Session 18 - Urinary system - Tubular Reabsorption and Secretion Flashcards
purpose of tubular reabsorption
return filtered water and solutes to blood stream
how is reabsorption achieved
Proximal convoluted tubule have microvilli - this is how most is reabsorbed.
- Solutes are reabsorbed by both active and passive transport
- Water follows by osmosis
- Small proteins by pinocytosis
tubular secretion definition
transfer of materials from blood and tubule cells into glomerular filtrate
- controls blood pH
- elimate certain substances
A - renal corpuscle
B - renal tubule and collecting duct
Two routes of reabsorption routes
- paracellular reabsorption
- movement between adjacent tubule cells
- via osmosis
- transcellular reabsorption
- movement through an individual tubule cells
- via active transport
transport mechanisms
- two main mechanisms
- active transport
- primary and secondary
- passive transport
- osmosis
- active transport
primary sctive transport
ATP used to pump across membrane
- sodium potassium ATPase pumps in basolateral membrane
secondary active transport
- ion electrochemical gradient drive substances across the membrane
- symporters: membrane proteins moving two or more substances in the same direction across a membrane
- antiporters: membrane proteins moving two or more substances in opposite directions across membrane
passive transport
- osmosis
-
obligatory water reabsorption
- water is obliged to follow the solutes which are being reabsorbed
- occurs in proximal convoluted tubule and descending limb of the loop of Henle
-
facultative water reabsorption
- adapted to specific needs
- occurs in the collecting duct
-
obligatory water reabsorption
facultative water reabosption controlled by
- antidiuretic hormone
- if more water is needed to be reabsorped by the body, ADH is released for insertion of aquaporins in the collecting duct
largest amount of solutes and water are reabsorped where
reabsorption in proximal convulted tubule
secretion from the proximal convoluted tubule
- deamination of the glutamine by PCT cells
- ammonia and urea in blood
- secreted into tubules
how and where is sodium reabsorbed
Achieved by several mechanisms in the proximal convoluted tubule:
- by sodium glucose symporters
-
sodium/hydrogen antiporters
- sodium reabsorp into blood and H secretion into tubular fluid
bicarbonate (HCO3-) reabsorption
- facilitated diffusion
- filtered through simulataneously with hydrogen
how are sodium, potassium, calcium, magnesium and urea reabsorped
passive diffusion into peritubular capillaries via both paracellular and transcellular routes