BCH Biochemical Functions of Organs Flashcards
Briefly describe the liver
The liver is a complex organ that is responsible for more than 500 vital functions in the body. The functional integrity of the liver is important to the health of the human organism and this depends on constant maintenance of the numerous biochemical functions of the liver and the diverse metabolic processes occurring in the hepatocytes and sinusoidal cells.
The liver accepts substances brought with blood through the portal vein and these penetrate the hepatocytes where they undergo chemical transformations to become intermediates or final metabolites before being carried to other organs and tissues.
Classification of liver function
Synthetic function
Metabolic function
Detoxification and Excretion
Homeostasis
Storage function
Production of bile salts
Describe the synthetic function of the liver
Synthetic function
-synthesis of plasma proteins (albumin, coagulation factors, globulins)
- cholesterol and bile acids
-triacylglycerol
-Lipoprotein
Describe the metabolic function of the liver
Metabolic function
-Carbohydrate(Glycolysis, glycogenesis, glycogenolysis, gluconeogenesis)
-Ketogenesis
- fatty acid synthesis and breakdown
-Protein catabolism
-Citric acid cycle, production of ATP
Describe the Detoxification and Excretion function of the liver
Detoxification and Excretion
-Ammonia to Urea
-Bilirubin (bile pigment)
-Drug metabolites
Describe the Homeostatic function of the liver
Homeostasis: Blood glucose regulation
Describe the Storage function of the liver
Storage function: Vitamin A, D, E, K and B12
Describe the Production of bile salts function of the liver
aids digestion
What is the liver function test?
Aliver function test is one of a group of tests that check levels of certain enzymes and other proteins in theblood.
Some of the tests look for enzymes that are present in the blood when the liver is damaged or has a disease. Other tests will check for the proper functioning of the liver.
General symptoms of liver problems include
-Lack of appetite
-Nausea or vomiting
-Weakness or feeling verytired
-Yellowisheyes or skin (jaundice)
- Dark urine or light poo
-Swelling of belly
Types of Tests and What They Measure
Alanine transaminase (ALT) test:ALT is anenzymethat helps break down proteins and is found mainly in the liver. High levels in the blood could mean liver damage.
Alkaline phosphatase (ALP) test.ALP is an enzyme in the liver, bile ducts, andbone. High levels could mean liver damage or disease, a blocked bile duct, or bone disease.
Albumin and total protein test.The liver makes two main proteins: albumin and globulin. Low levels might mean damage or disease.
Aspartate transaminase (AST) test.AST is another enzyme in the liver. High blood levels could be a sign of damage or disease.
Bilirubin test. The body makes bilirubin when red blood cells are broken down. Normally, liver cleans bilirubin out of the body. However, high levels in the blood, could mean jaundice, which indicates liver damage.
Gamma-glutamyltransferase (GGT) test.High levels of the GGT enzyme could indicate liver or bile duct damage.
Prothrombin time (PT) test.This test measures how long it takes the blood to clot. If it takes a long time, it could be a sign of liver damage.Medicationsthat thin the blood, such aswarfarin, can also lead to a longer PT. This test may not be necessary until other tests have been carried out
Kidney Functions
The major role of the kidneys is to maintain homeostasis.
Homeostasis: the management of fluid levels, electrolyte balance, and other factors to keep the internal environment of the body consistent and comfortable.
The Kidneys serve a wide range of functions:
Waste excretion
The kidneys remove waste products and get them into the urine e.g. urea, uric acid, creatinine, etc.
Reabsorption of nutrients:
They reabsorb other products to help maintain homeostasis. E.g. glucose, amino acids, bicarbonate, sodium, water, phosphate, chloride, sodium, magnesium, and potassium ions.
Maintaining pH
The acceptable pH level in human is between 7.36 and 7.44. The kidneys ensure a stable pH within the human body through two processes:
-Reabsorbing and regenerating bicarbonate from urine (Bicarbonate helps to neutralize acids). The kidneys can either retain bicarbonate if the pH is tolerable or release bicarbonate if acid levels rise.
-Excreting hydrogen ions and fixed acids (Fixed or nonvolatile acids are acids that do not occur as a result of carbon dioxide). These result from the incomplete metabolism of carbohydrates, fats, and proteins such as lactic acid, sulfuric acid, and phosphoric acid.
Osmolality regulation
Osmolality is a measure of the body’s electrolyte-water balance. Dehydration is a primary cause of electrolyte imbalance. If osmolality rises in the blood plasma, the hypothalamus in the brain responds by passing a message to the pituitary gland. This, in turn, releases antidiuretic hormone (ADH). In response to ADH, the kidney makes a number of changes, including: increasing urine concentration; increasing water reabsorption; reopening portions of the collecting duct that water does not normally enter, allowing water back into the body; retaining urea in the medulla of the kidney rather than excreting it, as it draws in water.
Endocrine function: Erythropoietin
This controls erythropoiesis, or the production of red blood cells. The liver also produces erythropoietin, but the kidneys are main producers in adults.
Renin: This manages the expansion of arteries and the volume of blood plasma, lymph, and interstitial fluid. Lymph is a fluid that contains white blood cells, which support immune activity, and interstitial fluid is the main component of extracellular fluid.
Calcitriol: This is the hormonally active metabolite of vitamin D. It increases both the amount of calcium absorbed by the intestines and the reabsorption of phosphate in the kidney.
Kidney Function Test
Kidney function tests areurine or blood tests that evaluate how well the kidneys are working. Most of these tests measure glomerular filtration rate (GFR). GFR assesses how efficiently the kidneys clear waste from the system.
The kidneys play avital role in the:
-excretion of waste products and toxins such as: -urea, creatinine and uric acid
-regulation of extracellular fluid volume, serum osmolality and electrolyte concentrations
-production of hormones like 1,25 dihydroxycholecalciferol (vit. D), erythropoietin and renin.
Tests of renal function are used in identifying the presence of renal disease, monitoring the response of kidneys to treatment, and determining the progression of renal disease.
What is the Glomerular Filtration Rate?
The normal GFR fr an adult male?
What are the characteristics of an ideal marker?
The best overall indicator of the glomerularfunction is the glomerular filtration rate (GFR). GFR is the rate in milliliters per minute at which substances in plasma are filtered through the glomerulus i.e. the clearance of a substance from the blood.
The normal GFR for an adult male is 90 to 120 mL per minute.
The characteristics of an ideal marker of GFR are as follows:
It should appear endogenously in the plasma at a constant rate
It should be freely filtered at the glomerulus
It should not be reabsorbed nor secreted by the renal tubule
It should not undergo extra renal elimination.
Exogenous markers
Exogenous markers of GFR are used in the absence of such endogenous marker.
Assessment of GFR using inulin, a polysaccharide, is a reference method for the estimation of GFR. It involves the infusion of inulin and then the measurement of blood levels after a specified period to determine the rate of clearance of inulin.
Others are radioisotopes such aschromium-51 ethylene-diamine-tetra-acetic acid (51 Cr-EDTA), and technetium-99-labeled diethylene-triamine-pentaacetate (99 Tc-DTPA).
