Lecture 23 Notes- Key Functions of the liver
Within the macrophage, haemoglobin is broken down into globin molecules (which are further
broken down into amino acids and released into the blood) and the heme group. The heme group
is then converted into biliverdin and then reduced to bilirubin. Bilirubin is released from the
macrophage and binds with plasma albumin in the blood which transports it to the liver. Within
the small intestine, bilirubin is metabolized by gut bacteria to produce urobilinogen.
Urobilinogen can remain in the gut and become oxidized by gut bacteria to produce stercobilin
which is voided in the feces (and gives the brown colour to feces). Urobilinogen can also leave
the gut and enter the kidney where it is converted to urobilin which is voided in the urine (and
gives urine its amber colour).
The liver can be damaged over time when it is constantly exposed to toxic substances. An
example of this is alcohol-induced liver damage. Over time, alcohol interferes with hepatocytes
mitochondrial function leading to accumulation of lipids and the formation of large lipid droplets
in the liver. This leads to a condition called a fatty liver.
Constant damage to the liver by toxic substances such as alcohol or infection by pathogens such
as the hepatitis C virus cause the formation of scar tissue and the gradual breakdown of healthy
liver tissue. This condition is termed cirrhosis
Metabolic Processing of Nutrients
The liver is involved in the metabolic processing of nutrients. After we eat, the liver receives
digested substances from the gut (via the hepatic portal vein) and can convert them into large
form for storage. For example, glycogen is synthesised from glucose, amino acids can be
converted to fatty acids (or proteins) and fatty a