The various homeostasis functions of the liver in mammals
Homeostasis is the self regulating process by which an organism can maintain internal stability while adjusting to changing external conditions. The liver is the body’s largest solid organ, and it is multifaceted functions are essential for life and maintenance of homeostasis. Key functions of the liver include ;deamination, regulation of iron homeostasis, detoxification, formation of red blood cells , regulation of plasma proteins, regulation of blood sugar levels, storage of blood, heat production, execution of immunological functions, bile production for fat metabolism, synthesis of hormones etc
Liver functions in production of hormones. The liver directly synthesise various hormones that have different functions in the body to control homeostasis in the body. They include: angiotensinogen, insulin-like growth factor one ( IGF-1) and 25-hydroxyvitamin D. Some of these hormones assists in stimulation of growth and also the development of the body tissues, which is a change in the environment and gives the adaptation factors which are essential
Furthermore it is essential during deamination process. Which is the process of removal of amino group from amino acid molecules that breakdown releasing nitrogen containing amine groups which can be toxic to cells, changes to ammonia which is then converted to urea. Urea is non-toxic substances and excreted from the body by the kidneys ( a component of urine). The liver ensures that the products released from the body is harmless to other organs and releases it to the environment if possible. This is how the liver normally ensures homeostatic changes that are normal to the body tissues and organs. The amine group if not broken down can also be transferred via transamination to make new amino acids. These amino acids are non-essential as they can be synthesized by the body example aspartate. The remaining carbon skeleton is recycled to produce compounds that can be oxidised to produce energy. These include the formation of glucose, ketone bodies and acetyl CoA. There is normally done in the liver to ensure the metabolic rate is being met properly.
Detoxification also is a key function of liver and it usually maintains the internal stability of compounds in the body. And it is the process where harmful compounds such as drugs and poisons are converted to less toxic compounds. Toxicity is mainly caused by medication, drugs and microorganisms that enters the body. The bloodstream carries numerous toxins which are the metabolic residues and wastes produced by the body performing several functions. The liver is one of the organs responsible for filtering these substances out of the blood so that they can be eliminated from the body. The liver performs this task by diluting them into bile, which allows them to exit the body through stool. The toxic compounds are also later excreted in the urine. It prevents the accumulation of toxins in the body cells which could lead to death or malfunctioning of the body cells. It also resists infections from the body by removing bacteria from the bloodstream. The liver maintains the stability level of the toxin in the body with its power in regulation.
The liver destructs worn-out red blood cells. Iron is produced in abundance from the liver cells and stored there. Hence it is used broadly in the production of red blood cells (RBCs), in a process called erythropoiesis, although the major production of RBCs happens in the bone marrow. The destruction of war-worn-out blood cells normally occurs in the liver after 120 days of its production, and it is done by Kupffer cells of the Liver. The destruction of RBCs ensures the formation of new ones in the bone marrow. This enhances oxygen and carbon IV oxide distribution. The liver normally regulates the production of red blood cells in the body and this enhances the best transportation of oxygen and carbon dioxide in the bloodstream hence ensuring proper supply in the blood and maintaining the body’s ability to work properly.
Production and regulation of plasma proteins. The amino acid entering the liver by the portal vein are transformed there into different proteins that are useful to the body. These include:
Prothrombin and fibrinogen; are manufactured in the liver using amino acid found in the liver and they play a major role in blood clotting. This prevents excessive blood loss and infection at the injured area.
Albumin; they contribute to the maintenance of osmotic pressure in the body. It is taken by the protein of blood and muscles.
Carrier proteins: These are substances used by the blood for transport. Lipids, hormones, medications and so forth do not independently circulate in the blood but are transported by a special support with a protein base. For example the lipoproteins carry fats( including cholesterol which otherwise would adhere to blood vessels walls), glycoproteins ensures the transport of sexual hormones and so forth.
Pro-inflammatory proteins: These proteins These cytokines triggers the defensive mechanism/reaction of inflammation, which allows the cells to destroy any injurious agent that threatens their physical integrity.
Non-essential amino acid including alanine, arginine, aspartate, glycine and many more are also synthesized by the liver for body use mainly in growth and development of tissues.
Liver plays a vital role in regulation of blood sugar levels in the body. This comes as a result that glycogen is stored in the liver as a reservoir for glucose in providing of energetic needs of extra-hepatic tissues. This accumulates after feeding which makes glucose available in abundance. Glucose is mobilised when the level of glycaemia tend to decrease by peripheral glucose utilisation. The stability of the normal glucose levels indicates that precise regulatory mechanisms governs the function of the liver to oscillate between the quantitatively balanced uptake and release of glucose. The interrelationships between the blood glucose and the liver is governed by homeostatic hepatic mechanisms that responds to the level of glycaemia with glucose uptake or production. There are different factors that influence the blood glucose levels maintained by the liver ; insulin lowers glucose levels and thus allows the organs to take up glucose at a lower glycemia. Also glycogen increases the levels of glucose in blood when it is at a higher level thus bringing it to the body’s natural homeostasis.
