Kidneys and posterior abdominal wall

Question 1

Where are the kidneys?

Answer 1

Lie outside the peritoneum (extra-peritoneal), behind the peritoneal cavity (retro-peritoneal), one on each side of the upper lumbar vertebrae. They typically extend from T12 to L3, although the right kidney is often situated slightly lower due to the presence of the liver.

Question 2

What structures surround the kidneys?

Answer 2

Each kidney is embedded in perinephric fat and is covered in renal fascia.
On the medial border of the kidney is the renal hilum, which is where the renal vessels, nerve, lymphatics and ureter enter or leave the kidney.
Posteriorly they lie against the muscles of the posterior abdominal wall, including the diaphragm, psoas major, quadratus lumborum and the transversus abdominis.
Anteriorly the right perinephric fat and kidney is in contact with the liver, duodenum and coils of intestine, whereas the left perinephric fat and kidney is in contact with the stomach, spleen, pancreas and coils of the intestine.

Question 3

What is the function of the kidneys?

Answer 3

Their main function is to filter and excrete waste products from the blood. They are also responsible for water and electrolyte balance in the body.

Question 4

What are the external layers of the kidneys?

Answer 4

Renal capsule – tough fibrous capsule.
Perirenal fat – collection of extraperitoneal fat.
Renal fascia (also known as Gerota’s fascia or perirenal fascia) – encloses the kidneys and the suprarenal glands.
Pararenal fat – mainly located on the posterolateral aspect of the kidney.

Question 5

What are the internal layers of the kidneys?

Answer 5

The renal parenchyma can be divided into two main areas – the outer cortex and inner medulla.
The cortex extends into the medulla, dividing it into triangular shapes – these are known as renal pyramids.
The apex of a renal pyramid is called a renal papilla.
Each renal papilla is associated with a structure known as the minor calyx, which collects urine from the pyramids. Several minor calices merge to form a major calyx.
Urine passes through the major calices into the renal pelvis, a flattened and funnel-shaped structure.
From the renal pelvis, urine drains into the ureter, which transports it to the bladder for storage.

Question 6

What is the renal hilum?

Answer 6

The medial margin of each kidney is marked by a deep fissure, known as the renal hilum. This acts as a gateway to the kidney – normally the renal vessels and ureter enter/exit the kidney via this structure.

Question 7

What is the blood supply for the kidneys?

Answer 7

The kidneys are supplied with blood via the renal arteries, which arise directly from the abdominal aorta. The renal artery enters the kidney via the renal hilum. At the hilum level, the renal artery forms an anterior and a posterior division, which carry 75% and 25% of the blood supply to the kidney, respectively. Five segmental arteries originate from these two divisions.

Question 8

How do the segmental arteries supply the kidneys?

Answer 8

Each segmental artery divides to form interlobar arteries. They are situated either side every renal pyramid.
These interlobar arteries undergo further division to form the arcuate arteries.
At 90 degrees to the arcuate arteries, the interlobular arteries arise.
The interlobular arteries pass through the cortex, dividing one last time to form afferent arterioles.
The afferent arterioles form a capillary network, the glomerulus, where filtration takes place. The capillaries come together to form the efferent arterioles.
In the outer two-thirds of the renal cortex, the efferent arterioles form what is known as a peritubular network, supplying the nephron tubules with oxygen and nutrients. The inner third of the cortex and the medulla are supplied by long, straight arteries called vasa recta.

Question 9

What is the venous drainage system of the kidneys?

Answer 9

The kidneys are drained of venous blood by the left and right renal veins. They leave the renal hilum anteriorly to the renal arteries, and empty directly into the inferior vena cava.

Question 10

What is the renal sinus?

Answer 10

The renal sinus is a fatty compartment located within the medial aspect of the kidney. It communicates with the perinephric space. It contains the renal hilum and is bordered by renal parenchyma laterally.

Question 11

What are the medullary columns?

Answer 11

A medullary extension of the renal cortex in between the renal pyramids. It allows the cortex to be better anchored. Each column consists of lines of blood vessels and urinary tubes and a fibrous material.

Question 12

What are the suprarenal glands?

