Renal Flashcards
What is the anatomical difference between the left and right gonadal veins?
- Left goes into left renal vein then to ivc
- Right goes straight into IVC
Describe the anatomical relationships between the renal vessels and ureter
-Renal vein most superficial, then renal artery then ureters
What is the trigone of the bladder and state its significance
- A triangle area between the two ureter orrifices and the internal urethral meatus.
- It is a non-distensible area which signals to the spinal cord when stretched
Name the segments of the male urethra
Which segment possesses the most resistance on passage of a catheter?
- Pre-prostatic
- Prostatic
- Membranous
- Spongy
- Membranous
Give 3 common places a renal stone can get stuck
- Pelviuretic junction (narrowing of the renal pelvis as it transitions into ureter)
- Pelvic brim
- Ureteral orrifice
What is the main function of the PCT?
-Site of major reabsorbtion of Na, K, bicard, glucose, amino acids and water
Briefly describe the development of the kidney
- First pronephros forms from intermediate mesoderm and develops a duct which extends caudally
- Mesonephros develops and commandeers pronephrotic duct. Caudal development continues until it makes contact with cloaca and ureteric buds begin to sprout
- Ureteric buds make contact with metanephric blastema driving development into metanephros which is fuctioning fetal kidney
What is the urogenital ridge?
-Area of intermediate mesoderm on the posterior abdominal wall which gives rise to the embryonic kidney and gonads
Describe how the ureteric bud develops into collecting system of the kidney
-Makes contact with the metanephric blastema and grows into it by expanding and branching to form the collecting tubules, renal pyramids, major and minor calyx, renal pelvis and ureter
What is renal agenesis and give one physiological cause of this
- Complete absence of a kidney
- Failed interaction of ureteric bud
What is a wilms tumour?
-Congenital tumour of the kidney
Describe one possible consequences of duplication defects of the ureteric bud
-Incontinence if complete duplicate ureter joins after external urethral sphincter
What is the function of the urorectal septum?
-Separates urinary tract from gut tube
What does the urogenital sinus develop into? How is it connected to umbilicus? Describe a pathology which is related to this
- Upper portion of UGS creased bladder and urethra. Lower portion creates lower 2/3 vagina in females and prostate/spongy urethra in males
- The allantois originally filters liquid waste via umbilicus in exchange with mother and it develops into urachus which is a fibrous remnant of allontois.
- A patent urachus is failed regression of the patent tube into the medial umbilical ligament. This can lead to urine leaking out through umbilicus
Describe the layers of the renal corpuscle which make the filtration barrier
- Fenestrated capillary endothelium
- Visceral layer of bowmans capsule
- Podocytes
What is the juxtaglomerular apparatus made up off and what is its function?
- Macula densa of DCT
- juxtaglomerular cells of afferent arteriole
- Extraglomerular mesangial cells
- Tubuloglomerular feedback -> Detects NaCl conc as a way of interpreting GFR. This results in either prostaglandin and renin secretion if decreased or adenosine secretion if increased leading to vasodilation and RAS activation or vasoconstriction respectively.
How do the collecting ducts form the minor calyx?
-Merging collecting ducts form renal pyramids which form renal papillae -> renal calyx
What epithelium lines the bladder and ureters?
-Transitional
Describe the charge on the glomerular basement membrane and state how this helps filtration
- negative charge
- Repels negatively charged proteins so even if they are small they may not pass through, attracts positively charged proteins so larger ones may pass through
Describe the forces which drive filtration
- Capillary hydrostatic pressure
- Bowmans capsule hydrostatic pressure
- Capillary oncotic pressure
Explain how autoregulation of the kidney works?
-Within 80-180mmHg range in BP the kidney can control its own perfusion pressure and thus GFR by detecting changes in stretch of smooth muscle. An increase in BP causes an increased delivery of blood to the kidney -> afferent vasoconstriction to reduce blood vol and maintain perfusion pressure and GFR. Decreased BP causes afferent vasodilation maintaining bp and GFR.
Which capillary is wider afferent or efferent? How does efferent constriction effect pressure in the glomerulus?
- Efferent
- Increases hydrostatic pressure
Why is water readily absorbed in the peritubular cappilaries of cortical nephrons?
-They have a high oncotic pressure
Describe Na and water resorption in PCT. Which important molecule is co-linked with Na resorption in pct and how?
- NaKATPase sets up Na gradient
- Na moves down conc gradient across apical membrane
- Water follows
- Glucose -> uses the Na gradient to move glucose against its concentration gradient by using SGLTs
In which part of the lumen does secretion of H, K and organic cations occur?
-DCT
How do you calculate filtered load?
-Plasma conc of substance(mg/ml) x GFR(ml/min) = x mg/min
Why can creatinine be used to calculate GFR? What would be an alternative in a hospital setting? How is GFR calculated?
- Freely filtered, not reabsorbed and not secreted
- Inulin
- [urine] x [urine volume]/[plasma]
What is renal clearance?
-The volue of plasma which is totally cleared of a substance by the kidneys per unit time
How do you calculate eGFR?
