Intro to Urinary Flashcards
How much of cardiac output goes to the kidney as a percentage?
22%
Where are the kidneys?
Retroperitoneal
T11/T12–>L2/L3
How much does a kidney weigh?
150g
How does the kidney connect to the bladder and what is the function of the bladder?
A single ureter leaves each kidney and take urine to the bladder in the pelvis.
The bladder stored urine until we decide to urinate at whhich point it ejects urine through the urethras.
What is a ureter?
Pulsatile smooth muscle tube from kidney to bladder. They run along the tips of the transverse processes to the sacroiliac joint to enter the
Which kidney sits lower?
The right, the liver is a big intra-abdominal organ that pushes stuff down.
What is the outer layer of kidney called?
Cortex
What is the inner area of kidney known as?
Medulla
Which part of the kidney does the ureter plumb into?
Renal pelvis
What is the function of the kidney?
Maintains a stable internal environment (milieu interieur)
- regulates key ECF substances
- excretes waste
- endocrine; renin, erythropoietin and prostaglandins
- metabolism; activates vitamin d, catabolises insulin, PTH and calcitonin
Review the body fluid compartments of a 70kg man
42L water—> 28L intracellular + 14L ECF–> 11L interstitium + 3L intravascular
What drives the movement of water across cell membranes?
Water crosses freely and is driven by osmotic force
Define Osmolality
Number of osmoles per litre of solute (conc of substances that cannot cross the membrane)- includes ions and proteins and is measured in milliosmoles
What is a normal plasma osmolality?
280-310mOsm/kg or 280-310mmol/L
note its the same in the intracellular fluid and interstitial fluid under normal conditions
If you have serum sodium how might you predict serum osmolality?
[Na+] x2
80% of serum osmolality is Na+ and Cl- and 20% is K+
Is a hypotonic solution dilute of concentrated?
Dilute
If ECF osmolarity is high what happens to the cells?
Water will be drawn out into the hypertonic ECF and so the cell will shrink
The concentration of which substances are higher in the cell?
K+ and many large organic anions (proteins)
Na+, Cl- and HCO3- are highest in concentration where?
Extracellularly
Which pump maintains the difference in ion concentrations inside and outside the cell?
Sodium Potassium ATPase
If the membrane potential is altered what can happen?
Electrical function disrupted, fluid balance may change
If ECF is not tightly regulated by the kidney what can go wrong?
BP changes
Cell function loss (ICF is dependent on ECF remember)
Oedema
How does the kidney contribute to plasma pH?
Kidney controls bicarbonate absorption
Which organ does all of the following- control volume control osmolarity helps maintain pH excretes waste
The Kidney
How much fluid does the kidney filter in a day?
180L
How much urine do we produce on average each day?
1.5L (almost all of the 180L of plasma that is filtered is reabsorbed)
What is found in ultrafiltrate?
Water, ions and other small molecules
What is the functional unit of the kidney?
The nephron (a filter connected to a long reabsorption tube) 1.5 million nephrons/kidney
Which bits of the nephron sit in the cortex?
Glomerulus
PCT
DCT
Where do you find the Loop of Henle and collecting duct?
The medulla
where is the filtrate relative to the body?
the filtrate in the lumen is outside the body (cavity with a cavity)
Outline the key reabsorption percentages in the kidney.
Substance % reabsorbed by PCT Na+, H2O 60-70 K+ 80-90 Bicarbonate 90 Glucose and amino acids 100
What substance might we actively secrete in the kidney (to get rid of it in urine)?
H+
How does the glomerulus filter fluid to the tubule?
Water, electrolytes and small molecules are forced out of the heavily fenestrated capillaries by a constant high filtration pressure. (slightly more dilated afferent arteriole than the efferent)
What is the major site of reabsorption?
PCT
60-70% Na+ and water, 80-90% K+, 90% bicarbonate, 100% of glucose and aminoacids
Is the filtrate in the PCT hypotonic, isotonic or hypertonic compared to plasma?
Isotonic (the water is following the osmoles)
Which tubule cell membrane has the sodium pump on it?
Basolatteral
Which lateral cell to cell junction are found in the kidney?
Tight Junctions
What property of the membrane of tubule cells allows for transport across them with different finishing concentrations either side?
Different membrane permeability on each side because of differing transporter expression.
Which membrane would express the SGLT?
The luminal one
What is the function of the Loop of Henle?
Creates osmolarity gradient from medulla to cortex by counter current multiplication
further salt reabsorption
Why do we need counter current multiplication?
The osmolarity gradient it creates is needed to make concentrated urine when we are trying to conserve fluids.
Where is the site of variable water and electrolyte reabsorption?
DCT
The fluid leaving the Loop of Henle is what tonicity?
Hypotonic- very dilute
What does the distal convolute tubule do interms of salt?
Removes more NaCl from the already hypotonic filtrate.
In the DCT what happens to H+ ions?
Active secretion
Where in the kidney does water not necessarily follow electrolytes?
the DCT
The Loop of henle sets up a very concentrated medulla relative to the cortex, where does this result in the formation of a concentrated urine?
The collecting duct- water will move out of the collecting duct
Which hormonal systems affect Na+ recovery?
RAAS (ECF volume the end result)
How is water recovery controlled?
Anti-diuretic hormone (DCT permeability changes with ADH so ECF osmolarity is affected)