Answer 12

AKA Adrenal glands
Close to the upper pole of each kidney lies a suprarenal gland embedded in the perinephric fat. The right suprarenal gland is tetrahedral and lies behind the liver and inferior vena cava. The left suprarenal gland is crescent-shaped and lies behind the stomach and pancreas.

Question 13

What do the suprarenal glands do?

Answer 13

They secrete steroid and catecholamine hormones directly into the blood.

Question 14

Are the suprarenal glands intraperitoneal or retroperitoneal?

Answer 14

They are retroperitoneal, with parietal peritoneum covering their anterior surface only.

Question 15

What is the structure of the suprarenal glands?

Answer 15

The adrenal glands consist of an outer connective tissue capsule, a cortex and a medulla.

Question 16

How do arteries, veins, nerves and lymphatics enter the suprarenal glands?

Answer 16

Veins and lymphatics leave each gland via the hilum, but arteries and nerves enter the glands at numerous sites.

Question 17

What does the cortex of the adrenal glands do?

Answer 17

The cortex is yellowish in colour. It secretes two cholesterol derived hormones – corticosteroids and androgens.

Question 18

What are the layers of the adrenal cortex?

Answer 18

Zona glomerulosa – produces and secretes mineralocorticoids such as aldosterone.
Zona fasciculata – produces and secretes corticosteroids such as cortisol. It also secretes a small amount of androgens.
Zona reticularis – produces and secretes androgens such as dehydroepiandrosterone (DHES). It also secretes a small amount of corticosteroids.

Question 19

What does the medulla of the adrenal glands do?

Answer 19

The medulla lies in the centre of the gland, and is dark brown in colour. It contains chromaffin cells, which secrete catecholamines (such as adrenaline) into the bloodstream in response to stress.

Question 20

What is the blood supply for the adrenal glands?

Answer 20

Supplied by the superior, middle and inferior adrenal arteries.

Question 21

What are the ureters?

Answer 21

The ureters are two thick tubes which act to transport urine from the kidney to the bladder. They arise from the renal pelvis, are approximately 25cm long and are situated bilaterally.

Question 22

What is the pathway of the ureters?

Answer 22

The ureters descend through the abdomen, along the anterior surface of the psoas major. Here, the ureters are a retroperitoneal structure (located behind the peritoneum).
Upon reaching the bladder wall, the ureters pierce its lateral aspect in an oblique manner. This creates a one way valve, where high intramural pressure collapses the ureters – preventing the back-flow of urine.

Question 23

What is the arterial and venous supply of the ureters?

Answer 23

The arterial supply to the ureters can be divided into abdominal and pelvic supply:
Abdominal – renal artery, testicular/ovarian artery, and ureteral branches directly from the abdominal aorta
Pelvic – superior and inferior vesical arteries.
Venous drainage is carried out by vessels that correspond to the aforementioned arteries.

Question 24

What is the nervous supply of the ureters?

Answer 24

Nervous supply to the ureters is delivered via the renal, testicular/ovarian and hypogastric plexuses. Sensory fibres from the ureters enter the spinal cord at T11-L2, with ureteric pain referred to those dermatomal areas.

Question 25

What is the posterior abdominal wall?

Answer 25

The region behind the abdominal cavity which extends from the attachments of the diaphragm above to the pelvic brim below.

Question 26

What makes up the posterior abdominal wall?

Answer 26

It consists of the lumbar spine together with the psoas and quadratus lumborum muscles. Structures running along the posterior abdominal wall include the inferior vena cava, the aorta with its associated autonomic plexuses and lymph nodes. The sympathetic trunk continues into the abdomen on either side of the lumbar spine. More laterally the ureters pass down from the kidneys towards the pelvis on the surface of the psoas muscle and the gonadal vessels run down over the ureters to supply the gonads.

Question 27

What is a Intravenous urogram (IVU)?

Answer 27

A chemical (contrast medium) has been injected into a vein and distributes throughout the body. The chemical has two properties, it absorbs X-rays and it is excreted by the kidney making the urine appear white on an X-ray.

Question 28

Where does the abdominal aorta bifurcate?

Answer 28

The abdominal aorta bifurcates into the common iliac arteries at L4 (the surface marking of the aortic bifurcation is the umbilicus).

