Renal Physiology Flashcards
Bladder filling (urine going from ureters to bladder)
-muscle layers of ureters
-frequency of peristaltic contractions of ureteric muscles
-Spiral/longitudinal/circular bundles
-1 to 5 times per minute
Bladder emptying
-muscle layers of bladder
-bladder volume and pressure relation
-at what volume does the urge to void start?
-at what volume will there be marked fullness?
-urine volume that would initiate a reflex contractions?
-like that of the ureters: spiral/longitudinal/circular bundles
-urine enters the bladder without producing much increase in intravesical pressure until the viscus is well filled
-150mL
-400mL
-300-400ml
Innervation of the bladder
Three sets of peripheral nerves from the autonomic and somatic nervous systems:
*Pelvic parasympathetic nerves
Originate in the sacral level of the spinal cord, causing the bladder to contract and the urethra to relax
*Lumbar sympathetic nerves
Originate in the T11-L2 level of the spinal cord, causing the bladder body to inhibit and the bladder base and urethra to excite
*Pudendal nerves
Originate in the S2-S3-S4 level of the spinal cord, causing the external urethral sphincter to excite
Osmolality of the pyramidal papilla
1200 mosm/kg
Osmolality of renal cortex
300 mosom/kg
Loop of Henle parts permeability to H2O and NaCL
The thin descending portion of the loop of Henle is highly permeable to H2O (4+) and only slightly permeable to NACL (+/-)
The thin ascending portion of the loop of Henle is not permeable to H2O (0) but highly permeable to NACL (4+)
The thick ascending portion of the loop of Henle is not permeable to H2O (0) and only slightly permeable to NACL (+/-)
The collecting tubules are only highly permeable to water in the presence of vasopressin. Without it they are only slightly permeable
Prostaglandin effect on renal blood flow
PG increase cortical blood flow
PG decrease medullary blood flow
Filtration Fraction
FF is the fraction of renal plasma flow (RPF~600ml/min) filtered across the glomerulus.
FF= eGFR/RPF=20% (0.2).
which means that the remaining 80% continues its pathway through the renal circulation.
eGFR varies less than the RPF
in case of hypotension–> eGFR falls less than RPF –> FF rises
Transport Maximum (Tm)
Maximal rate at which a substance can be reabsorbed by the renal tubule.
When a solute concentration increases the reabsorption rate won’t increase beyond a certain level called Tm.
Na+ Reabsorption
-Na+ reabsorption in PCT mainly by Na-H exchange (*60%)
Asc loop of Henle: Na-2CL-K CT (30%)
DCT: Na-CL CT (7%)
Collecting Tubules: ENaC (epithelial sodium) channels (3%)
-In PCT/DCT/Thick part of ascending loop of Henle/collecting tubules: Na+ moves by cotransport or exchange from the tubular lumen into the epithelial cells down its concentration gradient. (ex: Na/Glucose co-transporter, Na+/P CT, Na+/aa CT, Na+/lactate CT, Na/H exchanger…).
Then Na+ gets actively transported into the interstitial fluid by Na/K ATPase in the basolateral membrane.
-So, Na+ is actively transported out of all parts of the renal tubule except the thin portions of the loop of Henle.
-A small amount of Na+ and other solutes and H2O re-enter the tubular lumen by passive transport through tight junctions.
Glucose reabsorption
-Glucose/A.A/Bicarbonate are reabsorbed along with Na+ in the early portion of the PCT. (Secondary active transport)
-Glucose and N1+ are transported from lumen to the tubular cell through the SGLT2 transporter. Then Na+ is puped out by Na+/K+ ATPase and glucose out into blood by facilitated diffusion through GLUT2 transporter.
-All glucose is essentially reabsorbed and only a few mg appear in urine per 24h.
However when the Transport maximum is exceeded the glucose in urine rises. (Tm is 375mg/min for males and 300 for females). Which correspondence to venous levels of 180mg/dl (10 mmol/l)
PCT characteristics
1-Length
2-Diameter
3-Location
1-Length=15mm
2-Diameter=55 microg
3- Found in renal cortex
DCT characteristics
1-length
2-location
1-5mm
2-macula densa of the glomerulus
What affects renal acid secretion
Renal acid secretion is altered by changes in the intracellular PCO2, K concentration, carbonic anhydrase level and the adrenocortical hormone concentration (including aldosterone).
Tonicity of tubular fluids in the different tubular parts
-PCT: Isotonic
-Desc Loop of Henle: Hypertonic
-Asc Loop of Henle: Hypotonic
-DCT: Isotonic
Water Transport
-180mL of fluid is filtered through the glomeruli each day
-Average daily urine volume: 1L
-87% of filtered water is reabsorbed
-
RAAS
-Drop in BP or Drop in volume–> release of renin from the kidneys “Juxtaglomerular cells” (JG)
-Renis converts Angiotensinogen (Secreted by the liver) into Angiotensin1
ACE enzyme transforms angio 1 into angio 2
-Angio 2 vasoconstricts vessels and stimulates aldosterone secretions (increasing reabsorption of water and NaCL)
Effect of prostaglandins on renin
Stimulate renin secretion
Which components of the nephron has a brush border
PCT, due to the presence of innumerable microvilli
Clearance of Inulin formula
Clearance of inulin= (Urine concentration x urine flow) / Arterial plasma level
