1. The Urinary System and Tract
A continued examination

2. Figure 26.10 Glomerular Filtration
Figure 26.10a, b

3. Glomerular filtration rate (GFR)
Amount of filtrate produced in the kidneys each minute
Factors that alter filtration pressure change GFR

4. Factors controlling the GFR
A drop in filtration pressure can activate local mechanisms--results in vasodilation of afferent arterioles and vasoconstriction of efferent arterioles----> increase in glomerular (filtration) pressure
A drop in filtration pressure stimulates Juxtaglomerular apparatus (JGA)
Releases renin and erythropoietin

5. Figure 26.11 The Response to a Reduction in the GFR
Figure 26.11a

6. Figure 26.11 The Response to a Reduction in the GFR
Figure 26.11b

7. Sympathetic activation
Produces powerful vasoconstriction of afferent arterioles
Decreases GFR and slows production of filtrate
Usually in response to big drop in blood pressure
Changes the regional pattern of blood flow
Alters GFR

8. Reabsorption and secretion at the DCT
DCT performs final adjustment of urine
Active secretion or absorption
Absorption
Tubular cells actively resorb Na+ and Cl-
In exchange for potassium or hydrogen ions (secreted)

9. Figure 26.14 Tubular Secretion and Solute Reabsorption at the DCT
PLAY
Animation: Distal Convoluted Tubule
Figure 26.14

10. Figure 26.14 Tubular Secretion and Solute Reabsorption at the DCT
Figure 26.14c

11. Reabsorption and secretion along the collecting system
Water and solute loss is regulated by aldosterone and ADH
Reabsorption
Sodium ion, bicarbonate, and urea are resorbed
Secretion
pH is controlled by secretion of hydrogen or bicarbonate ions

12. Control of urine volume and osmotic concentration
Urine volume and osmotic concentration are regulated by controlling water reabsorption
Precise control allowed via facultative water reabsorption

13. Figure 26.15 The Effects of ADH on the DCT and Collecting Ducts

14. Figure 26.15 The Effects of ADH on the DCT and Collecting Ducts
Figure 26.15a, b

15. Function of the vasa recta
Removes solutes and water
Balances solute reabsorption and osmosis in the medulla

16. Composition of normal urine
Varies with the metabolic and hormonal events of the body
Reflects filtration, absorption and secretion activity of the nephrons
Urinalysis is the chemical and physical analysis of urine

17. Summary of renal function:
Each segment of nephron and collecting system contribute
Glomerulus
PCT
Descending limb
Thick ascending limb
DCT and collecting ducts
Concentrated urine produced after considerable modification of filtrate
PLAY
Animation: Late Filtrate Processing

18. Figure 26.16 A Summary of Renal Function

19. Figure 26.16 A Summary of Renal Function
Figure 26.16b

20. Chapter 26, part 4
The Urinary System

21. SECTION 26-6 Urine Transport, Storage, and Elimination

22. Urine production ends with fluid entering the renal pelvis
Rest of urinary system transports, stores and eliminates
Ureters
Bladder
Urethra

23. Figure 26.17 A Radiographic View of the Urinary System

24. The ureters Pair of muscular tubes
Extend from renal pelvis to the bladder
Peristaltic contractions force urine toward the urinary bladder

25. The urinary bladder Hollow, muscular organ Internal features include
Reservoir for the storage of urine
Contraction of detrusor muscle voids bladder
Internal features include
Trigone
Neck
Internal urethral sphincter
Ruggae

26. Figure 26.19 Organs for the Collection and storage of Urine
Figure 26.19a

27. Figure 26.19 Organs for the Collection and storage of Urine
Figure 26.19b

28. Figure 26.19 Organs for the Collection and storage of Urine
Figure 26.19c

29. The urethra
Extends from the urinary bladder to the exterior of the body
Passes through urogenital diaphragm (external urinary sphincter)
Differs in length and function in males and females

30. Figure 26.20 The Histology of the Organs that Collect and Transport Urine
Figure 26.20a

31. Figure 26.20 The Histology of the Organs that Collect and Transport Urine
Figure 26.20b, c

32. Micturition reflex and urination
Urination coordinated by micturition reflex
Initiated by stretch receptors in wall of bladder
Urination requires coupling micturition reflex with relaxation of external urethral sphincter

33. Figure 26.21 The Micturition Reflex

34. Figure 26.21 The Micturition Reflex

35. SECTION 26-7 Aging and the Urinary System

36. Changes with aging include:
Decline in the number of functional nephrons
Reduction of GFR
Reduced sensitivity to ADH
Problems with the micturition reflex

37. You should now be familiar with:
The components of the urinary system and their functions
The location and structural features of the kidneys
The structure of a nephron, and the processes involved in the formation of urine
The normal characteristics, composition, and solute concentrations of a representative urine sample

38. You should now be familiar with:
The factors that influence filtration pressure and the rate of filtrate formation
The types of transport mechanisms found along the nephron
How antidiuretic hormone and aldosterone levels influence the volume and concentration of urine