Male Urinary System and Genital Ducts

External GenitaliaScrotum – cutaneous fibromuscular sac for the testes and associated structures; it’s an outpouching of the anterior abdominal wall and so most layers of the anterior abdominal wall are representedDartos fascia – fat-free subcutaneous fascia of the scrotumDartos muscle – smooth muscle fibers in the dartos fascia that inserts into the skin; assists cremaster muscle in testicular elevation as it produces contraction of the skin of the scrotum; receives autonomic innervationScrotal ligament – anchors the inferior pole of the testis to the scrotum to limit degree of movement of the testis; remnant of the fetal gubernaculums testisScrotal septum – prolongation of the dartos fascia that divides the scrotum into two compartments, one for each testisDuctus deferens (vas deferens) – muscular tube that conveys sperm from the epididymis to the ejaculatory duct; courses through the substance of the prostate to open into the prostatic part of the urethra Coverings of the spermatic cord (derived from anterior abdominal wall): External spermatic fascia – derived from the external oblique aponeurosis

and its investing fascia Cremaster muscle and

fascia – derived from the internal oblique muscle; the cremaster fascia is from fascia of both the superficial and deep layers of the internal oblique; the muscle fibers are the lowest fascicles of the internal oblique; innervated by genital branch of the

genitofemoral nerve (L1) Internal spermatic fascia – derived from the transversalis fascia at the deep inguinal ringPampiniform plexus of veins – 8-12 anastomosing veins lying anterior to the ductus deferens and surrounding the testicular artery in the spermatic cord; formed by testicular veins emerging from the testis and epididymis; part of the thermoregulatory system of the testisArtery of the ductus deferens – arises from the inferior vesical artery, a branch of the internal iliac artery that supplies the prostate and seminal vesicles in malesTesticular artery – arises from the aorta (at vertebral level L2) and supplies the testis and epididymisTunica vaginalis – closed peritoneal sac surround the testis Visceral layer – covers the surface of each testis except where the

testis attaches to the epididymis and spermatic cord; glistening, transparent serous membrane that is closely applied to the testis, epididymis, and inferior ductus deferens

Parietal layer – adjacent to internal spermatic fascia; more extensive than the visceral layer since it extends superiorly into the distal part of the spermatic cord

Cavity of the tunica vaginalis – potential space between the visceral and parietal layer that contains a small amount of serous fluidEpididymis – elongated structure on the posterior surface of testis formed by minute convolutions of the duct of the epididymis Tail – continuous with the ductus deferens Body – convoluted duct of the epididymis Head – superior expanded part composed of lobules formed by coiled ends

of 12-14 efferent ductules Tunica albuginea – fibrous capsule of the testis; forms a ridge on its internal, posterior aspect as the mediastinum of the testisSepta – extension of the tunica albuginea and mediastinum that divides the testis up into lobulesLobules – contained within the interval between the septa; consists of 1-3 seminiferous tubulesSeminiferous tubules – contained within one lobule; where sperm are formed; joined by the straight tubules to the rete testis

Pelvic CavityPeritoneum(1) Descends anterior abdominal wall (loose attachment allows insertion of bladder is it

fills)(2) Reflects onto superior surface of bladder, creating supravesical fossa(3) Covers convex superior surface (roof) of bladder, sloping down sides of roof to ascend

lateral wall of pelvis, creating paravesical fossa on each side(4) Descends posterior surface of bladder as much as 2 cm(5) Laterally, forms folds over uterus (ureteric fold), ductus deferentes, and superior ends

of seminal glands(6) Reflects from bladder and seminal glands onto rectum, forming rectovesical pouch(7) Rectovesical pouch extends laterally and posteriorly to form pararectal fossa on each

side of the rectum(8) Ascends rectum (from superior to inferior, rectum is subperitoneal then

retroperitoneal)(9) Engulfs sigmoid colon beginning at rectosigmoid junctionRectovesical pouch – reflection of the peritoneum from the bladder and seminal glands onto the rectum; it’s the low point of the peritoneal cavity in erect positionParavesical fossa – a depression of the peritoneum on either side of the bladder; limited laterally by the peritoneum that covers the ductus deferens Pararectal fossa – extension of the rectovesical pouch posterior and laterally on each side of the rectum Perineal membrane – thin sheet of tough deep fascia that stretches between right and left sides of the pubic arch; located deep to the bulb of the penis; covers the anterior part of the pelvic outlet and is perforated by the urethra in both sexes and by the vagina of the female (Dissector fig 5.15, pg 122; Moore fig 3.43, pg 251)External urethral sphincter muscle – in males, only a part of the muscle forms a circular investment for the intermediate part of the urethra inferior to the prostate; trough-like part extends vertically to the neck of the bladder, displacing the prostate and investing the prosthetic urethra anteriorly and anterolaterally only; composed of somatically innervated voluntary smooth muscle that allows control of urinary continence (Moore fig 3.45A, pg 235)Membranous urethra (intermediate urethra) – 1-1.5 cm; part of the urethra surrounded by the external urethral sphincter; penetrates the perineal membrane; narrowest and least distensible part Prostatic urethra – 3-4 cm; part of the urethra surrounded by the anterior prostate; widest and most dilatable part; where urinary and reproductive tracts merge; interior of the prostatic urethra (Dissector fig 5.18, pg 126): Urethral crest – longitudinal fold on the posterior wall of the urethra

from uvula of bladder through the prostatic urethra; composed of muscular and erectile tissue; when distended, may prevent semen from entering the bladder

Seminal colliculus – enlargement of the urethral crest; landmark for the entrance of the seminal vesicles

Prostatic sinus – groove on either side of the seminal colliculus, perforated by apertures for the prostatic ducts from the lateral prostate

