Excretory (Urinary) System

Chapter 44Chapter 44Chapter 44Chapter 44

Urinary ComponentsFunctions of Urinary System1. Kidney Functions2. Urine transport3. Urine storage.4. Excretion

Kidney - Internal Anatomy

Kidney Functions1. Regulate blood ionic composition.

2. Regulate blood pH.

3. Regulate blood volume.

4. Regulate blood pressure.

5. Maintain blood osmolarity.

6. Production of hormones.

7. Regulation of blood glucose levels.

8. Excretion of wastes and foreign substances.

Corticalnephron

Juxtamedullarynephron

Collectingduct

(c) Nephron types

Torenalpelvis

Renalmedulla

Renalcortex

Animation: Nephron IntroductionAnimation: Nephron Introduction

Nephron

1. Glomerular Filtration

2. Tubular Reabsorption

3. Tubular Secretion

Fig. 44-14dAfferent arteriolefrom renal artery

Efferentarteriole fromglomerulus

SEM

Branch ofrenal vein

Descendinglimb

Ascendinglimb

Loop ofHenle

(d) Filtrate and blood flow

Vasarecta

Collectingduct

Distaltubule

Peritubular capillaries

Proximal tubule

Bowman’s capsuleGlomerulus

10 µm

1. Glomerular Filtration

2. Tubular Reabsorption

3. Tubular Secretion

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From Blood Filtrate to Urine: A Closer Look

Proximal Tubule

• Reabsorption of ions, water, and nutrients takes place in the proximal tubule

• Molecules are transported actively and passively from the filtrate into the interstitial fluid and then capillaries

• Some toxic materials are secreted into the filtrate

• The filtrate volume decreasesAnimation: Bowman’s Capsule and Proximal TubuleAnimation: Bowman’s Capsule and Proximal Tubule

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Descending Limb of the Loop of Henle

• Reabsorption of water continues through channels formed by aquaporin proteins

• Movement is driven by the high osmolarity of the interstitial fluid, which is hyperosmotic to the filtrate

• The filtrate becomes increasingly concentrated

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Ascending Limb of the Loop of Henle

• In the ascending limb of the loop of Henle, salt but not water is able to diffuse from the tubule into the interstitial fluid

• The filtrate becomes increasingly dilute

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Distal Tubule

• The distal tubule regulates the K+ and NaCl concentrations of body fluids

• The controlled movement of ions contributes to pH regulation

Animation: Loop of Henle and Distal TubuleAnimation: Loop of Henle and Distal Tubule

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Collecting Duct

• The collecting duct carries filtrate through the medulla to the renal pelvis

• Water is lost as well as some salt and urea, and the filtrate becomes more concentrated

• Urine is hyperosmotic to body fluids

Animation: Collecting DuctAnimation: Collecting Duct

Fig. 44-15

Key

ActivetransportPassivetransport

INNERMEDULLA

OUTERMEDULLA

H2O

CORTEX

Filtrate

Loop ofHenle

H2O K+HCO3–

H+ NH3

Proximal tubule

NaCl Nutrients

Distal tubule

K+ H+

HCO3–

H2O

H2O

NaCl

NaCl

NaCl

NaCl

Urea

Collectingduct

NaCl

Composition of Filtrate