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Ch. 26 The Urinary System
Martini - Fundamentals of Anatomy & Physiology 11th Edition
Martini, Nath, Bartholomew11th EditionFundamentals of Anatomy & PhysiologyISBN: 9780136874089Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoMartini, Nath, Bartholomew 11th EditionCh. 26 The Urinary SystemProblema 24
Capitolo 25, Problema 24

Describe two functions of countercurrent multiplication in the kidney.

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1
Understand that countercurrent multiplication is a mechanism in the nephron, specifically in the loop of Henle, that helps concentrate urine and conserve water.
Identify the first function: it creates a concentration gradient in the medulla of the kidney by actively transporting sodium and chloride ions out of the thick ascending limb, which is impermeable to water, thus increasing the osmolarity of the surrounding interstitial fluid.
Identify the second function: it allows the descending limb, which is permeable to water but not to solutes, to lose water to the hyperosmotic medullary interstitium, concentrating the filtrate as it moves down the loop.
Explain how this gradient established by countercurrent multiplication enables the kidney to reabsorb water efficiently from the collecting ducts under the influence of antidiuretic hormone (ADH), thus producing concentrated urine.
Summarize that these functions together help maintain body fluid balance by conserving water and regulating the concentration of urine.

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Countercurrent Multiplication Mechanism

Countercurrent multiplication is a process in the kidney's loop of Henle where fluid flows in opposite directions in adjacent tubules, creating a concentration gradient. This mechanism allows the kidney to concentrate urine by actively transporting ions out of the ascending limb, which is impermeable to water, thereby increasing osmolarity in the medulla.
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Internal Regulation - The Myogenic Mechanism

Role in Urine Concentration

Countercurrent multiplication helps the kidney produce urine that is more concentrated than blood plasma. By establishing a high osmolarity in the medullary interstitium, it enables water reabsorption from the collecting ducts, conserving water and maintaining body fluid balance.
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Concentration Gradients and Diffusion

Maintenance of Medullary Osmotic Gradient

This process maintains a steep osmotic gradient in the renal medulla, essential for water reabsorption. The active transport of sodium and chloride ions from the thick ascending limb into the interstitial space increases osmolarity, which drives water movement out of the descending limb and collecting ducts.
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Concentration Gradients and Diffusion
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Domanda del libro di testo

In a normal kidney, which of the following conditions would cause an increase in the glomerular filtration rate (GFR)? 

(a) Constriction of the afferent arteriole

(b) A decrease in the pressure of the glomerulus

(c) An increase in the capsular hydrostatic pressure

(d) A decrease in the concentration of plasma proteins in the blood

(e) A decrease in the net glomerular filtration process

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Domanda del libro di testo

What interacting controls stabilize the glomerular filtration rate (GFR)?

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Domanda del libro di testo

Describe the urine voiding reflex.

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What primary changes occur in the composition and concentration of filtrate as a result of activity in the proximal convoluted tubule?

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Domanda del libro di testo

How are proteins excluded from filtrate? Why is this important?

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Domanda del libro di testo

In response to excess water in the body, 

(a) Antidiuretic hormone is secreted by the anterior lobe of the pituitary gland.

(b) The active transport mechanisms in the ascending thick limb of the nephron loop cease functioning.

(c) The permeability of the distal convoluted tubules and collecting ducts to water is decreased.

(d) The permeability of the ascending limb of the nephron loop is increased.

(e) The glomerular filtration rate is reduced.

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