Genitourinary Flashcards
5 functions of the kidney?
Excretion if metabolic products Excretion of foreign substances Homeostasis Regulate BP Secrete hormones
What is the function of the detrusor muscle?
Contracts → bladder pressure rises → urination
What is the function of the trigone?
Sends signals to the brain when stretched to indicate need for urination
Function and control of internal and external sphincters?
Both prevent urination
Int - involuntary
Ext - voluntary
Function of bulbourethral gland?
Only in males
Produces thick lubricant which is added to semen to aid sperm survival
Which parts of the nephron are rich in mitochondria? (4)
PCT
DCT
Thick ascending LoH
Intercalated cells of CD
Nephron parts low in mitochondria?
Thin ascending and descending LoH
Principal cells of CD
What are the two types of nephron?
Superficial (cortex and outer medulla)
Juxtamedullary (cortex, outer and inner medulla)
More superficial
What are the constituents of the juxtaglomerular apparatus?
Macula densa - distal convoluted tubule
Extraglomerular mesangial cells
Juxtaglomerular cells - afferent arteriole
Function of the JGA?
GFR regulation via tubulo-glomerular feedback mechanism
Renin secretion for Bp
Which cells secrete renin?
Juxtaglomerular cells
How does fluid move from the glomerulus into bowmans capsule?
Passive
Hydrostatic pressure of heart
Describe how the structure of capillary endothelium supports transport?
It’s fennestrated so it’s highly permeable to fluid and solutes but impermeable to cells and proteins
Describe structure of glomerular basement membrane
Epithelial Podocytes
Slit diaphragm between podocytes thin and porous to allow through small molecules and water
What are the differences between hydrostatic and oncotic pressure?
HP - pressure exerted by fluid, solute and fluid are pushed out
OP - pressure exerted by solute, fluid molecules drawn in a cross semipermeable membrane
Net ultrafiltration pressure equation?
HP in glomerular capillaries - HP in BC - OP in GC
What is the glomerular filtration rate?
Amount of fluid filtered from glomeruli into bowmans capsules per unit time
GFR equation?
Ultrafiltration pressure x Kf (ultrafiltration coefficient)
Normal GFR ranges?
M - 90-140
F - 80 - 125
What can a fall in GFR show?
Renal disease
Increase in waste products in plasma
What are the 2 ways GFR is regulated?
Myogenic mechanism
Tubulo-glomerular feedback mechanism
Explain the myogenic mechanism
Arterial pressure increases Afferent arteriole stretches Arteriole contracts so vessel resistance rises Reduced blood flow GFR maintained
Explain the tubule-glomerular feedback mechanism
Increase GFR Increased NaCl in LoH Change detected by macula densa Increased ATP and adenosine discharged Afferent arteriole contracts GFR decreases to stabilise
Vice verse for decrease
What is renal clearance?
Volume of plasma that is completely cleared of a substance per unit time
Only concerned with excretory role of kidneys
Rate of removal of a substance from the blood via excretion in the urine
Renal clearance equation?
C= (u x v) / p
U : concentration of substance in urine
V : rate of urine production
P : concentration in plasma
How can GFR be measured practically?
By measuring the renal clearance for a substance that is freely filtered and not reabsorbed nor secreted in the nephron
Amount filtered = amount excreted
What is the ideal molecule for GFR measurement and why is it not used?
Inulin
Not toxic, measurable in urine and plasma
But not found in mammals so needs to be transfused
What molecule is commonly used to measure GFR and why?
Creatinine - waste product from creatine muscle metabolism
Amount released is fairly constant
Freely filtered and not reabsorbed
What can indicate renal foliage relating to creatniine?
Low creatinine clearance
High plasma creatinine
What is one problem with creatinine and how is it resolved?
A small amount is secreted into nephron but this is taken into account in GFR calculations
What is renal plasma flow?
Volume of plasma that reaches kidneys per unit time
When does renal clearance equal renal plasma flow?
When total amount of a molecule entering the kidney is excreted
What molecule is used in measured rpf and why?
Para aminohiupparte (PAH) All is removed from plasma via filtration and secretion
What is the filtration fraction?
The ratio of the amount plasma that is filtered and the amount that arrives at afferent arteriole
=GFR/RPF
What is the normal range for filtration fraction?
0.15 - 0.20
What substances are 100% reabskrbed in PCT?
Glucose
Amino acids
What other substances are reabsorbed in PCT?
Na+ Cl- HCO3- Water Urea
What substances are secrete into pct?
Drugs Ammonia Bile salts Prostaglandins Vitamins
What are the 3 transporters involved in sodium and bicarbonate reabsorption?
Na+ H+ antiporter
Na+K+ATPase pump
Na+HcO3- symporter
How are carbonate ions formed in pct cells?
CO2 diffuses into cell
Combines with water in presence carbonic anhydrase to form Hc and HCO3-
What are the 3 transporters in glucose reabsorption in the pct?
SGLT2 - Na+ glucose symporter
Na+K+ATPase pump
GLUT2 glucose transporter
What substances are reabsorbed in LoH?
Water
Na+
Cl-
Outline the reabsorption in LoH
Thin descending limb - water moves out, impermeable to ions
Bottom = hyperosmolar fluid
Thin ascending limb - impermeable to water, ions passively move out
Thick ascending limb - ions are actively pumped out
Top = hypo-osmolar fluid
What substance move through the paracellular pathway in thick AL?
Ca2+
Na+
K+
Mg2+
What 3 transporters are in the thick ascending limb?
Na+K+Cl- symporter
Na+K+ATPase pump
K+Cl- symporter
What substances are reabsorbed in the early DCT?
Na+
Cl-
Ca2+
What transporters are in the early DCT?
Na+ Cl- : Na+Cl- symporter , ATPase pump, K+Cl- symporter
Ca2+ : ATPase pump, Na+Ca2+ antiporter, Ca2+ATPase pump
What are the 2 types of cells in the distal DCT and CD? + functions
Principal - Na+ , water reabsorption, K+ secretion
Intercalated cell - maintain acid-base balance
How is Na+ reabsorption regulated?
Aldosterone increases apical Na+ channels and basolateral ATPase pumps
How is water reabsorption regulated?
ADH increases apical aquaporins
Outline reabsorption and secretion in distal DCT and CD
Sodium moves in through apical sodium channels
It is exchanged with potassium via basolateral ATP pump
Potassium is secreted into tubular fluid via potassium channels
Water is reabsorbed by aquaporins on apical and basolateral membranes
What are the 2 types of intercalated cells and their functions?
a - HCO3- reabsorption, H+ sercretion
B - H+ reabsorption, HCO3- secretion
What are the 2 transporters found on intercalated cells
H+ATPase pump
Cl-HCO3- antiporter