Prostatic utricle – small opening on the midline of the seminal colliculus, flanked laterally by openings of the ejaculatory ducts

Opening of the ejaculatory duct – ~2cm union of the ductus deferens and duct of the seminal vesicles Spongy urethra (penile urethra) - ~15 cm; courses through corpus spongiosum; initial widening occurs in the bulb of the penis then widens against distally as navicular fossa of the glans

penisDuctus deferens – enters the deep inguinal ring lateral to the inferior epigastric vessels; as it approaches midline, it passes superior and then medial to the branches of the internal iliac artery; crosses superior to the ureter; enters the retrovesical septum and is in contact with the fundus of the urinary bladderRectovesical septum – endopelvic fascia between the fundus of the bladder and the ampulla of the rectum; closely associated with seminal glands and prostate (Moore fig 3.8D, pg 216)Ampulla of the ductus deferens – enlargement of the ductus deferens before its termination

Seminal vesicle – elongated structure that lies between the fundus and the rectum, lateral to the ampulla of the ductus deferens; secrete a thick alkaline fluid that mixes with the sperm as they pass into the ejaculatory ducts and urethra; the superior ends are covered with peritoneum and lie posterior to the ureters, separated from the rectum by the rectovesical pouch; the inferior ends are closely related to the rectum and separated by the rectovesical septumEjaculatory duct – slender tube that arises by the union of the duct of a seminal gland with the ductus deferens; arise near the neck of the bladder and converge to open at the prostatic utricleProstate – secretes and stores a slightly alkaline fluid that is milky in appearance; prostatic secretions join the seminal fluid in the prostatic urethra after termination of the ejaculatory ducts; contains: Apex – superior aspect that is closely related to the neck of the bladder Base – inferior aspect that is in contact with fascia on the superior aspect of the urethral sphincter and deep perineal

musclesLobes of the prostrate – Isthmus – anterior muscular zone; represent the superior

continuation of the urethral sphincter muscle anterior to the urethra

Left and right lobes are divided into:o Inferoposterior lobule – superficial, posterior to the urethra and

inferior to the ejaculatory ducts; palpable by digital examo Inferolateral lobule – superficial, lateral to the urethra, forms the

major part of the prostateo Superomedial lobule – surrounds the ejaculatory duct, deep to

the inferoposterior lobeo Anteromedial lobule – deep to the inferolateral lobule; directly

lateral to the proximal prostatic urethra

Urinary BladderEndopelvic fascia – abundant connective tissue between the parietal and visceral membranous fasciaRetropubic space (prevesical space) – potential space between the pubic symphysis and urinary bladder that is filled with loose fatty tissue (part of endopelvic fascia) to accommodate the expansion of the urinary bladder Puboprostatic ligament – condensation of the parietal pelvic fascia that ties the prostate to the inner surface of the pubisApex – pointed part (superior end) directed toward the anterior abdominal wall; can be identified by attachment of the urachusBody – part between apex and fundusFundus – inferior part of the posterior on the opposite side of the apex (also called base of the urinary bladder); related to ductus deferens, seminal vesicles, and rectum in malesNeck – where the fundus and inferolateral surfaces converge inferiorly; where the urethra exits the urinary bladder; walls thicken to form the internal urethral sphincterSurfaces of the urinary bladder Superior – covered by peritoneum Posterior – covered by peritoneum on its superior part and by endopelvic fascia of the rectovesical septum on its inferior

part Inferolateral (2) – covered by endopelvic fasciaDetrusor muscle – bundles of smooth muscle that chiefly make up the walls of the bladderTrigone – angles are formed by the internal urethral orifice (apex) and the orifices of the ureters (posterolateral angles); the mucous membrane over the trigone are smooth, whereas elsewhere the bladder has folds; the area is very sensitive to stretch and signals to brain the need to emptyInternal urethral orifice – opening of the bladder into the urethra at the most inferior point in the bladder; fibers of the

detrusor muscle form the involuntary internal urethral sphincter around the orifice that contracts during ejaculation to prevent retrograde ejaculationOrifices of the Ureters – slit-like openings where the ureters enter the bladder; it passes through the muscular wall in an oblique direction and is encircled by loops of detrusor musculature that tighten when the bladder contracts to prevent reflux of urine into the ureter

Rectum and Anal CanalAmpulla of the rectum – dilated terminal part of the rectum; supports and retains fecal mass before defecationAnorectal flexure - ~80° bend at the ampulla before rectum continues as the anal canal; an important mechanism for fecal continence and is maintained during resting state by the tone of puborectalisTransverse rectal folds – 3 internal infoldings (2 on left and 1 on right) that overlie thickened parts of the circular muscle layer of the rectal wallAnal columns – 5-10 longitudinal ridges of mucosa in the proximal part of the anal canal; contain terminal branches of superior rectal arteries and veins (branches/tributaries of SMA and SMV)Anal valves – semilunar folds of mucosa that unite the distal ends of the anal columnsAnal sinus – small pocket between the anal valve and the wall of the anal canal; when compressed by feces, exude mucus that aids in evacuation of feces from the anal canalPectinate line – irregular line formed by the anal valves; indicates the junction of the superior part of the anal canal (visceral, derived from embryologic hindgut) and inferior part of the anal canal (somatic, derived from embryologic proctoderm); the two parts differ in their arterial supply, innervation, and venous and lymphatic drainageExternal anal sphincter – large voluntary sphincter; forms broad band on each side of the inferior 2/3rds of the anal canal; blends superiorly with puborectalis; supplied mainly by S4 through inferior anal (rectal) nerve

Internal anal sphincter – involuntary sphincter surrounding superior 2/3rds of the anal canal; thickening of the circular muscle layer; contraction is maintained by the sympathetic fivers from the superior rectal and hypogastric plexus; inhibition by the parasympathetic fibers