The liver system

30 September 2023

What is the hepatic system ?

The hepatic or hepatobiliary system comprises :

the liver
the gallbladder,
the cystic duct linking the liver to the gallbladder,
the common bile duct, formed by the union of the lobar ducts and the cystic duct and leading into the duodenum, the first portion of the small intestine,* and the various vessels that run through it.
as well as the various vessels that run through it, such as the hepatic artery and its branches, and the portal vein.

The liver has many roles

The liver, in ancient Greek ἧπαρ, hepar, is an organ said to be attached to the digestive system. Located in the cranial portion of the abdomen, it is in contact with the diaphragm and partially protected by the ribs. It is the largest gland in the body and consists of 6 lobes.

The liver is in fact an organ with multiple roles, with over 300 functions attributed to it.

It is involved in digestion, secreting bile, which is made up of both elimination products and secretion products – such as bile salts. This yellowish-coloured digestive juice is necessary for the digestion of lipids and the absorption of vitamins A, D, E and K.

It detoxifies the body by breaking down many toxic molecules into products that are less harmful and can be more easily eliminated. For example, ammonia – which is toxic to nervous system cells – is transformed into non-toxic urea, which is easily eliminated by the kidneys. Drugs can also be broken down in the liver, although the main route of elimination is via the kidneys.

It is in the liver cells that vitamins A, B and D and certain minerals – such as zinc, iron and copper – are stored. The liver is also an energy reserve, as it is able to store carbohydrates in the form of glycogen, which, if needed, can be re-transformed into molecules that can be used directly by the body’s cells. The same applies to lipids, stored in the form of triglycerides.

Finally, the liver has the capacity to synthesise blood proteins like globulins, albumin, coagulation factors, etc. – which are used by the body’s cells. It also plays a vital role in the activation of vitamin D.

What about the gallbladder ?

This small pouch, housed in the “gall bladder fossa”, has the unique role of storing the bile produced by the liver. It is thanks to the signal emitted during meals that the gallbladder contracts and the bile is transported to the small intestine.

*The cat has a particular anatomical feature. Whereas in the dog, the common bile duct and the pancreatic duct each end in the duodenum, in the cat these two ducts meet in the same papilla – the major duodenal papilla. This particularity makes this species prone to “feline triaditis“.

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The importance of diet for skin and coat quality in dogs and cats

The skin is the body's largest organ, representing between 12% and 24% of the animal's weight, and its surface area in a dog weighing around thirty kilograms is close to one square meter. It's hardly surprising, then, that the quality and quantity of the dog's diet can have an impact on this organ, and in the event of a deficiency can lead to problems that go far beyond a simple visual appearance.

Key nutrients for healthy skin and coat

Among the macro-nutrients, proteins play a crucial role. They provide amino acids, including sulphur amino acids, which are essential for the structure of the skin and coat. These are the main components of collagen, which gives the skin its suppleness and resistance, and of keratin, which plays a part in the effectiveness of the skin barrier. Lipids are also important; they make up the bulk of cell membranes and, in the skin, contribute significantly to the effectiveness of the cutaneous barrier. Among lipids, omega-3 and omega-6 fatty acids help maintain healthy skin, modulate inflammatory mechanisms and promote a shiny, soft coat. Vitamins and minerals are also involved. Vitamin A is necessary for cell renewal, as is vitamin D, which also plays a part in the skin's natural defences. Vitamin E acts as an antioxidant, while B vitamins and biotin are essential co-factors in the synthesis of various skin elements such as ceramides, keratin and collagen. Among the minerals, zinc is involved in synthesis, protection against free radicals and immune defence mechanisms.

Disorders linked to inadequate nutrition

Inadequate or poor-quality food can lead to skin problems in our pets. A deficiency in essential fatty acids leads to dry, flaky skin, a dull coat and brittle hair. When it's the vitamins and minerals that are in short supply, synthesis is affected, the skin barrier can be less effective and the breeding ground for infections and inflammations that can lead to itching. On the other hand, these nutritional benefits can be used to compensate for individual sensitivities and improve the quality of the skin and coat in the event of dermatological disorders or diseases.

Conclusion

The quality of a dog's skin and the beauty of its coat are directly influenced by the quality of its diet. However, some dogs and cats have increased needs, and it is therefore necessary to provide them with greater quantities of useful nutrients. This is particularly true in the case of certain dermatological disorders, to help compensate for imbalances and accompany the medical treatments prescribed by your vet.