W3: Male perineum and genital system

Question 1

Layers of scrotum

Answer 1

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Skin

Dartos

External spermatic fascia

Cremaster

Internal spermatic fascia

Parietal vaginalis

Visceral vaginalis

Tunica albinguea

Question 2

Which testicle lower?

Answer 2

Left

Question 3

Dartos muscle

Answer 3

The dartos muscle is contained within the subcutaneous tissue of the scrotum and acts to regulate the scrotal temperature by wrinkling the overlying skin, reducing surface area and minimising heat loss

Question 4

Cremaster muscle

Answer 4

The deeper cremaster muscle, which spirals around the spermatic cord, can raise and lower the testis within the scrotum to control its temperature. The cremaster reflex may be elicited by touching the medial aspect of the thigh.

Question 5

Discuss testes cells

Answer 5

The seminiferous tubules are lined by Sertoli cells that aid the maturation process of the spermatozoa. In the interstitial tissue lie the Leydig cells that are responsible for testosterone production.

Question 6

Where does sperm collect after seminiferous tubule?

Answer 6

Rete testes

Question 7

Where does sperm go after rete testes?

Answer 7

Ducts known as efferent tubules transport the sperm from the rete testes to the epididymis for storage and maturation.

Question 8

What are the testes surrounded by in the scrotum?

Answer 8

Inside the scrotum, the testes are covered almost entirely by the tunica vaginalis, a closed sac of parietal peritoneal origin that contains a small amount of viscous fluid. This sac covers the anterior surface and sides of each testicle and works much like the peritoneal sac, lubricating the surfaces of the testes and allowing for friction-free movement.

Question 9

What is the testicular parnchyma protected by?

Answer 9

The testicular parenchyma is protected by the tunica albuginea, a fibrous capsule that encloses the testes. It penetrates into the parenchyma of each testicle with diaphragms, dividing it into lobules.

Question 10

Layers of testes

Answer 10

Skin -> Dartos -> External spermatic fascia -> Cremasteric -> Vaginalis (parietal and visceral) -> Albuginea

Question 11

Discuss epididymis

Answer 11

The epididymis consists of a single heavily coiled duct. It can be divided into three parts; head, body and tail.

Head – The most proximal part of the epididymis. It is formed by the efferent tubules of the testes, which transport sperm from the testes to the epididymis.

Body – Formed by the heavily coiled duct of the epididymis.

Tail – The most distal part of the epididymis. It marks the origin of the vas deferens, which transports sperm to the prostatic portion of the urethra for ejaculation.

Question 12

Innervation of testes

Answer 12

The testes and epididymis receive innervation from the testicular plexus – a network of nerves derived from the renal and aortic plexi. They receive autonomic and sensory fibres.

Question 13

Arterial supply of testes

Answer 13

The main arterial supply to the testes and epididymis is via the paired testicular arteries, which arise directly from the abdominal aorta. They descend down the abdomen, and pass into the scrotum via the inguinal canal, contained within the spermatic cord.

However, the testes are also supplied by branches of the cremasteric artery (from the inferior epigastric artery, branch of external iliac) and the artery of the vas deferens (from the inferior vesical artery). These branches give anastomoses to the main testicular artery.

Question 14

Veins of testes

Answer 14

Venous drainage is achieved via the paired testicular veins. They are formed from the pampiniform plexus in the scrotum – a network of veins wrapped around the testicular artery. In the retroperitoneal space of the abdomen, the left testicular vein drains into the left renal vein, while the right testicular vein drains directly into the inferior vena cava.

Question 15

Lymph drainage of testes

How does it differ from the scrotum?

Answer 15

Since the testes are originally retroperitoneal organs, the lymphatic drainage is to the lumbar and para-aortic nodes, along the lumbar vertebrae.

This is in contrast to the scrotum, which drains into the nearby superficial inguinal nodes.

Question 16

Ampulla of vas deferens

Answer 16

The ampulla of vas deferens, also called the ampulla of ductus deferens, is an enlargement of the vas deferens at the fundus of the bladder which acts as a reservoir for sperm.

