ANATOMY

Detailed explanation-1: -Blood volume is determined by the amount of water and sodium ingested, excreted by the kidneys into the urine, and lost through the gastrointestinal tract, lungs and skin.

Detailed explanation-2: -When sodium is retained, less urine is produced, eventually causing blood volume to increase. The pituitary gland secretes vasopressin (sometimes called antidiuretic hormone). Vasopressin causes the kidneys to conserve water.

Detailed explanation-3: -To measure the volume of any fluid compartment within the body you must inject or infuse a marker substance that will equilibrate (diffuse freely to a uniform concentration) throughout this compartment. To be a perfect marker a substance must also not be metabolised.

Detailed explanation-4: -In lean healthy adult men, the total body water is about 60% (60–67%) of the total body weight; it is usually slightly lower in women (52-55%). The exact percentage of fluid relative to body weight is inversely proportional to the percentage of body fat.

Detailed explanation-5: -Retention of sodium by the kidneys increases the retention of water, resulting in increased blood volume and blood pressure (7).