-(140-age) x mass(kg) x 1.23(men) or 1.04(women)/serum creatinine
Describe the fluid volume in the different compartments
-3L blood
-13L ECF
25L ICF
Why must the kidneys be able to vary their Na excretion?
-To match excretion to ingestion to keep plasma volumes steady
Where in the nephron is the most Na reabsorbed?
-PCT (67%)
How does water move from the PCT into the vasa racta?
-Follows osmotic gradient into tubule cell and then pulled by oncotic gradient of blood and interstitial hydrostatic pressure
What is glomerulotubular balance?
-A mechanism to match Na resorption to GFR. As GFR increases Na resorption increase to make sure 67% is always reabsorbed
Describe what happens in the loop of henle in regards to Na and H2O resorption
- Descending limb is water permeable and the increasing electrolyte gradient in the interstitium of the medulla draws water out so by the time in the bottom of the loop there is hyperosmotic filtrate
- Ascending loop is impermeable to water and in thin ascending limb Na diffuses down its conc gradient into interstitium as it is a hyperosmotic filtrate
- In thick ascending limb NKCC2 pumps Na into the interstitium to create a hypoosmotic filtrate at the top of the loop
What electrolytes does NKCC2 transport and what other channel is it dependent upon?
- Na, K, Cl, Ca and Mg
- Requires ROMK channels to ensure leakage of K+ back into lumen so it works
Describe Na/H2O resorption in the DCT
- Uses NCCT channels on apical membrane
- Early DCT is poorly permeable to water and active Na resorption increase hypo-osmolarity
- NaKATPase pumps Na into interstitium to be reabsorbed
- Late DCT has ENaC in principle cells
Beside Na, what other electrolytes are controlled in the DCT?
- Major site of Ca resorption via Ca channel on apical membrane and NCX on basolateral membrane
- K secretion through apical K channels (attracted to negative lumen)
- H+ secreted by a-intercalated cells
- K+resorption by a-intercalated cells
- Active Cl- resorption through b-intercalated cells
Where is renin released from? Why?
- Juxtaglomerular cells of JGA
- Decreased NaCl in DCT detected by macula densa cells of DCT, decreased perfusion pressure and sympathetic stimulation of JGA
- Stimulates renin release to initiate RAS pathway to increase Na and H2O retention
Where is angiotensinogen made?
-Liver
Where is the main site of AgI conversion to AgII?
-Lungs
What are the actions of AgII?
- Stimulates SNS
- Stimulates Aldosterone production
- Vasoconstriction
- Direct effects on nephron to increase Na/H2O resorption
- Stimulates ADH release
- Stimulates thrist and salt intake
What 4 mechanisms are involved in long term regulation of BP?
- SNS
- RAAS
- ADH
- ANP/BNP
-How does the SNS use the kidney to alter BP?
-Causes vasoconstriction of afferent arterioles which decreases flow through the kidney and decreases GFR to decrease Na excretion
-Direct effect on nephron by stimulating NHE and basolateral NaKATPase
-Stimulates JGA to release renin to activate RAS
All together they increase BP
How do the natiuretic peptides function?
-Stimulated upon stretch of the atria or ventricles to cause vasodilation of the afferent arteriole to increase blood flow, increase GFR and increase Na excretion
What detects changes in plasma osmolarity? What is the outcome of detecting a increase in osmolarity
- Hypothalamic osmoreceptors in OVLT
- Stimulates ADH release from posterior pituitary via neural stalk
- Stimulated thirst
What is the consequence of ADH release? How does it effect the osmolarity of the urine?
- Enters circ and acts on kidney to cause insertion of aquaporin 2 channels into apical membrane of collecting duct which increases the permeability of the collecting duct to water and urea. Also causes vasoconstriction of glomerulus and increases activity of NKCC2
- Causes the urine to become hyperosmotic
What happens when a decrease in osmolarity is detected?
-Removal of AP2 via endocytosis and Na intake stimulated and diuresis occurs producing hypoosmotic urine
What is diabetes insipidus?
-Decreased ADH production by the pituitary or acquired kidney insensitivity -> hypernatraemia and hypokalaemia
What is SIADH?
-Excessive ADH production from the posterior pituitary or an ectopic source eg small cell lung cancer causes an excessive water resorption leading to dilutional hyponatraemia
What is counter current multiplication?
- A process which creates the descending osmotic gradient within the interstitium of the kidney from cortex to medulla
- isotonic filtrate enters descending limb which is permeable to water but impearmeable to solutes -> creates a hyperosmotic filtrate in the bottom of the loop as water moves into interstitium
- The ascending limb is permeable to solutes but not to water and Na diffuses into the interstitium. Most Na diffuses in the bottom of the limb as this is where the greatest gradient between limb and interstitium is. Then as the filtrate moves up the limb it becomes more hypotonic and thus not as much solute diffuses out and therefore the interstitium becomes less hyperosmotic as you move back towards to cortex. By the time the filtrate is at the top of the limb it is actually hypoosmotic