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D3 Functions of The Liver

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D3 Functions of The Liver

Flipped Learning Opportunity

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D3 Functions of The Liver

There is overwhelming evidence for the evolution of life on Earth.

Essential Idea

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D3 Functions of The Liver

D.3.A2: Dual blood supply to the liver and differences between sinusoids and capillarie

Hepatic Vein (to the Vena Cava)

Hepatic Artery (from the Aorta) 25% Blood (Oxygen Rich)

Hepatic Portal Vein (from the intestines) 75% Blood (Nutrient Rich)

Liver

Stomach

Bile Duct

Pancreas

Bile

Gall Bladder

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D3 Functions of The Liver

D.3.A2: Dual blood supply to the liver and differences between sinusoids and capillarie

Liver

Liver Lobules

Lobule

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D3 Functions of The Liver

D.3.A2: Dual blood supply to the liver and differences between sinusoids and capillarie

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Kupffer Cell

Single Layer Epithelial Cells

Branch of Hepatic Artery

Branch of Hepatic Vein

Branch of Portal Vein

Hepatocytes

Lumen of sinusoid

D3 Functions of The Liver

D.3.A2: Dual blood supply to the liver and differences between sinusoids and capillarie

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D3 Functions of The Liver

D.3.A2: Dual blood supply to the liver and differences between sinusoids and capillarie

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  • Sinusoids are small, irregular, vascular spaces which are closely surrounded by the cells of the organ. They replace capillaries in certain organs, like liver, spleen and bone marrow.
  • Sinusoids differ from capillaries in the following respects:
  • Their lumen is wider (up to 30 micron) and irregular.
  • Their walls are thinner and may be incomplete. They are lined by endothelium (Kupffer Cells) in which the phagocytic cells are often distributed.
  • These may connect arteriole with venule (spleen, bone marrow)

D3 Functions of The Liver

D.3.A2: Dual blood supply to the liver and differences between sinusoids and capillarie

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D3 Functions of The Liver

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  • The portal vein brings blood from parts of the digestive tract to the liver. Substances absorbed in the small intestine travel in the blood to the liver for processing before continuing to the heart and the rest of the body.
  • Since this blood is coming straight from the digestive tract, it is full of nutrients that have just been absorbed (glucose, amino acids, toxins, triglycerides)�

D3 Functions of The Liver

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a. both have walls 1 cell thick/same thickness�OR�both have a basement membrane;�b. sinusoids have pores/holes/fenestrations�OR�sinusoids have a wider lumen;

D3 Functions of The Liver

Compare sinusoids to capillaries.

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Hepatic Vein

Deoxygenated Blood

Hepatic Artery

Deoxygenated Blood

Gastrointestinal Tract (Small Intestine)

Hepatic Portal Vein (Full of nutrients)

Bile Duct

D3 Functions of The Liver

D.3.A2: Dual blood supply to the liver and differences between sinusoids and capillarie

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  • Try your hand at being an artist – sketch or model the liver

D3 Functions of The Liver

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D3 Functions of The Liver

D.3.A2: Dual blood supply to the liver and differences between sinusoids and capillarie

Hepatic Vein (to the Vena Cava)

Hepatic Artery (from the Aorta) 25% Blood (Oxygen Rich)

Hepatic Portal Vein (from the intestines) 75% Blood (Nutrient Rich)

Liver

Stomach

Bile Duct

Pancreas

Bile

Gall Bladder

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stores iron from the haemoglobin in a ferritin protein.store glucose as glycogen

stores glucose as glycogen

stores Vitamin A, D

synthesises amino acids and proteins such as globulins, albumin and fibrinogen

converts amino acids to glucose/lipids

removes ammonia

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D3 Functions of The Liver

D.3.U8 Some nutrients in excess can be stored in the liver.

 

Storage

Glucose is a fuel required for cellular respiration

 The liver will store glucose as glycogen when blood glucose levels are high and will break glycogen down to glucose when blood glucose levels are low. 

Iron is a component of haemoglobin and is required for oxygen transport to cells

 The liver breaks down erythrocytes (red blood cells) and stores the iron from the hemoglobin in a ferritin protein.

Vitamin A (AKA retinol) is part of the pigment rhodopsin found in eye rod cells

 Vitamin A absorbed by the digestive tract can be stored in lipids droplet inside the liver cells.

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Vitamin D (AKA calciferol) helps in the uptake of calcium by cells and can be made by the skin cells

 Storing vitamin D in the liver can supply the body’s needs through the winter months (when exposure to UV light is often reduced).

