Renal System Flashcards
State kidney functions.
Homeostasis: plasma water & ion content, BP, pH.
Excretion of metabolic waste
Hormone production
State hormones produced by the kidneys.
Erythropoietin, renin, Vit D activation, prostaglandins, kinins.
Erythropoietin function
RBC synthesis
Renin function
Na+ balance
Vit D function
Ca2+ balance, bones
Prostaglandins & kinins function
Renal blood flow
Nephron
Functional unit of the kidney.
State the 2 outer layers of the kidney
CORTEX & MEDULLA
80% of nephrons are ____, located in the ____
20% are ____ located in the _____
cortical, cortex
juxtamedullary, medulla
Renal corpuscle consists of:
Bowman’s capsule & glomerulus
What occurs in the Bowman’s capsule?
ULTRA-FILTRATION of plasma fluid
Outline the pathway plasma fluid takes through the nephron to reach the bladder collecting duct.
Renal corpuscle (Bowman’s capsule & glomerulus)
Proximal tubule
Loop of Henle: descending & ascending limb dips into medulla
Distal tubule
-> collecting duct
Distal tubules of up to __ nephrons drain into ______ ____ , which drain into the ____ _____.
The fluid is called ____.
8
collecting ducts
renal pelvis
urine
Blood flows from the ____ arteriole into the ______ and leaves via an ______ arteriole & ______ ______ surrounding the tubule.
Afferent, glomerulus
Efferent
peritubular capillaries
Vasa recta
Long peritubular capillaries which dip into the medulla.
Renal portal system function
filters fluid out blood & into the nephron lumen at the glomerulus
Fluids are reabsorbed from nephron tubules into the blood via _____ ________
Peritubular capillaries
State the 4 processes of nephron function
Filtration
Excretion
Reabsorption
Secretion
Vol. urine excreted =
vol. excreted = filtered - reabsorbed + secreted
State the average glomerular filtration rate (GFR)
~180 L/day
Filtration fraction
plasma that filters into the nephron
State 2 mechanisms of GFR autoregulation
Myogenic mechanism
Tubuloglomerular feedback
Describe myogenic regulation of GFR
Afferent & efferent arterioles have smooth muscle which can respond to pressure changes: vasoconstriction & vasodilation.
Describe tubuloglomerular feedback following a GFR & RBF (renal blood flow) increase.
Macula densa cells release PARACRINE FACTORS.
Afferent arteriole constricts -> resistance increases -> hydrostatic pressure in glomerulus decreases.
GFR decreases
Reabsorption of ~__% filtrate occurs in the ____ ____.
Reabsorption of salt & water is regulated by hormones in the ____ ____ and _____ _____.
70
proximal tubule
distal tubule, collecting duct
Clearance =
clearance = (urine conc x urine flow rate)/plasma conc
Define clearance
A vol. of plasma from which a substance has been removed & excrete into urine per unit time.
Use of clearance
A marker of kidney functionality.
State the 3 filtration barriers of glomerular filtration.
Function.
Capillary endothelium
Basal lamina
Podocytes
Proteins excluded from filtration via charge & MW.
Describe features of the capillary endothelium.
Fenestrations: RBCs cannot leave capillary.
surface (-) proteins repulse (-) plasma proteins (albumin)
Describe features of the basal lamina
NEGATIVE charge - excludes plasma proteins from filtration.
Describe podocytes
In Bowman’s capsule.
FOOT PROCESSES - filtration slits.
Which substances cannot be filtered?
Red blood cells
Serum albumin
Where does reabsorption occur?
Proximal tubule, loop of Henle, distal & collecting tubules.
PROXIMAL TUBULE
Reabsorption of:
Secretion of:
Reabsorption:
~66% Na+, H2O, K+, Cl-
~100% glucose, amino acids
urea, urate, HCO3-
Secretion: H+ K+
LOOP OF HENLE:
Descending limb epithelium is water ______ and NaCl _____.
Ascending limb epithelium is water _____.
Reabsorbs NaCl ______.
permeable, impermeable
impermeable, passively
LOOP OF HENLE:
Reabsorption:
Secretion of:
Reabsorption:
~25% NaCl, K+, Cl-
~15% H20, urate, HCO3-
Secretion of H+
Importance of the countercurrent multiplier exchanger.
Energy is used to generate an osmotic gradient to allow water reabsorption from tubular fluid -> produce concentrated urine.
DISTAL TUBULE & COLLECTING DUCT
Reabsorption:
Secretion
Reabsorption:
~8% NaCl, K+, Cl-
~8-17% H2O, HCO3-
Secretion of H+ & K+
Where does most reabsorption occur?
In the proximal convoluted tubule.
VASOPRESSIN (ADH) function & secretory organ.
Stimulates water recovery via aquaporin at collecting duct -> URINE CONCENTRATES.
Pituitary gland.
When is vasopressin released?
When Na+ levels rise.
ALDOSTERONE regulates [__]
Na+
Why does increased Na+ absorption increase blood pressure?
Na+ retention increases osmolarity -> increased thirst.
Drinking increases ECF, blood vol. increases -> BP rises.
Aldosterone is secreted by the ____ ____ and increases Na+ recovery via ____ channel.
Aldosterone acts on _____ cells of which tubules?
adrenal cortex, ENaC.
Principal
Distal tubule & collecting duct
If [Na+] is reduced in blood, is aldosterone secreted or inhibited?
Then what? What is the effect on the urine?
SECRETED
Increases Na+ recovery via ENaC.
URINE DILUTES
SEVERE DEHYDRATION HOMEOSTASIS mechanism
LOW BP
-> high osmolarity
RAAS system activated
ANG II -»_space;> water retention & BP, stimulates aldosterone.
Na+ reabsorption cannot occur.
VASOPRESSIN release -> water reabsorption.
OVERALL
Increased water retention, blood pressure & reduces osmolarity.
State 3 types of diuretic drugs
Loop acting
Thiazide
K+ sparing
Describe the mode of action of loop acting diuretics.
Inhibit Na+/K+/2Cl- transport and so reabsorption.
-> More ions in lumen.
Reduces BP.
Describe the mode of action of thiazide diuretics.
Inhibit NaCl reabsorption mechanism in distal convoluted tubule.
Less water reabsorption -> dilutes urine.
Describe the mode of action of K+ diuretics.
Inhibit ENaC
Block effects of aldosterone on ENaC channels.
Increased Na+ reabsorption & K+ secretion.
