Accessory Organs of Digestive Tract

Liver Is the largest visceral organ and the largest gland in the body. Plays an important role in production and secretion of bile (used in emulsification and digestion of fats) and detoxification (by filtering the blood to remove bacteria and foreign particles that have gained entrance to the intestine); storage of carbohydrate as glycogen and lipids as triglycerides; protein synthesis , such fibrinogen and prothrombin (blood coagulants), albumin, and lipoproteins; production of heparin (anticoagulant) and bile pigments (bilirubin and biliverdin) from the breakdown of hemoglobin; and storage of certain vitamins, iron, and copper. Is surrounded by the peritoneum and is attached to the diaphragm by the coronary and falciform ligament and the right and left triangular ligaments. Has a bare area on the diaphragmatic surface, which is limited by layers of the coronary ligament but devoid of peritoneum. Receives oxygenated blood from the hepatic artery and deoxygenated, nutrient-rich, sometimes toxic blood from the portal vein ; its venous blood is drained by the hepatic veins into the IVC. Contains the portal triad , which is a group of the branches of the portal vein, hepatic artery , and bile at every corner of the lobule, surrounded by a connective tissue sheath, the perivascular fibrous capsule. Is divided, based on hepatic drainage and blood supply, into the right and left lobes by the fossae for the gallbladder and the IVC. (These lobes correspond to the functional units or hepatic segments.) Lobes of the liver Right lobe Is divided into anterior and posterior segments , each of which is subdivided into superior and inf areas or segments. Left lobe Is divided into medial and lateral segments , each of which is subdivided into superior and inferior areas (segments). Includes the medial superior (caudate lobe), medial inferior (quadrate lobe), lateral superior , a lateral inferior segments. The quadrate lobe receives blood from the left hepatic artery and drains into the left hepatic duct, whereas the caudate lobe receives blood from the right and left hepatic arteries and drains bile into both right and left hepatic ducts. Fissures and ligaments of the liver Include an H-shaped group of fissures: Fissure for the round ligament (ligamentum teres hepatis ), located between the lateral portion of the left lobe and the quadrate lobe. Fissure for the ligamentum venosum , located between the caudate lobe and the lateral portion the left lobe. Fossa for the gallbladder , located between the quadrate lobe and the major part of the right lobe Fissure for the IVC , located between the caudate lobe and the major part of the right lobe. Porta hepatis. This transverse fissure on the visceral surface of the liver between the quadrate caudate lobes lodges the hepatic ducts, hepatic arteries, branches of the portal vein , hepatic nerve and lymphatic vessels. Gallbladder Is located at the junction of the right ninth costal cartilage and lateral border of the rectus abdominis, which is the site of maximum tenderness in acute inflammation of the gallbladder. Is a pear-shaped sac lying on the inferior surface of the liver in a fossa between the right and quadrate lobe with a capacity of about 30 to 50 mL and is in contact with the duodenum and transverse colon. Consists of the fundus, body, and neck: the fundus is the rounded blind end located at the tip of the right ninth costal cartilage in the midclavicular line and contacts the transverse colon; the body is the major part and rests on the upper part of the duodenum and the transverse colon; the neck is the narrow part and give rise to the cystic duct with spiral valves (Heister's valves). Receives bile, concentrates it (by absorbing water and salts), stores it, and releases it during digestion. Contracts to expel bile as a result of stimulation by the hormone cholecystokinin , which is produced by duodenal mucosa or by parasympathetic stimulation when food arrives in the duodenum. Receives blood from the cystic artery, which arises from the right hepatic artery within the cystohepatic triangle (of Calot) , which is formed by the visceral surface of the liver superiorly, the cystic duct inferio and the common hepatic duct medially. May have an abnormal conical pouch (Hartmann's pouch ) in its neck and the pouch is also called the ampulla of the gallbladder. Pancreas Lies largely in the floor of the lesser sac in the epigastric and left hypochondriac regions, where