Session 1 - Intro, absorption and secretion Flashcards
(40 cards)
What are the key structures of the urinary system?
Kidneys
Ureters
Bladder
Describe the location of the kidneys.
Retroperitoneal organs
At the level T11/12
What is the main function of the kidneys?
Maintain a stable internal environment. (Urinary)
Regulation: key substances/ extracellular fluid
Excretion: Excretes waste product
Endocrine: Synthesis of renin, erythropoietin, prostaglandins
Metabolism: Active form of vitamin D, catabolism of insulin, PTH, calcitonin.
What are the volumes of fluid in the extracellular compartments?
70kg person
42 L water (60%)
Intracellular: 28L
Extracellular (14L):
- Interstitial 11L
- Intravascular 3L
- Lymph
What would the osmolar value be of 1 mole of NaCl in 1L of solution?
2 Osmolar solution
What is the normal osmolality of blood plasma?
280-310 mOsm/kg
Which ions mainly determine the osmolality in extracellular fluid?
Na+ and Cl-
Which ions mainly determine the osmolality of intracellular fluid?
K+
How do the kidneys play a part in maintaining extracellular pH?
Kidneys control bicarbonate concentration.
How much urine is produced per day?
Around 1.5 L
What is a nephron?
A functional unit of the kidney.
A kidney can contain around 1 million of these!
How much of the food we eat goes to keep the kidneys functioning?
Almost 1/4!
Kidneys use 22% of the cardiac output at rest.
How is blood filtered at the kidney?
At the glomerulus.
Highly specialised filter.
Water, electrolytes and small molecules forced out. (By constant filtration pressure in capillaries)
Which hormonal system controls sodium reabsorption?
Renin-angiotensin system
Which hormone system controls water recovery? How?
Anti-diuretic hormone.
Controls permeability of DCT and collecting duct to water.
Name the main PRIMARY active transporters in the nephrons.
Na/K ATPase (3Na in, 2K out)
Plasma membrane calcium ATPase (Ca2+ out)
Proton ATPase (Pump H+ out into lumen)
Which important channels aid sodium uptake in the Thick ascending limb?
Na/K ATPase creates a gradient.
NKCC2 - sodium, potassium, 2 chloride co-transporter moves sodium in also.
ROMK - renal outer medullary K channel, move potassium back into lumen.
Potassium chloride co-transporter moves 1K+ and 1Cl- into capillary.
Chloride channels also allow Cl- into capillary.
Where do loop diuretics act in the kidneys?
At the thick ascending limb, loop diuretics block sodium, potassium, 2 chloride co-transporter, reducing Na uptake, and reduce water uptake.
This will increase urinary volume.
Which membrane channels and transporters allow sodium re-uptake in the distal convoluted tubule?
Na/K ATPase gradient established.
- NCCT Sodium chloride co-transporter, brings Na and Cl in.
- ENaC - epithelial sodium channel. If open, sodium moves into cell from lumen, down electrochemical gradient.
(-ve gradient in cell) - Chloride channels - allow Cl that was brought in, to leave in capillary.
- Possible that some chloride leaves via potassium chloride co-transporter (KClCT)
How does the drug thiazide act on the kidney?
Block the sodium chloride co-transporter in the distal convoluted tubule.
How does the drug Amiloride act on the nephron?
1) Amiloride blocks ENaC channels in the cortical collecting duct.
Urine.
2) It also blocks the sodium proton exchanger in the proximal tubules, reducing Na re-absorption.
How does anti-diuretic hormone affect the cortical collecting duct?
Increases water uptake by aquaporin water channel from lumen to cell.
How does aldosterone increase sodium reuptake in the cortical collecting duct of the nephron?
Aldosterone - steroid hormone acting on nuclear receptors.
Increases the expression of transporters in the cells which are responsible for Na re-uptake.
How does spironolactone work?
Is an ANTAGONIST of the aldosterone receptor, which prevents the action of aldosterone, and reduces the amount of Na re-uptake (less expression of transporters/channels)