Question 17

Contents of spermatic cord

Answer 17

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Pampinform venous plexus

Ductus deferens

Cremaster artery (from the inferior epigastric artery, branch of external iliac)

Testicular artery

Artery of vas deferens (from the inferior vesical artery)

Genital branch of genitofemoral nerve

Sympathetic/parasympathetic fibres

Lympatics

Question 18

Discuss fascia surrounding the spermatic cord

Answer 18

During the descent of the testes into the scrotum, the layers of the anterior abdominal wall are dragged along, creating three layers of fascia surrounding the spermatic cord. These layers are, superficial to deep:

1. External spermatic fascia, formed from external oblique aponeurosis.
2. Cremaster fascia, containing the cremaster muscle, formed from internal oblique muscle and aponeurosis.
3. Internal spermatic fascia, formed from transversalis fascia.

The three fascial layers themselves are covered by a layer of superficial fascia, which lies directly below the scrotal skin.

Question 19

Where does the vas deferens start and end?

Answer 19

The vas deferens is a muscular tube that conducts mature spermatozoa from the tail of the epididymis to the ejaculatory duct, formed when the vas deferens and seminal vesicle ducts join

Question 21

Describe path of vas

Answer 21

. As part of the spermatic cord, the vas deferens passes into the inguinal canal through the superficial inguinal ring and leaves through the deep inguinal ring. The vas deferens then turns medially to pass between the ureter posteriorly and the bladder anteriorly, before passing along the posterior surface of the bladder. Here, the vas deferens expands to form the ampulla of the vas.

Question 22

What is wall of vas made from?

Answer 22

Smooth muscle

Question 23

What happens after vas deferens/how does it end? The inferior narrow part of the ampulla joins the duct from the seminal vesicle to form the ejaculatory duct.

Answer 23

Ejaculatory duct -> sperm into prostatic urethra

Question 24

What do seminal vesicles do? Where are they located?

Answer 24

The seminal vesicles (also known as the vesicular or seminal glands) are a pair of glands found in the male pelvis, which function to produce many of the constituent ingredients of semen. They ultimately provide around 70% of the total volume of semen.

between the bladder fundus and the rectum

forms a part of the late ejaculate

Contains:

Alkaline fluid – neutralises the acidity of the male urethra and vagina in order to facilitate the survival of spermatozoa.

Fructose – provides an energy source for spermatozoa.

Prostaglandins – have a role in suppressing the female immune response to foreign semen.

Clotting factors – designed to keep semen in the female reproductive tract post-ejaculation.

Question 25

Vasculature of seminal gland

Answer 25

The arteries to the seminal gland are derived from the inferior vesicle, internal pudendal and middle rectal arteries, all of which stem from the internal iliac artery.

Question 26

Point shoot score

Answer 26

Parasympathic - erection

Sympathetic - emission

Somatic - ejaculation

Question 27

Function of prostate

Answer 27

It secretes proteolytic enzymes into the semen, which act to break down clotting factors in the ejaculate. This allows the semen to remain in a fluid state, moving throughout the female reproductive tract for potential fertilisation.

Question 28

Where is prostate positioned?

Answer 28

Inferiorly to neck of bladder

Superiorly to external urethral sphincter

Question 29

Discuss how prostate stuff enters

Answer 29

The proteolytic enzymes leave the prostate via the prostatic ducts. These open into the prostatic portion of the urethra, through 10-12 openings at each side of the seminal colliculus (or verumontanum); secreting the enzymes into the semen immediately before ejaculation.

Question 30

Discuss zones of the prostate

Answer 30

• Central zone – surrounds the ejaculatory ducts, comprising approximately 25% of normal prostate volume.
  
  • The ducts of the glands from the central zone are obliquely emptying in the prostatic urethra, thus being rather immune to urine reflux.
• Transitional zone – located centrally and surrounds the urethra, comprising approximately 5-10% of normal prostate volume.
  
  • The glands of the transitional zone are those that typically undergo benign hyperplasia (BPH)
• Peripheral zone – makes up the main body of the gland (approximately 65%) and is located posteriorly.
  
  • The ducts of the glands from the peripheral zone are vertically emptying in the prostatic urethra; that may explain the tendency of these glands to permit urine reflux.
  • That also explains the high incidence of acute and chronic inflammation found in these compartments, a fact that may be linked to the high incidence of prostate carcinoma at the peripheral zone.
  • The peripheral zone is mainly the area felt against the rectum on DRE, which is of irreplaceable value.

