2.70 Nephron Structure

•  Nephron: The functioning part of the kidney, it does the filtration and the controlling of the composition of the blood.
• Bowman's capsule: The dead end to the Nephron. 
• Proximal Convoluted tubule: The first twisted section.
• Distal Convoluted tubule: The second twisted section. 
•  Glomerulus: Filters the blood and is surrounded by the bowman's capsule
•  Loop of Henle: Leads the Proximal tubule to the distal tubule there are millions of Nephrons in the kidney.

2.71 Ultrafiltration

• The blood arrives in the kidney through the Afferent Arteriole.
• The Arteriole begins to branch off and create a twisted knot-like structure called the Glomerulus.
• The diameter of the Efferent Arteriole is smaller.
• This creates a high pressure.
• Plasma which is salts, water, amino acids, urea and glucose is forced out of the blood vessel and into the inside of Bowman's capsule.
• This is called the Glomerular filtrate.

2.72 Water re-absorbtion

• When the ultrafiltration occurs in the Bowman's capsule, too much water is filtered.
• The water is removed from the filtrate.
• It is then added into the blood vessels.
• This is called selective reabsorption.
• As it passes through the Collecting Duct, water is removed from the filtrate. 

2.73 Glucose re-absorption

• A molecule is selected and is reabsorbed back into the blood.
• The molecule gets removed from the blood and is put back in.
• If there is glucose in urine, the person could have diabetes.
• There usually is no glucose in urine.
• In the first convoluted tubule glucose is removed and out back into the blood.

2.74 ADH

• ADH- Anti Diuretic Hormone.
• ADH increases the permeability of the kidneys which allows them to re-absorb more water.
• It flows through the blood stream to the kidneys.
• It is produced in the region of the brain known as the hypothalamus. 
• It controls the amount of water in the blood.
• Tissue fluid should be isotonic with the cells.

2.75 Urine

• Urine contains water salts and urea.
• The removal of urea is a part of excretion and metabolic waste.
• Salts and urea is removed by osmoregulation to maintain isotonic tissue.
• The salt, water and urea composition in each person varies depending on the condition the person is in.