D.3 Functions of the liver Flashcards
Blood arrives at the liver from which two sources?
Hepatic artery and hepatic portal vein
Where does the hepatic artery come from and what blood does it bring?
- branches off from the aorta
- bringing oxygen-rich blood from the heart
What is majority of the blood circulating in the liver from?
From the hepatic portal vein
Where does the hepatic portal vein come from and what blood does it bring?
- brings blood from the stomach and the intestine to the liver
- blood can be rich in nutrients that have been absorbed from digested blood depending on how revently the individual has eaten
- Because the blood travelled from the heart to the stomach or intestine first, the oxygen content is relatively low
Why is the oxygen content relatively low in the blood from the haptic portal vein?
The blood travelled from the heart to the stomach or intestine first
Why is the oxygen content relatively low in the blood from the haptic portal vein?
The blood travelled from the heart to the stomach or intestine first
Within the liver, the vein subdivides into what?
into subdivisions called sinusoids
What are sinusoids like?
Like capillaries but are wider and the walls are not continuously lined with cells
What does the sinusoid allow for?
- Blood flowing through to come in contact with the hepatocytes (liver cells)
- allow proteins such as albumin to enter and leave the blood
What do hepatic artery subdivide into?
into arterioles, which join with the sinusoids at various points to provide oxygenated blood
What joins the sinusoid to provide oxygenated blood?
Arterioles subdivided from hepatic artery
What do sinusoids merge with?
with venules that lead to the hepatic vein
Why does the sinusoid merge with venules from the hepatic vein?
to carry the blood away fromthe liver to the vena cava
What is one of the main functions of the liver?
to regulate the quantity of nutrients circulating in the blood
* e.g. glucose -> glycogen -> glucose
How does the liver treat proteins?
- the body cannot store proteins or amino acids
- excess quantities are broken down in the liver and utilized as energy sources
- the liver processes the resulting nitrogenous waste
How does the liver respond to lipids?
- liver is responsible for managing circulating lipids which arrive in a variety of forms
- the liver processes lipids in one form and distributes it in other forms
How does the liver treat chylomicrons?
Some forms such as chylomicrons arriving from the intestine are broken down in the liver
How dos the liver transport tryglycerides?
Very low density lipoproteins (VLDL) are synthesized in the hepatocytes. Their purpose is to transport the triglycerides synthesized in the liver into blood plasma for storage or use in the body
What does the liver do to surplus cholesterol?
convert it into bile salt
How does the liver respond to high and low levels of glucose in the blood?
High
* release insulin
* insulin stimulates hepatocytes to take up the glucose and store as glycogen
Low
* hormones such as glucagon is released
* breakdown of glycogen, glycerol, amino acids and fatty acids in the liver
* release glucose to the blood stream
What minerals are stored in the liver in excess?
Iron, retinol (vitamin A), calciferol (vitamin D)
* released when there is a deficit in the blood
What is the typical lifespan of an erythrocyte?
(red blood cell)
in an adult, about 120 days
What changs do old and damaged erythrocytes undergo?
changes in their plasma membrane which make them susceptible to recognition by macrophages
What happens at the end of erythrocytes’ lifespan?
- removed from circulation
- broken down in the spleen and liver
- Liver breaks down the erythrocytes and hemoglobin
- most of the breakdown products are recycled