Urinary System 2
what kind of epithelium lines renal tubules?
simple cuboidal epithelial cells
what does vasoconstrictor chemical do?
causes vasoconstriction of afferent arteriole
-first process of nephron's urine formation
-the hydrostatic pressure of the blood in the glomerular capillaries pushes water and small solutes across the filtration membrane into the capsular space
-the resulting capsular fluid is called glomerular filtrate
what substances are found in the blood?
-nitrogenous wastes(ammonia, urea, uric acid, creatinine)
-organic nutrients(glucose, amino acids)
-inorganic ions (Na+, K+, Cl-, HCO3-, HPO42+, H+)
of the previous substances which are the "goodies" and which are "garbage" in the glomerular filtrate
-second process of nephron's urine formation
-as the filtrate flows along the renal tubule, the “goodies” move from the filtrate in the renal tubule, across the reabsorption-secretion membrane, and into the blood of the peritubular capillaries
-the garbage (for the most part) is left in the filtrate to be excreted in the urine
-most reabsorption occurs at the PCT
-garbage that escaped filtration moves from the blood in the peritubular capillaries, across the reabsorptionsecretion membrane, and into the filtrate of the renal tubule
-most tubular secretion occurs at the DCT
four forces at work across filtration membrane:
1. GBHP (glomerular blood hydrostatic pressure)
2. GBOP (glomerular blood osmotic pressure)
3. FHP (filtrate hydrostatic pressure)
4. FOP (filtrate osmotic pressure)
out of blood forces(forces promoting filtration)
into blood forces(forces opposing filtration)
out of-> GBHP (55mm Hg) + FOP (0mm Hg)= 55mm Hg
into---> GBOP (30mm Hg) + FHP (15mm Hg)= 45mm Hg
net filtration pressure= 10mm Hg
glomerular filtration rate
-the amount of filtrate formed per minute by the kidneys
-the greater the net filtration pressure, the greater the glomerular filtration rate
Hemorrhage-> ___1___ blood volume-> ___2___
MAP-> ___3___ GBHP->___4___ NFP-> ___5___ GFR
Glomerulonephritis-> __6____ GBOP and ___7___
FOP-> ___8___ NFP->___9___ GFR
-an autoimmune condition in which antibodies, produced in response to strep bacterial toxins, attack the filtration membrane
-the membrane becomes abnormally permeable and allows proteins to be filtered.
why is glomerular filtration rate so important?
1a) GFR below normal
(too little filtrate produced per minute)
2a) GFR above normal
(too much filtrate produced per minute)
1b) Fltrate flows too slowly through renal tubules 2b) Filtrate flows too fast through renal tubules
1c) Tubules allowed too much time for reabsorption
2c) Tubules not allowed enough time for reabsorp.
1d) Wastes reabsorbed
2d) "Goodies" lost in urine
how is GFR regulated?
1. intrinsic mechanisms (autoregulation) directly regulate GFR despite moderate changes in mean arterial blood pressure
• myogenic mechanism
• tubuloglomerular mechanism
2. extrinsic mechanisms indirectly regulate GFR by maintaining mean arterial pressure
• hormonal (Renin-angiotensin) mechanism
• neural mechanism
While an average of ___1___ liters of ___2___ are produced each day, we excrete an average of only ___3___ liters of ___4___ per day. That means that ___5___% of the ___2___ is reabsorbed! Most reabsorption occurs in the ___6___ and is linked to the reabsorption of ___7___.
___1___ in the basal membrane move ___2___ out of ___3___, keeping intracellular ___2___concentration low.
Because ___2___ is filtered, its filtrate concentration is ___4___. ___2___ diffuses through ___5___ in apical membrane in tubule cell.
Reabsorption of ___6___ across apical surface by ___7___ with ___2___. Reabsorption of ___6___ across basal membrane by ___8___.
1) Na+K+ pumps
3) tubule cell
5) cotransporters (symporters)
6) organic nutrients
7) secondary active transport
8) facilitated diffusion
Reabsorption of ___1___ creates ___2___that results in ___3___ reabsorption.
This reabsorption increases the ...(4)
___5___ substances ___6___ through apical and basal membrane bilayers.
______ and ______ (water soluble) diffuse between tubule cells.
2) osmotic gradient
4) concentration of solutes left behind
5) lipid soluble
the phenomenon of water (solvent) "dragging" solutes behind
how much of the glucose and amino acids in the filtrate are reabsorbed?
-sugar in the urine
-may indicate diabetes mellitus
insufficient insulin --> hyperglycemia --> abnormally high concentration of glucose in
the filtrate --> kidneys unable to reabsorb all the glucose --> glucosuria
abnormally high concentration of glucose in the filtrate can cause...
abnormally high filtrate osmotic pressure --> less H2O reabsorption --> polyuria