1. CHAPTER 25
The Urinary System
PART B

2. LEARNING OBJECTIVES
At the end of the lecture student should be able to:
Recognize and contrast anatomy and histology of ureter, urinary bladder and urethra.(ILO 1.1, 2.1)
Outline the development of urinary system.(ILO 1.1)

3. Explain the differences between male and female urethra. (ILO 1.2)
Label the organs of urinary system (ILO 2.2)

4. Lecture outline Ureters Urinary bladder Urethra
Developmental aspects of urinary system

5. Ureters Convey urine from kidneys to bladder Retroperitoneal
Enter the base of the bladder through the posterior wall

6. Ureters HISTOLOGY Three layers of wall of ureter
Lining of transitional epithelium
Smooth muscle muscularis
Contracts in response to stretch
Outer adventitia of fibrous connective tissue

7. Lumen Adventitia Circular layer Longitudinal layer Transitional
epithelium
Lamina
propria
Figure 25.20

8. Urinary Bladder Muscular sac for temporary storage of urine
Retroperitoneal, on pelvic floor posterior to pubic symphysis
Males—prostate gland surrounds the neck inferiorly
Females—anterior to the vagina and uterus

10. Urinary Bladder HISTOLOGY Layers of the bladder wall
Transitional epithelial mucosa
Thick detrusor muscle (three layers of smooth muscle)
Fibrous adventitia (peritoneum on superior surface only)

12. Urethra
Muscular tube, from neck of the urinary bladder to the external urethral orifice
Lining epithelium
Mostly pseudostratified columnar epithelium.

13. Urethra Sphincters Internal urethral sphincter
Involuntary (smooth muscle) at bladder-urethra junction
Contracts to open
External urethral sphincter
Voluntary (skeletal) muscle surrounding the urethra as it passes through the pelvic floor

15. Urethra Female urethra (3–4 cm):
Tightly bound to the anterior vaginal wall
External urethral orifice is anterior to the vaginal opening.

16. Peritoneum Ureter Detrusor muscle Internal urethral sphincter Trigone
External urethral
sphincter
Urogenital diaphragm
Urethra
External urethral
orifice
(b) Female.
Figure 25.21b

17. Urethra Male urethra Three named regions
Prostatic urethra (2.5 cm)—within prostate gland
Membranous urethra (2 cm)—passes through the urogenital diaphragm
Spongy urethra (15 cm)—passes through the penis and opens via the external urethral orifice

18. External urethral orifice
Ureter
Bladder neck
Internal urethral sphincter
Prostate
Prostatic urethra
Urogenital diaphragm
External urethral sphincter
Membranous urethra
Spongy urethra
External urethral orifice
Figure 25.21a

19. Developmental Aspects
Kidneys start to develop during 4th week of gestation.
Ureteric bud arise from the mesonephric duct and it is get surrounded by mesonephric tissue.

20. Mesonephric tissue Gives origin to kidney.
Ureter arise from the Mesonephric duct

21. (initially, pronephric duct) Ureteric bud
Degenerating
pronephros
Developing
digestive
tract
Urogenital
ridge
Duct to
yolk sac
Mesonephros
Allantois
Cloaca
Mesonephric duct
(initially, pronephric
duct)
Ureteric
bud
Hindgut
(a) Week 5
Figure 25.23a

22. Degenerating pronephros Duct to yolk sac Allantois Body stalk
Urogenital
sinus
Mesonephros
Rectum
Mesonephric
duct
Ureteric bud
Metanephros
(b) Week 6
Figure 25.23b

23. Key points
Ureter: muscular tubes starting from renal pelvis to the posterior wall of the bladder.
Transitional epithelium
Urinary bladder: retroperitoneal muscular sac, in females located anterior to uterus and vagina.
3 layers histologically

24. Urethra: pseudo stratified columnar epithelium
3-4 cm in females
20 cm in males (three parts)
Internal urethral sphincter: involuntary
External urethral sphincter: voluntary

25. Developmental aspects:
Kidneys start to develop during 4th week of gestation.
Mesonephric tissue give rise to kidneys
Mesonephric duct give rise to ureter.