TBL23 - Male Genitalia

Question 1

What does the cloacal membrane represent? What is the cloaca divided into and by what? What does the tip of the urorectal septum form?

Answer 1

1) The cloacal membrane represents the fused surface ectoderm and cloacal endoderm
2) The cloaca is divided into the anterior urogenital sinus and posterior anorectal canal by the urorectal septum
3) The tip of the septum forms the perineal body

Question 2

How is the genital tubercle formed? Caudal to the genital tubercle, what are the cloacal folds separated into?

Answer 2

1) Mesenchymal cells migrate onto the surface of the cloacal membrane to form a pair of elevated cloacal folds that join cranially to form the genital tubercle
2) Caudal to the genital tubercle, the cloacal folds are separated into anterior urethral folds and the posterior anal fold

Question 3

Under the influence of testosterone, what occurs to the genital tubercle? What does this structure do to the urethral folds? What does closure of the urethral groove form?

Answer 3

1) Under the influence of testosterone, the genital tubercle rapidly elongates to form the phallus
2) The phallus pulls the urethral folds forward thereby forming the lateral walls of the urethral groove
3) Closure of the groove forms the penile urethra

Question 4

What is hypospadias and where is it likely to occur?

Answer 4

In hypospadias, fusion of the urethral folds is incomplete, and abnormal openings of the urethra occur along the inferior aspect of the penis, usually near the glans, along the shaft, or near the base of the penis

Question 5

On the sides of the urethral folds, what forms the bilateral genital swellings? What does each genital swelling become?

Answer 5

1) On the sides of the urethral folds, another pair of elevations form the bilateral genital swellings
2) Each genital swelling becomes a scrotal swelling composed of heavily pigmented skin that overlies the dartos fascia and muscle

Question 6

During dissension of the testis and spermatic cord from the superficial ring of the inguinal canal, where does each genital swelling move and what does it create? What does midline fusion of the scrotal swellings form?

Answer 6

1) During dissension of the testis and spermatic cord from the superficial ring of the inguinal canal, each genital swelling moves caudally to create half of the scrotum
2) Midline fusion of the swellings forms the scrotal septum

Question 7

Where does the prostatic urethra become the membranous urethra?

Answer 7

The prostatic urethra becomes the membranous urethra in the deep perineal pouch

Question 8

What is the urethra surrounded by at the exit of the prostate gland? Where does the membranous urethra perforate and travel into? At this point what is its new name?

Answer 8

1) The urethra is surrounded by the external urethral sphincter
2) After perforating the perineal membrane into the superficial pouch, the spongy (aka penile) urethra courses through the root, body, and glans of the penis

Question 9

How do the sites of urine extravasation differ after injury to the penile and membranous urethra?

Answer 9

1) Rupture of the membranous part of the urethra results in the extravasation (escape) of urine and blood into the deep perineal pouch
2) The common site of rupture of the spongy urethra and extravasation of urine is in the bulb of the penis. Rupture of the corpus spongiosum and spongy urethra results in urine passing from it (extravasating) into the superficial perineal pouch

Question 10

What is the bulb of the penile root continuous with and what do these two structures surround? What are the crura of the penile root continuous with and what do these structures course parallel to?

Answer 10

1) The bulb of the penile root is continuous with the corpus spongiosum and together they surround the penile urethra along its entire course
2) The crura of the penile root are continuous with the corpus cavernosa and together they course parallel to the urethra in the root and body of the penis

Question 11

What does the thin bulbospongiosus muscle cover? What does the thin ischiocavernosus muscle cover?

Answer 11

1) The thin bulbospongiosus muscle covers the bulb and proximal body of the penis
2) The thin ischiocavernosus muscle covers the bilateral crura

Question 12

What type of tissue do the erectile tissues consist of and what does this tissue surround?

Answer 12

The erectile tissues consist of dense connective tissue surrounding venous sinuses and muscular helicine (convoluted) arteries

Question 13

What are the helicine arteries generated from? Where do the arteries empty into?

Answer 13

1) The helicine arteries are generated from branches (ignore names) of the internal pudendal artery
2) The arteries empty directly into the venous sinuses of the penile erectile tissues

Question 14

What do branches of the pudendal nerve support and transport and what do these nerve fibers mediate? What does this action normally restrict?

Answer 14

1) Branches of the pudendal nerve support and transport postsynaptic sympathetic fibers that mediate tonic convolution of the helicine arteries
2) The tonic convolution normally restricts blood flow into the venous sinuses

Question 15

What are the cavernous nerves of the prostatic plexus branches of and what do they inhibit? What does this inhibition cause?

