Liver and Pancreas Anatomy PDF

Liver The liver consists of four lobes: the larger right lobe and left lobe, and the smaller caudate lobe and quadrate lobe. The left and right lobe are divided by the falciform ligament, which connects the liver to the abdominal wall. Liver Lobes: The liver is divided into two primary lobes, the la...

Liver The liver consists of four lobes: the larger right lobe and left lobe, and the smaller caudate lobe and quadrate lobe. The left and right lobe are divided by the falciform ligament, which connects the liver to the abdominal wall. Liver Lobes: The liver is divided into two primary lobes, the larger right lobe and the smaller left lobe. These lobes are further divided into smaller functional units called lobules. The liver is divided in three vertical planes: The plane of the right hepatic vein divides the right lobe into anterior and posterior segments. The plane of the middle hepatic vein divides the liver into right and left lobes or right and left hemiliver. This plane runs from the inferior vena cava to the gallbladder fossa. The umbilical plane runs from the falciform ligament to the inferior vena cava and divides the left lobe into a medial part, which is segment IV and a lateral part formed by segment II and III. This division is the only vertically oriented plane that is not defined by a hepatic vein. Lobules: Lobules are the basic structural units of the liver. They are hexagonal in shape and consist of hepatocytes (liver cells) arranged in a radiating pattern. Each lobule has a central vein, and blood flows through the lobule from the periphery toward this central vein. Blood Supply: the blood supply of the liver is delivered through the portal vein and the proper hepatic artery. The proper hepatic artery (arises from the celiac trunk via common hepatic artery) brings oxygenated blood to the hepatic tissues, while the portal vein collects the deoxygenated blood from the abdominal contents and filters it, eliminating toxins and processing the nutrients it collects during absorption from the alimentary canal. Biliary System: The liver produces bile, which is essential for the digestion and absorption of fats. Bile is transported through a system of ducts that ultimately lead to the gallbladder for storage and release into the small intestine when needed. Gallbladder: Although not part of the liver itself, the gallbladder is closely associated with it. It stores and concentrates bile produced by the liver, releasing it into the small intestine when you eat a fatty meal. Hepatic Portal System: The hepatic portal system is a network of blood vessels that transport nutrient-rich blood from the gastrointestinal tract to the liver. This allows the liver to process and store nutrients and filter out toxins and other harmful substances before they enter the systemic circulation. Functions: The liver performs numerous vital functions, including: Metabolism: It metabolizes carbohydrates, fats, and proteins. Detoxification: The liver filters toxins and drugs from the bloodstream. Storage: It stores glycogen, vitamins, and minerals. Synthesis: The liver produces important proteins like albumin and blood-clotting factors. Bile Production: It produces bile, essential for fat digestion. Immunological Function: The liver plays a role in the immune system. Pancreas The pancreas is an organ located in the abdomen. It plays an essential role in converting the food we eat into fuel for the body's cells. The pancreas has two main functions: an exocrine function that helps in digestion and an endocrine function that regulates blood sugar. Location of the Pancreas The pancreas is located behind the stomach in the upper left abdomen. It is surrounded by other organs including the small intestine, liver, and spleen. It is spongy, about six to ten inches long, and is shaped like a flat pear or a fish extended horizontally across the abdomen. The wide part, called the head of the pancreas, is positioned toward the center of the abdomen. The head of the pancreas is located at the juncture where the stomach meets the first part of the small intestine. This is where the stomach empties partially digested food into the intestine, and the pancreas releases digestive enzymes into these contents. The central section of the pancreas is called the neck or body. The thin end is called the tail and extends to the left side. Blood supply Several major blood vessels surround the pancreas, the superior mesenteric artery, the superior mesenteric vein, the portal vein and the celiac axis, supplying blood to the pancreas and other abdominal organs. Functions of the Pancreas A healthy pancreas produces the correct chemicals in the proper quantities, at the right times, to digest the foods we eat. Almost all of the pancreas (95%) consists of exocrine tissue that produces pancreatic enzymes for digestion. The remaining tissue consists of endocrine cells called islets of Langerhans. These clusters of cells look like grapes and produce hormones that regulate blood sugar and regulate pancreatic secretions. Exocrine Function: The pancreas contains exocrine glands that produce enzymes important to digestion. These enzymes include trypsin and chymotrypsin to digest proteins; amylase for the digestion of carbohydrates; and lipase to break down fats. When food enters the stomach, these pancreatic juices are released into a system of ducts that culminate in the main pancreatic duct. The pancreatic duct joins the common bile duct to form the ampulla of Vater which is located at the first portion of the small intestine, called the duodenum. The common bile duct originates in the liver and the gallbladder and produces another important digestive juice called bile. The pancreatic juices and bile that are released into the duodenum, help the body to digest fats, carbohydrates, and proteins. Endocrine Function: The endocrine component of the pancreas consists of islet cells (islets of Langerhans) that create and release important hormones directly into the bloodstream. Two of the main pancreatic hormones are insulin, which acts to lower blood sugar, and glucagon, which acts to raise blood sugar. Maintaining proper blood sugar levels is crucial to the functioning of key organs including the brain, liver, and kidneys. Radiographic Anatomy Third Stage Dr. Amanj Jalal Namq General Surgeon Abdominal Radiography This chapter