16.1 Physiology- Kidney function 1 Flashcards
What ions need to be tightly regulated? 4)
K+
Ca2+
Mg2+
Cl-
What is the acid-base balance controlled by?
Kidney in tandem with lungs
What is a filtration unit of the kidney?
Glomerulus
Do we see albumin normally in the kidney? Why?
Doesn’t appear in health kidney, negative charge repels albumin from slits
What is the GFR /day, /min?
180L/day, 120mL/min
What is the order of structures in a nephron? (7)
Glomerulus (Bowman's capsule) Proximal tubule Descending limb of loop Loop of Henle Ascending limb of loop Distal tubule Collecting duct
What is the junction where the thick ascending loop meets the distal tubule?
Macula densa (contact point where distal dephron gets feedback)
Where does the bulk of reabsorption take place?
Proximal tubule
What sections of the nephron concentrate?
Thin descending and ascending limb of loop of Henle
Where does dilution take place?
Thick ascending limb
What is the macula densa part of? Where specifically is it located? What does it do?
Part of the JGA
Located in between efferent/afferent arterioles emerging from glomerulus
Important regulatory role
Where in the nephron does the fine-tuning take place?
Distal tubule
Where is the Aldo-dependent equilibrator? What does it do?
Collecting duct
Equilibrates osmolarity of total solute
How does water move from the collecting duct to the interstitium?
Via aquaporins (single water molecule channels)
Where is bulk flow taking place?
Bowman’s capsule
What are the 2 types of glomeruli? What is the diference?
Superficial cortical glomeruli (90%)
Juxtamedullary glomeruli (10%) (penetrates deep into the medulla)
What are the JM glomeruli responsible for?
What do their efferent arterioles become?
Medullary concentration gradient (increasing osmolarity
Become the vasa recta (capillaries that accompany loops of Henle)
Where does and doesn’t reabsorption take place?
Takes place throughout the nephron,
EXCEPT tALH and glomerulus
Is movement between capillary and interstitium active or passive?
Passive
Where does secretion occur? What does the pumping work?
PT
DT
CD
Epithelial cells lining the tubule
What is the formula for the amount of solute excreted?
Amount filtered- amount reabsorbed + amount secreted
F - R + S =E
What is normally filtered? (4)
Small ions, organic solutes (free), drugs (free) and very small amount of albumin
What surrounds each capillary? What is the relevance of this?
Podocyte foot processes (slits in between allowing filtration)
What is the filtration fraction (%)?
FF: 20% of renal plasma flow
What are the forces that effect GFR (4)?
Hydrostatic pressure (Glomerular capillary): 50mmHg Hydrostatic pressure (Bowman's capsule): 10mmHg Oncotic pressure (Glomerular capillary) 25-->40mmHg Oncotic prsesure (Bowman's capsule): 0mmHg
What happens to the pressure as we go across?
Resistance means that pressure drops (Pra=100 –> Pg=50–> Pcapp=10
How does RBF autoregulation work? How does GFR autoregulation work?
Altering resistance of afferent arteriole (glomerular pressure is held constant, hence GFR autoregulation)
What happens to GFR when the afferent arteriole constricts? (and capillary blood pressure)
GFR decreases (capillary blood pressure decreses)
What happens to GFR when the efferent arteriole constricts?
GFR increases (increased P (H))
What happens to GFR when MAP increases from 90-110mmHg?
GFR doesn’t change (due to autoregulation)
When does autoregulation maintain a constant GFR?
When MAP is 80-180mmHg
What is the myogenic response of the renal arteries?
Inherent property, afferent arteriole opposes distention (by contracting)
What is the tubuloglomerular feedback sensed by?
TGF: sensed by the macula densa (afferent contact)
What do macula densa cells respond to? How do they respond?
Chloride concentration (not flow), respond by opening calcium channels
What does calcium entering the macula densa cells trigger? What does this act on?
A paracrine signal into the nest of cells (e.g. adenosine), acts on granular cells
What are granular cells? What do they do?
Cells abutting against afferent arteriole. They have adenosine type I receptors, vasoconstrict and release renin
What is the purpose of the JBA?
Tubuloglomerular feedback
What are the steps in TGF negative feedback (e.g. GFR increases) (8)?
- GFR increases
- Flow though tubule increases
- Flow past macula densa increases
- Paracrine from MD to afferent arteriole
- Afferent arteriole constricts
- Resistance in afferent arteriole increases
- Hydrostatic pressure in glomerulus decreases
- GFR decreases
