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Pancreas

Other Terms: Pancréas, Pankreas, Lapay

Description

The pancreas is a compound racemose gland, similar in its appearance to the salivary glands, though softer and less compactly arranged than those organs. Its secretion, the pancreatic juice, carried by the pancreatic duct to the duodenum, is an important digestive fluid. In addition the pancreas has an important internal secretion, created by the islets of langerhans, insulin and glucagon, which is taken up by the blood stream and is concerned with glucose metabolism. It is long and irregularly prismatic in shape; its right extremity, being broad, is called the head, and is connected to the main portion of the organ, or body, by a slight constriction, the neck; while its left extremity gradually tapers to form the tail. It is situated transversely across the posterior wall of the abdomen, at the back of the epigastric and left hypochondriac regions. Its length varies from 12.5 to 15 cm, and its weight from 60 to 100 gm.

Description

The pancreas is a compound racemose gland, similar in its appearance to the salivary glands, though softer and less compactly arranged than those organs. Its secretion, the pancreatic juice, carried by the pancreatic duct to the duodenum, is an important digestive fluid. In addition the pancreas has an important internal secretion, created by the islets of langerhans, insulin and glucagon, which is taken up by the blood stream and is concerned with glucose metabolism. It is long and irregularly prismatic in shape; its right extremity, being broad, is called the head, and is connected to the main portion of the organ, or body, by a slight constriction, the neck; while its left extremity gradually tapers to form the tail. It is situated transversely across the posterior wall of the abdomen, at the back of the epigastric and left hypochondriac regions. Its length varies from 12.5 to 15 cm, and its weight from 60 to 100 gm.

Relations

Head

The head is flattened from before backward, and is lodged within the curve of the duodenum. Its superior border is overlapped by the superior part of the duodenum and its inferior border overlaps the horizontal part; its right and left borders overlap anterior, and insinuate themselves behind, the descending and ascending parts of the duodenum respectively. The angle of junction of the inferior and left lateral borders forms a prolongation, termed the uncinate process. In the groove between the duodenum and the right lateral and lower borders in front are the anastomosing superior and inferior pancreaticoduodenal arteries; the common bile duct descendsposterior, close to the right border, to its termination in the descending part of the duodenum.

Anterior surface

The greater part of the right half of this surface is in contact with the transverse colon, only areolar tissue intervening. From its upper part the neck springs, its right limit being marked by a groove for the gastoduodenal artery. The inferior part of the right half, below the transverse colon, is covered by peritoneum continuous with the inferior layer of the transverse mesocolon, and is in contact with the coils of the small intestine. The superior mesenteric artery passes down in front of the left half across the uncinate process; the superior mesenteric vein runs upward on the right side of the artery and, behind the neck, joins with the splenic vein to form the portal vein.

Posterior surface

The posterior surface is in relation with the inferior vena cava, the common bile duct, the renal veins, the right crus of the diaphragm, and the aorta.

Neck

The neck springs from the right superior portion of the front of the head. It is about 2.5 cm long, and is directed at first upward and forward, and then upward and to the left to join the body; it is somewhat flattened from above downward and backward. Its antero-superior surface supports the pyloris; its postero-inferior surface is in relation with the commencement of the portal vein; on the right it is grooved by the gastroduodenal artery.

Body

The body is somewhat prismatic in shape, and has three surfaces: the anterior, posterior, and inferior.

Anterior surface

The anterior surface is somewhat concave, and is directed forward and upward; it is covered by the postero-inferior surface of the stomach which rests upon it, the two organs being separated by the omental bursa. Where it joins the neck there is a well marked prominence, the tuberomentale, which butts against the posterior surface of the lesser omentum.

Posterior surface

The posterior surface is devoid of peritoneum, and is in contact with the aorta, the splenic vein, the left kidney and its vessels, the left suprarenal gland, the origin of the superior mesenteric artery, and the crura of the diaphragm.

Inferior surface

The inferior surface is narrow on the right but broader on the left, and is covered by peritoneum; it lies upon the duodenojejunal flexure and on some coils of the jejunum; its left extremity rests on the left colic flexure.

Superior border

The superior border is blunt and flat to the right; narrow and sharp to the left, near the tail. It commences on the right in the omental tuberosity, and is in relation with the celiac artery, from which the hepatic artery courses to the right just above the gland, while the splenic artery runs toward the left in a groove along this border.

Anterior border

The anterior border separates the anterior from the inferior surface, and along this border the two layers of the transverse mesocolon diverge from one another; one passing superior over the anterior surface, the other posterior over the inferior surface.

