Water balance is maintained in the body through the kidney as it is maintains its level. The control of water level is linked to the disposal of nitrogenous waste- nitrogenous would be toxic if it is accumulated, so it is vital to be removed from the body.
- Excess protein are broken down into amino acids, after which these then have the nitrogenous part removed as ammonia-within the liver, the ammonia is converted into urea, this process is know as Deamination.
Henceforth the urea is then transported in the blood to the kidney (where it is extracted and excreted via the bladder).
How the bowman’s work which is to do with ultra-filtration.
The Bowman's capsule contains a dense capillary network called the glomerulus. Blood flows into these capillaries through a wide afferent arteriole and leaves through a narrower efferent arteriole.
The control of water by the kidney takes place through a process known as ultra-filtration. Urea along with salt, water and glucose is extracted from the blood and into the kidney via the Bowman’s capsule which filters it. When blood passes through the nephrons it is usually under high pressure, so fluid is forced through the sieve like capillaries and into the capsule. However, much of what has been filtered are required to return to the blood as they are vital its function. When the filtrate reaches the proximal convoluted tubule; sodium (Na+) and chloride (Cl-), ions, glucose, amino acids and vitamins move back into the blood, they diffuse from the filtrate into the cells lining of the proximal convoluted tubule. They are then transferred out of these cells and into the blood capillaries, also some water follows by osmosis. This process is called glomerular filtration. The water, waste products, salt, glucose, and other chemicals that have been filtered out of the blood are known collectively as glomerular filtrate. The glomerular filtrate consists primarily of water, excess salts (primarily Na+ and K+), glucose, and a waste product of the body called urea. Urea is formed in the body to eliminate the very toxic ammonia products that are formed in the liver from amino acids. Since humans cannot excrete ammonia, it is converted to the less dangerous urea and then filtered out of the blood.
Proximal convoluted tubule
The Proximal convoluted tubule Tissues and cells connected with the structures that bonds the renal pelvis to the glomeruli; the convoluted section of the vertebrate nephron that is in between the Bowman's capsule and the loop of Henle, is made up of a single layer of cuboidal cells with striated borders- and its main function is in the resorption of sugar, sodium and chloride ions, and water from the glomerular filtrate, this stage is known as the tubular reaborption.
Reaborption of water
The Reaborption that takes place happens in a two-step process beginning with the active or passive extraction of substances from the tubule fluid into the renal interstitium (the connective tissue that surrounds the Nephron), and then the transport of these substances from the interstitium into the bloodstream. This is the stage when the kidney get a transmit from the Osmoreceptors in the hypothalamus. When there is an increase in blood osmotic potential (rises), decrease ADH (anti-diuretic hormone)output from the posterior lobe of the pituitary gland-permeability of distal collecting duct decreases, less water reabsorbed copious dilute urine is produced. Decrease in blood osmotic potential (water concentration falls), increase ADH output from the posterior lobe of the pituitary gland; permeability of distal tubule and collecting duct increases more water reabsorbed; small volume of concentrated urine produced- this is also when the brain tells the kidney which molecules it wants and which it doesn’t require, the basic is to create a strong salt concentration in the next part of the tubule; this will draw water out of the tube by osmosis, to be taken away from the blood this conserve water levels in the body. If the concentration is too high, impulse are sent to the pituitary gland which then releases more ADH. The water levels will be maintained to its appropriate level and the impulses would stop.
Descending and Ascending limb of the loop of Henle
The loop of Henle is known as the nephron loop, it goes through into the medulla (through its descending limb) and then back out (through its ascending limb). The loop of Henle and the collecting duct cooperate to maintain the gradient of osmolarity in the interstitial tissue of the kidney that makes it possible to concentrate the urine. As the filtrate flows through the proximal convoluted tubule, located in the kidney cortex, a large amount of water and salt is reabsorbed; thus the volume of filtrate decreases substantially at this stage, but the osmolarity remains about the same. Now the filtrate begins its serpentine trip, down into the medulla within the descending limb of the loop of Henle back up to the cortex in the ascending limb, and then down to the medulla one more time within the collecting duct. Water moves from areas of low concentration to areas of high concentration, and it will naturally want to pass from the filtrate to the saltier surrounding tissue this takes place in the loop on Henle. As filtrate moves down the loop of Henle, water is reabsorbed, but ions (Na, Cl) aren't. The removal of water serves to concentrate the Na and Cl in the lumen. Now, as the filtrate moves up the other side (ascending limb), Na and Cl are reabsorbed.
Filtrate passing down through the descending of the loop of Henle is flowing in the contrary direction to the fluid in the ascending limb. The fluid is increasing concentrated as it moves down and dilute as it moves up. This is known as counter-current flow (counter-current multiplier) allows concentrated urine to be produced.
This is important because more water is drawn out of the tube (this is when the water is at the collecting duct), when it passes through the medulla again, this is when concentrate urine is produce; moreover, any filtrate not reabsorbed (this is most of the urea) some water and salt are drained into the bladder.
Distal convoluted tubule
The convoluted section of the vertebrate nephron that is in between the loop of Henle and the non-secretory part of the nephron, and that is based with the concentration of urine that is made through the urea.
Collecting duct
The collecting ducts Reabsorbs Na+ ions through coupled secretion of H+ or K+ ions into the tubular fluid, a process which requires the presence of the adrenal hormone aldosterone. By acidifying the urine the distal convoluted tubule plays an important role in acid-base balance normally is relatively impermeable to water. However in the presence of anti-diuretic hormone (ADH) its permeability to water increases permitting concentration of the urine.
Each of the structure of the nephron has their duty in the participation of how it works and they are vital to the human body system.
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