Peculiarities of structure and function of the liver in newborn and children of early age

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SEMEY STATE MEDICAL UNIVERSITY

Essay

Topic: «Peculiarities of structure and function of the liver in newborn and children of early age»

Prepared by: Apoorv Chouhan 346 gr. G.M.

Checked by :Mylyshina Y.A.

Semey 2016

As the WHO reports are say infants and children are not miniature adults. The purpose of this essay is to bring together a profile of the anatomy, growth and development of the infant and child and explain the peculiarities of structure and function of the liver.

Human liver development begins during the third week of gestation and does not achieve mature architecture until about 15 years of age. It reaches its largest relative size, 10% of fetal weight, around the ninth week. It is about 5% of body weight in the healthy neonate. The liver is about 2% of body weight in the adult. It weighs around 1400g in an adult female and about 1800g in the male.

The liver is located in the right upper quadrant of the abdomen, just below the diaphragm. It is almost completely behind the rib cage but the lower edge may be palpated along the right costal margin during inspiration. A connective tissue layer called Glisson's capsule covers the surface of the liver. The capsule extends to invest all but the smallest the vessels within the liver. The falciform ligament attaches the liver to the abdominal wall and diaphragm and divides the liver into a larger right lobe and a smaller left lobe.

In 1957, the french surgeon Claude Couinaud described 8 liver segments. Since then, radiographic studies describe an average of twenty segments based on distribution of blood supply. Each segment has its own independent vascular and biliary branches. Surgeons utilize these independent segments when performing liver resection for tumor or transplantation. There are at least three reasons why segmental resection is superior to simple wedge resection. First, segmental resection minimizes blood loss because vascular density is reduced at the borders between segments. Second, it results in improved tumor removal for those cancers which are disseminated via intrasegmental branches of the portal vein. Third, segmental resection spares normal liver allowing for repeat partial hepatectomy.

Each segment of the liver is further divided into lobules. Lobules are usually represented as discrete hexagonal aggregations of hepatocytes. The hepatocytes assemble as plates which radiate from a central vein. Lobules are served by arterial, venous and biliary vessels at their periphery. This model is useful for teaching purposes but more closely resembles the adult pig lobule than the human. Human lobules have little connective tissue separating one lobule from another. The paucity of connective tissue makes it more difficult to identify the portal triads and the boundaries of individual lobules. Central veins are easier to identify due to their large lumen and because they lack connective tissue that invests the portal triad vessels.

Lobules consist of hepatocytes and the spaces between them. Sinusoids are the spaces between the plates of hepatocytes. Sinusoids receive blood from the portal triads. About 25% of total cardiac output enters the sinusoids via terminal portal and arterial vessels. Seventy-five percent of the blood flowing into the liver comes through the portal vein; the remaining 25% is oxygenated blood that is carried by the hepatic artery. The blood mixes, passes through the sinusoids, bathes the hepatocytes and drains into the central vein. About 1.5 liters of blood exit the liver every minute.

The liver regulates most chemical levels in the blood and excretes a product called bile. Bile helps to break down fats, preparing them for further digestion and absorption. All of the blood leaving the stomach and intestines passes through the liver. The liver processes this blood and breaks down, balances, and creates nutrients for the body to use. It also metabolized drugs in the blood into forms that are easier for the body to use. Many vital functions have been identified with the liver. Some of the more well-known functions include the following:

1. Production of bile, which helps carry away waste and break down fats in the small intestine during digestion

2. Production of certain proteins for blood plasma

3. Production of cholesterol and special proteins to help carry fats through the body

4. Store and release glucose as needed

5. Processing of hemoglobin for use of its iron content (the liver stores iron)

6. Conversion of harmful ammonia to urea (urea is one of the end products of protein metabolism that is excreted in the urine)

7. Clearing the blood of drugs and other harmful substances

8. Regulating blood clotting

9. Resisting infections by producing immune factors and removing bacteria from the bloodstream

10. Clearance of bilirubin (if there is a buildup of bilirubin, the skin and eyes turn yellow)

When the liver has broken down harmful substances, they are excreted into the bile or blood. Bile by-products enter the intestine and ultimately leave the body in the feces. Blood by-products are filtered out by the kidneys and leave the body in the form of urine.

But what is the difference in child liver?