Question 29

What is the internal iliac artery?

Answer 29

The internal iliac artery is the major artery of the pelvis. It originates at the bifurcation of the common iliac artery into its internal and external branches at L5-S1. At the superior border of the greater sciatic foramen, it divides into anterior and posterior trunks.

Question 30

What does the anterior trunk of the internal iliac artery give rise to?

Answer 30

Obturator artery - supplies the muscles of the thigh’s adductor region
Umbilical artery - supplies the superior aspect of the urinary bladder
Inferior vesical artery - supplies inferior bladder, prostate gland, seminal vesicles
Vaginal artery - additional branches to the inferior bladder and rectum
Uterine artery - travels within the cardinal ligament along the uterus
Middle rectal artery - supplies the distal part of the rectum
Internal pudendal artery - major supply of perineum
Inferior gluteal artery - supplies gluteal muscles and the hip joint

Question 31

What does the posterior trunk of the internal iliac artery give rise to?

Answer 31

The posterior trunk gives rise to arteries that supply the lower posterior abdominal wall, posterior pelvic wall and the gluteal region which are made up of 3 branches:
Iliolumbar artery - The lumbar branch supplies psoas major, quadratus lumborum and the posterior abdominal wall. The iliac branch supplies the muscles and bone around the iliac fossa.
Lateral sacral arteries (superior and inferior) - supply structures in the sacral canal, and the skin and muscle posterior to the sacrum.
Superior gluteal artery - major blood supply to the muscles and skin of the gluteal region.

Question 32

What are the gonadal arteries?

Answer 32

Gonadal arteries - the ovarian artery is the major gonadal artery in the female. It arises from the abdominal aorta and descends towards the pelvis and branches into an ovarian branch and tubal branches.

Question 33

What is the median sacral artery?

Answer 33

Median sacral artery - originates from the abdominal aorta where it bifurcates into the common iliac arteries. Contributes to the arterial supply of the L4 and L5 vertebrae, sacrum and the coccyx.

Question 34

What is the superior rectal artery?

Answer 34

Superior rectal artery - terminal continuation of the inferior mesenteric artery. It gives rise to branches that supply the rectum.

Question 35

What is the external iliac vein?

Answer 35

The external iliac vein is a continuation of the femoral vein (the major vessel draining the lower limb). It ascends along the medial aspect of the external iliac artery, before joining with the internal iliac vein to form the common iliac vein. During its short course, the external iliac vein receives the inferior epigastric and deep circumflex iliac veins.

Question 36

What is the internal iliac vein?

Answer 36

The internal iliac vein is responsible for the majority of pelvic venous drainage, and receives numerous tributaries from veins that drain the pelvic region.

Question 37

What veins drain into the internal iliac vein?

Answer 37

Superior and inferior gluteal veins – drains the buttock and upper thigh.
Internal pudendal vein – drains the reproductive organs and part of the rectum (via the inferior rectal vein).
Obturator vein
Lateral sacral veins – drains part of the sacrum.
Middle rectal vein – drains the bladder, prostate (in males only), and part of the rectum.
Vesical veins – drains the urinary bladder via the vesical venous plexus.
Uterine and vaginal veins – drain the female reproductive organs via the vaginal and uterine venous plexuses.

Question 38

What is the common iliac vein?

Answer 38

The common iliac vein is formed at the upper margin of the pubic symphysis by the union of the external and internal iliac veins. It receives two additional tributaries:
Iliolumbar vein – drains the L4 and L5 vertebrae, and the iliopsoas muscle.
Middle sacral veins – drain part of the sacrum.

Question 39

At what level do the common iliac veins become the vena cava?

Answer 39

The left and right common iliac veins combine at L5 to become the inferior vena cava, which empties into the inferior aspect of the right atrium.

Question 40

What is the sacral plexus?

Answer 40

The sacral plexus is a network of nerve fibres that supplies the skin and muscles of the pelvis and lower limb. It is located on the surface of the posterior pelvic wall, anterior to the piriformis muscle.The plexus is formed by the anterior rami (divisions) of the sacral spinal nerves S1, S2, S3 and S4. It also receives contributions from the lumbar spinal nerves L4 and L5.

