Session 2A: Male External Genitalia And Pelvic Organs

Question 1

What is the inguinal canal?

Answer 1

The inguinal canal is an oblique passageway through the muscles of the anterior abdominal wall and lies superior to the medial half of the inguinal ligament. It passes through each layer of the abdominal wall as it travels medially and inferiorly. The canal is about 5 cm long in the adult. It extends from the deep inguinal ring laterally (an aperture in the transversalis fascia) to the superficial inguinal ring medially (an aperture in the external oblique aponeurosis).

Question 2

What are the borders of the inguinal canal?

Answer 2

The borders of the inguinal canal are as follows:

Anterior border:
● External oblique aponeurosis
● Laterally only: internal oblique aponeurosis

Posterior border:
● Transversalis fascia
● Medially only: medial fibres of the aponeuroses of the internal oblique and transversus abdominis (which are together known as the conjoint tendon).

Roof:
● Transversalis fascia
● Arching fibres of the internal oblique and transversus abdominis.

Floor:
● Inguinal ligament (the lower border of the external oblique aponeurosis).

Question 3

What are the contents of the inguinal canal?

Answer 3

Contents of the Inguinal Canal
The contents of the inguinal canal are different in males and females. In females it contains three structures:
1. Round ligament of the uterus
2. Ilioinguinal nerve
3. Genital branch of the genitofemoral nerve.

Question 4

What is the inguinal canal like in males?

Answer 4

In males, the contents of the inguinal canal are all contained within the spermatic cord, except for the ilioinguinal nerve, which runs in the canal but lies outside the spermatic cord.

Question 5

What are the contents of the spermatic cord?

Answer 5

The contents of the spermatic cord can be divided in into two nerves, three arteries, three fascial layers and four other structures:

Two nerves:
• Genital branch of the genitofemoral nerve
• Sympathetic nerve fibres

Three arteries:
• Testicular artery
• Cremasteric artery
• Artery to the vas deferens

Three fascial layers:
• External spermatic fascia (derived from the external oblique aponeurosis)
• Cremaster muscle and fascia (derived from the internal oblique muscle)
• Internal spermatic fascia (derived from the transversalis fascia)

Question 6

What other structures are in the spermatic cord?

Answer 6

Four other structures:
• Pampiniform venous plexus
• Lymphatics
• Vas deferens (plural: vasa deferentia)
• Processus vaginalis (derived from the peritoneum).

Question 7

Where are the testes?

Answer 7

The testes are located within the scrotum. Scrotal skin is thin, wrinkled and more darkly pigmented than skin elsewhere. Beneath the skin is a thin layer of superficial fascia and a thin, involuntary muscle called the dartos. The superficial fascia extends between the testes to form a septum dividing the scrotum into right and left halves. Each half of the scrotum contains a testis, epididymis and distal part of the spermatic cord.

Question 8

What do the testes do?

Answer 8

The testes produce sperm and secrete testosterone. They are ovoid structures which are covered by the same three layers of spermatic fascia that cover the spermatic cord. The testes are also partially surrounded by a sac derived from the peritoneum called the tunica vaginalis.

Question 9

What is the epididymis?

Answer 9

The epididymis is a coiled tube lying along the posterior border of each testis, which has an expanded head superiorly, a body and a pointed tail lying at the lower pole of the testis. Spermatozoa are formed in the testis and stored in the epididymis. The vas deferens carries sperm from the epididymis and travels with the testicular vessels in the spermatic cord.

Question 10

What is the blood supply of the testes?

Answer 10

The testicular arteries are direct branches of the abdominal aorta. Venous blood from the testis and epididymis enters the pampiniform venous plexus. The pampiniform venous plexus forms the testicular vein. The right testicular vein enters the inferior vena cava. The left testicular vein joins the left renal vein.

Question 11

What is the structure of the penis?

Answer 11

The penis is composed of three cylinders of erectile tissue: two corpora cavernosa dorsally (along the ‘top’ of the penis) and one corpus spongiosum ventrally (along the ‘bottom’ of the penis). The corpora cavernosa and corpus spongiosum are enclosed within the deep fascia of the penis (Buck’s fascia). The end of the penis is called the glans and is an expansion of the corpus spongiosum. The circular base of the glans is called the corona. The skin of the shaft of the penis extends over the glans and is called the foreskin. The foreskin may be removed for religious, social, or medical reasons in a procedure called circumcision.

Question 12

What is the location of the corpus cavernous?

