Renal Physiology Flashcards
Nephron
The smallest kidney unit that makes urine and in making urine filters blood plasma and helps maintain homeostasis
What are the two main functions of the kidney
Excretion of wastes or products of metabolism.
They also maintain homeostasis by regulating levels of water and ions in the ECF within narrow limits
Examples: K+, Ca++, Na+, water
What basic renal processes occur in the nephron during urine formation
Glomerular filtration, tubular reabsorption, tubular secretion
What is the first step in urine formation
Glomerular filtration
Fluid (protein and cell free fluid) is forced through glomerular capillaries into the bowmans capsule.
Travels through 3 layers of membrane (capillary wall, basement membrane, and podocyte layer)
Allows water and small solutes (Na+ and Cl-) to pass through but not proteins and cells
It has same concentration of solutes in plasma except proteins
Tubular reabsorption
Moves filtered substances in tubule back into the blood (into peritubular capillaries)
Some of the ultrafiltrate like food molecules u still need so they are taken from forming urine and put into blood
Tubular secretion
Moves substances from the peritubular capillaries into the tubule
A way to add substances to the original filtrate
Not same as excretion but not lead there
What force causes glomerular filtration
Filtration is by bulk flow
The hydrostatic (or blood) pressure of glomerular capillaries causes filtration
What forced oppose glomerular capillary blood pressure
- Bowmans capsule hydrostatic pressure- “the pushing back force”
- Plasma colloid osmotic pressure- plasma proteins remain in glomerulus “pulling back force”
What factors affect glomerular filtration pressure and therefore GFR
- Decrease in plasma proteins- less force opposing filtration (increased GFR)
- Increase in hydrostatic pressure of bowman’s capsule- increased force opposing filtration (decreased GFR)
- Increase proteins in bowmans capsule- favors filtration (increased GFR)
What happens when afferents arterioles constrict
Causes decreased glomerular hydrostatic pressure (decreased downstream pressure)
Caused by increased sympathetic impulses
GFR decreases
What happens when afferents arterioles dilate
Increased pressure downstream
Caused by decreased sympathetic impulses
Increase in GFR
Tubular reabsorption
Reabsorption is active or passive
