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| Pancreas marked as red organ |
Features
The pancreas is a gland that partly exocrine and partly endocrine. The exocrine part secretes the digestive pancreatic juice; and the endocrine part secretes hormones, e.g. insulin. It is soft, lobulated and elongated organ.
Location
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| Location and parts of pancreas |
The pancreas lies more or less transversely across the posterior abdominal wall, at the level of first and second lumbar vertebrae.
Size and Shape
It is J-shaped or retort-shaped, set obliquely. The bowl of the retort represents its head, and the stem of the retort, its neck, body and tail. It is about 15-20 cm long, 2.5-3.8 cm broad and 1.2-1.8 cm thick and weighs about 90 g.The pancreas is divided (from right to left) into head, neck, body and the tail. The head is enlarged and lies within the concavity of the duodenum. The tail reaches the hilum of the spleen. The entire organ lies posterior to the stomach separated from it by the lesser sac.
HEAD OF THE PANCREAS
Head is the enlarged flattened right end of pancreas, situated within the "C-shaped" curve of the duodenum.
External Features
The head has three borders-superior, inferior and right lateral; two surfaces-anterior and posterior; and one process, called the uncinate process, which projects From the lower and left part of the head towards the left.
Relations
Relations of head of pancreas (a) Anterior (b) Posterior
Three Borders
The superior border is overlapped by the first part of the duodenum and is related to the superior pan- creaticoduodenal artery. The inferior border is related to the third part of the duodenum and to the inferior pancreaticoduodenal artery. The right lateral border is related to the second part of the duodenum, the terminal part of the bile duct and the anastomosis between the two pancreaticoduodenal arteries.
Two Surfaces
The anterior surface is related, from above downwards,
1 The first part of duodenum.
2 Transverse colon.
3 Jejunum which is separated from it by peritoneum.
The posterior surface is related to:
1 Inferior vena cava
2Terminal parts of the renal veins.
3 Right crus of the diaphragm.
4Bile duct which runs downwards and to the right and is often embedded in the substance of pancreas.
Uncinate Process
It is related anteriorly to the superior mesenteric vessels, and posteriorly to the aorta.
NECK OF THE PANCREAS
This is the slightly constricted part of the pancreas between its head and body. It is directed forwards, upwards and to the left. It has two surfaces, anterior and posterior.
Relations
The anterior surface is related to:
(1) The peritoneum covering the posterior wall of the lesser sac, and
(2) the pylorus.
The posterior surface is related to the termination of the superior mesenteric vein and the beginning or the portal vein.
BODY OF THE PANCREAS
The body of the pancreas is elongated. It extends from its neck to the tail. It passes towards the left with a slight upward and backward inclination.
External Features
It is triangular on cross-section, and has three borders (anterior, superior and inferior). A part of the body projects upwards beyond the rest of the superior border, a little to the left of the neck. This projection is known as the tuber omentale.
Relations
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| Posterior relations of the body of pancreas |
Three Borders
The anterior border provides attachment to the root of the transverse mesocolon. The superior border is related to coeliac trunk over the tuber omentale, the hepatic artery to the right, and the splenic artery to the left. The inferior border is related to the superior mesenteric vessels at its right end.
Three Surfaces
The anterior surface is concave and is directed forwards and upwards. It is covered by peritoneum, and is related to the lesser sac and to the stomach. The posterior surface is devoid of peritoneum, and is related to:
a. The aorta with the origin of the superior mesenteric artery.
b. Left crus of the diaphragm.
c. Left suprarenal gland.
d. Left kidney.
e. Left renal vessels.
f. Splenic vein.
The inferior surface is covered by peritoneum, and is related to the duodenojejunal flexure, coils of jejunum and the left colic flexure.
TAIL OF THE PANCREAS
This is the left end of the pancreas. It lies in the lienorenal ligament together with the splenic vessels. It comes into contact with the lower part of the gastric surface of the spleen.
DUCTS OF THE PANCREAS
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| The pancreatic ducts |
The exocrine pancreas is drained by two ducts, main and accessory.
1 The main pancreatic duct of Wirsung, 3 mm in diameter lies near the posterior surface of the pancreas and is recognised easily by its white colour. It begins at the tail; runs towards the right through the body; and bends at the neck to run downwards, backwards and to the right in the head.
2 It receives many small tributaries which join it at acute anglés to its long axis showing a 'V' shape pattern fórming what has been described as a herring bone pattern.
3 Within the head of the pancreas the pancreatic duct is related to the bile duct which lies on its right side. The two ducts enter the wall of the second part of the duodenum, and join to form the hepatopancreatic ampulla of Vater which opens by a narrow mouth on the summit of the major duodenal papilla, 8 to 10 cm distal to the pylorus.
4 The accessory pancreatic duct of Santorini begins in the lower part of the head, crosses the front of the main duct with which it communicates and opens into the duodenum at the minor duodenal papilla. The papilla of accessory pancreatic duct is situated 6 to 8 cm distal to the pylorus. The opening of the accessory duct lies cranial and ventral to that of the main duct. The two ducts remind the double origin of pancreas from the ventral and dorsal pancreatic buds.
Arterial Supply
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| Arterial supply of the pancreas |
The pancreas is supplied:
1 Mainly by pancreatic branches of the splenic artery,
2 The superior pancreaticoduodenal artery, and
3 The inferior pancreaticoduodenal artery.
Like the duodenum the pancreas develops at the junction of the foregut and midgut, and is supplied by branches derived from both the coeliac and superior mesenteric arteries.
Venous Drainage
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| Venous drainage of the pancreas |
Veins drain into splenic, superior mesenteric and portal veins.
Lymphatic Drainage
Lymphatics follow the arteries and drain into the pancreaticosplenic, coeliac and superior mesenteric groups of lymph nodes.
Nerve Supply
The vagus or parasympathetic and splanchnic sympathetic nerves supply the pancreas through the plexuses around its arteries. Sympathetic nerves are vasomotor. Parasympathetic nerves control pancreatic secretion. Secretion is also influenced by the hormone cholecystokinin produced by cells in the duodenal epithelium. The pancreatic juice contains various enzymes that help in the digestion of proteins, carbohydrates and fats.
Functions
1 Digestive: Pancreatic juice contains many digestive enzymes of which the important ones are as follows: Trypsin breaks down proteins to lower peptides. Amylase hydrolyses starch and glycogen to disaccharides. Lipase breaks down fat into fatty acids and glycerol.
2 Endocrine: Carbohydrates are the immediate source energy. Insulin helps in utilizations of the cells. Deficiency of insulin results in hyper- glycaemia. The disease is called diabetes mellitus. There appears to be poverty in plenty.
3 Pancreatic juice: It provides appropriate alkaline medium (pH 8) for the activity of the pancreatic enzymes.
HISTOLOGY
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| Histology of pancreas |
1 The exocrine part is a serous gland, made up of tubular acini lined by pyramidal cells with basal round nuclei, containing zymogen granules. It secretes the digestive pancreatic juice.
2 The endocrine part of pancreas is made up of microscopic elements called the pancreatic islets of Langerhans. These are small isolated masses of cells distributed throughout the pancreas. They are most numerous in the tail. The islets have various types of cells the most important of which are the beta cells which are granular and basophilic, forming about 80% of the cell population. They produce insulin. Other types of cells are alpha cells with subtype A1 and A2. These are granular and acidophilic and form about 20% of the cell population. A1 cells belong to enterochromaffin group and secrete pancreatic gastrin and serotonin. A2 cells secrete glucagon.
Source BD CHAURASIA'S Anatomy
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