Male and Female Genital Anatomy PDF

the seminal colliculus, flanked by the tiny openings of the ejaculatory ducts. The reproductive and urinary tracts merge within the prostatic urethra. The female urethra runs parallel to the vagina. It is firmly attached to and indents the anterior vaginal wall centrally and distally. Since it i...

the seminal colliculus, flanked by the tiny openings of the ejaculatory ducts. The reproductive and urinary tracts merge within the prostatic urethra. The female urethra runs parallel to the vagina. It is firmly attached to and indents the anterior vaginal wall centrally and distally. Since it is not shared with the reproductive tract, an internal urethral sphincter is not required at the neck of the female bladder. Rectum: The rectum accumulates and temporarily stores feces. The rectum begins at the rectosigmoid junction as the teniae of the sigmoid colon spread and unite into a continuous longitudinal layer of smooth muscle and the omental appendices cease. The rectum ends with the anorectal flexure as the gut penetrates the pelvic diaphragm, becoming the anal canal. Despite the Latin term rectus (straight), the rectum is concave anteriorly as the sacral flexure and has three lateral flexures formed in relation to the internal transverse rectal folds. The rectum enlarges into the rectal ampulla directly above the pelvic floor. The superior, middle, and inferior parts of the rectum are, respectively, intraperitoneal, retroperitoneal, and subperitoneal. Collateral arterial circulation and a portocaval venous anastomosis result from anastomoses of the superior and inferior rectal vessels. Sympathetic nerve fibers pass to the rectum (especially blood vessels and internal anal sphincter) from lumbar spinal cord segments via the hypogastric/pelvic plexuses and the peri-arterial plexus of the superior rectal artery. Parasympathetic and visceral afferent fibers involve the middle sacral spinal cord segments and spinal ganglia. Male Internal Genital Organs The male internal genital organs include the testes, epididymides (singular = epididymis), ductus deferentes (singular = ductus deferens), seminal glands, ejaculatory ducts, prostate, and bulbo-urethral glands (Fig. 6.34). The testes and epididymides (described in Chapter 5, Abdomen) are considered internal genital organs on the basis of their developmental position and homology with the internal female ovaries. However, because of their external position postnatally and because in dissection these organs are encountered during the dissection of the inguinal region of the anterior abdominal wall, they are considered with the abdomen in Chapter 5, Abdomen. FIGURE 6.34. Hemisected male pelvis and perineum (right half). The genital organs are demonstrated: testis, epididymis, ductus deferens, ejaculatory duct, and penis, with the accessory glandular structures (seminal gland, prostate, and bulbo-urethral gland). The spermatic cord connects the testis to the abdominal cavity, and the testis lies externally in a musculocutaneous pouch, the scrotum. DUCTUS DEFERENS The ductus deferens (vas deferens) is the continuation of the duct of the epididymis. The ductus deferens has relatively thick muscular walls and a minute lumen, giving it a cord-like firmness begins in the tail of the epididymis, at the inferior pole of the testis (see Fig. 5.21) ascends posterior to the testis and medial to the epididymis is the primary component of the spermatic cord penetrates the anterior abdominal wall via the inguinal canal crosses over the external iliac vessels and enters the pelvis passes along the lateral wall of the pelvis, where it lies external to the parietal peritoneum ends by joining the duct of the seminal gland to form the ejaculatory duct During the pelvic part of its course, the ductus deferens maintains direct contact with the peritoneum; no other structure intervenes between them (Fig. 6.34). The ductus crosses superior to the ureter near the posterolateral angle of the urinary bladder, running between the ureter and the peritoneum of the ureteric fold to reach the fundus of the bladder. The relationship of the ductus deferens to the ureter in the male is similar, although of lesser clinical importance, to that of the uterine artery to the ureter in the female. The developmental basis of this relationship is shown in Figure 6.35. Posterior to the bladder, the ductus deferens at first lies superior to the seminal gland and then descends medial to the ureter and the gland (Fig. 6.36A, B). Here, the ductus deferens enlarges to form the ampulla of the ductus deferens before its termination.  FIGURE 6.35. Structures crossing male ureter in abdomen and pelvis. During development, as the testis descends inferiorly and laterally from its original position (medial to the site of the kidneys on the posterior abdominal wall) to and then through the inguinal canal, the ureter is crossed by testicular vessels in the abdomen and by the ductus deferens in the pelvis. This relationship is retained throughout life. Arterial Supply and Venous Drainage of Ductus Deferens. The tiny artery to the ductus deferens usually arises from a superior (sometimes inferior) vesical artery (Fig. 6.37; see Fig. 6.15; Table 6.4) and terminates by anastomosing with the testicular artery, posterior to the testis. Veins from most of the ductus drain into the testicular vein, including the distal pampiniform plexus. Its terminal portion drains into the vesicular/prostatic venous plexus. SEMINAL GLANDS Each seminal gland (vesicle) is an elongated structure (approximately 5 cm long, but sometimes, it is much shorter) that lies between the fundus of the bladder and the rectum (Figs. 6.34, 6.36, and 6.37). The seminal glands are obliquely placed superior to the prostate and do not store sperms (as the term “vesicle” indicates). They secrete a thick alkaline fluid with fructose (an energy source for sperms) and a coagulating agent that mixes with the sperms as they pass into the ejaculatory ducts and urethra.  