Urinary System Flashcards
Excretion
The removal of metabolic wastes produced in the body
Kidneys
Regulate salt and water concentration in the blood through formation and excretion of urine
Outer cortex, inner medulla and renal pelvis
Contains million nephrons
Nephron
Bowman’s capsule, proximal convoluted tubule, loop of Henle, distal convoluted tubule, and collecting duct
Loop of Henle and collecting duct through the medulla. Convoluted tubules and Bowman’s capsule in the cortex
Bowman’s capsule
Embraces the special capillary bed glomerulus
Peritubular capillary
Surrounds most of the nephron to facilitate reabsorption of amino acids, glucose, salts, and water
Urine Formation
Filtration - blood pressure forces 20% of the blood plasma entering the glomerulus through its capillary walls and into the Bowman’s capsule
Secretion - secretes waste substances from the interstitial fluid into the filtrate by passive and active transport
Reabsorption - essential substances and water reabsorbed from the filtrate and returned to the blood
Filtrate
The fluid and small solute entering the nephron
Isotonic with blood plasma
Proximal convoluted tubule
Primary site of nutrient reabsorption
Descending loop of Henle
Permeable to water
Impermeable to ions and urea
Thin ascending limb
Permeable to ions, passive
Impermeable to water
Thick ascending limb
Actively reabsorb sodium, potassium, and chloride
Osmolarity gradient
Exiting and re-entering solutes at different segments of the nephron create an osmolarity gradient between the tubules and interstitial fluid
Increases from cortex to inner medulla
Depends on a counter-current-multiplier system
Counter-current-multiplier system
Uses energy to create a concentration gradient
causes interstitial space in medulla to be hyperosmolar
Water exists the collecting ducts by osmosis
Antidiuretic hormone (ADH)
Vasopressin
Increases the permeability of the collecting duct to water creating more concentrated urine
Open aquaporins in the distal convoluted tubule and collecting ducts for water reabsorption
Aldosterone
A steroid hormone that causes increased transport of sodium and potassium ions along the distal convoluted tubule and collecting duct, decreasing excretion of sodium ions and increasing potassium excretion
Increases water reabsoprtion
