CC - Filtration Flashcards
What type of system is the glomerulus?
A high pressure filtration system
What 3 layers does the filtrate have to pass through?
- Glomerular capillary endothelium - has gaps allowing passage of small molecules
- Basal lamina (separates endothelium and epithelium
- Epithelium of the bowman’s capsule (podocytes)
What is Glomerular Filtration Rate (GFR)?
Filtrate efficiency
What 3 forces influence GFR?
1) Capillary blood pressure (55mmHg)
2) Osmotic pressure (30mmHg)
3) Fluid pressure (15mmHg)
What is the most common physiological regulator of GFR?
Changes in afferent arteriole resistance
What occurs in the afferent and efferent arteriole when blood pressure (BP) changes?
- ↑BP → constrict afferent arteriole, dilate efferent
- ↓BP → dilate afferent arteriole, constrict efferent
What is the main way to increase GFR using just the efferent arteriole?
Constriction of the efferent arteriole increases hydrostatic pressure in the capillaries
→ GFR increases
What are 2 auto-regularity mechanims of GFR?
- Myogenic Response
- Tubuloglomerular Feedback
How does the Myogenic Response regulate GFR?
- An increase in BP activates stretch-sensitive ion channels to open
- Smooth muscle cells depolarise and contract
- Vasoconstriction increases (increases blood flow resistance)
- Decrease in pressure
How does Tubuloglomerular Feedback regulate GFR?
- A high GFR increases blood flow past the macula densa cells
- Paracrine diffuses from macula densa to afferent arteriole
- Afferent arteriole constricts
- Increase in resistance decreases GFR flow
What hormones regulate GFR levels? (2)
Angiotensin II (vasoconstrictor)
Prostaglandins (vasodilater)
What is a measure of kidney function and helps measure GFR?
Measuring blood creatinine level