it forms a major portion of the stomach bed. Is a retroperitoneal organ except for a small portion of its tail , which lies in the lienorenal (splenorenal) ligament. Has a head that lies within the C-shaped concavity of the duodenum. If tumors are present in the head, bile flow is obstructed, resulting in jaundice. Bile pigments accumulate in the blood, giving the skin and eyes characteristic yellow coloration. Has an uncinate process , which is a projection of the lower part of the head to the left side behind the superior mesenteric vessels. Receives blood from branches of the splenic artery and from the superior and inferior pancreaticoduodena arteries. Is both an exocrine gland , which produces digestive enzymes that help digest fats, proteins, and carbohydrates, and an endocrine gland (islets of Langerhans), which secretes the hormones insulin and glucagon, which help the body to use glucose for energy, and also secretes somatostatin. Insulin lowers sugar levels by stimulating glucose uptake and glycogen formation and storage. Glucagon enhances blood sugar levels by promoting conversion of glycogen to glucose. Somatostatin suppresses insulin and glucagon secretion. Has two ducts, the main pancreatic duct and the accessory pancreatic duct. Main pancreatic duct (duct of Wirsung) Begins in the tail, runs to the right along the entire pancreas, and carries pancreatic juice containing enzymes Joins the bile duct to form the hepatopancreatic ampulla (ampulla of Vater) before entering the second part of the duodenum at the greater papilla. Accessory pancreatic duct (Santorini's duct) Begins in the lower portion of the head and drains a small portion of the head and body. Empties at the lesser duodenal papilla about 2 cm above the greater papilla. Duct system for bile passage Right and left hepatic ducts Are formed by union of the intrahepatic ductules from each lobe of the liver and drain bile from the corresponding halves of the liver. Common hepatic duct Is formed by union of the right and left hepatic ducts. Is accompanied by the proper hepatic artery and the portal vein. Cystic duct Has spiral folds (valves) to keep it constantly open, and thus bile can pass upward into the gallbladder while the common bile duct is closed. Runs alongside the hepatic duct before joining the common hepatic duct. Is a common site of impaction of gallstones. Common bile duct (ductus choledochus) Is formed by union of the common hepatic duct and the cystic duct. Is located lateral to the proper hepatic artery and anterior to the portal vein in the right free margin of the the lesser omentum. Descends behind the first part of the duodenum and runs through the head of the pancreas. Joins the main pancreatic duct to form the hepatopancreatic duct (hepatopancreatic ampulla) , which joins the second part of the duodenum at the greater papilla. Contains the sphincter of Boyden , which is a circular muscle layer around the lower end of the duct. Hepatopancreatic duct or ampulla (ampulla of Vater) Is formed by the union of the common bile duct and the main pancreatic duct and enters the second part of the duodenum at the greater papilla. This represents the junction of the embryonic foregut and midgut. Contains the sphincter of Oddi , which is a circular muscle layer around it in the greater duodenal papilla Spleen Is a large vascular lymphatic organ lying against the diaphragm and ribs 9 to 11 in the left hypochondral region. Is developed as a thickening of the mesenchyme in the dorsal mesogastrium and supported by the lienogastric (splenogastric) and lienorenal (splenorenal) ligaments. Is composed of white pulp , which consists of lymphatic nodules and diffuse lymphatic tissue Is hematopoietic in early life and later destroys aged (i.e., worn out) red blood cells in the red pulp. The hemoglobin is the respiratory protein of erythrocytes and is degraded into (a) the globin (protein part), which is hydrolysed to amino acid and reused in protein synthesis; (b) the iron released from the heme, which is transported to the bone marrow and reused in erythropoiesis; and (c) the iron-free heme, which is metab to bilirubin in the liver and excreted in the bile. Filters blood (removes aged erythrocytes, particulate matter, and cellular residue from the blood); stores blood and platelets; and produces lymphocytes, macrophages, and antibodies in the white pulp. Is supplied by the splenic artery and is drained by the splenic vein. ◄.....Go back to the Gross Anatomy homepage