It has rich supply and storage of blood which circulates in it. The liver is unique among the mammalian organs in that it is fed independently by two blood supplies hence it is highly vascularised. The portal vein and its branches are the major circulatory source of the liver, which roughly comprises two thirds of the supply while a third is given by hepatic artery which is a branch of celiac artery. Venous blood and arterial blood from these two sources mix together as they percolate through a series of liver capillaries known as sinusoids , until they come in contact with branches of central vein , the vascular egress system of the liver. These supplies makes it to control the functions it has to the body, it is necessary in stabilization of metabolic and control of temperature of the body to that of the environment by the help of endocrine and nervous systems incorporated.
Body temperature regulation. Many metabolic activities take place in the liver releasing heat energy that is distributed by the blood to the other parts of the body. This helps in thermoregulation, storage of vitamins A,B, C, E and K and mineral salts. The liver is an important component in regulation of core body temperature and as such display significant physiological and metabolic changes in response to different temperatures. Adrenergic stimulation activates hepatic gluconeogenesis , providing glucose for BAT (brown adipose tissue) thermogenesis which eventually controls the temperature in the blood during cold weather and energy balance.
The liver synthesizes the lipids that are helpful to the body, such as phospholipids. It can either send these substances directly into the bloodstream or store them in its reserves to cover for future needs. When the liver has to store too many fats , which is the case when we eat too much food with lipids, it becomes congested with fats, a condition that can lead to the fat degeneration of the liver.
Common factors that can lead to a fatty liver include:
• Obesity
• High levels of fats in blood
• Diabetes
• Genetic propensity
• Rapid weight loss
• Side effects of some medications
The liver produces bile which is used for metabolism of fats. The liver cells produces bile which is a yellow, brownish or olive green liquid which is collected in small ducts and then passed onto the main bile duct which carries bile into the duodenum for fats breakdown and eventually producing energy which the body uses. Liver plays an essential role in preservation and regulation of lipid levels. Presence of liver ensures
The liver is the major site for converting excess carbohydrates and proteins into triglycerides and fatty acids. It is also responsible for the synthesis of large quantities phospholipids and cholesterol. Low density lipoproteins (LDL) transports cholesterol to cells, for use in the cell membrane and in steroid synthesis. High density lipoproteins (HDL) transports excess cholesterol from cells back to the liver ( for storage or conversion). LDL is considered ’bad’ as it raises blood cholesterol levels while HDL lowers cholesterol levels and therefore considered ‘good’.
The liver executes itself in immunological functions. Organs such as thymus, lymph nodes and spleen are “classically” lymphoid organs. However other organs such gut and liver consists of the cells whose primary function may not be immunological but they still perform essential immune tasks. Within these organs there are resident cells of the innate and adaptive immune system. Within a normal liver, the lymphocyte population is largely resident in the portal tract but scattered throughout the parenchyma. The hepatocytes and BECs are sites for immune mediated destruction induced by variety of infectious xenobiotic and tumour originated source. The anatomical position of the liver and it’s vasculature account for its unique ability to exchange immunological information.
The liver participate in maintaining the acid base balance of the organism. The liver is important in acid base physiology and this is because it is metabolically active organ which maybe either a significant net producer or consumer of hydrogen ions. The amount of acid involved maybe large. The acid base role of the liver are considered as:
• Carbon dioxide production from complete oxidation of substrate.
• Metabolism of organic acid anions ( such as lactate, ketones and amino acid)
• Metabolism of ammonia
• Production of plasma proteins especially albumin.
The liver has remarkable capabilities to regenerate, employing mechanisms to ensure stable liver to bodyweight ratio for the body homeostasis. These organ is very vital in homeostatic functions and helps human being to adapt well in environment if it is well also and it assists in several functions as stated above
REFERENCE
1. ROS S, Garcia – Rocha M, Dominguez J, Ferrer JC, Guinovart JJ. Control of liver glycogen synthase activity and intracellular distribution by phosphorylation. The J Biol Chem 2009; 284; 6370-6378 (PubMed) (Google Scholar).
2. Gary A. Thibodeau and Kevin T. Patton. Structure and function of the body . 2011.
3. Oren Tirosh. Liver metabolism and fatty liver disease. 2014.
4. Christopher Vasey. N.D. Liver Detox, cleansing through diet, herbs and massage. 2018.
5. Ann Waugh and Allison Grant. ROSS AND WILSON Anatomy and Physiology in Health and Illness 13th edition.2018; 336- 340.
6. Field KM, Dow C, Michael M. Part I: liver function in oncology: biochemistry and beyond. Lancet Oncol. 2008; 9: 1092-1101.- PubMed
7. Alvarez-Dolado M, Pardal R, Garcia-Verdugo JM, Fike JR, Lee HO, Pfeffer K, Lois C, Morrison SJ, Alvarez-Buylla A. Fusion of bone-marrow-derived cells with Purkinje neurons, cardiomyocytes and hepatocytes. Nature. 2003;425:968–973. [PubMed] [Google Scholar]
8. Chen F, Jimenez RJ, Sharma K, Luu HY, Hsu BY, Ravindranathan A, Stohr BA, Willenbring H. Broad distribution of hepatocyte proliferation in liver homeostasis and regeneration. Cell Stem Cell. 2020;26:27–33 e24. [PMC free article] [PubMed] [Google Scholar]
The article is very essential in gaining a lot of knowledge of our body
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