0141-00 Liver and Gallbladder
0141-00 Liver and Gallbladder
50% larger than life, the ventral surface of this replica is dissected to expose major blood vessels and bile ducts in deep relief. Color-coding clarifies the complex vascular network, with contrasting colors differentiating the portal vein and its branches, the gallbladder and bile ducts, the hepatic artery and the hepatic veins. 28 hand numbered structures are identified in the accompanying key.
Overall dimensions: 13x11x6 inches (33x28x15 cm).
Interesting Facts About the Liver:
The liver is the largest gland in the human body.
It has four interconnected vascular systems: hepatic portal system, hepatic arteries, biliary ducts, and hepatic venous system.
The liver weighs about one-fortieth (1/40) of the body weight in an adult. In fetal life and in childhood the proportion is greater. Adult livers typically average from three and a half to four pounds.
The working unit of the liver is the lobule which is about the size of a sesame seed or, in other words, from one to one and a half millimeters (1-1.3 mm) in diameter and one and a half to two millimeters tall (1.5-2.0mm). The liver contains more than of one million lobules.
The liver contains approximate 2 km of bile ducts.
Surface Landmarks and Location
within the Abdominal Cavity
Beginning with the study of the liver in its proper body location, we should inform the students as to its relation to the outside surface of the body. The surface landmarks of the liver are as follows. The right upper margin of the liver reaches the superior border of the fifth rib on the right side and runs nearly horizontal across the midline
to the left side not quite reaching the left mid clavicular line. The right margin of the liver is bound by the lateral right ribs with the lower right margin nearly reaching the 10th rib. The inferior margin of the liver stretches diagonally from the 10th right rib superiorly across the midline to meet the upper margin on the left side.
Utilize additional Denoyer-Geppert teaching aids showing the liver in the body:
0700-00 ThinManTM Sequential Anatomy Figure 0708-00 KnowBody Torso
0712-00 MultiTorso System
It may be helpful to draw an outline of the body on the blackboard with the liver marked in by means of dotted lines.
The liver can also be marked on the actual surface of the body by means of a grease make-up pencil. If this is an age or maturity-appropriate activity for your classroom, some male student in class may be willing to strip to the waist for demonstration purposes.
Because it is a heavy, dense solid structure, it would follow that the liver should rest on the floor of the abdominal cavity instead of being suspended in the upper part. However, several structures contribute to supporting the liver allowing it to be in the right upper quadrant of the abdominal cavity. Two peritoneal folds, the coronary ligament (20, 21) and the triangular ligament (not shown) attach the liver to the diaphragm, a strong muscular dome just above it. The inferior vena cava (7) and its network
of veins within the liver help to support the posterior portion. Additionally, because the abdominal viscera completely fill the abdominal cavity a good share of support is given by
them as long as the proper muscle tone in the abdominal wall is maintained. In other words, posture has something to do with the support
of the liver as well as the proper placement of
all the viscera. The liver fits so perfectly against the diaphragm that atmospheric pressure would tend to hold it in place. The diaphragm itself is supported in part by the negative pressure in the lungs.
The falciform ligament* (19) is slightly lax
and could hardly carry much weight, yet it prevents displacement of the liver sideways.
The round ligament (18), a remnant of the umbilical vein in the fetus, does not play a direct role in supporting, but also prevents lateral displacement. Another ligament, closely akin
to the round ligament in that it is a remnant of the fetal circulation, is the ligament of ductus venosus (22). It helps to maintain the liver in its proper position.
Review of supporting structures on the
Permit the students to observe it from
different angles. Let them try to describe its actual shape and make a rough drawing of it.
Be sure that each student is able to hold the liver model so that it is in the same relative position as his own.
The liver is shaped somewhat by its surroundings, in that the structures immediately adjacent to it press against the liver and form indentations or impressions.
Consider the colic impression (27) made by the colon, the esophageal impression (28), the renal impression (26), the duodenal (25 and pyloric 24) impressions. In addition the entire upper dome shaped surface is “molded” by the diaphragm.