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Role of Nutrient in the Body

Storage

Glucose

Fuel required for cellular respiration

The liver will store glucose as glycogen when blood glucose levels are high and will break glycogen down to glucose when blood glucose levels are low. 

 

D3 Functions of The Liver

D.3.U8 Some nutrients in excess can be stored in the liver.

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Regulation and Storage of Iron

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D3 Functions of The Liver

D.3.U8 Some nutrients in excess can be stored in the liver.

Role of Nutrient in the Body

Storage

Iron

Iron is a component of hemoglobin and is required for oxygen transport to cells

The liver breaks down erythrocytes (red blood cells) and stores the iron from the hemoglobin in a ferritin protein. Ferritin protein can store iron in a non-toxic form transport it to areas where iron is required.

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Iron is a vital component of the hemoglobin transport protein and is required for oxygen to be transported to cells.

D3 Functions of The Liver

Regulation and Storage of Iron

D.3.U8 Some nutrients in excess can be stored in the liver.

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  • Iron is toxic to cells when it is free floating.
  • Ferritin protein can store iron in a non-toxic form transport it to areas where iron is required.
  • Ferritin has a quaternary protein structure made up of 24 polypeptide subunits!
  • The ferritin protein is shaped as a hollow sphere in which iron can be stored in the center.
  • Each ferritin protein can store about 4500 iron ions!

D3 Functions of The Liver

Ferritin: the iron storage protein

D.3.U8 Some nutrients in excess can be stored in the liver.

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D3 Functions of The Liver

Foods Rich in Vitamin A (retinol)

D.3.U8 Some nutrients in excess can be stored in the liver.

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Role of Nutrient in the Body

Storage

Vitamin A

Vitamin A (AKA retinol) is part of the pigment rhodopsin found in eye cone cells

Vitamin A absorbed by the digestive tract can be stored in lipids droplets inside the liver cells.

D3 Functions of The Liver

Regulation and Storage of Vitamin A

D.3.U8 Some nutrients in excess can be stored in the liver.

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Regulation and Storage of Vitamin D

  • Vitamin D is also known as calciferol
  • An inactive precursor of vitamin D is synthesized in skin cells from cholesterol
  • The liver and kidney then convert the precursor molecule to active vitamin D
  • Vitamin D is needed by cells so they can absorb calcium (especially important for heart, nerve and bone health).

D3 Functions of The Liver

Regulation and Storage of Vitamin D

D.3.U8 Some nutrients in excess can be stored in the liver.

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Regulation and Storage of Vitamin

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Role of Nutrient in the Body

Storage

Vitamin D

Vitamin D (AKA calciferol) helps in the uptake of calcium by cells and can be made by the skin cells

Storing vitamin D in the liver can supply the body’s needs through the winter months (when exposure to UV light is often reduced).

D3 Functions of The Liver

Regulation and Storage of Vitamin D

D.3.U8 Some nutrients in excess can be stored in the liver.

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Some nutrients in excess can be stored in the liver.

  • List four example nutrients that can be stored by the liver.

D3 Functions of The Liver

Checkpoint

D.3.U8 Some nutrients in excess can be stored in the liver.

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D3 Functions of The Liver

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  • Many digested food molecules absorbed into the blood in the small intestine are carried to the liver for assimilation (when food molecules are converted to other molecules that the body needs)
  • These include amino acids, which are used to build proteins such as fibrinogen, a protein found in blood plasma that is important in blood clotting
  • Excess amino acids absorbed in the blood that are not needed to make proteins cannot be stored, so they are broken down in a process called deamination
  • Enzymes in the liver split up the amino acid molecules
  • The part of the molecule which contains carbon is turned into glycogen and stored
  • The other part, which contains nitrogen, is turned into ammonia, which is highly toxic, and so is immediately converted into urea, which is less toxic
  • The urea dissolves in the blood and is taken to the kidney to be excreted
  • A small amount is also excreted in sweat

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D3 Functions of The Liver

Liver Comprehension

D.3.U1 The liver removes toxins from the blood and detoxifies them.

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D3 Functions of The Liver

D.3.U2 Components of red blood cells are recycled by the liver.

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D3 Functions of The Liver

D.3.U6 Endoplasmic reticulum and Golgi apparatus in hepatocytes produce plasma proteins.

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D3 Functions of The Liver

Synthesis of Albumins and Globulins 

D.3.U6 Endoplasmic reticulum and Golgi apparatus in hepatocytes produce plasma proteins.

