L22 - Renal Function 1: Excretion Flashcards
Is K, PO4, urea and creatinine more concentrated in the urine or the plasma?
more concentrated in the urine
Is HCO3, glucose and albumin more concentrated in the urine or the plasma?
more concentrated in the plasma
Why is glucose and HCO3 not found in the urine?
completely reabsorbed by the kidney
Why is albumin not found in the urine?
the molecule is too large to be filtered into the urine
How many nephrons are in each kidney?
approximately one million
Where does filtration occur in the kidney?
at the glomerulus where blood flows in and out
Which structures are found in the nephron in order?
glomerulus, proximal convoluted tubule, descending limb, loop of Henle, thick ascending limb, distal convoluted tubule, connecting tubule, collecting duct
Why must the glomerulus be positioned right next to the thick ascending limb?
enables cells of the glomerulus to sample from the thick ascending limb and determine if there is adequate urine filtration / reabsorption
What is Bowman’s capsule?
space where filtrate comes out from the capillaries i.e. where filtration occurs
How is the amount of solute excreted?
amount filtered - amount reabsorbed + amount secreted = amount of solute excreted
Where does reabsorption and secretion occur?
between the peritubular capillaries and the nephron
Where does filtration occur?
between the glomerulus and the rest of the nephron
Which substances are filtered and reabsorbed in the body?
water, sodium, potassium, calcium, phosphate, glucose and urea
Which substance is only filtered into urine and not reabsorbed?
creatinine
Which substance is secreted into the nephron?
potassium
What are podocytes and what is their role?
foot processes which surround each capillary in the glomerulus and leave slits through which filtration can take place
What is the role of mesangial cells?
provide structure to the capillaries so that they are suspended in the glomerulus
Why are podocytes important?
provides a size barrier of what can be filtered and what can’t
What are the steps behind glomerular filtration?
- plasma volume enters afferent arteriole = 100%
- 20% of volume filters in the glomerulus
- 19% of fluid is reabsorbed by the efferent arteriole
- > 99% of plasma entering kidney returns to systemic circulation
- <1% of volume is excreted to external environment
What is oncotic pressure in Bowman’s capsule?
zero, if it was greater than zero, this means albumin is present in Bowman’s capsule resulting in oncotic pressure drawing fluids inward
What is the glomerular filtration rate?
volume of plasma filtered through the glomerulus per unit time
What is the most important force that affects glomerular filtration rate?
hydrostatic pressure in the glomerulus