Question 41

What is the pathway of the sacral plexus?

Answer 41

At each vertebral level, paired spinal nerves leave the spinal cord via the intervertebral foramina of the vertebral column.
Each nerve then divides into anterior and posterior nerve fibres. The sacral plexus begins as the anterior fibres of the spinal nerves S1, S2, S3, and S4. They are joined by the 4th and 5th lumbar roots, which combine to form the lumbosacral trunk. This descends into the pelvis to meet the sacral roots as they emerge from the spinal cord.
The anterior rami of the S1-S4 spinal roots (and the lumbosacral trunk) divide into several cords. These cords then combine together to form the five major peripheral nerves of the sacral plexus.

Question 42

What are the two major destinations of the peripheral nerves of the sacral plexus?

Answer 42

These nerves then descend down the posterior pelvic wall. They have two main destinations:

• Leave the pelvis via the greater sciatic foramen – these nerves enter the gluteal region of the lower limb, innervating the structures there.
• Remain in the pelvis – these nerves innervate the pelvic muscles, organs and perineum.

Question 43

What are the branches of the sacral plexus?

Answer 43

Superior gluteal nerve - L4, L5, S1, innervates the gluteus minimus, gluteus medius and tensor fascia lata.
Inferior gluteal nerve - L5, S1, S2, innervates the gluteus maximus
Sciatic nerve - L4, L5, S1, S2, S3

Question 44

How does the sacral plexus provide motor innervation?

Answer 44

Tibial portion – Innervates the muscles in the posterior compartment of the thigh (apart from the short head of the biceps femoris), and the hamstring component of adductor magnus. Innervates all the muscles in the posterior compartment of the leg and sole of the foot.

Common fibular portion – Short head of biceps femoris, all muscles in the anterior and lateral compartments of the leg and extensor digitorum brevis.

Question 45

How does the sacral plexus provide sensory innervation?

Answer 45

Tibial portion: Innervates the skin on the posterolateral and medial surfaces of the foot as well as the sole of the foot.
Common fibular portion: Innervates the skin on the anterolateral surface of the leg and the dorsal aspect of the foot.
- Posterior femoral cutaneous - S1, S2, S3, Innervates the skin on the posterior surface of the thigh and leg. Also innervates the skin of the perineum.
- Pudendal nerve - S2, S3, S4, Innervates the skeletal muscles in the perineum, the external urethral sphincter, the external anal sphincter, levator ani. Innervates the penis and the clitoris and most of the skin of the perineum.

Question 46

What are the crura of the diaphragm?

Answer 46

The crus of diaphragm (pl. crura), refers to one of two tendinous structures that extends below the diaphragm to the vertebral column. There is a right crus and a left crus, which together form a tether for muscular contraction.

Question 47

What are the arcuate ligaments?

Answer 47

Arcuate ligaments (median, medial, lateral) - formed from the attachments of the diaphragm over the aorta, the psoas and quadratus lumborum respectively.

Question 48

What is the quadratus lumborum?

Answer 48

Your deepest abdominal muscle. It’s found in your lower back, between the top of your pelvis and your lowest rib. The QL supports good posture and helps stabilize your spine when you bend to the side or extend your lower back.

Question 49

What is the psoas muscle?

Answer 49

Takes its origin from the fascia on the sides of the lumbar vertebra and the intervertebral discs and runs almost vertically down the sides of the spinal column. It passes along the pelvic brim and under the inguinal ligament to enter the thigh where it is attached to the lesser trochanter of the femur.

Question 50

What is the genitofermoral nerve?

Answer 50

Has genital and femoral branches. The femoral branch passes under the inguinal ligament and is sensory to the inside of the thigh. The genital branch passes through the deep inguinal ring and supplies the cremaster muscle, when the inside of the thigh is tickled the testis retracts upwards.

Question 51

Where is the iliacus muscle?

Answer 51

Passes under the inguinal ligament just lateral to the psoas, they attach to the lesser trochanter of the femur.

Question 52

What is the lateral cutaneous nerve of the thigh?

