The liver is an amazing organ within the body. It is something we abuse with excessive alcohol, medication drugs, those of you who are naughty and take illegal drugs, poor diets, too much caffeine and processed foods.
The liver is the largest organ in the body, second only in size to the skin, supplying the body with 25% of its total blood flow. It is the heaviest gland of the body averaging out at about 14kg – this is roughly the weight of a staffordshire bull terrier or 7 1/2 2 litre bottles of pop. It alters in its size and shape dependant on the amount of blood present. Without a liver our life is reduced to about six hours and death results from multiple factors such as an accumulation of toxic metabolites in the blood stream, this is less time than if we didn’t have water or food!! It converts glucose which is a sugar that we get from most carbohydrates in our diet into glucogen a process aided by insulin. Today there is currently a diabetes epidemic which is due to people eating high carb high sugar foods and overloading the liver and the pancreas. The liver can store around half the bodies sugar reserves and up to about 10% the weight of the liver, so when we need to access our energy the liver releases the glucogen to be used as fuel for the muscles.
Anatomically it sits just below the diaphragm and is situated on the right hand side of the body. The liver can be felt under the rib cage in slim people or when the liver has enlarged due to health issues such as fatty liver disease.. It is suspended in the cavity from the diaphragm by ligaments. The liver tissue is made up of liver cells (hepatocytes), small canals (bile canaliculi) and blood capillaries (hepatic sinusoids). Histologically, the liver can be described as having 2 vascular trees (portal and hepatic) within it, the branches close but not touching each other.
The Liver Cells (Hepatocytes):
These liver cells perform numerous metabolic, secretary and endocrine functions so they have an impact on how we burn our energy (therefore how easily/hard we gain/lose weight), they also deal with all of the hormones in our body as well as making hormones itself. They are specialized cells with 5 to 12 sides and they make up 80% of the volume of the liver. They contain more rough and smooth endoplasmic reticular, mitochondria and lysosomes are more abundant than most other cells within the body – this means that there are more power houses for producing energy within the liver than anywhere else. Alcohol or drug abuse increases the number of enzymes within the hepatocytes this is know as induction and is a process to help keep up with the excessive amount of poison that people chuck into their bodies.
Hepatocytes are arranged into complex plates called hepatic laminae which are one cell thick and are highly branched. Hepatocytes are lined by vascular spaces called hepatic sinusoids with grooves in their membrane for the canaliculi to secrete bile into.
When stressed, the cortex of the adrenal gland releases cortisone and hydrocortisone (the stress hormones) which stimulates gluconeogenisis by the liver, a sympathetic response, inducing the liver to breakdown glycogen (sugars) by hepatocytes and produces a surge of glucose into the blood which is ultimately the fight or flight response.
Conjucation is the process where hepatocytes create compounds which can be excreted via the bilary system, so the liver also plays an important process when it comes to digesting food and accessing certain nutrients. Unborn babies don’t have conjucating enzymes in their livers and so their unconjucated bilirubin diffuses through the placenta and is taken up by the mother for excretion. Premature babies are frequently jaundiced (have yellow coloured skin) because the conjucating enzymes develop a few days prior the birth, late in the third trimester and therefore they do not have this ability.
Canals in the liver (Bile canaliculi):
These are small canals in branched structures lining the grooves of the hepatocytes that assist digestion with the absorption of food and the excretory process. The secretion of bile salts only occurs within the liver – these have a detergent action emulsifying fats so that we can access their nutrition.
Blood capillaries within the liver (Hepatic sinusoids):
These are highly permeable capillaries in branched structures between the hepatocytes. They receive two blood supplies, via the hepatic artery they receive oxygenated blood (red blood) and via the hepatic portal vein they receive nutrient rich deoxygenated blood (blue blood) from the gastrointestinal organs and the spleen.
Kupffer cells are located within the hepatic sinusoids, they are part of the immune system and are fixed white blood cells which destroy old blood cells, bacteria and other particles in the venous blood draining from the gastrointestinal tract. Old haemoglobin (red blood cells) are recycled by cells within the liver, the central iron particle is stored for reuse within the liver and the haem (the red transporter of the iron molecule) is converted into bilirubin – a large amount of bilirubin in the blood stream causes jaundice.
Functions of the Liver:
The liver does so much for us and yet we do take it for granted. Liver disease and abuse can cause life threatening problems which can greatly shorten our life expectancy. Here is a list of what the liver does for us on a daily basis for our entire lives.
- carbohydrate metabolism, the assimilation of sugars within the body – glucose levels
- regeneration – creating new liver cells if we really abused our liver
- lipid metabolism – the assimilation of fats within the body
- protein metabolism – making, storing and breaking down proteins (meat, fish, eggs, pulses etc)
- processing drugs and hormones – endocrine function either reacts with or destroys most hormones – detoxification
- excretion of bilirubin
- sodium metabolism – the assimilation of salt from our diet
- in fetus’ and new born babies the liver produces red blood cells (erythropoiesis)
- synthesis of bile salts
- storage of: glycogen, Vitamins A, B12, D, E and K, iron, copper
- kupffer cells kill/recycle aged cells and pathogens (any germs) this is known as phargocytosis
- activation of Vitamin D
- processing all of the blood within the body
- regulation of blood clotting
As you can see the liver is essential to our health and wellbeing. I sell herbal capsules on my website: http://www.herbsforhealthandwellbeing.co.uk where you can purchase Milk Thistle and give you liver some tender loving care.
Homer Andrews, W.H. (1979) Liver. Edward Arnold Publishers Limited
Kumar, P. Clark, M. (2009) Clinical Medicine 7th Edition. Elsevier Limited
Tortora, G. Dickenson, B. (2009) Principles of Anatomy and Physiology 12th Edition. John Wiley & Sons Ltd