Human Excretary system
13. Human Body - Excretary system
Excretary system
Excretory systems regulate the chemical composition of body fluids by removing metabolic wastes and retaining the proper amounts of water, salts, and nutrients. Components of this system in vertebrates include the kidneys, liver, lungs, and skin. The main waste products in all organisms are carbon dioxide (from carbohydrates and fat oxidation) and nitrogenous wastes (ammonia, urea & uric acid) from protein metabolism. Ammonia is very toxic and usually is excreted directly by marine animals. Terrestrial animals usually need to conserve water. Ammonia is converted to urea, a compound the body can tolerate at higher concentrations than ammonia. Birds and insects secrete uric acid that they make through large energy expenditure but little water loss. Amphibians and mammals secrete urea that they form in their liver. Amino groups are turned into ammonia, which in turn is converted to urea, dumped into the blood and concentrated by the kidneys.
Excretory systems regulate the chemical composition of body fluids by removing metabolic wastes and retaining the proper amounts of water, salts, and nutrients. Components of this system in vertebrates include the kidneys, liver, lungs, and skin. The main waste products in all organisms are carbon dioxide (from carbohydrates and fat oxidation) and nitrogenous wastes (ammonia, urea & uric acid) from protein metabolism. Ammonia is very toxic and usually is excreted directly by marine animals. Terrestrial animals usually need to conserve water. Ammonia is converted to urea, a compound the body can tolerate at higher concentrations than ammonia. Birds and insects secrete uric acid that they make through large energy expenditure but little water loss. Amphibians and mammals secrete urea that they form in their liver. Amino groups are turned into ammonia, which in turn is converted to urea, dumped into the blood and concentrated by the kidneys.
Kidney
ALL vertebrates have paired kidneys. These are two bean-shaped organs, one on each side of the backbone. Kidneys regulate body fluid levels as a primary duty, and remove wastes as a secondary one. The nephron is the kidneys functional unit. Each kidney contains from one to two million nephrons.
Main components of nephron -
- Glomerulus: mechanically filters water and solutes from the blood. Bowmans Capsule: mechanically filters blood .
- Proximal Convoluted Tubule: Reabsorbs 75% of the water, salts, glucose, and amino acids.
- Distal Convoluted Tubule: Tubular secretion of H ions, potassium, and certain drugs.
Urine formation
The formation of urine had three processes: filtration, reabsorption, and tubular excretion During filtration, or glomerular excretion, blood pressure forces all the small molecules in the blood into the lumen of the nephron through the pores both in the walls of the glomerular capillaries and in the wall of the Bowmans capsule. The filtrate has the same concentration of dissolved substances as the blood minus the formed elements and the plasma proteins which are too large to fit through the pores of the capillaries and the Bowmans capsule. As the filtrate passes through the tubules of the nephron, water and many dissolved materials are reabsorbed by the blood. In fact, during the filtrates passage through the tubules up to 99 percent of the water is reabsorbed. In addition, the tubules also remove substances from the blood. This process, called tubular excretion, supplements the initial glomerular filtration.
Hormones of the Kidneys: The human kidney is also an endocrine gland secreting two hormones: 1) Erythropoietin (EPO) 2) Calcitriol, the active form of vitamin D as well as the enzyme renin.
Diseases of Kidney
Acute Renal Failure: No urine is formed by kidney and the wastes and water accumulates in the body. It can be treated by dialysis, by an artificial filtration of blood through semi permeable membaranes.
Kidney stone: It is also known as renal calculi, kidney stones are the result of crystallization of certain substances found in urine, including calcium, phosphate, oxalic acid, and uric acid. Stones may form in the urine collecting area (pelvis) of the kidney, as well as the ureters (narrow tubes connecting the kidney to the urinary bladder).
Acute Renal Failure: No urine is formed by kidney and the wastes and water accumulates in the body. It can be treated by dialysis, by an artificial filtration of blood through semi permeable membaranes.
Kidney stone: It is also known as renal calculi, kidney stones are the result of crystallization of certain substances found in urine, including calcium, phosphate, oxalic acid, and uric acid. Stones may form in the urine collecting area (pelvis) of the kidney, as well as the ureters (narrow tubes connecting the kidney to the urinary bladder).
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