covers the anatomy and positioning for what are sometimes called “plain films” (images) of the abdomen. The most common image is an anteroposterior (AP) supine abdomen, also sometimes called a KUB (kidneys, ureters, and bladder). These radiographs are taken without the use of contrast media. Plain radiographs of the abdomen (KUB) commonly are taken before abdominal examinations are performed without the use of contrast media to rule out certain pathologies. • Acute abdominal series Certain acute or emergency conditions of the abdomen may develop from conditions such as bowel obstruction, perforations involving free intraperitoneal air (air outside the digestive tract), excessive fluid in the abdomen, or a possible intra-abdominal mass. These acute or emergency conditions require what is commonly called an “acute abdominal series,” or a “two- way” or “three-way abdomen” series, where in several abdominal radiographs are taken in different positions to demonstrate air-fluid levels or free air or both within the abdominal cavity. • Abdominal radiography requires an understanding of anatomy and relationships of the organs and structures within the abdominopelvic cavity. Abdominal muscles Many muscles are associated with the abdominopelvic cavity. The three that are most important in abdominal radiography are the diaphragm and the right and left psoas (so′-es) major. The diaphragm is an umbrella-shaped muscle that separates the abdominal cavity from the thoracic cavity. The diaphragm must be perfectly motionless during radiography of either the abdomen or the chest. Motion of the patient’s diaphragm can be stopped when appropriate breathing instructions are given to the patient. The two psoas major muscles are located on either side of the lumbar vertebral column. The lateral borders of these two muscles should be faintly visible on a diagnostic abdominal radiograph of a small to average-sized patient when correct exposure factors are used. Abdominal Organ Systems The various organ systems found within the abdominopelvic cavity are presented briefly in this chapter. Each of these systems is described in greater detail in later chapters devoted to the specific systems. Digestive system The digestive system, along with its accessory organs, the liver, gallbladder, and pancreas, fills much of the abdominal cavity. The pancreas is located posterior to the stomach and is not well visualized on this drawing. The spleen (part of the lymphatic system) is also partially visible in the left upper abdomen posterior to the stomach. The six organs of the digestive system are as follows: Oral cavity Pharynx Esophagus Stomach Small intestine Large intestine Oral Cavity, Pharynx, and Esophagus The oral cavity (mouth) and the pharynx (oropharynx and laryngopharynx) are common to the respiratory system and the digestive system. The esophagus is located in the mediastinum of the thoracic cavity. Stomach and Small and Large Intestines The three digestive organs within the abdominal cavity are the stomach and small and large intestines. Stomach The stomach is the first organ of the digestive system that is located within the abdominal cavity. The stomach is an expandable reservoir for swallowed food and fluids. The size and shape of the stomach vary depending on the volume of its contents and on the body habitus. Gastro is a common combining form denoting a relationship to the stomach (the Greek word gaster means “stomach”). The term gastrointestinal (GI) tract or system describes the entire digestive system, starting with the stomach and continuing through the small and large intestines. Small intestine The small intestine continues from the stomach as a long, tube like convoluted structure about 4.5 to 5.5 m (15 to 18 feet) in length. The three parts of the small intestine duodenum (doo ̋o-de′-num); jejunum (je-joo′-num); ileum (il′eum). The first portion of the small intestine, the duodenum, is the shortest but widest in diameter of the three segments. It is about 25 cm (10 inches) in length. When filled with contrast medium, the duodenum looks like the letter C. The proximal portion of the duodenum is called the duodenal bulb, or cap. It has a characteristic shape that usually is well seen on barium studies of the upper GI tract. Ducts from the liver, gallbladder, and pancreas drain into the duodenum. The remainder of the small bowel lies in the central and lower abdomen. The first two-fifths following the duodenum is called the jejunum, and the distal three-fifths is called the ileum. The orifice (valve) between the distal ileum and the cecum portion of the large intestine is the ileocecal valve. Radiograph of stomach and small intestine Air seldom is seen filling the entire stomach or small intestine on a plain abdominal radiograph of a healthy, ambulatory adult. This radiograph shows the stomach, small intestine, and proximal large intestine because they are filled with radiopaque barium sulfate. Note the duodenal bulb and the long convoluted loops of the three labeled parts of the small intestine located in the mid-abdomen and lower abdomen. Blood supply of small and large intestine Venous drainage of small and large intestine Large intestine The sixth and last organ of digestion is the large intestine, which begins in the right lower quadrant at the junction with the small intestine at the ileocecal valve. The portion of the large intestine below the ileocecal valve is a saclike area called the cecum. The appendix (vermiform appendix) is attached to the posteromedial aspect of the cecum. The vertical portion of the large bowel above the cecum, the ascending colon, joins the transverse colon at the right colic (kol′-ik, referring to colon) flexure. The transverse colon joins the descending colon at the left colic flexure. Alternative secondary names for the two colic flexures are hepatic and splenic flexures based on their proximity to the liver and spleen, respectively. The descending colon continues as the S-shaped sigmoid colon in the lower left abdomen. The rectum is the final 15 cm (6 inches) of the large intestine. The rectum ends at the anus, the sphincter muscle at the terminal opening of the large intestine. The shape and location of the large intestine vary greatly, with the transverse colon located high in the abdomen on wide hypersthene types and low in the abdomen on slender hyposthenia and asthenic types.