Answer 52

Runs under the inguinal ligament to supply the skin over the lateral thigh

Question 53

What is the retro-vesical pouch?

Answer 53

Found in males
The peritoneal covering creates a continuous surface coursing over the superior part of the urinary bladder to the middle and upper rectum. A depression exists at the junction of the two surfaces that is referred to as the rectovesical pouch.

Question 54

What is the retro-uterine pouch?

Answer 54

Found in females
In the female pelvic cavity, the uterus and vagina occupy the space between the urinary bladder and the rectum. The peritoneum is continuous over all three structures and consequently, an additional space is created. The space between the middle and superior rectum and the uterus is known as the rectouterine pouch of Douglas. A potential route for harvesting ova during IVF treatment.

Question 55

What is the utero-vesical pouch?

Answer 55

Found in females
The space exists between the posterior surface of the urinary bladder and the anterior surface of the uterus. This space is also continuous superiorly with the peritoneal cavity.

Question 56

What are renal calculi?

Answer 56

Urine, in health and disease, may be almost supersaturated with mineral ions and these can precipitate out to form stones. Commonly small stones pass down the ureter into the bladder causing severe pain as they do so. The ureter has three narrowings which may be too small for the stone to pass through - where the kidney becomes the ureter, at the pelvic brim and where the ureter passes through the bladder wall.

Question 57

What is a left varicocele?

Answer 57

The left testicular vein passes into the left renal vein. Disease of the left kidney may block drainage of blood from the left testicle causing the veins in the scrotum to become varicose which can be easily seen on examination.

Question 58

What is a psoas spasm?

Answer 58

The appendix may lie on the psoas muscle and when it becomes inflamed causes the muscle to go into spasm. The muscle is a flexor of the hip so the patient will have a flexed hip and trying to extend the hip will cause pain.

Question 59

What is a recurrent UTI?

Answer 59

In patients with duplex ureters the valve at the bottom of one of the ureters does not function and, during micturition, urine passes back up the ureter to the kidney. This has two consequences during a UTI, it is easy for the infection to pass up the the kidney and urine is never completely expelled (because there is always some infected urine passing up into the ureter) and this continually re-infects the bladder.

Question 60

What is the pathway of the spermatic cord?

Answer 60

Structures making up the spermatic cord run from the deep inguinal ring, through the inguinal canal, out of the superficial inguinal ring and down into the scrotum passing above and medial to the pubic tubercle as they go.

Question 61

What are the three layers of the spermatic cord?

Answer 61

As they pass through the inguinal canal they acquire a layer of tissue from each of the three abdominal wall layers so that after leaving the superficial ring, the spermatic cord has three layers of covering.

• External spermatic fascia
• Cremaster muscle and fascia
• Internal spermatic fascia

Question 62

What is the cremaster muscle?

Answer 62

The cremaster muscle forms the middle layer of the spermatic cord fascia. It is a discontinuous layer of striated muscle that is orientated longitudinally.

Question 63

What is contained with the spermatic cord?

Answer 63

Testicular artery – branch of the aorta that arises just inferiorly to the renal arteries.
Cremasteric artery and vein – supplies the cremasteric fascia and muscle.
Artery to the vas deferens – branch of the inferior vesicle artery, which arises from the internal iliac.
Pampiniform plexus of testicular veins – drains venous blood from the testes into the testicular vein.
Genital branch of the genitofemoral nerve – supplies the cremaster muscle.
Autonomic nerves
Vas deferens – the duct that transports sperm from the epididymis to the ampulla ready for ejaculation.
Processus vaginalis – projection of peritoneum that forms the pathway of descent for the testes during embryonic development. In the adult, it is fused shut.
Lymph vessels – these drain into the para-aortic nodes, located in the lumbar region.

Question 64

What is the pampiniform plexus?

Answer 64

Network of veins responsible for the venous drainage of the testes. It has a unique configuration wrapping itself around the testicular artery. The testes function best at a temperature just below that of the body. The pampiniform plexus acts as a heat exchanger, cooling the arterial blood before it reaches the testes.

Question 65

Where does the pampiniform plexus drain to?

Answer 65

As it travels through the inguinal canal, the pampiniform plexus condenses into a single testicular vein.The right testicular vein drains into the inferior vena cava and the left testicular vein drains into the left renal vein.