Answer 12

The corpora cavernosa are symmetrical and originate along the left and right ischial rami to converge in the midline. The parts of the corpora cavernosa that are attached to the ischial rami are known as ‘crura’ (singular: crus), which means ‘legs’, so ‘crura of the penis’ simply refer to the parts of the corpora cavernosa that are attached to the ischial rami. Distally, the corpora cavernosa contribute to the body of the penis.

Question 13

What is the location of the corpus spongiosum?

Answer 13

The corpus spongiosum sits in the midline. In the male, it has an expanded part proximally which rests on the perineal membrane - the ‘bulb’ of the penis (the bulb is just the name of the part of the corpus spongiosum that is attached to the perineal membrane).

Question 14

Where is the penile urethra?

Answer 14

The penile urethra (which carries urine and semen) lies within the corpus spongiosum. As the urethra approaches the end of the penis, it opens via the external urethral meatus.

Question 15

What do muscles cover?

Answer 15

The corpora cavernosa are covered by the ischiocavernosus muscles, and the corpus spongiosum is covered by the bulbospongiosus muscle. Ischiocavernosus forces blood into the body of the penis from the crura. Bulbospongiosus forces blood into the glans penis, assists in maintaining erection by compressing the veins that drain erectile tissues and it contracts to squeeze any remaining urine or semen from the urethra.

Question 16

What is the blood supply to the penis?

Answer 16

The arterial supply to the penis is via the internal pudendal arteries, which themselves branch from the internal iliac arteries. Branches of the internal pudendal include the deep artery of the penis and the artery of the bulb of the penis.

Question 17

What is the innervation of the penis?

Answer 17

The nerve supply to the penis is from the S2-S4 nerves. Both general sensation and sympathetic innervation are carried by the dorsal nerve of the penis, which is a branch of the pudendal nerve. Parasympathetic nerve fibres (responsible for causing erection by dilating the arteries of the corpora) arise from the peri-prostatic nerve plexus. Ischiocavernosus and bulbospongiosus are innervated by the pudendal nerve (S2-S4).

Question 18

What is the penile erection?

Answer 18

The corpora cavernosa are primarily responsible for the increase in size and rigidity of the penis during an erection. During sexual arousal, arterial blood flow into the corpora of the penis increases, so the corpora become engorged with blood. Although the corpus spongiosum becomes engorged as well, it does not do so to the same extent as the corpora cavernosa. The main role of the corpus spongiosum during erection is to prevent the urethra from being compressed, which would prevent ejaculation.

Question 19

What do the male pelvic organ contain?

Answer 19

The male pelvic organs include the intra-abdominal parts of the paired vasa deferentia, the seminal vesicles, ejaculatory ducts, bulbo-urethral glands, prostate gland, bladder and rectum. The testes, epididymides, part of the vasa deferentia and penis, the bladder and rectum have been discussed previously.

Question 20

What is the structure of the vas deferens?

Answer 20

Vas deferens - this tube (also referred to as ‘ductus deferens’) carries sperm from the epididymis up the spermatic cord and through the inguinal canal into the pelvis. From the deep inguinal ring, the vas deferens passes across the side wall of the pelvis, then turns medially onto the back of the bladder. Here it has a dilated portion, the ampulla, which lies medial to the seminal vesicle. The vas deferens terminates by joining the duct of the seminal vesicle to form the ejaculatory duct.

Question 21

What is the structure of the seminal vesicle?

Answer 21

Seminal vesicle - each seminal vesicle is a lobulated sac, about 4cm long, lying lateral to the ampulla of the vas deferens. They secrete a thick alkaline fluid which forms the bulk of seminal fluid (also known as semen). The duct of the seminal vesicle joins the vas deferens to become the ejaculatory duct which pierces the back of the prostate gland to enter the prostatic urethra.

Question 22

What is the structure of the prostrate?

Answer 22

Prostate - the prostate gland is a roughly spherical fibromuscular gland about the size of a walnut. It lies against the neck of the bladder and is pierced by the urethra and ejaculatory ducts. Secretions of the prostate are added to the seminal fluid during ejaculation.

Question 23

What is the blood supply of the male pelvic organs?

Answer 23

The vas deferens, seminal vesicle and prostate are all supplied by branches of the internal iliac artery.

Question 24

What is the hydrocoele?

