Excretory system has organs {kidney}| in middle-trunk back wall. Kidney regulates blood pH, blood salt, blood volume, and total body water. Increasing blood water increases blood pressure. Increasing blood pressure increases water filtration into kidney, reducing water in blood and reducing blood pressure. Kidney problems can cause edema. Kidney makes aldosterone, which controls blood pressure.
Kidneys have outer layers {cortex, kidney}.
Kidneys have inner layers {medulla, kidney}.
In kidney cortex, blood capillaries {glomerulus, kidney} {glomeruli, kidney} surround nephrons.
In kidney cortex, glomeruli surround small tubules {nephron}.
In kidney cortex, sacs {Bowman's capsule} {Bowman capsule} surround capillaries. Urea, creatinine, uric acid, ammonia, and ions diffuse under pressure into Bowman's capsule.
Below Bowman's capsule, tubules loop {proximal convoluted tubule}, and active transport returns glucose, amino acids, salts, and water by reabsorption to blood.
Proximal convoluted tubules dip down into kidney medulla and then back up to kidney cortex {Henle loop} {loop of Henle}.
In kidney cortex, looped regions {distal convoluted tubule} secrete selected substances back into urine from blood for augmentation.
Distal convoluted tubules go into kidney medulla {collecting tubule}, where countercurrent processes regulate water concentration, as low-concentration fluid passes by high-concentration fluid in opposite direction and diffusion balances water in blood and urine.
Collecting tubules can become funnel-shaped chambers {renal pelvis}.
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Date Modified: 2022.0225