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31 Cards in this Set

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Tubule
-Distal convoluted tubule
* permeability is limited
-Collecting duct
*control of permeability by ADH
* Diabetes insipidus
Countercurrent mechanism (Tubule continued)
-Countercurrent multiplier- Loop of Henle (conversion of water)
- Countercurrent exchange- vasa recta (blood supply to area that moves very slowly)

Two important factors: ADH and aldosterone
Juxtglomerular Apparatus (Tubule continued)
- production of renin
- brings about increase in blood pressure by increasing the adrenal cortex's production of aldosterone
1. glomerular filtration
1. globular filtration refers to the movement of fluid and solutes from the glomerular capillaries into Bowman's space
2. tubular secretion
Tubular secretion refers to the secretion of solutes from the peritubular capillaries into the tubules
3. tubular reabsorption
tubular reabsorption refers to the movement of materials from the filtrate in the tubules into the peritubular capillaries
Formation of the glomerular filtrate in Bowman's capsule is the outcome of opposing pressures
hydrostatic pressure from the heart favors filtration; osmotic and hydrostatic pressure of the filtrate oppose it.
vasodilation and vasoconstriction
as vasodilation and vasoconstriction of the afferent and efferent arterioles alter the blood flow through the glomerular capillaries, there are corresponding alterations in the glomerular filtration rate (GFR)
- alterations in GFR are mediated by a variety of neural and endocrine factors, and constitute a major influence on the amount of water lost from the body in urine
Renal clearance
the renal clearance of any substance is the volume of plasma from which that substance is completely removed by the kidneys per unit of time. Every substance has its own distince clearance value, but the units are always in volume of plasma per time

S = L/h (liters/hour)
Renal clearance of inulin
-assume inulin is given intravenously at a rate sufficient to maintain a plasma concentration constant at 4 mg/L
- urine collected over a 1-h period has a volume of 0.1 L and an inulin concentration of 300mg/L or 300mg/h.
how much plasma had to be completely cleared of inulin to supply this 30mg/h?
-it is known that inulin is filterable at the renal corpuscle but is not reabsorbed, secreted, or metabolized by the tubule.
- therefore, the mass of inulin excreted in the experiement-30 mg/h- must be equal to the mass filtered over that same time period
-accordingly, the clearance of inulin must equal the volume of plasma originally filtered; that is, inulin clearance is equal to GFR
Important generalizations about renal clearance
-when the clearance of any substance is greater than the GFR, as measured by the inulin clearance, that substance must undergo tubular secretion
-when the clearance of a filterable substance is less than the GFR, as measured by inulin, that substnace must be undergoing reabsorption
porin trimers
-can be opened or closed
-channels
excretory system functions
-nitrogen waste elimination
(mammals use urea; birds and reptiles use uric acid)
- blood volume regulation
- electrolyte balance
- blood pressure regulation
- blood pH regulation
- elimination of toxic waste
Nitrogen Waste
- ammonia is used by fish
- uric acid is used by birds and reptiles and to some extent by one breed of dogs (Dalmations)
- urea is formed by mammals (by the liver, not the kidney)
Ammonia vs. Uric Acid
- Ammonia- harder to excrete
- Urea- in between
- Uric acid- harder to produce
Renal Cortex is the site of...
glomerular filtration as well as the convoluted tubules
Renal Medulla is the site of...
location of the loops of Henle and the drainage of the collecting ducts into the renal pelvis and ureter
Renal corpuscle
Filtering component:
- includes the glomerulus (interconnected capillary loops)
- includes Bowman's capsule (glomerulus protrudes into this fluid-filled capsule)
Nephron types
1. Cortical nephron
2. Juxtamedullary (has loop of Henle)
podocytes
epithelial cells in this region of the kidney
Anatomy of the nephron
- Renal Corpuscle
* Bowman's capsule
* Bowman's space
* Glomerulus
Glomerulus
-arterioles supplying the glomerulus have an unusual arrangement: the capillaries begin and end in arterioles (usually begin after an arteriole and end by connecting to a venule)
- Afferent arteriole- entering the glomerulus
- Efferent arteriole- exits the glomerulus
Tubule Types
1. Proximal convoluted tubule
- Loop of Henle
2. Distal convoluted tubule (permeability is limited)
- Collecting duct
Proximal convoluted tubule
-reabsorption of water
- reabsorption of glucose
Loop of Henle
- Descending and Ascending
- target of aldosterone (steroid hormone produced in adrenal cortex)
- impervious to water. Sodium ions actively exported into the interstitial region around the tubule
Collecting duct
- control of permeability by ADH
- diabetes insipidus
Decreased GFR
- constricted afferent arterioles
- dilated efferent arterioles
Increased GFR
- constricted efferent arterioles
- dilated afferent arterioles
micturition
- release of urine from the bladder
- coordination of smooth and skeletal muscle relaxation and contraction
Cs =
Cs = UsV / Ps

- Cs- clearance of s
- Us- urine concentration of s
- V- urine volume per unit time
- Ps- plasma concentration of s