Changes

==Why is it Important?==

==Why is it Important?==

Water has multiple functions: it is the solvent in which the majority of intra- and extracellular processes occur, it facilitates the transport of oxygen and nutrients in blood, it is needed for normal digestive function, [[Thermoregulation - Anatomy & Physiology|thermoregulation]] and the excretion of waste products. It is the major component of most body tissues accounting for approximately 60% of the total body weight in adult mammals with 2/3 in the Intracellular and 1/3 in the Extracellular compartment. Extracellular water is further dispersed between the interstitium (3/4) and plasma volume (1/4)<ref name="Wellman">Wellman ML, et al. Applied Physiology of Body Fluid in Dogs and Cats. In Fluid, Electrolyte, and Acid-Base Disorders in Small Animal Practice. 2012 4th Ed. St. Louis: Elsevier Saunders  p.2-22.</ref>.

Water has multiple functions: it is the solvent in which the majority of intra- and extracellular processes occur, it facilitates the transport of oxygen and nutrients in blood, it is needed for normal digestive function, [[Thermoregulation - Anatomy & Physiology|thermoregulation]] and the excretion of waste products. It is the major component of most body tissues accounting for approximately 60% of the total body weight in adult mammals with 2/3 in the Intracellular and 1/3 in the Extracellular compartment. Extracellular water is further dispersed between the interstitium (3/4) and plasma volume (1/4)<ref name="Wellman">Wellman ML, et al. Applied Physiology of Body Fluid in Dogs and Cats. In Fluid, Electrolyte, and Acid-Base Disorders in Small Animal Practice. 2012 4th Ed. St. Louis: Elsevier Saunders  p.2-22.</ref>.

Water balance is regulated by [[Pituitary Gland - Anatomy & Physiology#Antidiuretic Hormone|antidiuretic hormone]] (ADH) produced in the [[Hypothalamus - Anatomy & Physiology|hypothalamus]] and released in response to decrease in blood volume or increases in plasma [[Nutrition Glossary#Osmolarity|osmolarity]] (determined mainly by plasma Na concentrations). Mild dehydration resulting in a loss of 0.5% fluid volume or an increase in [[Nutrition Glossary#Osmolality|osmolality]] of 1-3% stimulates production of ADH resulting in water reabsorption in the [[Nephron Microscopic Anatomy#Proximal Tubule|renal tubules]] and activation of the [[Renin Angiotensin Aldosterone System|renin-angiotensin system]] with angiotensin II stimulating the thirst response<ref name="Robinson">Robinson EA and Adolph EF. Pattern of normal drinking in dogs. Am J Physiol 1943;139:39-44.</ref><ref name="Anderson">Anderson RS.Water balance in the dog and cat. J Small Animal Practice 1982;23:588-598.</ref><ref name="O'Connon">O’Connon WJ and Potts DJ. The external water exchange of normal laboratory dogs. Q J Exp Physiol  Cogn Med Sci 1969;54:244-265.</ref>.  

Water balance is regulated by [[Pituitary Gland - Anatomy & Physiology#Antidiuretic Hormone|antidiuretic hormone]] (ADH) produced in the [[Hypothalamus - Anatomy & Physiology|hypothalamus]] and released in response to decrease in blood volume or increases in plasma [[Nutrition Glossary#Osmolarity|osmolarity]] (determined mainly by plasma [[Sodium - Nutrition|Na]] concentrations). Mild dehydration resulting in a loss of 0.5% fluid volume or an increase in [[Nutrition Glossary#Osmolality|osmolality]] of 1-3% stimulates production of ADH resulting in water reabsorption in the [[Nephron Microscopic Anatomy#Proximal Tubule|renal tubules]] and activation of the [[Renin Angiotensin Aldosterone System|renin-angiotensin system]] with angiotensin II stimulating the thirst response<ref name="Robinson">Robinson EA and Adolph EF. Pattern of normal drinking in dogs. Am J Physiol 1943;139:39-44.</ref><ref name="Anderson">Anderson RS.Water balance in the dog and cat. J Small Animal Practice 1982;23:588-598.</ref><ref name="O'Connon">O’Connon WJ and Potts DJ. The external water exchange of normal laboratory dogs. Q J Exp Physiol  Cogn Med Sci 1969;54:244-265.</ref>.

==Regulation of Water Balance==

==Regulation of Water Balance==