In the Urinary system there are two kidneys, each with their own separate blood supply. Each carrying out the process of excretion and filtration osmoregulation.
From each Kidney there is a tube that leads to the bladder called the Ureter. The ureter carries Urine from the kidney to the common bladder.
Urine is then conducted to the outside of the blood to be excreted down a structure called the Urethra, which either down through the vagina or penis.
Osmoregulation = Osmosis/regulation (control of composition of blood) Tissue flood surrounds cells must be Isotonic with the cytoplasm of the cells. This means that the amount of water going into and out of these cells is equal and the cells shall remain the same size and function.
The danger to the tissue is that blood that is circulating into the tissue would be concentrated causing a hypertonic tissue flood. Or may be very dilute causing a hypotonic tissue flood. Both of these are undesirable. Hypertonic would remove too much water and Hypotonic would add too much water. We want to keep the tissue fluid Isotonic to the cell cytoplasm.
This is achieved my controlling the composition of blood. Blood forms the tissue fluid. It is the role of the kidney to control the composition of blood. Blood which circulates though our kidney excess water + salts can be removed and excreted down the ‘Ureter’.
By controlling the content of water and salts in the blood, the kidney can keep the blood and tissue fluid isotonic with the cell cytoplasm, maintaining the functions of the cells.
Excretion of the molecule known as Urea (contains Nitrogen = toxic to body and cannot be stored)
The original form of nitrogen = Amino Acids (excess). Amino Acids that are in excress must be removed; this is role of the liver and the kidney. Blood circulates to the Liver and Amino acids are broken down and converted into the molecule Urea.
This reenters the blood steam and enters both kidneys. The Kidneys will filter the Urea from the blood and the urea will be added to water to create Urine. The Urine travels down the ‘Ureter’ in the Kidneys to collect in the bladder.
1. Photosynthesis = Leaf absorbing light energy. Combines Carbon dioxide + water ---> molecules (i.e Glucose) + Oxygen. In this case Oxygen is a waste molecule. Oxygen is an example of Excretion.
2. Respiration = Glucose + oxygen ---> ATP + Carbon dioxide + water. The Carbon dioxide is the excretion in this case.
