1. Excretory (Urinary) System
Chapter 44

2. Urinary Components Functions of Urinary System 1. Kidney Functions
2. Urine transport
3. Urine storage.
4. Excretion

3. Kidney - Internal Anatomy

4. Kidney Functions 1. 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.

5. Animation: Nephron Introduction
Juxtamedullary
nephron
Cortical
nephron
Renal
cortex
Collecting
duct
Figure 44.14c The mammalian excretory system
Renal
medulla To
renal
pelvis
Animation: Nephron Introduction
(c) Nephron types

6. Nephron 1. Glomerular Filtration 2. Tubular Reabsorption
3. Tubular Secretion

7. 1. Glomerular Filtration 2. Tubular Reabsorption
Fig d
Afferent arteriole
from renal artery
Glomerulus
10 µm
Bowman’s capsule
SEM
Proximal tubule
Peritubular capillaries
Efferent
arteriole from
glomerulus
Distal
tubule
1. Glomerular Filtration
2. Tubular Reabsorption
3. Tubular Secretion
Branch of
renal vein
Collecting
duct
Descending
limb
Figure 44.14d The mammalian excretory system
Loop of
Henle
Ascending
limb
Vasa
recta
(d) Filtrate and blood flow

8. 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 decreases
Animation: Bowman’s Capsule and Proximal Tubule

9. 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

10. 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

11. Animation: Loop of Henle and 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 Tubule

12. Animation: 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 Duct

13. Proximal tubule Distal tubule Filtrate CORTEX Loop of Henle OUTER
Fig
Proximal tubule
Distal tubule
NaCl
Nutrients
H2O
HCO3–
H2O K+
NaCl
HCO3– H+
NH3 K+ H+
Filtrate
CORTEX
Loop of
Henle
NaCl
H2O
OUTER
MEDULLA
NaCl
NaCl
Collecting
duct
Figure The nephron and collecting duct: regional functions of the transport epithelium
Key
Urea
Active
transport
NaCl
H2O
Passive
transport
INNER
MEDULLA

14. Composition of Filtrate