Renal Physl 4 Flashcards
What kind of regulation occurs at the nephron?
Dehydration and blood volume regulation
What are the basic renal processes?
Filtration, reabsorption and secretion
What are the three processes that go into the formation of urine?
- Glomerular filtration
- Tubular reabsorption
- Tubular secretion
What occurs in Glomerular Filtration?
Blood flows into glomerular capillaries and protein free fluid leaves the glomerular capillaries
What occurs in Glomerular Filtration?
Blood flows into glomerular capillaries and protein free fluid leaves the glomerular capillaries
Where the fluid from the glomerulus go?
It enters bowman’s capsule
What do not usually cross the glomerular capillary wall?
Proteins
How much fluid is filtered at the glomerular capillaries?
180 liters per day
What are some renal functions?
- Efficiently removing metabolic wastes
- Maintaining fluid and electrolyte homeostasis
- Stabilizing blood volumes and pressure
What is filtrate subject to one it leaves the bowman’s capsule?
It is subject to both reabsorption and secretion
What is Reabsortion?
The movement of water and solutes from the tubular lumen into the renal interstitium and back into the blood circulating
What blood vessels circulates the nephrons?
The peritubular capillaries and the vasa recta
What is secretion?
The selective removal of substances from circulation into the tubular filtrate that is destined for excretion
What separates glomerular filtration from secretion?
Secretion is selective and glomerular filtration is not (with the exception of proteins)
What is the selectivity of secretion useful for?
Enhancing metabolic waste products
What happens once substances enter the peritubular capillaries?
They travel to the venous blood eventually reaching the heart and are pumped throughout the body
Why do different segments of the nephron modify the filtrate in different ways?
Due to properties of the tubular epithelial cells
Why is filtrate considered isosmotic in the bowman’s capsule?
Because its composition is quite similar to plasma
What amount of filtrate is reabsorbed in the proximal tubule?
70% of filtrate volume
How is solute reabsorbed in the proximal tubule?
It is actively absorbed so they are transported out of the lumen across the tubular epithelial cell and into the renal interstitium
What happens when solutes are transported out of the lumen and into the renal interstitium?
Water follows solute and leaves the lumen and enters the interstitial space
After water and solute are reabsorbed in the proximal tubule what is the molarity of the filtrate?
It is still isosmotic
Where does filtrate go after the proximal tubule?
It enters the descending limb of the loop of henle
What occurs in the descending limb of the loop of henle?
More water is absorbed compared to solute
What is the permeability in the descending loop of henle?
It has a low permeability for solutes and a high permeability for water to leave
What occurs in the ascending loop of henle?
Solute is actively reabsorbed and water is not due to relative permeability
What is the molarity of the filtrate after leaving the ascending loop of henle?
It is dilutes because solute is reabsorbed and water is not
Where does filtrate go from the ascending loop of Henle?
It enters the distal tubules and eventually the collecting duct
What are the collecting duct and distal tubule sensitive to?
Hormones that regulate salt and water balance
What can the Distal Tubule and Collecting duct do?
It can facilitate significant reabsorption of sodium and water or virtually none at at all
What is the formula for the amount of solute excreted?
Amount of Solute Excrete = Amount Filtered - Amount reabsorbed + amount secreted
What does it mean to be secreted?
It means that it goes into the lumen of the nephron to be excreted
