38 Questions
Where is the liver located in the body?
Immediately beneath the diaphragm, mostly on the right side
What is unique about the capillaries in the liver sinusoids?
They have a large fenestrae with no diaphragm or basement membrane
What is the function of the Kupffer cells in the liver sinusoids?
To engulf foreign particles and bacteria
What is the function of the hepatic portal vein?
To deliver absorbed nutrients from the GI tract to the liver
Where does the blood flow after circulating through the liver capillaries?
To the inferior vena cava
What is the percentage of cardiac output that is directed towards the liver?
25%
What is the arrangement of hepatic plates in a liver lobule?
Around a central vein
What opens into the sinusoids between the hepatic plates?
Hepatic artery and hepatic portal vein
Where is bile secreted by hepatocytes initially released?
Bile canaliculi
What is the main purpose of enterohepatic circulation?
To reabsorb substances into the bloodstream
What is the daily production of bile by the liver?
250-1,500 ml
What is bilirubin derived from?
Heme without iron from hemoglobin
What happens to free bilirubin in the liver?
It is conjugated with glucuronic acid
What is the function of urobilinogen in the small intestine?
To make feces brown
What is the function of bile salts in the small intestine?
To emulsify fats for digestion
What happens to substances that are not reabsorbed in the enterohepatic circulation?
They are excreted in feces
What is the main function of emulsification in fat digestion?
To increase the surface area for lipase enzyme activity
What is the source of lipase enzyme involved in fat digestion?
Pancreas
What is the role of bile acids in fat digestion?
To form micelles that increase the surface area for lipase activity
What is the polar component of bile acids responsible for?
Attracting water molecules
What is the primary function of the liver listed in the content?
Detoxification of blood
What is the result of lipase activity on fat molecules?
Breakdown into fatty acids
What is the structure formed by bile acids and fat molecules?
Micelle
What is the purpose of the micelle structure in fat digestion?
To increase the surface area for lipase activity
What percentage of urobilinogen is absorbed by the intestines and taken back to the liver?
30-50%
What is the purpose of some urobilinogen in the body?
To make bile
What is the function of bile salts in the body?
To form micelles
What is the origin of bile acids?
Cholesterol
What is the role of bacteria in the process of urobilinogen formation?
To convert bilirubin to urobilinogen
What is the final destination of urobilinogen in the urine?
It gives an amber color to the urine
What is the main component of bile salts?
Bile acids conjugated with taurine
What is the main function of the enterohepatic circulation?
To recycle bile acids
Which of the following is NOT a way the liver removes biologically active substances?
Excreted into urine
What is the product of gluconeogenesis in the liver?
Glucose
What is the function of glycogenolysis in the liver?
To break down glycogen and release glucose into the blood
Which of the following is NOT produced by the liver?
Hemoglobin
What is the purpose of glycogenesis in the liver?
To store glucose as glycogen
What is the liver's role in ketone production?
To convert fatty acids into ketones
Study Notes
Liver Structure and Function
- Located immediately beneath the diaphragm, mostly on the right side
- Composed of hepatocytes that form hepatic plates separated by capillaries called sinusoids
- Sinusoids have large fenestrae with no diaphragm or basement membrane, making them very permeable
- Kupffer cells (macrophages) are also present in the sinusoids
Hepatic Portal System
- Absorbed nutrients from the GI tract are delivered first to the liver via the hepatic portal vein
- Veins from the pancreas, gallbladder, stomach, intestine, and spleen join with the hepatic portal vein
- After circulating through liver capillaries, the blood leaves via the hepatic vein to join regular venous circulation
- Hepatic artery provides about 25% of cardiac output to maintain hepatic clearance
Liver Lobules
- Hepatic plates arranged with hepatic arteries, hepatic portal veins, and a central vein
- Hepatic artery and hepatic portal vein open into the sinusoids between the plates
- Bile secreted by hepatocytes is released into bile canaliculi, which drain into bile ducts
Enterohepatic Circulation
- Involves substances metabolized in the liver, excreted into bile, and reabsorbed across the intestinal mucosa
- Substances not reabsorbed are excreted in feces
Bile Production and Secretion
- Liver produces 250-1,500 ml of bile per day
- Bile is composed of bile pigment (bilirubin), urobilinogen, bile salts, phospholipids, cholesterol, and inorganic ions
- Bile can also contain exogenous compounds removed by hepatocytes from the blood
Bile Pigment (Bilirubin)
- Produced in the spleen, liver, and bone marrow from heme (minus iron) from hemoglobin
- Bilirubin is not water-soluble and is carried attached to albumin in the blood
- Conjugated bilirubin is secreted into the bile, where it is taken to the small intestine
Bile Salts
- Made from bile acids conjugated with glycine or taurine
- Bile acids are derived from cholesterol and have four polar groups on each molecule
- Form micelles with polar groups toward water and nonpolar groups inward, allowing for emulsification of fats for digestion
Liver Functions
- Detoxification of Blood: removes hormones, drugs, and biologically active substances through phagocytosis, excretion into bile, and chemical alteration
- Metabolism of Carbohydrates and Lipids: helps balance blood glucose levels through glycogenesis, glycogenolysis, gluconeogenesis, ketogenesis, and lipogenesis
- Production of Plasma Proteins: produces plasma albumin, globulins, clotting factors, and angiotensinogen
This quiz covers the structure and function of the liver, including its location, composition, and microscopic features. It also touches on the role of hepatocytes, sinusoids, and Kupffer cells.
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