Clinical Chemistry Test 2 Preps
Chapter 25 Liver function
BACKGROUND
• It is the largest internal organ of the human body
• It plays a critical role in the metabolism, digestion, detoxification and elimination of substances from
the body.
• It is involved in a number of excretory, synthetic, metabolic and detoxification functions that are
essential for life.
• Unique organ that regenerates the cells that have been destroyed by short term injury or disease.
• Irreversible changes also occur caused by repeated long term damage
• Laboratory tests are used to assess or diagnose the liver disorders
GROSS ANATOMY
• It is the large complex organ and weighs appr. 1.2 – 1.5kg in healthy adults.
• It is located beneath and it is attached to diaphragm and is protected by the rib cage and hold by
ligamentous attachments.
• It is divided unequally into two lobes right lobe is larger than the left lobe.
• It is the very vascular organ that receives blood supply from hepatic artery(oxygen-rich 25%) and
portal vein(nutrient-rich 75%).
• The two blood supplies eventually merge into the hepatic sinusoid, which is lined with hepatocytes
capable of removing potentially toxic substances from the blood
MICROSCOPIC ANATOMY
• It is divided into microscopic units called lobules and they are responsible for metabolic and
microscopic functions of the liver.
• Each lobule is roughly a six-sided structure with a centrally located vein (called the central vein) with
portal triads at each of the corners. Each portal triad contains a hepatic artery, a portal vein, and a
bile duct surrounded by connective tissue.
• It contained two major cell types, hepatocytes (80%) and Kupffer cells.
BIOCHEMICAL FUNCTIONS
• It performs 4 major functions
• Excretion and secretory
• Synthesis/Metabolic
• Detoxification
• Storage
Death will occur in 24hrs if it becomes non functional due to hypoglycemia.
EXCRETION AND SECRETORY
• The important function is excretion of endogenous and exogenous substances into the bile or urine
i.e heme to bilirubin.
• Bilirubin is the principal pigment in bile and bile is made of bile acids , salts, bile pigment,
cholesterol and other substances from the blood.
, • 3L of bile is secretes and 1L is excreted per day.
• Bilirubin is derived from breakdown of RBC’s appr. 126 days.
• Hb is broken to heme, globin , iron and iron is stored in iron stores, globin in degraded to its AA
• RBC destruction-------Heme—(converted)-----Bilirubin----( binds to albumin)----uncoj bili---- (flows to
the liver)--------- (esterification occurs in the presence of UDPGT)- conjugated bili--------flows to
intestines(bacterial action)---mesobilirubin------- urobilinogen.
METABOLISM
• The liver is responsible for carbohydrates, lipids & protein synthesis.
• The carbohydrate synthesis is the most important function of the liver.
• Carbohydrates are ingested and the liver does 3 things:
• provide energy cellular requirements
• Circulate glucose to peripheral tissues
• Store glucose as glycogen
Liver plays a part in keeping glucose levels stable
• Lipids are synthesized in the liver under normal circumstances when nutrition is adequate and
glucose demand is being met.
• It is responsible for gathering free fatty acids from the diet and producing acetyl CoA and then Acetyl
CoA enter several pathways.
• All proteins are synthesized by the liver except for immunoglobulin and adult Hb.
• It plays an essential role in infant Hb.
• It is responsible for synthesizing albumin, acute phase reactants and coagulation proteins
DETOXIFICATION
• It serves as a gatekeeper (first pass) between substances coming from GIT and those released into
systemic circulation.
• It serves as a barrier to prevent toxic or harmful substances form reaching the systemic circulation.
• It can either bind the substance to inactivate or chemically modify the substance to excrete it.
• It does it through oxidation, reduction, hydroxylation, carboxylation and demethylation.
