urine is formed based on three steps that will be discussed : -filtration -re-absorption -secretion...
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Urine is formed based on three steps that will be discussed :-Filtration-Re-absorption-Secretion
- wastes are filtered from the blood by the kidneys and sent to the urinary bladder by ureters-a urinary sphincter located at the bottom of the bladder acts as a valve allowing urine to be excreted -urine is voided through the urethra-bladder can hold 200-600ml of urine
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( one million tubules)-afferent arterioles supply nephrons with blood- afferent arterioles branch into a capillary bed called glomerules- efferent arterioles transfer blood out of the glomerulus- the blood from the efferent arterioles is carried to a net of capillaries called pertibular capillaries
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surrounds the glomerulus-Bowmans processes fluids from the blood into urine- a thin tubule called the proximal tubule is attached to the capsule- urine travels from the loop of henle - - ->through the distal tubule - - -> into the collecting ducks
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Each nephron has its own blood supply in the kidney whish allows blood to flow into the glomerulus.
Dissolved solutes are able to pass through and into bowmans capsule.
- this is due to the materials moving from high pressure to low pressure, but not all materials are able to pass through.
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Transfer of glomerular filtrate back into the capillaries● Focuses on changes in concentration of fluids as they go through kidneys● About 600ml of fluid flows through kidneys every minute● About 20%(120ml) of this liquid is filtered into nephron● If liquid was not reabsorbed it would be impossible to maintain homeostasis unless 1 litre of fluid was consumed every ten minutes● because of reabsorption only 1ml of urine is formed for every 120ml of fluids that enter nephron● the rest of the 120ml of fluids and solutes is reabsorbed
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Selective Reabsorption● occurs in passive and active transport
● carrier molecules move Na+ ions across cell membranes of the cells that line nephron● negative ions like Cl- and HCO3- follow positively charged Na+ ions by attraction● Mitochondria supply energy needed for transport● reabsorption occurs until the threshold level is reached● excess NaCl remains in nephron and is excreted with urine● other molecules are actively transported through the proximal tubule● Glucose and amino acids are attached to specific carrier molecules which shuttle them out of nephron and into blood stream● only so much solute can be reabsorbed
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● solutes that exit nephron create an osmotic gradient that draws the water from nephron● a second osmotic force created by proteins also helps reabsorb ○ these proteins remain in the bloodstream and draw water from the interstitial fluid into the blood● as water is reabsorbed from nephron, remaining solutes become more concentrated ● Molecules such as urea and uric acid will diffuse from nephron, back into blood stream
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“The movement of wastes from the blood into the nephron”
-Cells loaded with mitochondria line the distal tubule.- It is then when tubular secretion occurs in the active transport then molecules are moved from the blood into the nephrons
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Complicated
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Less Complicated
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