Answer 24

This is a painless scrotal swelling caused by accumulation of peritoneal fluid between the layers of the tunica vaginalis around the testis. When a light is shone through a hydrocoele, it can be seen from the other side. This is called ‘transillumination’ and is often used in diagnosis of scrotal swellings.

Question 25

What is the varicocele?

Answer 25

This is an abnormal dilation of the pampiniform venous plexus which causes a scrotal swelling. Varicoceles are often described as feeling like a ‘bag of worms’ on palpation, due to the dilated veins. They are much more common on the left side because the left testicular vein drains into the left renal vein before it drains into the inferior vena cava. Because of this, development of a left-sided varicocele may be caused by obstruction of the left renal vein.

Question 26

What is epididymo-orchitis?

Answer 26

Epididymo-orchitis
This condition is a painful inflammation of the epididymis and testis. Epididymo-orchitis in sexually active patients is very often caused by a sexually transmitted infection such as chlamydia or gonorrhoea. It may also be caused by a urinary tract infection.

Question 27

What is testicular torsion?

Answer 27

This is caused by twisting of the testis on the spermatic cord, which can lead to ischaemia of the testis and represents a surgical emergency. Patient’s often present suddenly with a very painful and tender testis which may be positioned higher or at an unusual angle. If left untreated, it can lead to necrosis and loss of the affected testis.

Question 28

What is cryptorchidism?

Answer 28

Cryptorchidism (undescended testis)
During foetal development, the testes form in the abdomen and descend through the inguinal canal to reach the scrotum before birth. If this fails to occur, the infant is born with one or both testes absent from the scrotum, and the affected testis will be stuck somewhere along the path of descent. As spermatogenesis is optimal just below core body temperature, the testes will only function correctly if they are in the scrotum. Additionally, there is an increased risk of testicular cancer if the undescended testis is left inside the abdomen. For these reasons, undescended testes are often brought into the scrotum surgically.

Question 29

What is the CR of testicular cancer?

Answer 29

Testicular cancer
Cancer of the testis is an important diagnosis to consider in any scrotal lump or swelling. The prognosis is excellent if detected and treated early, usually with surgery to remove the testis and part of the spermatic cord (orchidectomy) plus chemotherapy or radiotherapy if required. In the same way that females are advised to examine their breasts for lumps on a regular basis, males should regularly examine their testes for lumps and seek medical advice from their GP if they are concerned about a new lump.

If a testicular cancer metastasises, it will likely follow the lymphatic drainage which follows the testicular arteries back to lymph nodes around the aorta. For this reason, testicular cancer metastasises first to the para-aortic or retroperitoneal lymph nodes.

Question 30

What is a vasectomy?

Answer 30

Vasectomy is a means of male sterilisation (permanent male contraception). It is considered a relatively straightforward surgical procedure where the scrotum is incised and the vasa deferentia are located on each side. They are then ligated, cauterised or clamped to prevent the passage of sperm from the testes.

Question 31

What is erectile dysfunction?

Answer 31

Historically referred to as impotence, erectile dysfunction describes the inability to achieve or maintain an erection during sexual activity. It is common and will affect most males at some point. As achieving and maintaining an erection relies on intact nerve pathways and reflexes, controlled blood flow in and out of the corpora of the penis, and psychological arousal, a problem with any of these may lead to erectile dysfunction. Management includes identifying the cause and treating that or using medications such as sildenafil (Viagra) which increase blood flow into the corpora of the penis.

Question 32

What is benign prostatic hyperplasia and prostatic malignancy?

Answer 32

The prostate gland completely encircles the urethra. With progressing age, benign enlargement of the prostate is common and is called ‘benign prostatic hyperplasia’ (BPH) or ‘benign prostatic enlargement’ (BPE). This may lead to compression of the urethra and the inability to pass any urine - called urinary retention - which requires catheterisation (insertion of a catheter into the bladder) to drain the urine.

Prostate cancer is common. Venous blood from the prostate passes into a plexus of veins which lie anterior to the sacrum and communicate with veins which run up to the azygos vein in the chest. These veins communicate with veins in the vertebral bodies which explains why prostate cancer commonly metastasises to the vertebrae.

The prostate can be examined during a digital rectal exam (DRE), also known as a ‘per rectum’ exam (PR). This involves pushing a gloved and lubricated finger into the rectum via the anus and flexing it anteriorly to palpate the prostate which sits immediately anterior to the anal canal and rectum. A clinician can feel the size, contour and firmness of the prostate during this examination, and this can help guide diagnosis. A hard, craggy prostate is concerning for malignancy.