The Liver

Question 1

What are the functions of the Liver?

Answer 1

1. Metabolism (Proteins, Carbs, and Lipids) MOSTLY
2. Regulates Cholesterol Production and Excretion
3. Beta-Oxidation of FAs (for energy)
4. Bile Production
5. Degrades Hormones
6. Detoxifies Drugs and Toxins
7. Vitamin and Mineral Storage (B12, A, D, and Fe)

Question 2

How much blood is in the Liver at any given time?

Answer 2

“Think of the Liver like a wet sponge”

At any given time has almost 0.5 L of blood from the Systemic Circulation

Roughly 1 L deoxygenated blood is also moving through from the Portal System

Question 3

What is the Blood Supply to the Liver?

Answer 3

2 different sources:

1. Portal Vessels (1 L DEOXYGENATED BLOOD/min) come from intestines
2. Hepatic Artery (450 ml OXYGENATED BLOOD/min

Question 4

Liver has what percentage of Cardiac Output?

Answer 4

Roughly 25%

Question 5

Fill in the blanks:

Normally, the Liver has (BLANK) Capillary Pressures and (BLANK) Venous Pressures.

Answer 5

Normally, the Liver has VERY LOW Capillary Pressures and VERY LOW Venous Pressures.

Question 6

What is the normal Hepatic Vein pressure? Why?

Answer 6

LESS than 1 mmHg so that blood will not back up and can flow freely into the Vena Cava

Question 7

What is Portal Hypertension? What are the types of Portal Hypertension?

Answer 7

1. An increase in the normally very low (<1 mmHg) pressures of the Liver
2. 3 types:
   A. Pre-Hepatic Portal Hypertension (somewhere in the Portal System)
   B. Hepatic (scarring and cirrhosis of the liver)
   C. Post-Hepatic Portal Hypertension (in Portal Vein or Vena Cava)

Question 8

What could lead to Post-Hepatic Portal Hypertension?

Answer 8

Congestive Heart Failure increasing the pressure in the Vena Cava which increases the Hepatic Vein pressure causing a backup of blood in the Liver

Question 9

What cells make up the Liver?

Answer 9

1. Parenchymal cells secrete products into the Space of Disse (Interstitial Fluid) that can go into Lymphatic Vessels, Blood, or Bile Canaliculi
2. Kupffer Cells- fixed macrophages of the Liver that phagocytose waste like old RBCs

Question 10

Why is Cirrhosis so bad for the Liver?

Answer 10

1. Destroys Parenchymal Cells and Tissues

2. Creates scar tissue so blood CANNOT MOVE FREELY causing it to back up and INCREASE PRESSURE

Question 11

Obstructed Blood flow through the Liver can result in what symptoms?

Answer 11

1. Ascites (fluid in the Abdomen)
2. Acromegaly
3. Jaundice

Question 12

Ascites:

1. What is it?
2. How is it caused?
3. What are compensatory methods in the body?

Answer 12

1. A collection of fluid in the Abdomen
2. Cause of Ascites:
   A. Blood backed up in the Liver’s capillaries causes an increase in Hydrostatic Pressure of the Liver
   B. Increased Pressure causes Serous parts of the Blood (plasma and proteins) to be squeezed out into the Abdomen
3. Kidneys and Heart must compensate to elevate BP (possibly get Hepatomegaly?

Question 13

Hepatomegaly:

1. What is it?
2. How is it caused?
3. What are compensatory methods in the body?

Answer 13

1. Increase in Liver size
2. Fluid retention or excess fat causes the Liver to increase from around 0.5 L blood to around 1 L blood
3. Heart must increase TPR to increase BP

Question 14

Jaundice:

1. What is it?
2. How is it caused?
3. What are compensatory methods in the body?

Answer 14

1. Increased Bilirubin in the blood causing yellowing of skin, nail beds, eyes, etc.
2. 4 different kinds with different causes:
   A. Obstructive Jaundice (obstructed Bile Ducts leads to lower excretion of Bile)
   B. Hepatic Jaundice (Hepatitis, Drugs, Cirrhosis can lead to nonfunctional Hepatocytes)
   C. Hemolytic Jaundice (increased hemolysis of RBCs due to Malaria, Sickle-Cell, etc)
   D. Neonatal Jaundice (Liver is “Not ready to work yet” in newborns)

Question 15

What is the only cause of Jaundice that is unrelated to the Liver?

Answer 15

Hemolytic Jaundice which is caused by an increase in the hemolysis of RBCs due to genetic diseases such as Malaria and Sickle-Cell that release Bilirubin into the blood faster than the Bile can excrete it

Question 16

How does the Liver metabolize Carbohydrates?

Answer 16

The Liver is a “Blood Glucose Monitor” because without it levels could be 3x as high

1. Glycogen Storage
2. Glycolysis
3. Gluconeogenesis (from AAs and Triglycerides)
4. Conversion of Monosaccharides to Glucose
5. Formation of Chemical Compounds

Question 17

What is important about the Liver’s Glucose Transporters?

Answer 17

Liver has INSULIN-INDEPENDENT GLUT2 Glucose transporters that allow for high capacity transport

Question 18

How does the Liver metabolize Lipids?

Answer 18

Lipids come into the Liver via Systemic Circulation and are metabolized into building blocks for steroids and cell membranes, made into energy, and regulate cholesterol

1. High rate of Beta-Oxidation of Fatty Acids for energy (TCA)
2. Forms most Lipoproteins (VLDL, LDL, HDL)
3. Synthesizes a lot of Cholesterol and Phospholipids (HMG CoA Reductase catalyzes cholesterol synthesis)
4. Converts unused carbs to Triglycerides (make fat)

Question 19

What are Lipoproteins?

Answer 19

1. Carrier Substances made of lipids and proteins that travel to tissues that need supplies
2. 3 main types:
   A. Low Density (LDL)- BAD because they are mostly cholesterol and phospholipids that stick to arteries
   B. High Density (HDL)- GOOD 50% protein; get rid of fats
   C. Very Low (VLDL)- take triglycerides to be stored as fat

Question 20

How does the Liver metabolize Protein?

Answer 20

MOST DETRIMENTAL IF BAD because it BUFFERS ACID

1. Deaminate Amino Acids not being used into Ammonia (toxic)
2. Produces Urea from toxic Ammonia for excretion
3. Synthesize 90% of Plasma Proteins (Albumins, Globulins, Fibrinogen)
4. Interconversion of Amino Acids transforming them into ones that may be needed