Introduction to Physiology: The Cell and General PhysiologyReabsorción y secreción Tubular
Figure 27-2;
Figure 27-3;
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Transporte Máximo de Glucosa
Fluido
Intersticial
Reasorbción Pasiva de Agua está acoplada a Reabsorción de Na+
Na +
K+
ATP
Na +
K+
ATP
Na +
H20
Cl-
Urea
Na +
H +
Figure 27-5;
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Ultraestructura Celular y Características del Transporte Primario del Túbulo Proximal
*
Figure 27-8;
Guyton and Hall
Ultraestructura Celular y Características del Transporte de las Asas Delgada y Gruesa de Henle
Impermeable
Figure 27-9;
Guyton and Hall
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Copyright © 2006 by Elsevier, Inc.
Figure 28-3; Guyton and Hall
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Net Effects of
Countercurrent Multiplier
1. More solute than water is added to the renal medulla
(i.e., solutes are “trapped” in the renal medulla).
2. Fluid in the ascending loop is diluted.
3. Horizontal gradient of solute concentration established
by the active pumping of NaCl is “multiplied” by
countercurrent flow of fluid.
The vasa recta
Vasa recta blood
flow is low
(only 1-2 % of
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Figure 27-10;
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Cellular Ultrastructure and Transport
and Collecting Tubules
Figure 27-12;
Secretion in Collecting Tubule Principal Cells
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Tubular Lumen
Tubular Cells
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Cellular Ultrastructure and Transport Characteristics of Medullary Collecting Tubules
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0.6 %
(1789 mEq/d)
Osmolarity in Different Parts of the Tubule
Proximal Tubule: 65% reabsorption, isosmotic
Desc. loop: 15-20% reabsorption, osmolarity increases
Asc. loop: 0% reabsorption, osmolarity decreases
Early distal: 0% reabsorption, osmolarity decreases
Late distal and coll. tubules: ADH dependent
water reabsorption and tubular osmolarity
Medullary coll. ducts: ADH dependent water
reabsorption and tubular osmolarity
Concentration and
Obligatory Urine Volume
solute can be dissolved and excreted.
Example:
and 600 mOsm of solute must be excreted each
day to maintain electrolyte balance, the
obligatory urine volume is:
Maximum Urine Concentration of Different Animals
Animal Max. Urine Conc. (mOsm /L)
Beaver 500
Pig 1,100
Human 1,400
Dog 2,400
Collecting Tubules
Tubular Lumen
Principal Cells
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Na+ retention, hypokalemia, alkalosis,
Na+ wasting, hyperkalemia, hypotension,
Interstitial
Fluid
Tubular
Cells
Tubular
Lumen
Na+
H+
Na
ATP
Ang II
Ang II
K
Effect of Angiotensin II on Peritubular Capillary Dynamics
Peritubular
Capillary
Glomerular
Capillary
Ra
Re
Arterial
Pressure
Copyright © 2006 by Elsevier, Inc.
Ang II Constriction of Efferent Arterioles Causes Na+ Retention and Maintains Excretion of Waste Products
Na+ depletion
Filt. Fraction
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Angiotensin II Blockade Decreases Na+ Reabsorption and Blood Pressure
ACE inhibitors (captopril, benazipril, ramipril)
Ang II antagonists (losartan, candesartin, irbesartan)
decrease aldosterone
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Continue electrolyte reabsorption
Decrease water reabsorption
in distal and collecting tubules
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Continue electrolyte reabsorption
Increase water reabsorption
High osmolarity of renal medulla
Countercurrent flow of tubular fluid
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Formation of a Concentrated Urine when
Antidiuretic Hormone (ADH) Levels are High
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Figure 28-8;
fluid osmolarity
Figure 28-9;
Guyton and Hall
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Factors that Decrease
Other factors:
Stimuli for Thirst
Factors that Decrease Thirst
Atrial Natriuretic Peptide (ANP)
Renin release aldosterone GFR
Tubular Lumen
Tubular Cells
H20 (depends
on ADH)
cAMP
H20
Aquaporin-2
Aquaporin-3
H20
Figure 27-9;
Guyton and Hall
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Figure 27-10;
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Figure 27-12;
Secretion in Collecting Tubule Principal Cells
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