CHAPTER 25 The Urinary System PART B

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)

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

Lecture outline Ureters Urinary bladder Urethra Developmental aspects of urinary system

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

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

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

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

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)

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

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

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

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

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

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

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.

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

(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

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

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

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

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