Male Internal Genital Organs Pelvis & Perineum Unit Lecture 3 د. حيدر جليل الأعسم

Vas Deferens It is thick-walled tube about 45 cm long that conveys mature sperm from epididymis to ejaculatory duct and urethra. It arises from lower end or tail of epididymis and passes through inguinal canal. It emerges from deep inguinal ring and passes around lateral margin of inferior epigastric artery. It then passes downward and backward on lateral pelvic wall and crosses ureter in region of ischial spine. Vas deferens then runs medially and downward on posterior surface of bladder. Terminal part of vas deferens is dilated to form ampulla of vas deferens. Inferior end of ampulla narrows down and joins duct of seminal vesicle to form ejaculatory duct.

Seminal Vesicles They are two lobulated organs about 5 cm long lying on posterior surface of bladder. On medial side of each vesicle lies terminal part of vas deferens. Posteriorly, seminal vesicles are related to rectum. Inferiorly, each seminal vesicle narrows and joins vas deferens of same side to form ejaculatory duct. Blood Supply: Arteries: inferior vesicle and middle rectal arteries. Veins: drain into internal iliac veins. Lymph Drainage: internal iliac nodes Function: produce a secretion that nourishes spermatozoa. During ejaculation seminal vesicles contract and expel their contents into ejaculatory ducts, thus washing spermatozoa out of urethra.

Ejaculatory Ducts They are short (less than 2.5 cm) long and are formed by union of vas deferens and duct of seminal vesicle. Ejaculatory ducts pierce posterior surface of prostate and open into prostatic part of urethra, close to margins of prostatic utricle; their function is to drain seminal fluid into prostatic urethra. 

Prostate It is a conical fibromuscular glandular organ that surrounds prostatic urethra. It is about 3 cm long and lies between neck of bladder above and urogenital diaphragm below. Prostate is surrounded by a fibrous capsule and has base, which lies against bladder neck above, and apex, which lies against urogenital diaphragm below. The two ejaculatory ducts pierce upper part of posterior surface of prostate to open into prostatic urethra at lateral margins of prostatic utricle.

Relations of Prostate Superiorly: bladder neck, smooth muscle passing without interruption from one organ to other. Urethra enters center of base of prostate. Inferiorly: upper surface of urogenital diaphragm. Urethra leaves prostate just above apex on anterior surface. Anteriorly: Symphysis pubis (separated by extraperitoneal fat in retropubic space (cave of Retzius). Prostate is connected to posterior aspect of pubic bones by fascial puboprostatic ligaments. Posteriorly: anterior surface of rectal ampulla (separated by rectovesical septum - fascia of Denonvilliers) formed in fetal life by fusion of walls of lower end of rectovesical pouch of peritoneum. Laterally: prostate is embraced by anterior fibers of levator ani as they run posteriorly from the pubis (levator prostatae).

Lobes of Prostate It is incompletely divided into five lobes: Anterior lobe lies in front of urethra & is devoid of gland tissue. Median, or middle, lobe is wedge of gland situated between urethra and ejaculatory ducts. Its upper surface is related to trigone of bladder and projects into forming uvula vesicae; rich in glands. Posterior lobe is situated behind urethra & below ejaculatory ducts & also contains glandular tissue. Right and left lateral lobes lie on either side of urethra and are separated from one another by a shallow vertical groove on posterior surface of prostate. Lateral lobes contain many glands.

Lobes of Prostate Blood Supply Arteries: inferior vesical and middle rectal arteries. Veins: prostatic venous plexus, which lies outside the capsule of prostate. Prostatic plexus receives deep dorsal vein of penis and numerous vesical veins and drains into internal iliac veins. Lymph Drainage: Internal iliac nodes. Nerve Supply: Inferior hypogastric plexuses. Sympathetic nerves stimulate smooth muscle of prostate during ejaculation.

Prostatic Urethra It is about 3 cm long and begins at bladder neck. It passes through prostate from base to apex, where it becomes continuous with membranous part of urethra. Prostatic urethra is the widest and most dilatable portion of entire urethra. On posterior wall is a longitudinal ridge called urethral crest. On each side of this ridge is a groove called prostatic sinus; prostatic glands open into these grooves. On summit of urethral crest is a depression, prostatic utricle, which is an analog of uterus and vagina in females. On edge of mouth of the utricle are openings of the two ejaculatory ducts.

Male Pelvic Peritoneum Peritoneum passes down from anterior abdominal wall onto upper surface of urinary bladder. It then runs down on posterior surface of bladder for a short distance until it reaches upper ends of seminal vesicles. Here it sweeps backward to reach anterior aspect of rectum, forming shallow rectovesical pouch. Peritoneum then passes up on front of middle third of rectum and front and lateral surfaces of upper third of rectum. It then becomes continuous with parietal peritoneum on posterior abdominal wall. Rectovesical pouch is the lowest part of abdominopelvic peritoneal cavity in erect position. Peritoneum covering superior surface of bladder passes laterally to lateral pelvic walls and does not cover lateral surfaces of bladder. It is important to remember that as bladder fills, superior wall rises up into abdomen and peels off peritoneum from anterior abdominal wall so that bladder becomes directly in contact with abdominal wall.

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