the right is representing damage to the nervous system, diabetic neuropathy, the nerves of the peripheral nervous system can become damaged by disruptions of blood flow, leading to itching and tingling sensations and burning sensations, and over time as nerve function deteriorates, sensation can be lost. Other common complications of diabetes mellitus include an increased risk of cardiovascular diseases like heart attack and stroke or increased incidence. Also the wound healing process is impaired by the elevated blood glucose damaging small blood vessels of the skin, and the immune system becomes suppressed, leading to slow wound healing and increased risk for infections.