Answer 15

1) The cavernous nerves of the prostatic plexus, branches of the parasympathetic pelvic splanchnic nerves, inhibit the sympathetic-mediated tonic convolutions
2) The resultant uncoiling of the helicine arteries engorges the venous sinuses with blood to induce penile erection

Question 16

Why can radical prostatectomy cause erectile dysfunction?

Answer 16

1) Radical prostatectomy: the entire prostate is removed
along with the seminal glands, ejaculatory ducts, and terminal parts of the deferent ducts
2) Erectile dysfunction (ED) may occur in the absence of a nerve insult, specifically the prostatic plexus or cavernous nerves

Question 17

What does sympathetic-mediated contraction of smooth muscle in the vas deferens, seminal vesicles, and ejaculatory ducts do? What results in ejaculation?

Answer 17

1) Sympathetic-mediated contraction of smooth muscle in the vas deferens, seminal vesicles, and ejaculatory ducts delivers semen to the prostatic urethra
2) Sympathetic-mediated contraction of the prostatic fibromuscular stroma and pudendal nerve-mediated contraction of the thin bulbospongiosus muscle results in ejaculation

Question 18

What nerve innervations do the posterior and anterior surfaces of the scrotum receive?

Answer 18

The posterior and anterior surfaces of the scrotum receive somatic sensory innervation from the pudendal nerve and the ilioinguinal nerve, respectively

Question 19

In response to cold, what muscle of the scrotum contracts and what nerve fibers innervate this muscle? What does contraction of this muscle cause?

Answer 19

1) In response to cold, sympathetic fibers conveyed by the two somatic nerves involuntarily contract the dartos muscle
2) This decreases scrotal surface area, which maintains scrotal temperature a few degrees below body temperature to insure spermatogenesis

Question 20

How does the pampiniform venous plexus contribute to the thermoregulatory function of the dartos muscle contraction?

Answer 20

The pampiniform venous plexus of the spermatic cord contributes to this thermoregulatory function by cooling the blood in the testicular arteries

Question 21

Compare primary lymph drainage from the penis and scrotum with lymph drainage from the testes.

Answer 21

1) Lymph from the skin of all parts of the perineum, including the hairless skin inferior to the pectinate line of the anorectum but excluding the glans penis, drains to the superficial inguinal nodes
2) Lymphatic drainage from the intermediate and proximal parts of the urethra and cavernous bodies drain into the internal iliac lymph nodes, whereas most vessels from the distal spongy urethra and glans penis pass to the deep inguinal nodes, but some lymph passes to the external inguinal nodes
3) Reflective of their abdominal origins, lymph from the testes follow a route, independent of the scrotal drainage, along the testicular veins to the intermesenteric portion of the lumbar (caval/aortic) and pre-aortic lymph nodes

Question 22

Why do injection sites differ for anesthetizing the anterior and posterior surfaces of the scrotum?

Answer 22

Since the anterolateral surface of the scrotum is supplied by the lumbar plexus (primarily L1 fibers via the ilio-inguinal nerve) and the postero-inferior aspect is supplied by the sacral plexus (primarily S3 fibers via the pudendal nerve), a spinal anesthetic agent must be injected more superiorly to anesthetize the anterolateral surface of the scrotum than is necessary to anesthetize its postero-inferior surface

Question 23

How can testicular cancer and cancer of the scrotum be distinguished by lymphogenous metastasis?

Answer 23

1) Cancer of the testis: metastasizes initially to the retroperitoneal lumbar lymph nodes, which lie just inferior to the renal veins. Subsequent spread may be to mediastinal and supraclavicular nodes
2) Cancer of the scrotum: metastasizes to the superficial inguinal lymph nodes, which lie in the subcutaneous tissue inferior to the inguinal ligament and along the terminal part of the great saphenous vein

Question 24

After germ cells invade the indifferent gonads, what forms the testis cords and what do these structures do? What are the testis cords separated from the genital ridge epithelium by?

Answer 24

1) After germ cells invade the indifferent gonads, proliferation of the primitive sex cords creates testis cords, which transforms the gonads into the testes
2) The testis cords are separated from the genital ridge epithelium by a layer of dense connective tissue designated the tunica albuginea

Question 25

What forms the rete testis? What do the solid testis cords acquire at puberty?

Answer 25

1) Portions of the testis cords adjacent to the intermediate mesoderm form short tubules called the rete testis 2) At puberty, the solid testis cords acquire a lumen to become the seminiferous tubules

Question 26

What does the mesonephric duct generate to unite with the rete testis? What does the mesonephric duct become below the efferent ductules? Where does the mesonephric duct form the vas deferens?