FIGURE 6.36. Posterior aspect of male pelvic viscera. A. Overview. The posterior pelvic wall, rectum, and rectovesical septum have been removed. The umbilical ligaments, like the urinary bladder, are embedded in extraperitoneal or subperitoneal fascia (mostly removed in this dissection). B. Posterior dissection of prostate. The ejaculatory ducts are formed by the merger of the duct of the seminal gland and the ductus deferens. The vestigial prostatic utricle, usually seen as an invagination in an anterior view, appears in this posterior dissection as an evagination lying between the ejaculatory ducts. The superior ends of the seminal glands are covered with peritoneum and lie posterior to the ureters, where the peritoneum of the rectovesical pouch separates them from the rectum. The inferior ends of the seminal glands are closely related to the rectum and are separated from it only by the rectovesical septum (Fig. 6.34). The duct of the seminal gland joins the ductus deferens to form the ejaculatory duct. Arterial Supply and Venous Drainage of Seminal Glands. The arteries to the seminal glands derive from the inferior vesical and middle rectal arteries (Fig. 6.37; see Figs. 6.15 and 6.17; Table 6.4). The veins accompany the arteries and have similar names (Fig. 6.19C). FIGURE 6.37. Pelvic part of ureters, urinary bladder, seminal glands, terminal parts of ductus deferens, and prostate. The left seminal gland and ampulla of the ductus deferens are dissected free and sliced open. Part of the prostate is also cut away to expose the ejaculatory duct. The perineal membrane lies between the external genitalia and the deep part of the perineum (anterior recess of ischio-anal fossa). It is pierced by the urethra, ducts of the bulbo-urethral glands, dorsal and deep arteries of the penis, cavernous nerves, and the dorsal nerve of the penis. EJACULATORY DUCTS The ejaculatory ducts are slender tubes that arise by the union of the ducts of the seminal glands with the ductus deferentes (Figs. 6.34, 6.36, and 6.37). The ejaculatory ducts (approximately 2.5 cm long) arise near the neck of the bladder and run close together as they pass antero-inferiorly through the posterior part of the prostate and along the sides of the prostatic utricle. The ejaculatory ducts converge and open on the seminal colliculus by tiny, slit-like apertures on, or just within, the opening of the prostatic utricle (Fig. 6.30). Although the ejaculatory ducts traverse the glandular prostate, prostatic secretions do not join the seminal fluid until the ejaculatory ducts have terminated in the prostatic urethra. Arterial Supply and Venous Drainage of Ejaculatory Ducts. The arteries to the ductus deferens, usually branches of the superior (but frequently inferior) vesical arteries, supply the ejaculatory ducts (Fig. 6.37). The veins join the prostatic and vesical venous plexuses (Fig. 6.19C). PROSTATE The prostate (approximately 3 cm long, 4 cm wide, and 2 cm in anteroposterior [AP] depth) is the largest accessory gland of the male reproductive system (Figs. 6.34, 6.36, and 6.37). The firm, walnut-size prostate surrounds the prostatic urethra. The glandular part makes up approximately two thirds of the prostate; the other third is fibromuscular. The fibrous capsule of the prostate is dense and neurovascular, incorporating the prostatic plexuses of veins and nerves. All of this is surrounded by the visceral layer of the pelvic fascia, forming a fibrous prostatic sheath that is thin anteriorly, continuous anterolaterally with the puboprostatic ligaments, and dense posteriorly where it blends with the rectovesical septum. The prostate has a base closely related to the neck of the bladder an apex that is in contact with fascia on the superior aspect of the urethral sphincter and deep perineal muscles a muscular anterior surface, featuring mostly transversely oriented muscle fibers forming a vertical, trough-like hemisphincter (rhabdosphincter), which is part of the urethral sphincter. The anterior surface is separated from the pubic symphysis by retroperitoneal fat in the retropubic space. a posterior surface that is related to the ampulla of the rectum inferolateral surfaces that are related to the levator ani  Although not clearly distinct anatomically, the following lobes of the prostate are traditionally described (Fig. 6.38A): The isthmus of the prostate (commissure of prostate; historically, the anterior “lobe”) lies anterior to the urethra. It is fibromuscular, the muscle fibers representing a superior continuation of the external urethral sphincter muscle to the neck of the bladder, and contains little, if any, glandular tissue. Right and left lobes of the prostate, separated anteriorly by the isthmus and posteriorly by a central, shallow longitudinal furrow, may each be subdivided for descriptive purposes into four indistinct lobules defined by their relationship to the urethra and ejaculatory ducts and—although less apparent —by the arrangement of the ducts and connective tissue: 1. An inferoposterior (lower posterior) lobule that lies posterior to the urethra and inferior to the ejaculatory ducts. This lobule constitutes the aspect of the prostate palpable by digital rectal examination. 