220 Alimentary System: Pancreas Pancreas The exocrine part (C)ispurely serous, and its secretory units, or acini (C15), contain Gross and Microscopic Anatomy polarized epithelial cells. Draining the secre- tory units are long intercalated ducts (C16) The pancreas (A1) is a wedge-shaped organ, that begin within the acini and form the 13–15cm long, that lies on the posterior first part of the excretory duct system. In abdominal wall at the level of L1–L2. It ex- cross-section the invaginated intercalated tends almost horizontally from the C- ducts appear as centroacinar cells (CD17). shaped duodenum to the splenic hilum and The intercalated ducts drain into larger ex- may be divided by its macroscopic features cretory ducts which ultimately unite to form into three parts: the pancreatic duct. The fibrous capsule sur- Head of pancreas (B2). The head of the pan- rounding the pancreas sends delicate creas, which lies in the duodenal loop, is the fibrous septa into the interior of the organ, thickest part of the organ. The hook-shaped dividing it into lobules. uncinate process (B3) projects posteriorly and Alimentary System inferiorly from the head of the pancreas sur- Neurovascular Supply and Lymphatic rounding the mesenteric vessels (B4). Be- Drainage tween the head of the pancreas and the un- Arteries. Arterial supply to the head of the cinate process is a groove called the pan- pancreas, like that of the duodenum (see p. creatic notch (B5). 200), is provided by branches of the ǟ Body of pancreas (B6). Most of the body of gastroduodenal artery ( common hepatic the pancreas lies in front of the vertebral artery): the posterior superior pancreati- column. The body has an eminence, near coduodenal artery and the anterior superior the neck, called the omental tuberosity (B7) pancreaticoduodenal artery. Both vessels which extends into the omental bursa (see anastomose with the inferior pancreati- p. 222). coduodenal artery from the superior mesen- teric artery. The body and tail of the pan- Tail of pancreas (B8). The tail of the pan- creas receive their blood supply from the creas extends to the splenorenal ligament of pancreatic branches which are branches of the spleen. the splenic artery. The retroperitoneal pancreas is covered on all Veins. Venous drainage is via short veins sides by connective tissue. The transverse named after the corresponding arteries. mesocolon (B9) passes horizontally along They empty via the splenic vein and superior the anterior surface of its head and body. mesenteric vein into the hepatic portal vein. The anterior surface is divided by the root of the mesocolon into an anterosuperior surface Nerves. Sympathetic fibers to the pancreas (B10), which faces upward, and an antero- arise from the celiac plexus; parasympathetic inferior surface (B11), facing downward. fibers arise from the vagus nerve. The 2mm thick pancreatic duct (B12) runs Regional lymph nodes. Lymph from the along the long axis of the gland near its pos- head of the pancreas drains into the pan- terior surface. It usually opens with the bile creaticoduodenal nodes and from there usu- duct onto the major duodenal papilla (B13). ally to the hepatic nodes. Lymph from the In rare instances, the ducts may open inde- body and tail of the pancreas drains to the pendently into the duodenum. A patent ac- pancreatic nodes lying along the superior and cessory pancreatic duct (B14) is not uncom- inferior borders of the pancreas. The pan- mon. It drains above the main excretory creatic nodes drain into the celiac nodes. duct into the minor duodenal papilla. Function. The exocrine pancreas produces a Microanatomy. The pancreas is a predomi- secretion containing lipase which breaks down fat, amylase which breaks down carbohydrates, nantly exocrine gland. The endocrine part and precursors of protease which breaks down consists of the pancreatic islets (see p. 324). protein. aus: Fritsch, Kuehnel, Internal Organs (ISBN 9783135334059), ᮊ 2008 Georg Thieme Verlag KG Pancreas: Gross Anatomy and Microanatomy 221 A Position of pancreas 1 6 8 7 Alimentary System 14 2 13 4 12 10 11 9 3 B Pancreas and excretory 12 5 ducts, in situ 17 16 17 15 D Acinus in longitudinal and transverse section C Microanatomy of pancreas aus: Fritsch, Kuehnel, Internal Organs (ISBN 9783135334059), ᮊ 2008 Georg Thieme Verlag KG 222 Alimentary System: Pancreas Topography of the Omental Bursa patic portal vein the inferior vena cava can and Pancreas be palpated. The pulse of the left gastric artery (B10) can be palpated in the gastro- Omental Bursa pancreatic fold (A4). The omental bursa is a nearly completely closed peritoneal cavity containing a capillary Pancreas film that lies behind the stomach (A1) and The pancreas lies on the posterior wall of the lesser omentum and in front of the parietal omental bursa.Itsanterior surface is covered peritoneum-covered pancreas (A2). The by parietal peritoneum, and its head is sur- omental