CH. 18 Urinary System: Renal Function Flashcards
What are the 5 main functions of the urinary system?
- regulate plasma ionic composition
- regulate plasma volume
- regulate plasma osmolarity
- regulate plasma pH
- remove metabolic waste products and foreign substances from plasma
What are the 4 main structures of the kidneys and what are their functions?
- kidneys: form urine
- ureters: transport urine from kidneys to bladder
- bladder: store urine
- urethra: excrete urine from bladder to outside of body
What is the renal corpuscle composed of?
- glomerulus: capillary network for filtration
- bowman’s capsule:
- receives the filtrate
- inflow to renal tubules
What is the renal corpuscle composed of?
- glomerulus: capillary network for filtration
- bowman’s capsule:
- receives the filtrate
- inflow to renal tubules
What are the differences between the cortical and juxtamedullary nephrons?
cortical
- short loop of henle
- most numeroous
juxtamedullary nephron
- long loop of henle extends into medulla
- responsible for the medullary osmotic gradient
What percent of cardiac output do the kidneys receive at rest?
20%
What does glomerular filtration refer to?
from glomerulus to Bowman’s capsule
What does reabsorption refer to?
from tubules to peritubular capillaries
What does secretion refer to?
from peritubular capillaries to tubules
What does excretion refer to?
from tubules out of body
What is the glomerular filtration rate in a healthy individual?
125 mL/min or 180 L/day
What three barriers must glomerular filtrate cross in order to enter Bowman’s capsule?
- capillary endothelial layer
- surrounding epithelial layer
- basement membrane sandwiched between these two layers
What are the starling forces of glomerular filtration?
- glomerular capillary hydrostatic pressure
- bowman’s capsule oncotic pressure
- bowman’s capsule hydrostatic pressure
- glomerular oncotic pressure
Which of the glomerular filtration starling forces favor filtration?
glomerular capillary hydrostatic pressure: fairly high hydrostatic pressure
bowman’s capsule oncotic pressure: low hydrostatic pressure
Which of the glomerular filtration starling forces oppose filtration?
- bowman’s capsule hydrostatic pressure: 15 mmHg (large volume of filtrate in closed space
- glomerular oncotic pressure: plasma proteins in smaller volume of plasma
What is the equation for filtration fraction?
glomerular filtration rate / plasma flow rate
What conversion can be made for 100 mg/dL?
1 mg/mL
What does a small increase in GFR lead to?
large increase in volume of fluid filtered and excreted
What are two ways that glomerular filtration rate is intrinsically regulated?
- myogenic regulation: smooth muscle in wall of afferent arteriole contract in response to stretch
- tubuloglomerular feedback: macula densa cells secrete paracrine factors in response to an increase in flow of fluid past them
- smooth muscles of arterioles contract in response to these paracrines
What is one way in which glomerular filtration rate can be extrinsically controlled?
a decrease in blood pressure can decrease glomerular filtration rate
What is one way in which glomerular filtration rate can be extrinsically controlled?
a decrease in blood pressure can decrease glomerular filtration rate
What does most reabsorption take place?
proximal tubules
What substances only get partially reabsorbed? and which is less reabsorbed than the other?
urea and potassium
- urea less reabsorbed
What is the filtration and reabsorption rate of urea?
filtration rate: 993 mM/day
reabsorption rate: 467 mM/day
