Liver

Topic: Digestive System

The liver, the largest internal organ in humans, plays a vital role in the digestion of fats and detoxifying the blood. It produces bile: a digestive juice that is required for the breakdown of fatty components of the food in the duodenum.

The liver is an accessory organ of the digestive system, not part of the main path of the food. It produces bile that helps in the digestion of fats present in the food. The bile is stored in the gall bladder from where it is secreted in the small intestine. It helps in the digestion of fats and its absorption in the small intestine.

The liver is primarily composed of cells called hepatocytes. Hepatocytes contain large amounts of rough endoplasmic reticulum and free ribosomes. Hepatocytes are involved in the synthesis of cholesterol, bile salts, and phospholipids. They also take part in the detoxification, modification, and excretion of chemicals.

Excess glucose present in the blood is stored in the form of glycogen in the liver. This is known as glycogenesis. This glycogen is converted back to glucose whenever the body needs glucose, and blood glucose levels are low.  This is known as gluconeogenesis. This helps in the regulation of glucose levels in the blood.

The liver also detoxifies the blood by removing ammonia, and it also metabolizes alcohol and some drugs/toxins. Blood comes directly from the small intestine to the liver where it is detoxified.

Liver tissue also has the unique ability to regenerate partially after injury or illness.


Practice Questions

 

Khan Academy

 

MCAT Official Prep (AAMC)

Biology Question Pack, Vol. 1 Passage 9 Question 58

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Practice Exam 2 B/B Section Passage 6 Question 29

 

Key Points

• The liver is an accessory digestive organ that secretes bile. The bile is stored in the gall bladder and secreted into the small intestine.

• Bile helps in the digestion of fats and their absorption.

• The liver helps to maintain blood sugar level by storing excess glucose present in the blood as glycogen (glycogenesis) and converting it back to glucose when the blood glucose level is low (gluconeogenesis).

• The liver detoxifies blood by removing ammonia, alcohol and drugs or toxins by metabolizing them.


Key Terms

Bile: a fluid produced by the liver to digest the fats in the small intestine.

Duodenum: the first part of the small intestine

Detoxify: removal of toxins

Metabolize: breakdown of molecules or converting into other molecules

Hepatocyte: Any of the cells in the liver responsible for the metabolism of proteins, carbohydrates, and lipids, and detoxification

Glycogenesis: the storage of glucose as glycogen in the liver

Glycogen: a multibranched polysaccharide of glucose that serves as a form of energy storage in animals

Gluconeogenesis: the break down of glycogen stored into the liver to glucose

Ammonia: is a waste product made by your body during the digestion of protein



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