The Liver

Question 1

What is the liver?

Answer 1

• it is the largest gland in the body
• it is situated in the upper right section of the abdominal cavity
• with the right hypochondriac region under the diaphragm

Question 2

Describe the macrostructure of the liver

Answer 2

• the liver is enclosed in a dense capsule of connective tissue an is covered almost completely by peritoneum
• it is divided into right and left lies by the falciform ligament, it is attached it the under-surface of the diaphragm and holds the liver in position
• a second ligament (ligamentum teres) extends from th falciform ligament to the umbilicus
• the portal fissure is a structure situated on the posterior surface of the liver, where vessels and nerve fibres enter and leave

Question 3

Describe the microstructure of the liver

Answer 3

• the liver is composed of a large number of hepatic lobules formed from hepatocytes
• a central sinusoid is situated within each one
  - -> they carry a mixture of venous and arterial blood which come into close contact with the lobules
• situated around the walls of the sinusoids are Kupffer cells, these are hepatic phagocytes
  - -> their function is to destroy worn-out blood cells, bacteria and toxins
• around the circumference of the lobules are portal canals carrying a branch of the portal vein and hepatic artery and a small bile duct

Question 4

What is bile and what is its function?

Answer 4

• bile is produced by the adult liver and stored in the gall bladder situated beneath the liver
• bile is a thick, alkaline, greenish-yellowish substance containing water, bile salts, bile pigments and cholesterol
• it is released intermittently into the duodenum via the bile duct and has a role in digestion and excretion
• bile aids the digestion of fats in the small intestine
• most of the bile salts are reabsorbed in the ileum and returned to the liver via the portal vein for recycling

Question 5

What are the functions of the liver?

Answer 5

• metabolism
  - -> the liver regulates blood sugar levels by converting glucose to glycogen in response to insulin and glycogen back to glucose in response to glucagon
  - -> it also metabolises stored fat for use by body cells, proteins are broken down and their waste products are prepared for excretion while the useful molecules are used in the production of other proteins, blood-clotting factors, antibodies and antitoxins
  - -> the liver is also involved in the detoxification of drugs and poisons as well as deactivating hormones no longer required by the body
• storage
  - -> the liver stores vitamin A, B12, D, E and K
  - -> it also stores, iron, copper and glycogen
• secretion
  - -> bile is produced by the liver and secreted from the gall bladder into the digestive tract to aid the breakdown of fats
  - -> urea is formed in the liver from waste products such as ammonia and carbon dioxide and is excreted as urine

Question 6

Describe the blood and nerve supply to the liver

Answer 6

• the hepatic artery supplies the liver with oxygenated blood
• the portal vein brings nutrient-rich blood directly from the digestive organs
• the hepatic veins drain into the inferior vena cava
• the autonomic nervous system controls the liver function

Question 7

Describe the changes that take place during pregnancy

Answer 7

• forced into a more superior posterior position by gravid uterus
• increased glycogen and triglyceride storage occurs in hepatic cells
• the raised level of oestrogen affects hepatic synthesis of plasma proteins, enzymes and lipids
• decrease in albumin (exaggerated by haemodilution) increase in fibrinogen and increased cholesterol synthesis