All About ... The Liver

This is the largest gland in a horse's body and it is vital because every organ depends on it!  It has a large number of functions and is central to preventing harmful substances from reaching the general circulatory system and so the rest of the body.  It is also an accessory organ to the digestive system as it supplies bile to the intestines to aid digestion. Unlike humans, horses do not have a gall bladder and so the bile is directly secreted into the intestines.  

The functions of the liver include:

• Detoxification of waste products and toxins 
• Removal and breakdown of old Red Blood Cells 
• Maintaining blood glucose levels 
• Converting ammonia to urea - to be excreted to the kidneys 
• Removal of lipids from the blood 
• Storage of blood 
• Regulation of body temperature 
• Storage of iron and vitamins A, D & B12 
• Synthesis of blood plasma proteins and blood clotting agents - these are then taken around the body to repair and regenerate cells and organs.

The liver has a double blood supply.  The hepatic artery brings oxygenated blood to the liver cells so that they are able to generate energy.  The hepatic portal vein takes blood from the intestines to the liver, the liver then processes the substances which have been absorbed from the gut and detoxifies poisons.  Lymphatic vessels also take fatty substances to the liver to be processed before they reach the rest of the body.

Anatomy of the Liver

The liver is made up of lobules, these are made up of liver cells (hepatocytes).  Within each lobule blood from the hepatic portal vein and hepatic artery flows through sinusoids (blood filled spaces).  The sinusoids flow past each liver cell which have microvilli on the surface (folds of membrane) which increase the surface area for taking in substances from the blood.

Substances from the blood; lipids, vitamins, glucose and toxic substances  (all taken in from the hepatic portal vein) are taken into the hepatocytes where they are processed, stored, altered and detoxified  before being released back into the blood or into the bowel to be eliminated.


Liver Damage

Each liver cell can be quickly replaced, in fact, the whole liver is replaced every few weeks.  This means that it can repair considerable damage to itself.  However, cumulative damage (eg: eating Ragwort) can be irreparable.  Once 75% of the liver is damaged it is usually too late.  

Symptoms of liver damage include:

• Reduced performance 
• Jaundice 
• Diarrhoea 
• Weight Loss 
• Poor appetite 
• Oedema on the chest, abdomen and legs due to a disturbance in the fluid balance 
• Photosensitivity 
• Bleeding with no clotting 
• Yawning - repeatedly 
• Poor coat

More serious ...

• Aimless walking, staggering 
• Depression 
• Seizures 
• Blindness 
• Swelling of head 
• Running into objects 
• Coma 
• Death

The liver is such an important part of the body that it is vital to keep it healthy.  Ragwort poisoning affects the liver's ability to repair itself - all the more reason to keep your field clear.

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Until next time!

Jo