Please enable JavaScript.
Coggle requires JavaScript to display documents.
the functions carried out by the liver and jaundice (Regulation of…
the functions carried out by the liver and jaundice
Detoxification
alcohol is converted into a less toxic substance by the enzyme ethanol
dehydrogenase.
The liver converts toxic ammonia into urea.
Liver cells absorb toxic substances from the blood and convert them into non- toxic or less toxic
substances, using a range of chemical conversions.
Hepatocytes are the most numerous cells in the liver, and are the most active in removing and
processing chemical toxins from the blood.
They extract toxins from the plasma and begin a process to eliminate the toxins.
i. They chemically modify the toxin to make it less destructive.
ii. They add chemical components that make the (now modified) toxin water soluble.
iii. The water-soluble modified substance can be added back into the blood in order to be eliminated
by the kidneys as a component of urine.
Regulation of nutrient levels
Because the body cannot store proteins or amino acids, excess quantities of these in the diet are
broken down in the liver to be utilized as energy sources.
The liver processes the resulting nitrogenous waste.
It plays a key role in the regulation of circulating glucose by either storing glucose as glycogen or
breaking glycogen down to glucose.
One of the main functions of the liver is to regulate the quantity of nutrients circulating in the
blood.
The liver is responsible for managing circulating lipids which arrive in a variety of forms.
very low density lipoproteins (VLDL) are synthesized in hepatocytes.
Their purpose is to transport the triglycerides synthesized in the liver into blood plasma for
storage or use in the body.
Surplus cholesterol is converted into bile salts
Formation of bile
• Hepatocytes convert surplus cholesterol into bile salts.
• These bile salts are added to bilirubin to make the substance bile.
When bile is secreted into the small intestine, the bile salts emulsify droplets of lipid, greatly
speeding up lipid digestion by lipase.
Conversion of cholesterol to bile salt
Production of plasma proteins
The sequence of events for the production and secretion of protein for use outside of the cell
i. DNA within the nucleus of a hepatocyte synthesizes messenger RNA for a particular protein (transcription)
ii. mRNA exits the nucleus through a nuclear pore.
iii. mRNA binds a ribosome located on rough endoplasmic reticulum (ER).
iv. Plasma protein is synthesized (translation).
v. Plasma protein is transported by a vesicle to the Golgi apparatus.
vi. The Golgi apparatus possibly modifies the protein and surrounds the protein with another vesicle.
vii. The vesicle goes to the plasma membrane for exocytosis (secretion).
viii. The plasma protein enters the blood plasma.
Plasma proteins are processed by the Golgi apparatus in hepatocytes before being released into
the blood
Storage of nutrients in excess
iron
released when there is a deficit in the blood
fat soluble,the bile secreted during digestion is essential for absorbing them so that the body can use them. If bile production is compromised by liver damage, the proper absorption of these vitamins may be affected.
vitamin A,E, D, K
when the blood glucose level is too high, insulin stimulates hepatocytes to absorb glucose and convert it to glycogen for storage
some amino acids are stored as glycogen in the liver ans muscle cells
Breakdown of the RBCs
Components of red blood cells are recycled by the liver and the breakdown of erythrocytes starts with phagocytosis of red blood cells by Kupffer cells and iron is carried to the bone marrow to produce hemoglobin in new red blood cells
Kupffer cells in the walls of sinusoids in the liver are specialized macrophages that absorb and
break down damaged red blood cells by phagocytosis and recycle their components.
Some of this iron is stored within the liver and some is sent to bone marrow to be used in the
production of hemoglobin for new red blood cells.
The iron atom is removed from each heme group.
Once iron has been removed from the haem group, what remains of the molecule is a yellow
colored substance called bile pigment (bilirubin).
The globins are hydrolyzed to amino acids by peptidases, which are either recycled by being
released into the blood or metabolized by the liver.
The hemoglobin is split into iron containing heme groups and globins.
This is absorbed by the nearby hepatocytes and becomes a key component of bile
Causes of jaundice
Damage to red blood cells-Increased destruction of erythrocytes(e.g. anemia) will cause bilirubin levels to rise
Obstruction of the gallbladder or bile duct Preventing the secretion of bile, which will cause bilirubin levels to increase
Liver disease-Impaired removal of bilirubin by the liver may cause levels to build within the body
Consequences of jaundice
a form of brain damage that results in deafness and cerebral palsy
itchiness, paler than usual stools and darkened urine
Yellowish discoloration of the skin and whites of the eyes due to an accumulation of bilirubin in blood plasma and skin tissues