Question 66

What is the vas deferens?

Answer 66

The vas deferens is a straight, thick muscular tube that conveys sperm from the epididymis to the ampulla and eventually, to the ejaculatory duct (formed by the convergence of the vas deferens and seminal vesicle duct). From the ejaculatory duct, sperm can pass through to the prostatic urethra.

Question 67

What are the 3 muscle layers of the vas deferens?

Answer 67

Made up of 3 muscle layers:
Inner layer: longitudinal smooth muscle
Intermediate layer: circular smooth muscle
Outer layer: longitudinal smooth muscle

Question 68

What aids the movement of sperm through the spermatic cord?

Answer 68

There is a rich autonomic innervation of these muscle fibres, which permits fast movement of sperm towards the ejaculatory duct. This movement is also facilitated by the inner mucosal layer of the vas deferens – which is lined by cells that possess microvilli. Their seaweed-like movement helps advance spermatozoa through the spermatic tube.

Question 69

What are the testes and epididymis?

Answer 69

The testes and epididymis are paired structures, located within the scrotum. The testes are the site of sperm production and hormone synthesis, while the epididymis has a role in the storage of sperm.
The testes are located within the scrotum, with the epididymis situated on the posterolateral aspect of each testicle.

Question 70

What is the role of the testes?

Answer 70

The testes are the main male reproductive organs, producing spermatozoa and secreting the sex hormone testerone.

Question 71

What is inside the testes?

Answer 71

They consist of a series of lobules, each containing seminiferous tubules supported by interstitial tissue. 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. Spermatozoa are produced in the seminiferous tubules. The developing sperm travels through the tubules, collecting in the rete testes. Ducts known as efferent tubules transport the sperm from the rete testes to the epididymis for storage and maturation.

Question 72

What is the tunica vaginalis?

Answer 72

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 73

What is the tunica albuginea?

Answer 73

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 74

What is the structure of the epididymis?

Answer 74

There is a coiled tube lying along the posterior border of each testis, the epididymis which has an expanded head superiorly, a body and a pointed tail lying at the lower pole of the testis to run with the testicular vessels in the spermatic cord.

Question 75

How are the testes and epididymis innervated?

Answer 75

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

Question 76

What is the arterial blood supply of the testes and epididymis?

Answer 76

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.

Question 77

What is the scrotum?

Answer 77

The scrotum is a pendulous pouch of skin containing the testes, epididymis and lower part of the spermatic cord. Scrotal skin is thin, wrinkled and more darkly pigmented.

Question 78

How is the scrotum divided into left and right halves?

Answer 78

Beneath the skin is a thin layer of superficial fascia, which is devoid of fat, but contains fibres of the involuntary muscle dartos. The superficial fascia extends between the testicles to form a septum dividing the scrotum into right and left halves.

Question 79

What is the arterial blood supply of the scrotum?

Answer 79

The scrotum receives arterial supply from the anterior and posterior scrotal arteries. The anterior scrotal artery arises from the external pudendal artery, while the posterior is derived from the internal pudendal artery.

Question 80

What is the venous drainage of the scrotum?

Answer 80

The scrotal veins follow the major arteries, draining into the external pudendal veins.

Question 81

How is the scrotum innervated?

Answer 81

Anterior and anterolateral aspect – Anterior scrotal nerves derived from the genital branch of genitofemoral nerve and ilioinguinal nerve
Posterior aspect – Posterior scrotal nerves derived from the perineal branches of the pudendal nerve and posterior femoral cutaneous nerve.

Question 82

What is the penis?

Answer 82

Male organ of copulation (sexual intercourse). There is an expanded distal part, the glans penus, where the urethra reaches the surface and this is the common outlet for urine and semen.

Question 83

What are the roles of the penis?

Answer 83

During erotic stimulation, the penis undergoes erection, becoming engorged with blood. Following emission, (mixing of the components of semen in the prostatic urethra) ejaculation can occur, whereby semen moves out of the urethra through the external urethral orifice. Finally, the penis undergoes remission, returning to a flaccid state.
The penis also has an important urinary role. It contains the urethra, which carries urine from the bladder to the external urethral orifice, where it is expelled from the body.