In the cut away section of the model, certain blood vessels are colored lavender. These are
the portal vein (10), and its ramifications (11) within the liver also known as the hepatic portal system. These veins branch many times until small capillaries reach the working units of the liver, the lobules. The portal vein originated
in the small intestine where, as capillaries, it
picks up the products of digestion. From there, the veins run through the mesentery, joining together to form the hepatic portal vein which in turn enters the liver and starts dividing as described above. (A distinctive feature of venous portal systems is that they begin and end in capillaries.) In addition to the portal system
of blood vessels, the liver has arteries (12) and veins (23) just as any other structure in the body. A large percentage of blood in the body is in the liver at all times. The working unit of the liver is the lobule which is supplied by capillaries of the arteries (12 and 13) and hepatic portal vein (10 and 11). The end products, bile and metabolic wastes of the lobules, are carried away by the capillaries of the veins (23, 8, 9), the bile ducts (14 and 15), and the lymph vessels (not shown). So far nothing has been said about the lymph vessels, but they are found throughout the fibrous supporting tissue of the liver carrying on with their normal function, which is the carrying away of the serous portion of the blood that escapes from the capillaries into the intercellular spaces.
Other structures are labeled for more detailed study.
Physiological Functions 3.) Production and Secretion of Bile
The liver is recognized for five principle roles • in physiological homeostasis. The functions
are wide ranging and of great importance to
multiple organ systems including the digestive system, endocrine system, and immune system.
Each role is subsequently described along with the key anatomical structures relating to that function which can be identified on the model. 1.) Metabolism of Biological Molecules
• Conversion of vitamins and hormones into active form
Bile is composed of a number of chemical components that aid in digestion by helping to eliminate bilirubin and cholesterol and by assisting in the absorption of lipids. Within each hepatic lobule are found small bile passages, or bile canaliculi. These pick up the bile as
it is produced by the hepatocytes. The canaliculi open into interlobular bile ducts at the periphery of the lobule, which in turn join other ducts of similar size until by a constant uniting of tributary vessels, fairly large vessels are formed (15). These
• Conversion of lipophilic compounds into
hydrophilic compounds that are easier to
excrete larger bile ducts continue to join until two
Regulated synthesis of plasma proteins, carrier proteins, and precursors of hormones.
The waste products of muscle metabolism are brought into the liver by means of the hepatic arteries, and converted to urea, which is then returned to the blood stream by way of the hepatic veins. In the form of urea, the kidneys can separate these waste products from the blood and excrete them in urine.
Maintenance of blood glucose levels
through production of glucose via • gluconeogenesis and glycogenolysis and
uptake of glucose via glycogen synthesis.
Uptake and conversion of dietary amino acids into alpha-keto acid and glutamine.
2.) Storage of Carbohydrates, Lipids, Vitamins, and Minerals
The liver is the site of storage for Vitamins
A, D, E, K and copper and iron.
The liver is also a repository for
carbohydrates and lipids in the form of polymer molecules that it synthesizes such as glycogen and triglycerides.
large trunks unite to form the hepatic duct (14). Leading from the hepatic duct is the cystic duct (16), running to a bile reservoir or gallbladder (17). The gallbladder can store bile between meals, allow it to become more concentrated, and release
it into the duodenum immediately when eating begins. Where the cystic duct joins the hepatic duct, we have the common bile duct which joins a duct from the pancreas forming a small tube or ampulla-shaped opening into the duodenum.
We often hear of an ailment called gallstones (cholelithiasis). These are “stones” formed by the solidification of bile salts in the gallbladder (17). When these stones pass through the cystic and common bile ducts, they give considerable pain - if they are a little too large for the ducts. This is especially true in the cystic duct the lumen of which follows a slightly spiral course. Many times the stones get too large in the gallbladder to even start passing through the cystic duct. When this condition causes objectionable symptoms, a surgeon can remove the gallbladder.
Another condition, jaundice, results from too much bilirubin in the blood stream (hyperbilirubinemia).
Jaundice presents as a yellowish tint to the skin and sclera of the eye. Severe jaundice can cause light colored stools, dark colored urine, abdominal pain and swelling, nausea, and loss of appetite. It can be caused by numerous underlying conditions of the liver and biliary tree.
4.) Detoxification of Blood
• The liver is key for inactivation or export of
endogenous (e.g. bilirubin and urea) and exogenous (e.g. drugs and environmental toxins) contaminates in the blood stream. The toxins enter the liver circulation through either the portal vein or the hepatic artery. The blood supply diverging into the hepatic sinusoids eventually reaches the hepatocytes which intake the toxins, package them intracellularly, and then either digest the contaminate, or
export it in to the biliary system.
• Large phagocytes called Kupffer’s cells
are prevalent throughout the liver serve in a filtering function by removing and digesting particulate matter in the blood stream.
5.) Elimination of Spent Red Blood Cells
When red blood cells have outlived their usefulness, they disintegrate and become broken down. The liver picks the remnants out of the blood stream and eliminates them through the bile.
We Also Recommend