Lecture 18 Renal Physiology Flashcards
angiotensin bruv
What are the various functions of the kidneys?
- Maintain purity and chemical consistency of plasma and interstitial fluid and in the process form urine
- Regulate volume of blood plasma, waste products in blood, concentration of electrolytes, and plasma pH
What are the 3 main metabolic wastes that are excreted by the urinary system?
Urea, uric acid, and creatinine
What microscopic structures does the renal cortex contain?
- many peritubular capillaries
- outer parts of nephrons: glomerular capsule, PCT, DCT
What does the renal medulla consist of?
Renal pyramids separated by renal columns
What microscopic structures do the renal pyramids contain?
Nephron loops (loops of henle),most of the length of the collecting ducts, and the vasa recta capillaries
All blood vessels that supply and drain the kidney are (in the correct path of blood flow through renal blood vessels):
Aorta –> Renal artery –> segmental artery –> interlobar artery –> arcuate artery –> cortical radiate artery –>
(nephron-associated blood vessels) afferent glomerular arteriole –> glomerulus (capillaries) –> efferent glomerular arteriole –> peritubular capillaries/ vasa recta –> cortical radiate vein –> arcuate vein –> interlobar vein –> renal vein –> inferior vena cava
What is the nephron and its function?
- The basic structural and functional (urine-producing) unit of the kidney
- To regulate the concentration of water and soluble substances by filtering the blood, reabsorbing what is needed back to blood, secreting what is not, and excreting the rest as urine
What are the 3 mechanisms/ processes that occur during urine production?
- Glomerular filtration
- Reabsorption
- Secretion
What is glomerular filtration and where does it occur?
A filtrate of the blood leaves glomerular capillaries (glomerulus) and enters the glomerular capsule of nephron.
Explain the process of reabsorption
Most of the nutrients, water and essential ions are recovered from the filtrate and returned to the blood of capillaries (peritubular capillaries or vasa recta) in the surrounding CT
Explain the process of secretion
Remaining wastes and unnecessary substances in blood are moved into renal tubules from surrounding peritubular capillaries.
What are the 3 layers of the filtration membrane in order (innermost to outermost)
- Fenestrated endothelium of glomerular capillaries
- Glomerular basement membrane
- Filtration slits and slit diaphragm of visceral layer of glomerular capsule (podocytes)
What is the main job of the fenestrated endothelium of glomerular capillaries?
Prevent passage of RBCs, WBCs, and platelets into the filtrate
The glomerular basement membrance (basal lamina) helps prevent the passage/ filtration of…
Larger proteins
Genetic defects in the proteins that compose the slit diaphragms result in massive leakage of plasma proteins into the filtrate leads to what?
Proteinuria
What is the name of the fluid that enters the glomerular capsule?
Filtrate or ultrafiltrate
True or False: Reabsorption happens only in the PCT and DCT
FALSE: Reabsorption happens at all 3 parts of the renal tubule
(PCT, Loop of Henle, DCT and collecting duct)
What is obligatory water loss?
Minimum of urine (400ml/ day) necessary to excrete metabolic wastes
At the PCT, the filtrate is isosmotic, which means the osmolality of the filtrate is essentially the same as that of plasma.
Can reabsorption of water by osmosis occur in this state? Why?
No it cannot because osmosis requires a concentration gradient. There is no concentration gradient if the filtrate is isosmotic.
What is the glomerular filtration rate (GFR)?
Volume of filtrate produced by BOTH kidneys
App. 125 ml/min or 180l/day
What is step 1 of reabsorption at the PCT?
- Na+ is actively transported from renal tubular fluid to peritubular fluid (aka interstitial fluid) surrounding the PCT
Occurs via sodium/ glucose cotransport. This creates a potential difference across the wall of the tubule, with the tubular lumen as the negative pole.
What is step 2 of reabsorption at the PCT?
Electrical gradient favors the passive transport of Cl- toward the higher Na+ concentration in the peritubular fluid
What is step 3 for reabsorption at the PCT?
- Accumulation of NaCl increases the osmolarity in the peritubular fluid above that of the tubular fluid. An osmotic gradient is then created that moves water from the tubular fluid into the peritubular fluid.
What is the final step of reabsorption at the PCT?
- The salt and water that were reabsorbed from tubular fluid can then move passively into plasma of the surrounding peritubular capillaries