Liver Structure• Blood from hepatic portal vein and hepatic artery mix in sinusoids• The sinusoids empty into central veins, which send the blood to the hepatic vein and inferior vena cava
Liver Structure (cont.)• Hepatic cells lie along the sinusoids and pick up chemicals from the blood• They modify the blood’s composition
Liver Structure (cont.)• At the back end of each hepatic cell, bile is released into a canaliculus• The bile is carried to the bile duct and then to the gallbladder
Liver Structure (cont.)• Many sinusoids come together to empty into one vein• The section of the liver emptying into one vein is a lobule
QuestionTell whether the following statement is true or false.The gallbladder stores bile that has been produced by the liver.
True AnswerRationale: The liver makes bile and secretes it into the small intestine via the common bile duct. Excess bile is stored in the gallbladder, where it also enters the small intestine through the common bile duct when it is needed.
Metabolic Functions of the Liver• Carbohydrate, protein, and lipid metabolism – Sugars stored as glycogen, converted to glucose, used to make fats – Proteins synthesized from amino acids; ammonia made into urea – Fats oxidized for energy, synthesized, packaged into lipoproteins
Metabolic Functions of the Liver (cont.)• Drug and hormone metabolism – Biotransformation into water-soluble forms – Detoxification or inactivation• Bile production
QuestionWhich of the following substances makes bile more susceptible to digestive enzymes?b. Carbohydratec. Proteind. Fate. All of the above
a. Fat AnswerRationale: Bile (produced in the liver) emulsifies fat molecules so that they are easier to digest. An emulsion is a mixture of two immiscible (unblendable) substances, in this case bile and fat.
ScenarioMr. M had a donut for breakfast.Question:• Explain how the sugar in the donut left his small intestine and ended up as fat in his carotid artery, giving the: – Anatomical structures – Chemical processes – Hormones that controlled them
ScenarioMs. B was prescribed an oral medication for her skin problem. She took it twice a day.• The day after she started the medication, Ms. B drank wine with a friend right after taking the prescribed dosageQuestion:• Ms. B got terribly ill. Why? She said, “I drink that kind of wine all the time.”
Liver Failure• Hematologic disorders – Anemia, thrombocytopenia, coagulation defects, leukopenia• Endocrine disorders – Fluid retention, hypokalemia, disordered sexual functions – Which hormones would cause these endocrine disorders?
Answera. Increased bilirubin levelsRationale: Erythrocytes are normally broken down in the spleen at the end of their life span. The end product of RBC metabolism is bilirubin. Bilirubin is sent to the liver to be metabolized; if the liver is not functioning properly, the bilirubin accumulates and causes jaundice (an abnormal yellowing of the skin and mucous membranes).
Hepatitis• Viral hepatitis• Hepatitis A virus (HAV)• Hepatitis B virus (HBV)• Hepatitis B–associated delta virus (HDV)• Hepatitis C virus (HCV)• Hepatitis E virus (HEV)
DiscussionWhich hepatitis viruses are most likely to be the problem in:• An asymptomatic drug abuser?• A nursing student who has spent the last two months volunteering in an orphanage in Mali?• An infant whose mother has hepatitis?
Chronic Viral Hepatitis• Caused by HBV, HCV, and HDV• Principal worldwide cause of chronic liver disease, cirrhosis, and hepatocellular cancer• Chief reason for liver transplantation in adults
Alcoholic Liver Disease• Fatty liver (steatosis) – Liver cells contain fat deposits; liver is enlarged• Alcoholic hepatitis – Liver inflammation and liver cell failure• Cirrhosis – Scar tissue partially blocks sinusoids and bile canaliculi
QuestionWhich of the following is the least virulent strain of hepatitis?b. HAVc. HBVd. HCVe. HDV
a. HAV AnswerRationale: HBV, HCV, and HDV are all virulent strains that may lead to chronic viral hepatitis. HAV is most commonly transmitted by the fecal-oral route (e.g., contaminated food or poor hygiene) and does not typically have a chronic stage (it does not cause permanent liver damage).
Veins Draining into the Hepatic Portal System• Portal hypertension causes pressure in these veins to increase• Varicosities and shunts develop• Organs engorge with blood
Cholestasis and Intrahepatic Biliary Disorders• Bile flow in the liver slows down• Bile accumulates and forms plugs in the ducts – Ducts rupture and damage liver cells • Alkaline phosphatase released into blood• Liver is unable to continue processing bilirubin – Increased bile acids in blood and skin • Pruritus (itching)
unconjugated The Fate of Bilirubin bilirubin in blood• Hemoglobin from old red blood cells becomes bilirubin bilirubinemia liver links it• The liver converts to bilirubin into bile gluconuride• Why would a man with jaundice liver failure develop jaundice? conjugated bilirubin bile
Biliary Tract Gallbladder Hepatic Cystic duct duct Common bile ductAmpulla of VaterSphincter of Oddi Pancreatic duct
Disorders of the Gallbladder• Cholelithiasis (gallstones) – Cholesterol, calcium salts, or mixed• Acute and chronic cholecystitis – Inflammation caused by irritation due to concentrated bile• Choledocholithiasis – Stones in the common bile duct• Cholangitis – Inflammation of the common bile duct
Bile in the Intestines• Emulsifies fats so they can be digested• Passes on to the large intestine – Bacteria convert it to urobilinogen º Some is lost in feces º Most is reabsorbed into the blood Returned to the liver to be reused Filtered out by the kidneys urine
The Pancreas Pancreas Exocrine Endocrine pancreas pancreas releases digestive juices through a releases hormones duct into the blood to the duodenum
Exocrine Pancreas• Acini produce: – Inactive digestive enzymes – Trypsin inactivator – Bicarbonate (antacid)• These are sent to the duodenum when it releases secretin and cholecystokinin• In the duodenum, the digestive enzymes are activated
QuestionTell whether the following statement is true or false.The exocrine pancreas produces insulin.
False AnswerRationale: Beta cells of the endocrine pancreas produce insulin; the exocrine pancreas produces digestive enzymes that are secreted into the small intestine through the common bile duct.
Biliary Reflux 5. Bile in1. Gallbladder pancreascontracts disrupts2. Bile is sent tissues;down common digestivebile duct enzymes activated3. Blockage formsin ampulla of Vater: 4. Bilebile cannot enter goes upduodenum pancreatic duct
Autodigestion of the Pancreas• Activated enzymes begin to digest the pancreas cells – Severe pain results – Inflammation produces large volumes of serous exudate hypovolemia• Enzymes (amylase, lipase) appear in the blood• Areas of dead cells undergo fat necrosis – Calcium from the blood deposits in them º Hypocalcemia
Chronic Pancreatitis and Pancreatic• Cancer to acute pancreatitis Have signs and symptoms similar• Often have: – Digestive problems because of inability to deliver enzymes to the duodenum – Glucose control problems because of damage to islets of Langerhans – Signs of biliary obstruction because of underlying bile tract disorders or duct compression by tumors