Physiology of the Kidney Urine Formation

Filtration  Occurs in the glomerulus  Renal artery branches off into tiny capillaries upon entering the kidney = increased pressure, which drives filtration  Occurs in the glomerulus  Renal artery branches off into tiny capillaries upon entering the kidney = increased pressure, which drives filtration

Filtration  Plasma is filtered through capillary walls and passes into the Bowman’s capsule  Size determines what will be filtered; anything small enough is forced out by the filtration process  Plasma is filtered through capillary walls and passes into the Bowman’s capsule  Size determines what will be filtered; anything small enough is forced out by the filtration process

Filtration Examples: water, salts, glucose, amino acids, urea, some drugs, etc. Blood cells & plasma proteins are too large to be forced out of capillaries - move into efferent vessel which contains very concentrated blood Examples: water, salts, glucose, amino acids, urea, some drugs, etc. Blood cells & plasma proteins are too large to be forced out of capillaries - move into efferent vessel which contains very concentrated blood

Reabsorption  Occurs primarily in the PCT (~80%) but some occurs in the DCT & Collecting Duct  Prevents the loss of nutrients by reabsorbing useful substances from the filtrate back into the bloodstream  Occurs primarily in the PCT (~80%) but some occurs in the DCT & Collecting Duct  Prevents the loss of nutrients by reabsorbing useful substances from the filtrate back into the bloodstream

Reabsorption  Passive transport occurs naturally & allows substances such as water & urea back into the bloodstream (urea is a waste product but kidneys aren’t 100% efficient at removing it so some is reabsorbed)

Reabsorption  Active transport is when the body expends energy to get desired substances back from the filtrate such as glucose or amino acids

Secretion  Occurs mainly in the DCT & Collecting Tubule  Substances move from the blood into the kidney tubules to be excreted in the urine  Occurs mainly in the DCT & Collecting Tubule  Substances move from the blood into the kidney tubules to be excreted in the urine

Secretion  Examples of substances secreted: urea, creatinine, hydrogen, bicarbonate, & hormones  Purpose is to eliminate waste products not already present in the filatrate & to maintain proper pH, fluid, & electrolyte balance  Examples of substances secreted: urea, creatinine, hydrogen, bicarbonate, & hormones  Purpose is to eliminate waste products not already present in the filatrate & to maintain proper pH, fluid, & electrolyte balance

Secretion  Hormones involved in Secretion: -ADH (anti diuretic hormone) +helps regulate water balance +secreted by pituitary gland when blood pressure too high (too much salt)  Hormones involved in Secretion: -ADH (anti diuretic hormone) +helps regulate water balance +secreted by pituitary gland when blood pressure too high (too much salt)

Secretion  Hormones involved in Secretion: -ADH (anti diuretic hormone) +prevents excessive water loss by causing collecting tubules to reabsorb water back into the blood stream  Hormones involved in Secretion: -ADH (anti diuretic hormone) +prevents excessive water loss by causing collecting tubules to reabsorb water back into the blood stream

Secretion  Hormones involved in Secretion: -ADH (anti diuretic hormone) +results in more concentrated urine & a smaller volume of urine *Diuretic = a substance that inactivates ADH & increases the amount of urine produced Ex: water, milk, coffee, tea, alcohol, pop, etc.  Hormones involved in Secretion: -ADH (anti diuretic hormone) +results in more concentrated urine & a smaller volume of urine *Diuretic = a substance that inactivates ADH & increases the amount of urine produced Ex: water, milk, coffee, tea, alcohol, pop, etc.

Secretion  Hormones involved in Secretion: - Aldosterone (salt & water hormone) +helps regulate electrolyte & fluid balance +secreted by adrenal glands when blood pressure low (not enough salt) = “Dilute Blood”  Hormones involved in Secretion: - Aldosterone (salt & water hormone) +helps regulate electrolyte & fluid balance +secreted by adrenal glands when blood pressure low (not enough salt) = “Dilute Blood”

Secretion  Hormones involved in Secretion: - Aldosterone (salt & water hormone) +Retains more sodium than normal & excretes more potassium than normal; also results in water retention because “water follows salt”  Hormones involved in Secretion: - Aldosterone (salt & water hormone) +Retains more sodium than normal & excretes more potassium than normal; also results in water retention because “water follows salt”

Secretion  Hormones involved in Secretion: - Aldosterone (salt & water hormone) +Addison’s disease (aldosterone deficiency) = fatigue, loss of appetite, weight loss, low blood pressure, nausea, vomiting, diarrhea, muscle spasms & weakness, emotional changes such as irritability & depression, salt cravings, & “bronzing” of the skin  Hormones involved in Secretion: - Aldosterone (salt & water hormone) +Addison’s disease (aldosterone deficiency) = fatigue, loss of appetite, weight loss, low blood pressure, nausea, vomiting, diarrhea, muscle spasms & weakness, emotional changes such as irritability & depression, salt cravings, & “bronzing” of the skin

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