Question 84

What are the major parts of the penis?

Answer 84

Root – the most proximal, fixed part of the penis. It is located in the superficial perineal pouch of the pelvic floor, and is not visible externally. The root contains three erectile tissues (two crura and bulb of the penis), and two muscles (ischiocavernosus and bulbospongiosus).
Body – the free part of the penis, located between the root and glans. It is suspended from the pubic symphysis. It is composed of three cylinders of erectile tissue – two corpora cavernosa, and the corpus spongiosum.
Glans – the most distal part of the of penis. It is conical in shape, and is formed by the distal expansion of the corpus spongiosum. This contains the opening of the urethra, termed the external urethral orifice.

Question 85

Where are the erectile tissues of the root of the penis located?

Answer 85

The bulb is situated in the midline of the penile root, and is traversed by the urethra. The left and right crura are located laterally; attached to the ipsilateral ischial ramus, and covered by the paired ischiocavernosal muscles. Together these cylindrical bodies or corpora are enclosed by a dense, strong fascial layer, which limits expansion during erection of the penis.

Question 86

Where are the erectile tissues of the body of the penis located?

Answer 86

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. The male urethra runs through the corpus spongiosum – to prevent it becoming occluded during erection the corpus spongiosum fills to a reduced pressure.
Distally, the corpus spongiosum expands to form the glans penis.

Question 87

What are the muscles found in the root of the penis?

Answer 87

Bulbospongiosus (x2) – associated with the bulb of the penis. It contracts to empty the spongy urethra of any residual semen and urine. The anterior fibres also aid in maintaining erection by increasing the pressure in the bulb of the penis.
Ischiocavernosus (x2) – surrounds the left and right crura of the penis. It contracts to force blood from the cavernous spaces in the crura into the corpus cavernosa – this helps maintain erection.

Question 88

What are the fascial coverings of the penis?

Answer 88

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 89

What are the ligaments found in the root of the penis?

Answer 89

Suspensory ligament – a condensation of deep fascia. It connects the erectile bodies of the penis to the pubic symphysis.
Fundiform ligament – a condensation of abdominal subcutaneous tissue. It runs down from the linea alba, surrounding the penis like a sling, and attaching to the pubic symphysis.

Question 90

What is the prepuce?

Answer 90

The prepuce (foreskin) is a double layer of skin and fascia, located at the neck of the glans. It covers the glans to a variable extent. The prepuce is connected to the surface of the glans by the frenulum, a median fold of skin on the ventral surface of the penis. The potential space between the glans and prepuce is termed the preputial sac.

Question 91

What is a Micturating cystogram?

Answer 91

Contrast medium has been injected into a vein and is excreted by the kidney, making the urine appear white on an X-ray. Some hours after the injection the patient passes urine whilst being X-rayed.

Question 92

What are the different types of inguinal hernia?

Answer 92

In both sexes the inguinal canal provides a route from the inside of the abdomen to the external genitalia. It is common for the abdominal contents to pass through the inguinal canal to form a hernia which may extend into the external genitalia.
There are two types of inguinal hernia, both are very common.
If the hernia passes along the length of the canal it passes through each of the three layers of the abdominal wall in a different position and is an indirect hernia.
If it passes through the transversalis fascia of the posterior wall, directly through the internal oblique layer and directly through the external ring it is a direct hernia.

Question 93

Where is renal/gonadal pain felt?

Answer 93

The kidney and gonad have the same autonomic nerve supply derived from the thoracic 10 to lumbar 2 nerve root. Pain in either organ can be felt in the dermatome for these nerves which extend from the midline at the back immediately posterior to the kidney down to the groin and the scrotum, loin to groin pain. Kidney pain may be felt in the scrotum and gonadal pain in the loin.

Question 94

What is a hydrocoele?

Answer 94

The testis is partially surrounded by a sac of peritoneum, the tunica vaginalis. Disease of the testes or scrotum may cause fluid to collect in this sac creating a swelling which feels fluid and transmits light when a torch is shone through it, this is a hydrocoele. A very full hydrocele may feel tense rather than fluid.