  • Albumin and globulin proteins are the main types of protein found in human blood plasma and are used to transport molecules in the blood.  
    • Cations (such as Ca2+, Na+ and K+), fatty acids, hormones, bilirubin and pharmaceuticals are transported in the blood attached to albumins.
    • Oxygen is transported in the blood attached to hemoglobin.

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D3 Functions of The Liver

D.3.U6 Endoplasmic reticulum and Golgi apparatus in hepatocytes produce plasma proteins.

Synthesis of Albumins and Globulins

Rough ER in hepatocytes produce 90% of the proteins in blood plasma.

Synthesis of Fibrinogens

Fibrinogen is synthesized in the liver by the hepatocytes. Fibrinogen is required in the formation of blood clots.

Conversion of amino acids to glucose or lipids

Amino acids and proteins are not stored in the body. Excess quantities of protein in the diet are broken down and converted in the liver to be stored as carbohydrate or lipid energy sources.

Removing ammonia from the body

The toxic byproduct ammonia comes from the metabolism of amino acids into glucose.

Synthesis of amino acids

All tissues have some capability for synthesis of the non-essential amino acids. However, the liver is the major site of amino acid synthesis in the body.

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D3 Functions of The Liver

D.3.A1 The breakdown of erythrocytes starts with phagocytosis of red blood cells by Kupffer cells.

Transferrin Receptors allows transferrin (Fe) in from the blood are: spleen, liver and bone marrow

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  • Jaundice is a condition caused by an excess of bile pigment – bilirubin – within the body
  • Bilirubin is produced as part of the natural breakdown of haemoglobin by the liver
  • Normally, the liver conjugates this bilirubin to other chemicals and then secretes it in bile
  • When there is an excess of bilirubin, it may leak out into surrounding tissue fluids
  • Jaundice may be caused by any condition which impairs the natural breakdown of red blood cells, including:
  • Liver disease – impaired removal of bilirubin by the liver may cause levels to build within the body
  • Obstruction of the gall bladder – preventing the secretion of bile will cause bilirubin levels to accumulate
  • Damage to red blood cells – increased destruction of erythrocytes (e.g. anemia) will cause bilirubin levels to rise�The main consequence of jaundice is a yellowish discoloration of the skin and whites of the eyes (sclera)
  • Other common symptoms include itchiness, paler than usual stools and darkened urine
  • Jaundice may be resolved by treating the underlying cause for the build up of bilirubin within the body

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D3 Functions of The Liver

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  • Cholesterol is transported from the liver to body cells as part of low density lipoprotein (LDL).
  • Excess cholesterol is transported from body cells to the liver for removal from the body as part of high density lipoprotein (HDL).

D3 Functions of The Liver

D.3.U5 Surplus cholesterol is converted to bile salts.

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BILE

Bile is a dark green to yellowish brown fluid, produced by the liver of most vertebrates that aids the digestion of lipids in the small intestine. In humans, bile is produced continuously by the liver, and stored and concentrated in the gallbladder. After eating, this stored bile is released into the small intestine. Bile is made of water, bile salts, bilirubin and fats.

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HDL brings excess cholesterol to the liver.

So, how does the liver get rid of it?

Hint! Hint! Hint!

D3 Functions of The Liver

D.3.U5 Surplus cholesterol is converted to bile salts.

Bile is made of

Bile Salts

Cholesterol

Phospholipids

Bilirubin

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  • AKA “bile pigments”
  • The waste product of hemoglobin recycling that is excreted as waste

Remember me?

D3 Functions of The Liver

Bilirubin

D.3.U5 Surplus cholesterol is converted to bile salts.

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  • Made from cholesterol in liver hepatocytes
  • The functional part of bile

You should recognize this shape as being very much like cholesterol… that’s because bile salts are derived from excess cholesterol!

D3 Functions of The Liver

Bile Salts

D.3.U5 Surplus cholesterol is converted to bile salts.

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All these O atoms make these blue parts hydrophilic (water can form H-bonds with polar and ionic)

The yellow parts are hydrocarbons, so they are hydrophobic (nothing for water to form H bonds with)

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Lipid GLOBULES in chyme

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Outline use of excess cholesterol as a component of bile.

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D3 Functions of The Liver

Checkpoint

D.3.U5 Surplus cholesterol is converted to bile salts.

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  • Outline the function and source of bilirubin.
  • Explain the role of hepatocytes and glucuronic acid in the conversion of bilirubin.
  • List components of bile
  • Outline the role of bile ducts and gall bladder in the transport and storage of bile.
  • Describe when, where and why bile is secreted during digestion.
  • Define and list causes and symptoms of jaundice.
  • Describe the use of UV light as a treatment for jaundice.

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D3 Functions of The Liver