Inferior border

The inferior border separates the posterior from the inferior surface; the superior mesenteric vessels emerge under its right extremity.

Tail

The tail is narrow; it extends to the left as far as the lower part of the gastric surface of the spleen, lying in the splenorenal ligament, and it is in contact with the left colic flexure.

Pancreatic duct

The pancreatic duct extends transversely from left to right through the substance of the pancreas. It commences by the junction of the small ducts of the lobules situated in the tail of the pancreas, and, running from left to right through the body, it receives the ducts of the various lobules composing the gland. Considerably augmented in size, it reaches the neck, and turning downward, backward, and to the right, it comes into relation with the common bile duct, which lies to its right side. Leaving the head of the gland, it passes very obliquely through the mucous and muscular coats of the duodenum, and ends by an orifice common to it and the common bile duct upon the summit of the duodenal papilla, situated at the medial side of the descending portion of the duodenum, 7.5 to 10 cm below the pylorus. Sometimes the pancreatic duct and the common bile duct open separately into the duodenum. Frequently there is an additional duct, which is given off from the pancreatic duct in the neck of the pancreas and opens into the duodenum about 2.5 cm above the duodenal papilla. It receives the ducts from the lower part of the head, and is known as the accessory pancreatic duct.

Development

The pancreas is developed in two parts, a dorsal and a ventral. The former arises as a diverticulum from the dorsal aspect of the duodenum a short distance above the hepatic diverticulum, and, growing upward and backward into the dorsal mesogastrium, forms a part of the head and uncinate process and the whole of the body and tail of the pancreas. The ventral part appears in the form of a diverticulum from the primitive bile duct and forms the remainder of the head and uncinate process of the pancreas. The duct of the dorsal part (accessory pancreatic duct) therefore opens independently into the duodenum, while that of the ventral part (pancreatic duct) opens with the common bile duct. About the sixth week the two parts of the pancreas meet and fuse and a communication is established between their ducts. After this has occurred the terminal part of the accessory duct, the part between the duodenum and the point of meeting of the two ducts, undergoes little or no enlargement, while the pancreatic duct increases in size and forms the main duct of the gland. The opening of the accessory duct into the duodenum is sometimes obliterated, and even when it remains open it is probably that the whole of the pancreatic secretion is conveyed through the pancreatic duct. At first the pancreas is directed superior and posterior between the two layers of the dorsal mesogastrium, which give to it a complete peritoneal investement, and its surfaces look to the right and left. With the change in the position of the stomach the dorsal mesogastrium is drawn inferior and to the left, and the right side of the pancreas is directed posterior and the left forward. The right surface becomes applied to the posterior abdominal wall, and the peritoneum which covered it undergoes absorption; and thus, in the adult, the gland appears to lie behind the peritoneal cavity.

Structure

In structure, the pancreas resembles the salivary glands. It differs from them, however, in certain particulars, and is looser and softer in its texture. It is not enclosed in a distinct capsule, but is surrounded by loose connective tissue, which dips into its interior, and connects together the various lobules of which it is composed. Each lobule, like the lobules of the salivary glands, consists of one of the ultimate ramifications of the main duct, ending in a number of cecal pouches or alveoli, which are tubular and somewhat convoluted. The minute ducts connected with the alveoli are narrow and lined with flattened cells. The alveoli are almost completely filled with secreting cells, so that scarcely any lumen is visible. The true secreting cells which line the wall of the alveolus are very characteristic. The pancreas functions as both an endocrine and an exocrine gland. The endocrine secretions, from the islets of langerhans, are insulin, glucagon, pancreatic polypeptide, and somatstatin. The exocrine secretions, pancreatic juice, consists of digestive enzymes and a basic solution which are emptied into the small intestine via the duodenal papilla. The digestive enzymes are created by the acinar cells, and the basic solution of bicarbonate is created by the centroacinar cells.

Vessels and nerves

Blood Supply

The arteries of the pancreas are derived from the splenic, and the pancreaticoduodenal branches of the hepatic and superior mesenteric. Its veins open into the splenic and superior mesenteric veins.

Lymphatics

The lymphatic vessels of the pancreas follow the course of its blood vessels. Most of them enter the pancreaticolienal glands, but some end in the pancreaticoduodenal glands, and others in the preaortic glands near the origin of the superior mesenteric artery.

Innervation

Its nerves are branches from the splenic plexus.

French

Pancréas

German

Pankreas

Spanish

Páncreas

Filipino

Lapay

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