OR

The prostate gland is a walnut-sized muscular gland located around the proximal urethra, which produces and secretes an alkaline fluid containing simple sugars and proteolytic enzymes that contributes to 30% of the vol- ume of semen. The prostate may be divided into a left and right lobe, separated by a superficial median furrow (or groove) on its posterior surface. Functionally, the prostate gland is divided into three histological regions:

Central zone – surrounds ejaculatory ducts, accounting for 25% of the prostate volume.

Transition zone – located anterolateral to the proximal urethra. The site in which benign prostatic hyperplasia occurs.

Peripheral zone – surrounds the more distal prostatic urethra at the apex of the prostate, accounting for around 70% of the prostate volume. The site in which prostate cancer typically occurs.

Question 31

Arterial supply prostate

Venous drainage

Answer 31

The arterial supply to the prostate comes from the prostatic arteries, which are mainly derived from the internal iliac arteries. Some branches may also arise from the internal pudendal and middle rectal arteries.

Venous drainage of the prostate is via the prostatic venous plexus, draining into the internal iliac veins. However, the prostatic venous plexus also connects posteriorly by networks of veins, including the Batson venous plexus, to the internal vertebral venous plexus.

Question 32

What can the penis be split into?

Answer 32

Root

Body

Glans

Question 33

What is the root made up of?

Answer 33

Most proximal

The root contains three erectile tissues (two crura and bulb of the penis), and two muscles (ischiocavernosus and bulbospongiosus).

Question 34

What is glans formed from? What does it contain?

Answer 34

corpus spongiosum. This contains the opening of the urethra, termed the external urethral orifice.

Question 35

Discuss erectile tissue

Answer 35

In the root, these tissues are known as the left and right crura, and the bulb of the penis. The bulb is situated in the midline of the penile root, and is traversed by the urethra.

The erectile tissues continue into the body of the penis. The left and right crura continue anteriorly into the dorsal part of the penis – they form the two corpora cavernosa.

They are separated by the septum of the penis, although often incompletely.

The bulb forms the corpus spongiosum, which lies ventrally.

Question 36

Where does urethra pass? Through which part of body?

Answer 36

The male urethra runs through the corpus spongiosum – to prevent it becoming occluded during erection the corpus spongiosum fills to a reduced pressure.

Question 37

Fascial coverings of the penis

Answer 37

Each mass of erectile tissue has two fascial coverings. The most superficial layer, immediately under the skin, is the external fascia of Colles (which is in continuity with the fascia of Scarpa which covers the abdominal wall).

A deeper stratum is the deep fascia of the penis (also known as Buck’s fascia). This is a continuation of the deep perineal fascia, and forms a strong membranous covering which holds all three erectile tissues together.

Underneath the deep fascia is the strong fascia called tunica albuginea, forming an individual capsule around each cavernous body and fused in the midline. The incomplete septum between the two corpora is comprised of tunica albuginea.

Question 38

Arteries of penis

Answer 38

The penis receives arterial supply from three sources:

Dorsal arteries of the penis

Deep arteries of the penis

Bulbourethral artery

These arteries are all branches of the internal pudendal artery. This vessel arises from the anterior division of the internal iliac artery.

Question 39

Venous drainage of penis

Answer 39

Venous blood is drained from the penis by paired veins. The cavernous spaces are drained by the deep dorsal vein of the penis – this empties into the prostatic venous plexus. The superficial dorsal veins drain the superficial structures of the penis, such as the skin and cutaneous tissues.

Question 40

Innervation of the penis

Answer 40

The penis is supplied by S2-S4 spinal cord segments and spinal ganglia.

Sensory and sympathetic innervation to the skin and glans penis is supplied by the dorsal nerve of the penis, a branch of the pudendal nerve.

Parasympathetic innervation is carried by cavernous nerves from the peri-prostatic nerve plexus, and is responsible for the vascular changes which cause erection.

Question 41

What happens during erection?

Answer 41

Parasympathetic fibres from the pelvic splanchnic nerves (S2-S4) cause dilatation of the arteries and arterioles of the erectile tissue of the penis, leading to increased blood flow into the expanding sinusoids within the cor- pora cavernosa and venous compression, reducing venous outflow. This increases the intra-cavernous pressure, resulting in penile erection. The corpus spongiosum resists compression of the urethra during erection.

