1. H4 Functions of the Liver
Liver Video (3:51)

2. Blood Flow Through The Liver
The liver is the largest organ in the abdomen.
Blood Supply
Hepatic portal vein
Carries blood away
Brings blood from the gut
Hepatic portal artery
Oxygen rich blood from the heart

3. Functions
Regulate levels of nutrients before blood flows back to the rest of the body
Glucose regulation
Stores glycogen (controlled by insulin produced by the β-islet cells in the pancreas)
Breaks down glycogen to glucose (controlled by the glucagon released from α cells of pancreas)
Excess amino acids and proteins are broken down in the liver and used for energy.
Processes the nitrogenous waste (Ammonia is converted to Urea).
Production of plasma proteins
Albumin – used to regulate osmolarity of blood

4. Functions: Regulates circulation of lipids
Cholesterol
Phospholipids
Bile – responsible for emulsifying fat molecules to allow for absorption.
Detoxification (e.g. alcohol, drugs)
Store fat soluble vitamins
Vit. A and D , E & K
Water soluble B12 and minerals such as Fe and Cu
Breaks down erythrocytes (life span 120 days) and Hemoglobin
Kupffer cells engulf and break down

5. H.4.1  Outline the circulation of blood through liver tissue, including the hepatic artery, hepatic portal vein, sinusoids and hepatic vein
The liver is divided into segments called lobules which contain liver cells (hepatocytes)
Each lobule is surrounded by branches of the hepatic artery and the hepatic portal vein
The hepatic artery carries oxygenated blood from the heart to the liver
The hepatic portal vein carries nutrient-laden blood from the intestines

6. circulation of blood through liver tissue
The hepatic artery and hepatic portal vein both connect to blood vessels called sinusoids
The sinusoids drain into a central vein, which feeds into the hepatic vein
The hepatic vein carries deoxygenated blood from the liver to the heart

7. Liver Lobule

10. H.4.2  Explain the role of the liver in regulating levels of nutrients in the blood
Many substances in the blood need to be kept within homeostatic limits to prevent damaging effects
Sugar and salt levels need to be controlled in order to maintain the osmolarity of the blood and surrounding tissue
Amino acids cannot be stored by the body and must be detoxified when in excess
Many minerals and vitamins are essential for specific biological processes (e.g. vitamin A and vision), and so must be sequestered when not in use

11. Nutrient regulation cont.,
Absorbed nutrients pass through the liver (via the hepatic portal vein) prior to entering general circulation
This enables the liver to regulate and maintain viable levels of nutrients in the blood in spite of variations in dietary intake and feeding frequency
The liver stores excess glucose as glycogen granules within hepatocytes, and digests this glycogen when blood glucose levels are low
The liver is responsible for the deamination of excess amino acids (made into ammonia before being converted into urea)

12. H.4.3  Outline the role of the liver in the storage of nutrients, including carbohydrate, iron, vitamin A and vitamin D

13. H.4.4 State that the liver synthesizes plasma proteins and cholesterol
The liver synthesis cholesterol, which is involved in bile production and is a component of animal cell membranes
S-ER
The liver is also involved in the synthesis of plasma proteins, which serve a variety of roles
R-ER in liver produced 90% plasma proteins.
Albumin – helps regulate osmotic pressure of body fluids
Fibrinogen – soluble precursor of the clotting protein fibrin

14. H.4.5 State that the liver has a role in detoxification
Detoxification is the removal of a toxic substance from a living organism
The liver plays a role in the detoxification of a number of molecules, including:
alcohol
metabolic products
food preservatives
Drugs
and poisons

16. H.4.6  Describe the process of erythrocyte and hemoglobin breakdown in the liver, including phagocytosis, digestion of globin and bile pigment  formation
Erythrocytes rupture when they reach the end of their life span (~ 120 days)
Kupffer cells are phagocytes found within the sinusoid lumen which engulf the contents and break down hemoglobin into globin and heme groups
Globin is digested by peptidases to produce amino acids (which are either used in the synthesis of new proteins or metabolized by the liver)
iron removed from heme group / heme broken down to form bilirubin/bile pigment;

17. Heme groups are broken down into iron and bilirubin (bile pigment)
The iron is transported to either the liver (for storage) or the bone marrow (to make new blood cells)
The bilirubin is transported to the liver to be released as part of bile into the alimentary canal

18. Process of Erythrocyte and Haemoglobin Breakdown

19. Be able to label
I. Hepatic cells; 2. Central vein; 3. sinusoids

20. Label

21. H.4.7 Explain the liver damage caused by excessive alcohol consumption
Alcohol is metabolized by the liver to form products that may be toxic to cells (alcohol consumption also reduces cellular antioxidant activity)
Ethanol →acetaldehyde C2 H5OH→ CH3CHO),

22. liver damage
This leads to the replacement of healthy liver cells with fibrous scar tissue, which reduces the liver's ability to:
Metabolize the body's supply of carbohydrates, fats and proteins
Produce bile and remove toxins from the body
Transport materials around the body (blocks blood flow to and from liver)
nutritional deprivation / susceptible to infection/hepatic viruses;
products of alcohol metabolism toxic to cells / alcohol consumption reduces antioxidant activity;
scar tissue blocks blood flow through liver / loss of functional liver cells / blocks normal metabolic carbohydrates/fats/proteins;

23. liver damage
Over time this may lead to nutritional deprivation and an increased susceptibility to infection

24. Long term alcohol abuse (i. e
Long term alcohol abuse (i.e. excessive drinking) results in three primary effects upon the liver:
1.  Inflammation – swelling of damaged liver tissue (sometimes called alcoholic hepatitis)
2.  Fat accumulation – build up of fat in place of normal liver tissue
3.  Cirrhosis – scar tissue left when areas of liver are destroyed by prolonged alcohol exposure