3.  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

4.  ( 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

6.  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

8.  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.

10.  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

11.  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

12.  ● 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

13.  “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

14. Complicated

15. Less Complicated