Pancreas

History

The pancreas, étymologiquement " all in viande" (side: all; kréas: meat), was described for the first time by Herophilus, a Anatomiste and Greek surgeon. It was named a few hundred years later by another Greek anatomist, Ruphos.

Embryology

It is resulting from the Endoblaste digestive tract by buddings (one ventral and the other dorsal one) on the level of the hepatic outline. These buddings (or diverticula) are formed respectively with the 26 and 29e days of the embryonic life at the Man. At the 5th week, the ventral bud migrates in the dorsal area and amalgamates, at the 6th week, with the dorsal bud. The endocrine pancreas derives from the only dorsal bud whereas the pancreas exocrine comes partly from both.

Anatomy

The pancreas is a body rétropéritonéal, located in front of the Aorte, of the Vena cava and the renal veins, behind of the Estomac and the transverse Côlon. It extends transversely from right to left, of the Duodénum to the vascular pedicle of the Rate (one distinguishes over its length the head, the isthmus, the body, and the tail of the pancreas, from right to left). It has " reports/ratios; intimes" with the veins splenic and mesenteric lower, whose junction forms the spléno-mésaraïque trunk, in contact with the body and of the tail of the pancreas; and of the higher mesenteric vein, which joined this venous trunk to form the Portal vein, behind of the pancreatic isthmus and in front of the pancreatic uncus (or small retro-venous pancreas). The cœliaque trunk divides on the higher edge, in hepatic Artère common, which gains the hepatic Hile while walking on on the higher edge of the head of the pancreas (it gives up the artery gastro-duodénale, which runs on the former face of the pancreatic isthmus), and splenic Artère, which describes a sinuous way on the higher edge of the body and the tail of the pancreas (the stomachic coronary artery, third branch of the cœliaque trunk, does not maintain relationship with the pancreas; but the stomachic coronary vein follows it false of the common hepatic artery to join the portal vein).

In addition the framework duodénal surrounds the head of the pancreas, like a tire its wheel, maintaining the vascular intimate reports/ratios. Finally the Cholédoque penetrates in the head of the pancreas, before being brought together in the duodenum by a common structure with the Canal of Wirsung: the papilla duodénale.

The pancreas is a gland Endocrine (secretion of the Insuline and other hormones pancreatic in blood), and Exocrine (excretion of the pancreatic enzymes towards the duodenum) via pancreatic canaliculi, which confluent to form the channel of Wirsung.

Histology

The pancreas is the second largest gland in volume after the liver. However, contrary to his/her hepatic big sister, the gland which constitutes the pancreas comprises two distinct parts as well at the anatomical level as functional:

a exocrine part,
an endocrine part.

The pancreas exocrine

The function exocrine of the pancreas is the secretion of the pancreatic enzymes in the Duodénum, by the Canal of Wirsung. Pancreatic juice contains the proenzymes biosynthetized by the acinous cells. These proenzymes are inactive: they will be activated in the digestive tract by the gastric juices to destroy more or less large molecules, they will then be called hydrolases. Among the enzymes secreted by the acini, one finds proteolytic enzymes (trypsin, chymotrypsine, carboxypeptidase…) but also of ribonucleases (RNase) and the désoxyribonucléases (DNase) which degrade residues nucleotidic. Pancreatic secretions have a pH ranging between 7,5 and 8,2. Pancreatic juice is thus alkaline, which makes it possible to plug the stomachic chyme.

The endocrine pancreas

Like all endocrine glands, the pancreas synthesizes products of secretion which are released in blood circulation where they remotely will act worms of fabrics (or cells) target. The endocrine part accounts for only 1% of the pancreas (of many cells and in mass) but grants 10% of its blood irrigation. The products synthesized by the endocrine pancreas are mainly the four following hormones:

insulin (only hormone hypoglycémiante)
glucagon (hyperglysemic hormone)
the somatostatine
pancreatic polypeptide

The Insulin and the Glucagon are thus two hormones necessary to the regulation of the glycemia (concentration of the Glucose in blood). Glucagon and insulin are produced on the level of the small islands of Langerhans; by the insular cells has and B respectively. The cells D secrete as for them the Somatostatine which has an inhibiting effect on glucagon and insulin secretion; the cells F (also named PP cells) produce the pancreatic Polypeptide. The proportions of the cells has, B, D and F within the endocrine pancreas account for 20,70,5 and 5% respectively. The distribution of these cells is particular, each small island of Langerhans making up of a central mass of cells with insulin, the cells with glucagon, the cells with somatostatine and the cells with pancreatic polypeptide finding itself with the periphery. The proportion of these cells varies according to whether they are located in the low part of the head of the pancreas or, on the contrary, in the high part, the body or the tail of the pancreas.

In simple terms, glucagon accelerates the Glycogénolyse. Insulin, it, makes the contrary effect, because it supports the Glycogénogénèse.

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