2. An inferolateral (lower lateral) lobule directly lateral to the urethra, forming the major part of the right or left lobe 3. A superomedial lobule, deep to the inferoposterior lobule, surrounding the ipsilateral ejaculatory duct 4. An anteromedial lobule, deep to the inferolateral lobule, directly lateral to the proximal prostatic urethra  FIGURE 6.38. Lobules and zones of prostate. A. Anatomical sections. The lobules are poorly demarcated. B. Anatomical section with correlated ultrasound (US) scan. The US transducer was inserted into the rectum to scan the anteriorly located prostate. The ducts of the glands in the peripheral zone open into the prostatic sinuses, whereas the ducts of the glands in the central (internal) zone open into the prostatic sinuses and the seminal colliculus. An embryonic middle (median) lobe gives rise to items 3 and 4 above. This region tends to undergo hormone-induced hypertrophy in advanced age, forming a middle lobule that lies between the urethra and the ejaculatory ducts and is closely related to the neck of the bladder. Enlargement of the middle lobule is believed to be at least partially responsible for the formation of the uvula (L. uva, a grape) that may project into the internal urethral orifice (see Fig. 6.30). Some clinicians, especially urologists and sonographers, divide the prostate into peripheral and central (internal) zones (Fig. 6.38B). The central zone is comparable to the middle lobe.  The prostatic ducts (20–30) open chiefly into the prostatic sinuses that lie on either side of the seminal colliculus on the posterior wall of the prostatic urethra (Fig. 6.37). Prostatic fluid, a thin, milky fluid, provides approximately 20% of the volume of semen (a mixture of secretions produced by the testes, seminal glands, prostate, and bulbo-urethral glands that provides the vehicle by which sperms are transported) and plays a role in activating the sperms. Arterial Supply and Venous Drainage of Prostate. The prostatic arteries are mainly branches of the internal iliac artery (Fig. 6.37; see Fig. 6.17A; Table 6.4), especially the inferior vesical arteries, but also the internal pudendal and middle rectal arteries. The veins join to form a plexus around the sides and base of the prostate (Fig. 6.37; see Fig. 6.19C). This prostatic venous plexus, between the fibrous capsule of the prostate and the prostatic sheath, drains into the internal iliac veins. The prostatic venous plexus is continuous superiorly with the vesical venous plexus and communicates posteriorly with the internal vertebral venous plexus. BULBO-URETHRAL GLANDS The two pea-size bulbo-urethral glands (Cowper glands) lie posterolateral to the intermediate part of the urethra, largely embedded within the external urethral sphincter (Figs. 6.30B, 6.34, 6.36, and 6.37). The ducts of the bulbo- urethral glands pass through the perineal membrane with the intermediate urethra and open through minute apertures into the proximal part of the spongy urethra in the bulb of the penis. Their mucus-like secretion enters the urethra during sexual arousal. INNERVATION OF INTERNAL GENITAL ORGANS OF MALE PELVIS The ductus deferens, seminal glands, ejaculatory ducts, and prostate are richly innervated by sympathetic nerve fibers. Presynaptic sympathetic fibers originate from cell bodies in the intermediolateral cell column of the T12–L2 (or L3) spinal cord segments. They traverse the paravertebral ganglia of the sympathetic trunks to become components of lumbar (abdominopelvic) splanchnic nerves and the hypogastric and pelvic plexuses (see Fig. 6.29).  Presynaptic parasympathetic fibers from S2 and S3 spinal cord segments traverse pelvic splanchnic nerves, which also join the inferior hypogastric/pelvic plexuses. Synapses with postsynaptic sympathetic and parasympathetic neurons occur within the plexuses, en route to or near the pelvic viscera. As part of an orgasm, the sympathetic system stimulates contraction of the internal urethral sphincter to prevent retrograde ejaculation. Simultaneously, it stimulates rapid peristaltic-like contractions of the ductus deferens, and the combined contraction of and secretion from the seminal glands and prostate that provide the vehicle (semen), and the expulsive force to discharge the sperms during ejaculation. The function of the parasympathetic innervation of the internal genital organs is unclear. However, parasympathetic fibers traversing the prostatic nerve plexus form the cavernous nerves that pass to the erectile bodies of the penis, which are responsible for producing penile erection (see Fig. 6.64). CLINICAL BOX MALE INTERNAL GENITAL ORGANS Male Sterilization The common method of sterilizing males is a deferentectomy, popularly called a vasectomy. During this procedure, part of the ductus deferens is ligated and/or excised through an incision in the superior part of the scrotum (Fig. B6.11). Hence, the subsequent ejaculated fluid from the seminal glands, prostate, and bulbo-urethral glands contains no sperms. The unexpelled sperms degenerate in the epididymis and the proximal part of the ductus deferens. FIGURE B6.11. Vasectomy. Reversal of a deferentectomy is successful in favorable cases (patients