Due to the different rates of enlargement livers weight and body in children from 1 year to 3 years of life edge of the liver is getting out of the right hypochondrium and easily detectable at 1-2 cm below the costal arch on the mid-clavicular line. With 7 years in the supine position the lower edge of the liver is not palpable, and on the median line does not extend beyond the upper third of the distance from the navel to the xiphoid process.

Liver parenchyma not differentiated, lobed structure is revealed only at the end of the first year of life. The liver is full-blooded, so that increases rapidly with the infection and intoxication, circulatory disorders and easily degenerates under the influence of adverse factors. By 8 years of morphological and histological structure of the liver is the same as adults.

The role of the liver in the body is different. First of all - is the production of bile, participating in the intestinal digestion, stimulating the motor function of the intestine and sanitizing its contents. Bile has been celebrated at the 3-month-old fetus, however, bile formation at an early age is not enough.

Bile is relatively poor in bile acids. A characteristic and a favorable feature is the prevalence in child bile taurocholic acid over than glycocholic, because taurocholic acid enhances the bactericidal effect of bile and accelerated pancreatic juice secretion.

Liver deposits nutrients, primarily glycogen and fats, and proteins. As necessary, these substances enter the bloodstream. The individual elements of the liver cell (stellate reticuloendoteliotsities or Kupffer cells, the endothelium of the portal vein) are part of the reticuloendothelial system, having a phagocytic function and actively participate in the exchange of iron and cholesterol.

Liver performs the barrier function, neutralizes the number of endogenous and exogenous harmful agents including toxins, coming from the intestines and is involved in the metabolism of drugs.

Thus, the liver plays an important role in carbohydrate, protein, bile, fat, water, vitamins (A, D, K, B, C) metabolism, and in utero is also forming organs.

In young children, the liver is able to function failure, particularly its enzymatic system inconsistent, resulting in transient neonatal jaundice due to incomplete free bilirubin metabolism, resulting in hemolysis of erythrocytes.

So as the conclusion the liver performs the following functions in infants and early aged children:

1) produces bile, which participates in the intestinal digestion;

2) stimulates intestinal motility, due to the action of bile;

3) deposits the nutrients;

4) provides a barrier function;

5) involved in metabolism, including - to transform vitamins A, D, C, B12, K;

6) during the prenatal period is a hematopoietic organ.

After birth, there is a further formation of the lobes in the liver. Liver function may be low in children: in infants no direct bilirubin metabolism, so it is not fully implemented. liver diaphragm child

In young children, the liver is in a state of functional failure, especially untenable its enzyme system, resulting in transient neonatal jaundice due to incomplete metabolism of free bilirubin, formed by hemolysis. Liver parenchyma little differentiated, lobed structure is revealed only at the end of the first year of life. The liver is full-blooded, so that increases rapidly with the infection and intoxication, circulatory disorders and easily degenerates under the influence of adverse factors. By 8 years of morphological and histological structure of the liver is the same as adults.

References

1. Wanless IR. Anatomy, histology, embryology, and developmental anomalies of the liver. In: Feldman M, Friedman LS, Sleisenger MH, eds. Sleisenger & Fordtran's Gastrointestinal and Liver Disease. 7th ed. Philadelphia, PA: WB Saunders; 2002:1195-1201

2. Karpen SJ, Suchy FJ. Structural and functional development of the liver. In: Suchy FJ, Sokol RJ, Balistreri WF, eds. Liver Disease in Children. 2nd ed. Philadelphia, PA: Lippincot Williams & Wilkins; 2001:3-21

3. Barriault C, Desmoulire A, Costa AMA. Evaluation of chemical-induced bile duct proliferation. In: Plaa GL, Hewitt, WR, eds. Toxicology of the Liver. 2nd ed. Washington, DC: Taylor and Francis; 1998:401-416

4. Stolz A. Liver physiology and metabolic function. In: Feldman M, Friedman LS, Sleisenger MH, eds.Sleisenger & Fordtran's Gastrointestinal and Liver Disease. 7th ed. Philadelphia, PA: WB Saunders; 2002:1202-1226

5. Kahl R. The liver. In: Marquart H, Schдfer S, McClellan RO, Welsch F, eds. Toxicology. San Francisco, CA: Academic Press; 1999:273-296

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