Anatomy of the urethra

Anatomy

1. Anatomy of the urethra Prepared by Kamal SAlih

2. FEMALE URETHRA

3. The female urethra is about 4 cm long, passing from the neck of the bladder at the lower angle of the trigone to the external urethral meatus, which is in front of the vaginal orifice and 2.5 cm behind the clitoris .

4. Except its uppermost end, the urethra is embedded within the anterior vaginal wall . As it leaves the bladder, fibres of the pubovaginalis part of the levator ani lie adjacent to it, and they play some part in compressing it.

5. With the urethra being such a short straight tube, catheterization in the female is simple compared with the male, but it must be remembered that in the later stages of pregnancy the urethra may be considerably stretched so that the catheter may have to be passed for more than twice the normal distance.

6. Vaginal stretching during birth can increase the urethral length to 10 cm .

7. FEMALE URETHRA The short female urethra passes anteroinferiorly from the internal urethral orifice of the urinary bladder, posterior, and then inferior to the pubic symphysis to the external urethral orifice in the vestibule of the vagina

8. FEMALE URETHRA The urethra passes with the vagina through:- Pelvic diaphragm External urethral sphincter Perineal membrane

9. FEMALE URETHRA Urethral glands are present, particularly in its superior part The paraurethral glands are homologs to the prostate. These glands have a common paraurethral duct, which opens (one on each side) near the external urethral orifice.

10. FEMALE URETHRA The inferior half of the urethra is in the perineum and is discussed in that section.

11. Vasculature of Female Urethra Blood is supplied by the internal pudendal and vaginal arteries The veins follow the arteries and have similar names . Most lymphatic vessels from the urethra pass to the sacral and internal iliac lymph nodes A few vessels drain into the inguinal lymph nodes.

12. Vasculature of Female Urethra The upper part of the urethra is supplied by the inferior vesical and vaginal arteries, with the lower end receiving contributions from the internal pudendal artery. Veins drain to the vesical plexus and the internal pudendal vein .

13. Innervation of Female Urethra The nerves to the urethra arise from the :- 1-Vesical ( nerve ) plexus 2-T he pudendal nerve The pattern is similar to that in the male, given the absence of a prostatic plexus and an internal urethral sphincter.

14. Innervation of Female Urethra. Visceral afferents from most of the urethra run in the pelvic splanchnic nerves, but the termination receives somatic afferents from the pudendal nerve.

15. MALE URETHRA

16. MALE URETHRA The male urethra is a muscular tube that conveys urine from the internal urethral orifice of the urinary bladder to the exterior through the external urethral orifice at the tip of the glans penis The urethra also provides an exit for semen (sperm and glandular secretions).

17. MALE URETHRA For descriptive purposes, the urethra is divided into four parts: 1-intramural part of the urethra (preprostatic urethra) 2- prostatic urethra 3- intermediate (membranous) part of the urethra 4 - spongy (penile) part of the urethra

18. The intramural part of the male urethra(prostatic ) The intramural part of the male urethra is surrounded by an internal urethral sphincter composed of sympathetically innervated smooth muscle

19. The internal urethral sphincter The internal urethral sphincter prevents semen from entering the bladder during ejaculation (retrograde ejaculation). The prostate surrounds the prostatic urethra.

20. The intermediate part of the male urethra The intermediate part of the male urethra is surrounded by the external urethral sphincter, composed of somatically innervated voluntary muscle .

21. The tonic and phasic contraction of this muscle primarily controls urinary continence , but several other muscles may also contribute by compressing the urethra. Stimulation of both sphincters must be inhibited to enable urination

22. Vasculature of Male Urethra The intramural part of the urethra and the prostatic urethra are supplied by the prostatic branches of the inferior vesical and middle rectal arteries . The intermediate and spongy parts of the urethra are supplied by the internal pudendal artery .

23. Vasculature of Male Urethra The veins accompany the arteries and have similar names. The lymphatic vessels drain mainly into the internal iliac lymph nodes but some lymph passes to the external iliac lymph nodes. Lymphatic vessels from the spongy urethra pass to the deep inguinal lymph nodes.

24. Innervation of Male Urethra. The nerves of the male urethra are derived from the prostat ic nerve plexus (mixed sympathetic, parasympathetic, and visceral afferent fibers ) This plexus is one of the pelvic plexuses (an inferior extension of the vesical plexus) arising as an organ