Removal of Urine
- After selective reabsorption, the remaining filtrate travels down the collecting duct to the renal pelvis
- The liquid exits the kidneys and travels via the ureters to the bladder
- This waste solution is called urine; it is stored in the bladder before being released from the body via the urethra
- Urine produced by the kidneys contains:
- Urea
- Excess salts
- Excess water
Urine composition and health
- Glucose in the urine can be a sign of diabetes
- In a person with normal blood glucose levels, we would expect all of the glucose to be reabsorbed from the filtrate back into the blood
- People with diabetes often have unusually high blood glucose concentrations, meaning that not all of the glucose is reabsorbed
- The glucose in the filtrate ends up in the urine, so the presence of glucose in the urine can indicate diabetes
- The presence of blood, cells, or proteins in the urine can indicate disease in the kidney
- Kidney disease can cause damage to the lining of the capillaries in the capillary knot
- Large molecules, such as proteins, as well as whole cells, can be forced out of the blood during the process of filtration under pressure
- These substances end up in the urine, where their presence indicates kidney damage
