Renal Processes Flashcards
What does the renal system do?
-Filters your blood
-Excretory (whatever it filters out is in your urine)
-Homeostatic regulation of volume, osmolarity, pH balance
-also produces hormone renin
Kidney anatomy
-Nephron: urine directly comes from nephron
-Cortex and Medulla: have nephrons
-Renal pelvis: collects urine
-Ureter: sends urine to bladder
Renal artery
-dirty blood goes through renal artery to the cortex
Renal vein
-clean blood goes through here
Blood Flow
-blood will go to renal artery and diverge out and eventually reach afferent artery. From afferent artery it goes to nephron
what does the nephron consist of?
-Head (capillary network called glomerulus)
-tube (descending, ascending, loop of henle)
-loop (goes deep into the medulla)
-outside of nephron covered in capillaries
What are the three portal systems?
- hepatic portal system (wont talk about in class)
- hypophyseal portal system (hypothalamus and pituitary gland)
- Renal portal system
What is the renal portal system
-Afferent arteriole connects to glomerulus (capillary) connects to efferent arteriole which connects to peritubular capillaries
Structure on the nephron
lumen enters Bowman’s capsule (in glomerulus) -> goes to proximal tube -> descending loop/limb -> loop of henle -> ascending loop/limb -> distal tubule -> collecting duct -> to bladder
-lumen at the beginning similar to plasma
-lumen at the end similar to urine
Tubular elements of the nephron
-80% of the tube is non-modulated, meaning that theyre working at their max
-last 20% is what determines the concentration of your urine
Processes of nephron
Filtration: filter the liquid from glomerulus into Bowman’s residence
Reabsorption: take back from the lumen to the blood
Secretion: dump molecules into the lumen
Excretion: when it goes to the bladder
renal calculation
Filtration -reabsorption + secretion = amount of excretion
Filtration
-need a fast and simple mechanism (do not have a membrane with selective permeability)
-Instead creates a slit and any molecule bigger than the slit cannot go through
-> molecules that go through are water, glucose, and salt which are eventually reabsorbed
Structure of the slit
made of three layers
1. capillary endothelium cell (blocks really big molecules)
2. basal lamina (membrane not cell, have negative charge so prevents most proteins from going through)
3. podocyte (like pole?)
Driving force of filtration
-driving force comes from the heart pushing blood to renal artery (favors )
-osmotic pressure works against filtration because there is more solute in the glomerulus and so the water wants to go back
-hydrostatic pressure is due to the fluid created in bowman’s capsule (works against filtration)
Ph (hydrostatic pressure)- pi(osmolarity) - Pfluid(fluid pressure) = net filtration pressure
Glomerular filtration rate
-volume of plasma water filtered per time (avg 180L/day or 125 ml/min)
-renal plasma flow 600 ml/min
-125/600= 20% of blood filtered by kidney
The filter fraction
-99% of plasma entering kidney returns to systemic circulation
-1% of volume is secreted to external environment
Regulation of GFR
-regulated by dilation and constriction
-main driving force is the blood pressure
want GFR to be constant so if your flow increases then artery will constrict and if flow decreases then it will dilate so that the rate is held constant with changing blood pressure
-maintained at 80-180 mmHg for GFR
Mechanism of GFR regulation
Local control: plays bigger role than systemic
-> myogenic response (afferent arteriole)
->tubuloglomerular feedback!!!
Systemic control:
neural: sympathetic, NE, alpha-r, afferent arteriole constrict
Hormonal: ANG II (vasoconstrictor), ANP (dilate afferent, relax mesengial cells)
Local control
-myogenic response is when your BP increases (afferent artery will constrict more to decrease effect of increased BP)
-Macula densa cells: (in the distal tubule) will release paracrine signal to regulate afferent arterial constriction
