Question

Please answer this all question :

1. Is there any other factor besides the nephron which control the reabsorption of water and certain molecules for osmoregulation? Substantiate your answer with reasons? .

2. Analyze the specific role of liver in each of the following: 1. Carbohydrate, lipid and protein metabolism, 2. Processing of drugs and hormones, 3. Excretion of bilirubin, 4. Synthesis of bile salts and 5.Activation of vitamin D? .

Answer 1

The main function of nephron is filtration,reabsorption ,secreation and excreation.Nephron is the functional unit of kidneys.Tree function occurs in the excreation of urine.They are filtration ,secreation and reabsorption.

Nephrons are the filtering unit of kidneys.It contains glomerulus and a tubule.Glomerulus is made up of small blood vessels.It is known as tuft.It is located at the very first of the kidney.Across the capillary walls of this tuft the blood is filtered.Water and soluble substance are filtered to a cup like sac called bowmans capsule.The filtrate then enters the renal tubule .

  

Secreation occurs in the proximal tubule of the nephron.Hydrogen ions,pottassium and some xenobiotics are included in the secreated substances.By active transport mechanisn secreation occur.

2 In the metabolism of carbohydrate ,the liver helps in constantly watching the level of sugar in the blood by maintaining a normal range of glucose concentrations.By atightly regulated system of enzymes and kinase regulatingtheir glucose breakdown or synthesis in hepatocytes.Excess glucose can be stored within the liver as glycogen.At the time of exercise or fasting this glycogen is degraded to release glucose.

A large amount of lipo proteins are synthesized in the liver.A large quantities of cholesterol and phospholipids are synthesized by theliver.Some of the cholesterol and phospholipids are packaged with lipopproteins and made available to the body.Afetr that the remaining is excreated in bile as cholesterol.

Protein metabolism in liver incluse transamination and deamination of amino acids followed by the convertion of those molecules to glucose or lipids.Ammonia is very toxic and it should be removed from the circulation otherwise it will lead to central nervous system disorders.Another important step in protein metabolism is synthesis of non essential aminoacids.Albumin and blood clotting factors is synthesized in the liver.

some hormones produced in the liver are angiotensin,thrombopoetin,betatropin,insulin like gwowth factor ,angiotensin Being the site of transport protein synthesis liver influences hormne blood levels.The drugs must passs through the liver.It convert prodrugs to active metabolites.Through  specific group of cytochrome P 450 enzymes the livers is metabolising drugs.

3. Bilirubin is carried inthe blood stream to the liver.Then the bilirubin binds with the bile.Liver produces bile.After binding the bilirubin is passed through the bile ducts into the digestive tract.

In the liver cells ,bile acid synthesis occurs.An increased secreation of bile acids produce an increase in bile flow.It facilitate digestion of dietary fats and oils.Once it is secreated into the lumen of the intestine,by gut bacteria it gets modified.   

Vitamin D iis obtained mainly from sunlight,food.For activation it undergoes two hydroxylations.In fist,Calcidol forms when vitamin D converts to 25 hydroxy vitamin D and it occurs in the liver.Second is done in the kidneys.