foramen (arrow) is the only natural rounded by the duodenum. The pancreas entrance to the omental bursa. The peri- lies in close proximity to the large trunks in toneal relations in and around the omental the upper abdomen. Running along its supe- bursa have already been discussed in rior border (B11) is the splenic artery (B12) greater detail (see p. 188). which is accompanied by the splenic vein (B13) passing deep to it. Behind the body of Alimentary System The omental bursa is visible in its entirety only after it has been freed by one of various the pancreas, the splenic vein receives the surgical routes (dividing the lesser omen- inferior mesenteric vein which unites behind tum, gastrocolic ligament, or transverse me- the head of the pancreas with the superior socolon). mesenteric vein (B14) to form the hepatic portal vein (B9). The superior mesenteric Vestibule of omental bursa. The omental artery (B15), which originates from the foramen leads to the vestibule of the omen- aorta, passes behind the pancreas and de- tal bursa which is bounded anteriorly by the scends along the duodenojejunal flexure lesser omentum and posteriorly by the pa- (B16) before proceeding through the pan- rietal peritoneum. Projecting into the vesti- creatic notch to the uncinate process, over bule is the papillary process of the caudate the superior border of the horizontal part of lobe of the liver (AB3). To the left of the the duodenum and into the root of the papillary process is the prominent gastro- mesenteries. pancreatic fold (A4) that divides the vestibule from the main part of the cavity. Additional structures lying posterior to the pancreas are, from right to left: the bile duct, Main cavity. The greater part of the omental inferior vena cava, aorta, left adrenal gland, bursa consists of the superior recess of omen- left kidney, and vessels of the left kidney. The tal bursa, extending upward between the tail of the pancreas projects into the splenic esophagus and inferior vena cava; the splenic hilum and thus also has a topographical re- recess of omental bursa (A5), extending to the lationships to the left colic flexure and de- left between the splenic ligaments and stom- scending colon (B17). ach; and the inferior recess of omental bursa (A6), extending downward between the Clinical note. Disorders of the pancreas (inflam- stomach and transverse colon. mation, cancer of the pancreatic head) can spread to the adjacent duodenum or cause ob- Omental foramen. The anterior boundary struction of the hepatic, bile, and pancreatic of the omental foramen is formed by the ducts with resultant obstructive jaundice. Pan- hepatoduodenal ligament, a part of the lesser creatic disease can also cause a backup in the omentum. Lying in the hepatoduodenal hepatic portal vein or inferior vena cava. ligament are the hepatic artery proper (B7), the bile duct (B8), and the hepatic portal vein Diagnosis of pancreatic disease has been greatly im- (B9). On inserting a finger into the omental proved by the use of modern imaging techniques foramen, the hepatic portal vein, lying fur- such as CT and ultrasonography. thest posteriorly in the hepatoduodenal AB18 Right lobe of liver, AB19 Gallbladder, A20 ligament, can be felt at the anterior bound- Round ligament of liver, AB21 Left lobe of liver, ary of the omental foramen; behind the he- AB22 Spleen aus: Fritsch, Kuehnel, Internal Organs (ISBN 9783135334059), ᮊ 2008 Georg Thieme Verlag KG Topography of Omental Bursa and Pancreas 223 21 20 1 3 19 4 Alimentary System 2 5 18 22 6 A Topography of omental bursa 21 10 3 22 19 7 8 12 13 9 18 11 17 15 14 16 B Topography of pancreas aus: Fritsch, Kuehnel, Internal Organs (ISBN 9783135334059), ᮊ 2008 Georg Thieme Verlag KG 298 Pregnancy: Early Development Early Development tocyst (BC2). At the same time, the en- dometrium (C78) is prepared for blastocyst Ovulation is the release of the egg cell with implantation by progesterone secreted by its surrounding zona pellucida and corona the corpus luteum. The lining of the uterus radiata (= follicular/granulosa cells) and re- thickens and becomes more vascularized ception by the infundibulum of uterine tube and receptive to implantation, allowing the via the abdominal ostium of uterine tube. blastocyst to burrow into it and receive Fertilization must occur within 6–12hours, nourishment. Implantation (C) (nidation) of after which the egg cell is no longer viable. the blastocyst in the endometrium occurs at Fertilization normally occurs in the ampulla a favorable site (from which it will not be of uterine tube. The zygote is transported to easily moved), usually in the posterior (D9) the uterus within 4 or 5days, propelled by or anterior wall (D10) of the uterine cavity. ciliary action of the tubal epithelial cells, the C7 Functional layer of endometrium, C8 Uterine production (flow) of tubal fluid, and con- epithelium tractions of the muscular wall of the uterine tube.