Pancreas

From New World Encyclopedia
Pancreas
Illu pancrease.jpg
Illu pancreas duodenum.jpg
1: Head of pancreas
2: Uncinate process of pancreas
3: Pancreatic notch
4: Body of pancreas
5: Anterior surface of pancreas
6: Inferior surface of pancreas
7: Superior margin of pancreas
8: Anterior margin of pancreas
9: Inferior margin of pancreas
10: Omental tuber
11: Tail of pancreas
12: Duodenum
Gray's subject #251 1199
Artery Inferior pancreaticoduodenal artery, Superior pancreaticoduodenal artery
Vein Pancreaticoduodenal veins
Nerve Pancreatic plexus, celiac ganglia, vagus[1]
Precursor pancreatic buds

The pancreas is a pinkish white glandular organ found in vertebrates near the stomach and small intestine. It is one of the few organs that has both an endocrine and an exocrine function. Its exocrine function involves the secretion of bicarbonate and digestive enzymes into the small intestine. Its endocrine function involves the regulation of blood sugar levels by secreting the hormones insulin , glucagon and somatostatin directly into the blood. Although the organ only weighs about 160 grams in the adult human being, it secretes over one liter of fluid per day.


Anatomy

In adult human beings, the pancreas is a 6-10 inch elongated organ weighing about 160 grams and lying in the abdominal cavity . It is posterior to the stomach and in close association with the duodenum portion of the small intestine.

It has three major regions: a head, body and tail.

  • The pancreatic head touches the duodenum.
  • The body of the pancreas lies at the level of second lumbar vertebrae of the spine.
  • The tail of the pancreas extends towards the spleen.

The pancreatic duct or duct of Wirsung runs the length of the pancreas and empties into the second part of the duodenum at the ampulla of Vater. The common bile duct usually joins the pancreatic duct at or near this point. Many people also have a small accessory duct, the duct of Santorini, which extends from the main duct more upstream (towards the tail) to the duodenum, joining it more proximally than the ampulla of Vater.

Blood supply

The pancreas is supplied arterially by the pancreaticoduodenal arteries:

  • the superior mesenteric artery provides the inferior pancreaticoduodenal arteries
  • the gastroduodenal artery provides the superior pancreaticoduodenal artery

Venous drainage is via the pancreaticoduodenal veins which end up in the portal vein. The splenic vein passes posterior to the pancreas but is said to not drain the pancreas itself. The portal vein is formed by the union of the superior mesenteric vein and splenic vein posterior to the neck of the pancreas. In some people (some books say 40% of people), the inferior mesenteric vein also joins with the splenic vein behind the pancreas (in others it simply joins with the superior mesenteric vein instead).

Nerve supply

The pancreas receives neural innervation from the vagus (cranial X)


Microscopic anatomy

The microscopic appearance of the pancreas shows a series of islands (the Islets of Langerhans) consisting of small cells packed closely together ,surrounded by much larger and less dense acinar cells. The islands have an endocrine function and the surrounding cells have an exocrine function.


File:Pancreas.jpg
endocrine and exocrine pancreas


Under a microscope, when properly stained, it is easy to distinguish different types of cells in the pancreas. These regions correspond to the main pancreatic functions:

Appearance Region Function
centralized islands(islets of Langerhans) endocrine pancreas secretes hormones that regulate blood glucose levels
surrounding tissue exocrine pancreas produces enzymes that break down digestible foods

Function

Endocrine function

There are four main types of cells in the islets of Langerhans. They are relatively difficult to distinguish using standard staining techniques, but they can be classified by their secretion:

Name of cells Product % of islet cells Representative function
beta cells Insulin and Amylin 50-80% lower blood sugar
alpha cells Glucagon 15-20% raise blood sugar
delta cells Somatostatin 3-10% inhibit endocrine pancreas
PP cells Pancreatic polypeptide 1% inhibit exocrine pancreas

The islets are a compact collection of endocrine cells arranged in clusters and cords and are crisscrossed by a dense network of capillaries. The capillaries of the islets are lined by layers of endocrine cells in direct contact with vessels, and most endocrine cells are in direct contact with blood vessels, by either cytoplasmic processes or by direct apposition.

The endocrine function of the pancreas is to produce important hormones including insulin, glucagon and somatostatin and export them to the blood supply on demand.

Exocrine function

There are two main classes of exocrine pancreatic secretions:

Secretion Cell producing it Primary signal
bicarbonate ions Centroacinar cells Secretin
digestive enzymes (pancreatic amylase, trypsin, chymotrypsin, etc.) Basophilic cells CCK

Diseases of the pancreas

Due to the importance of its enzyme contents, injury to the pancreas is potentially very dangerous. A puncture of the pancreas generally requires prompt surgical intervention.

  • Diabetes mellitus
  • tumours both benign and cancerous
    • Carcinoma of the pancreas
    • Insulinoma
    • Glucagonoma
  • Cystic fibrosis
  • Exocrine pancreatic insufficiency
  • Hemosuccus pancreaticus, or bleeding from or through the pancreatic duct
  • Pancreatitis
  • Pancreatic pseudocyst

History

The pancreas was discovered by Herophilus (335-280 B.C.E.), a Greek anatomist and surgeon. Only a few hundred years later, Ruphos, another Greek anatomist, gave the pancreas its name. The term "pancreas" is derived from the Greek pan,meaning "all", and kreas,meaning "flesh". [2]

Diabetes and the Pancreas

A new discovery might have important implications for treatment of diabetes. Researchers at the Toronto Hospital for Sick Children injected capsaicin into mice with type 1 diabetes , in an attempt to destroy the pancreatic sensory nerves. This treatment reduced the development of diabetes in these mice by 80%, suggesting a link between neuropeptides and the development of diabetes. When the researchers injected the pancreas of the diabetic mice with sensory neuropeptide (sP), they were cured overnight of diabetes for as long as 4 months. Also, insulin resistance (characteristic of type 2 diabetes) was reduced. These research results are in the process of being confirmed, and their applicability in humans will have to be established in the future.reference??


Additional images

References
ISBN links support NWE through referral fees

  1. Physiology at MCG 6/6ch2/s6ch2_30
  2. Harper, Douglas. Pancreas. Online Etymology Dictionary. Retrieved April 4, 2007.

Template:Endocrine pancreas

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