Describe the male urethra.
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The male urethra extends from the internal urethral orifice to the external urethral orifice and can be described in 4 parts:
- Pre-prostatic urethra: Runs a vertical course from bladder neck to prostate.
- Prostatic urethra: Is the widest and distensible part of the urethra. Courses through the prostate, contains the urethral crest with prostatic sinuses both sides and the central seminal colliculus. Ends at the urethral sphincter.
- Membranous urethra: Shortest, narrowest part of the urethra. Surrounded by the external urethral sphincter. Has the bulbourethral glands posteriorly.
- Spongy (penile) urethra: Longest part of the urethra. The bulbourethral glands open into it proximally. Has two expansions - intrabulbar fossa in the bulb of the penis and navicular fossa in the glans. Ends at the external urethral orifice.
Why is understanding of bladder anatomy important in suprapubic catheterisation?
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- When empty, the bladder is tetrahedral in shape. The apex lies anteriorly, with the body between the apex and the fundus.
- The fundus meets the remaining surfaces of the bladder at the bladder neck. As the bladder fills with urine, it extends superiorly between the rectus abdominis muscle and the peritoneum but without entering the peritoneal cavity. Therefore in a normal abdomen suprapubic catheterisation can be performed safely extra-peritoneally.
- However, in patients with previous intra-abdominal surgery causing adhesion and/or in the presence of lower abdominal scars, bowel may lie anterior to the bladder and could be injured.
Describe the relations of the bladder in the male.
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In the male the relations of the bladder are:
Superior : Peritoneum.
Inferolateral surfaces : Levator ani.
Inferior : Ductus deferens, pubic bones, obturator internus, levator ani.
Fundus : Rectum.
Bladder neck : Prostate, with seminal vesicles posteriorly.
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Describe the blood supply to the bladder.
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- The blood supply to the bladder is by branches of the internal iliac arteries.
- The superior vesical arteries (from the umbilical artery - a branch of the anterior division of the internal iliac artery) supply the apex and superior part of the bladder.
- In males, the blood supply to the postero-inferior bladder is from the inferior vesical arteries (from the anterior division of the internal iliac artery) and in females it is from the vaginal arteries (originating from the uterine artery).
- Contributions are also made from the obturator and inferior gluteal arteries (also branches of the anterior division of the internal iliac artery).
Describe the layers of the bladder.
"The bladder consists of three distinct layers. The innermost layer is the muscosa formed by specialized transitional cells. The middle layer is the lamina propria which contains the network of vessels and nerves. The outermost layer is the thickest part of the bladder comprising of the detrusor muscle.
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Where are the seminal vesicles located?
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The seminal vesicles are located between the fundus of the bladder and the rectum, superior to the prostate.
Note: Above these is a reflection of peritoneum - the rectovesical pouch.
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Describe the lobes of the prostate
The prostate can be described in lobes:
Anterior lobe : Anterior to the urethra; primarily fibromuscular.
Posterior lobe : Posterior to the urethra; this is the part palpated on digital rectal examination.
Lateral lobes : Form the bulk of the prostate.
Median lobe : Between the urethra and ejaculatory ducts, close to the bladder neck.
What is the most common prostatic malignancy?
"The most common prostatic malignancy is adenocarcinoma, with 75% occurring in the peripheral zone of the prostate.
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How does prostate cancer metastasise?
"Commonly local invasion of prostate cancer is perineural, following the autonomic nerves. Other common sites of metastasis from the prostate are via lympatic channels to sacral, iliac and para-aortic nodes, as well as haematological spread to bone (pelvis, femur, vertebrae) and to distant viscera; liver and lungs.
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