Pancreas

The Pancreas

The pancreasA gland that produces digestive enzymes and hormones like insulin and glucagon. is an organ. It has two separate functions. These functions are dictated by two separate populations of cellsThe basic structural and functional units of life. within this one organ. The bulk of pancreatic cells are exocrineGlands that secrete substances via ducts (e.g., sweat glands). cells that secrete digestive enzymesProteins that speed up chemical reactions in the body. into the small intestine. These cells function as part of the digestive system. The pancreas also has cells that release hormones such as insulin. These cell populations have an endocrine function because they release these hormones into blood circulation.

Pancreas Anatomy

Your pancreas is tucked between your small intestine and stomach. It’s referred to as a retroperitoneal Referring to organs located behind the peritoneum, such as the kidneys and pancreas. organ because it is not contained fully within the peritoneal cavity. The pancreas is vascularizedTo invade a tissue with blood capillaries. like any other organ and can therefore secrete its hormones directly into circulation. The duct work on this pancreas collects the digestive enzymes. It spews them into the small intestine. We discuss this process more in the digestive system lectures. This section A cut or slice of the body or an organ for study. here of the pancreas is referred to as the headRounded proximal end that fits into the acetabulum of the hip bone.. This is the tail. You can see there are many, many lobes within the pancreas.

Pancreas Histology

When we zoom in on the pancreas with the microscope, we can readily see the acinar cells. These cells generate all of those digestive enzymes. However the cells that have an endocrine function are isolated to what are referred to as pancreatic islets. These pancreatic eyelets look like scattered splotches throughout the pancreas. Within these pancreatic eyelids are various populations of cells that secrete hormones. The two most important to us are alpha cells that create Glucagon and beta cells that make insulin and amylinHormone secreted with insulin to slow glucose absorption..  The effects of insulin are covered in the next slide.  Amylin, in general, works to reduce spikes in blood glucoseA simple sugar that is the main source of energy for cells.. It moderates transitions from hunger to fed states. In general, alpha cells are found toward the inside of the pancreatic islet. Beta cells are found toward the outside. Alpha cells usually stain with a bright pink nucleusThe control center of the cell that contains DNA and directs cellular activities. and pink cytoplasmThe gel-like substance within a cell that contains organelles and cytosol.. Beta cells tend to have a more purple-colored cytoplasm. In addition to these two main populations of cells are other populations such as delta cells and F cells. Delta cellsPancreatic islet cells that secrete somatostatin, which inhibits insulin and glucagon secretion. are difficult to differentiate with alpha cells.  Delta cells secrete somatostatinInhibits GH, insulin, and glucagon secretion. which acts as a local regulator for alpha and beta cells.

Antagonistic Hormones

Insulin and glucagonIncreases blood sugar by promoting glycogen breakdown. regulate blood glucose levels. When blood glucose rises, the alpha cells secrete insulin. When blood glucose drops, the beta cells secrete glucagon to raise it. Remember that neither of these hormones make a change for blood glucose. But both of these hormones send signals to organs and tissues. They can adjust the blood glucose levels. Remember that an effector and its effect need to be differentiated when thinking about effects of a hormone.  Insulin increases the permeability of cells to glucose. This enables glucose uptake. The liverA large organ that produces bile, detoxifies blood, and stores nutrients. stores glucose as glycogenA storage form of glucose found in animals. or as adipose tissue. Glucagon prompts the liver to break down glycogen into glucose, releasing it into the blood to raise blood glucose levels.  Insulin and glucagon have a humoral trigger. The pancreas acts as both the receptorA structure that detects stimuli. and the control centerThe part of a feedback loop that processes information and initiates a response.. 

Diabetes Mellitus

Diabetes can occur when the body fails to produce insulin effectively. It can also happen when the body does not use insulin properly. Additionally, it may occur when cells become insulin resistant. In advanced stages like diabetes mellitus, symptomsSubjective experiences reported by the patient (e.g., nausea, fatigue). include extreme thirst (polydipsiaExcessive thirst.), excessive urination (polyuriaExcessive urine output.), and extreme hunger (polyphagia). These symptoms arise because glucose cannot enter the cells. This leads to “starving in the land of plenty” despite abundant food intake.