Answer 26

1) The mesonephric duct generates efferent ductules that unite with the rete testes 2) Below the efferent ductules, the mesonephric duct becomes the convoluted epididymis 3) From the end of the epididymis to the outbudding of the seminal vesicle, the mesonephric duct forms the vas deferens

Question 27

Where is the tunica albuginea thickened and what does this accomodate? What are seminiferous tubules lined by? What are Sertoli and spermatogenic cells derived from and what do they constitute?

Answer 27

1) The tunica albuginea becomes thickened along the posterior border of the testis to accommodate the rete testes 2) Seminiferous tubules are lined by stratified epithelium 3) Sertoli cells, derivatives of genital ridge epithelium, and spermatogenic cells, derived from the germ cells, constitute the seminiferous epithelium

Question 28

Where do spermatogonia reside? What does their continuous renewal generate? Where do the nonproliferating, columnar-shaped Sertoli cells extend from and to?

Answer 28

1) Spermatogonia reside on a basement membrane 2) Their continuous renewal generates spermatocytes with dark spherical nuclei that become progressively smaller as the cells move toward the tubular lumen 3) The nonproliferating, columnar-shaped Sertoli cells extend from the basement membrane to the tubular lumen

Question 29

Where are developing spermatocytes embedded? Interpret how Sertoli cells assist spermatogenesis, including the function of the Sertoli cell-derived blood-testis barrier.

Answer 29

1) Developing spermatocytes are embedded in crypt-like recesses of the Sertoli cells 2) Sertoli cells play a critical role in support and maturation of spermatozoa 3) Sertoli cells phagocytose spermatid remnants and secrete fluid and many substances, including androgen binding protein, essential for spermatozoa survival 4) The extensive cytoskeletal network of Sertoli cells helps provide for spermatozoa movement 5) The resulting blood-testis permeability barrier separates spermatogonia and primary spermatocytes from more apical secondary spermatocytes and spermatids

Question 30

What completes spermatogenesis? What does the head of the spermatozoa contain and what does this surrounding layer do? What is the middle piece of the spermatozoa filled with and what function does this serve?

Answer 30

1) Maturation of the spermatocyte-derived spermatozoa completes spermatogenesis 2) The head contains a small condensed nucleus with surrounding acrosome, which contains proteolytic enzymes that allow spermatozoa to penetrate the corona radiata at fertilization 3) The middle piece of the spermatozoa is filled with mitochondria, which provide energy to the single mobile cilium that forms the tail

Question 31

Where do intermediate mesoderm derived Leydig cells reside? Under LH stimulation, what do Leydig cells locally release and what is this essential for? What does Leydig cell-released testosterone enter and what is it essential for?

Answer 31

1) The intermediate mesoderm derived Leydig cells reside in loose connective tissue between the seminiferous tubules 2) Under LH stimulation, Leydig cells locally release testosterone that is essential for spermatogenesis 3) Leydig cell-released testosterone, which enters the bloodstream, is essential for normal functioning of the prostate and seminal vesicles

Question 32

What is the epidydmus and where does it extend between? Interpret how spermatozoa are affected by the epididymal epithelium during their several week passage in the epididymis.

Answer 32

1) The epididymis is a tortuous (6 m long) passageway between the efferent ductules and vas deferens 2) Stereocilia in the efferent ductules amplify the cell surface area and function in absorption of excess fluid that accompanies spermatozoa from the testis 3) In transit, spermatozoa mature and acquire cilium motility and fertilizing capacity

Question 33

What are seminomas and what is their relationship to cryptorchidism?

Answer 33

1) Seminomas are invasive germinal cell tumors accounting for 95% of solid tumors in men 15-35 years old 2) Although testicular tumors in children are rare, the developmental anomaly known as cryptorchidism, or undescended testis, predisposes boys to develop germ cell tumors

Question 34

What is the potential for surgical reversal of a vasectomy? Does a vasectomy affect endocrine function of the testes?

Answer 34

1) Microsurgery can reverse a vasectomy and restore fertility but is successful in only about 70% of cases 2) No because the Leydig cells of the testis are not affected

Question 35

What is the pathogenesis of epididymitis and what is the possible consequence of severe bilateral cases?

Answer 35

1) Infections of the epididymis are common after puberty. Bacteria most often cause inflammation of the epididymis, known as epididymitis 2) Scrotal pain and edema are characteristic 3) In severe cases, bilateral epididymitis can lead to male infertility