HRR: glomerular filtration Flashcards
What are the vasa recta?
Straight fenestrated capillaries that surround the loop of Henle and reabsorb water. It is also called peritubular capillaries.
What are the layers of the glomerular filtration barrier?
- Fenestrated endothelial cells with an overall negative charge
- Basement membranes with small pores
- Podocytes with slit diaphragm
What are some purposes of the glomerular basement membrane?
They provide structure, scaffolding for podocytes, and a filtration barrier.
Describe the structure of the glomerular basement membrane.
Lots of type IV collagen, but also negatively charged proteoglycans that help prevent filtration of negatively charged macromolecules aka proteins!
What is the selectivity of filtration determined by in the glomerulus?
- Size (large particles/cells don’t pass)
- Charge (negative particles don’t pass)
- Most proteins don’t pass
What happens if endothelial cells in the glomerulus are damaged?
Increased amounts of large molecules, albumin, and proteins may be able to enter the urine.
What is GFR?
The rate at which filtrate flows out of the glomerular capillary loop, across the basement membrane, and into the tubule.
What filtration pressures contribute to filtration in the glomerulus?
- Hydrostatic pressure of the capillary promotes filtration
- Oncotic pressure of the capillary favors reabsorption
- Hydrostatic pressure in Bowman’s space favors reabsorption
Compare the capillary permeability and surface area in the glomerulus to that of other capillaries.
Higher permeability and surface area for optimal filtration!
What makes glomerular capillaries unique?
They have higher hydrostatic pressure to allow for filtration, which occurs because there is no venous end. This allows net filtration pressure to be constant and high. Oncotic pressure will never exceed hydrostatic pressure!
GFR is primarily controlled by…
Afferent arteriole diameter.
Afferent arteriole is constricted. Does filtration increase or decrease?
Decrease.
Efferent arteriole is constricted. Does filtration increase or decrease?
Increase.
What happens to GFR as BP goes up?
It’s usually able to be maintained due to intrarenal regulation mechanisms. The kidneys can manage this themselves!
What is tubuloglomerular feedback?
Macula densa senses salt content, which allows the tubule to determine how much fluid is being filtered. If it isn’t the right amount, tubular feedback to glomerular arterioles causes a corrective response in GFR.