Question 42

Discuss ejaculation

Answer 42

Ejaculation is used as a synonym for the external ejection of semen and is comprised of two phases: emission and expulsion.

Emission is the term used when spermatozoa moves into the prostatic urethra. The vas deferens, seminal vesicles and prostate smooth muscle all receive post-ganglionic sympathetic innervation that causes emission of their contents into the prostatic urethra, to form semen.

Contraction of the internal sphincter of the bladder simultaneously prevents retrograde movement of semen into the bladder.

Question 43

Discuss explusion

Answer 43

Expulsion is triggered by somatic pudendal nerve fibres, which generate contractions of the striated bulbospon- giosus muscle at the base of the penis, leading to ejaculation.

Question 44

Discuss scrotal innervation

Answer 44

The scrotum and its contents are innervated by:

1. Sympathetic fibres (T1-L1) – supply the testis, vas deferens and epididymis.
2. Somatic fibres (L1-L2) – supply the outer surface of the testis, tunica vaginalis and anterior scrotum, via the

genitofemoral (supplying cremaster) and ilioinguinal nerves. 3. Somatic fibres (S2-S3) – supply the rest of the scrotum.

Question 45

Cremasteric Reflex

Answer 45

This reflex is triggered by stroking the superomedial aspect of the thigh in a downward direction. The normal response is a contraction of the cremaster muscle, pulling up the scrotum and testis on the side stimulated. Upper and lower motor neuron lesions can cause an absence of the cremasteric reflex. The genitofemoral nerve (L1/L2) is responsible for the afferent and efferent limbs of the reflex arc.

Question 46

Hydrocoele and Varicocoele

Answer 46

A congenital hydrocoele describes a collection of fluid within the scrotum, between the parietal and vis- ceral layers of the tunica vaginalis. This may occur in combination with a patent processus vaginalis and thus communicate with the peritoneal cavity. Hydrocoele usually presents as a painless, enlarged scrotum and may resolve spontaneously, but typically needs surgical repair if persisting beyond 12 months.

A varicocoele is an abnormal dilatation of the testicular veins of the pampiniform venous plexus, caused by reflux of blood into the plexus. Varicocoeles are more common on the left due to the angle at which the left testicular vein drains into the left renal vein and lack of effective venous valves. Patients describe the scrotum as feeling like a bag of worms, and only rarely do they report pain. Treatment may involve surgical ligation of the veins to prevent abnormal blood flow.

Question 47

Testicular Torsion

Answer 47

The blood supply to the testis can become compromised if the spermatic cord twists within the tunica vaginalis, which can rapidly lead to ischaemic damage and loss of the testis. Testicular torsion is a medical emergency and causes acute scrotal pain and swelling, nausea and vomiting. Treatment is by immediate manual de-torsion followed by surgical fixation of the testis to prevent further episodes of torsion.

Question 48

Mal-descent of Testes

Answer 48

By 28 weeks of gestation, the right and left testes reach the inguinal canals, and by 28-40 weeks, they descend to their final place within the scrotum. An undescended testis is a testis that is absent from the scrotum. This may be due to failure of formation, testicular retraction or failure of descent. Mal-descent may result from an anatomical or hormonal abnormality, although most will descend into the scrotum within the first three months of life.

Question 49

Testicular Cancer

Answer 49

Testicular cancer is the most common non-blood cancer in young men. Symptoms may include a painless mass in the groin and occasionally groin tenderness. Testicular cancers most commonly metastasise via lymphatic drainage, usually to the retroperitoneal lymph nodes (para-aortic). Diagnosis is usually made by ultrasound scanning. Treatment involves surgical removal of the testis and sometimes lymph node dissec- tion and chemo-radiotherapy.

Question 50

Prostate Cancer

Answer 50

A rich venous plexus surrounds the base of the prostate. Cancer cells originating from the prostate may metastasise via these venous channels to the IVC and lungs, as well as spreading to the rich venous plexus of the pelvic bones, sacrum and vertebral column.

Question 51

Vasectomy

Answer 51

Division and ligation of the vas deferens is a surgical method by which male infertility can be achieved for contraceptive purposes. Each vas deferens us divided along its scrotal part, just beneath the superfi- cial inguinal ring. As a result, spermatozoa fail to reach the prostatic urethra and degenerate within the epididymis.