Lecture 5 - Male pelvis and perineum Flashcards
What is the X distance a measure of?
Distance between the pubic symphysis and the anterior margin of the acetabulum.
What is the Y distance a measure of?
Diameter of the acetabulum.
What is the shape of the male pelvic inlet?
Narrow and heart-shaped.
What is the sub-pubic angle in males?
Narrow - roughly 50-60 degrees.
What is the sub-pubic angle in females?
Wide - roughly 80-85 degrees.
What is the shape of the female pelvic inlet?
Oval or round - wider than male pelvic inlet.
How does the ischial spine differ between males and females?
In males it projects medially however in females it does not.
What is the X:Y ratio for males and females?
Male - less than 1
Female - 1 or larger
How do the greater and lesser pelvises differ in male and females?
Greater (false)
Male - deep
Female - shallow
Lesser (true)
Male - narrow, deep and tapering
Female - wide, shallow and cylindrical
Where does the parietal peritoneum end?
Continues into the pelvic cavity but does not reach the pelvic floor.
What is covered in peritoneum?
All of the pelvic viscera, apart from the uterine tubes/
What is found between the pelvic wall and peritoneum?
If it is not occupied by viscera, it will contain pelvic fascia.
What do pelvic fascial condensations do?
Form ligaments that support the viscera, such as the cervix, vagina and prostate.
What is found in the male pelvic cavity?
- Ureter (25cm long), bladder and urethra
- Prostate, ductus deferens, seminal vesicles and bulbourethral glands
- Rectum
- Some of the GI tract (laterally - caecum, appendix, parts of the sigmoid colon and ileum)
- Vessels, nerves and lymphatics
How long is the male and female urethra?
Male - 20cm
Female - 4cm
Where is the prostate gland found?
Surrounds the first part of the urethra, known as the prostatic part - the bladder sits on top of it.
Where can the catheter get stuck sometimes?
The tip of a urinary catheter can become lodged in the prostatic utricle (a cul-de-sac)
How is urine prevented from passing through the urethra during ejaculation?
The internal urethral sphincter is closed during ejaculation by sympathetic stimulus.
How is the internal urethral sphincter opened and closed?
Opened - parasympathetic
Closed - sympathetic
Describe the pathway of the ductus deferens?
Passes from the testis through and then over the inguinal canal, behind the ureter to enter the urethra through the prostate gland.
Where are the seminal vesicles located?
Situated at the back of the bladder, which open into the ductus deferens between the ampulla and ejacultatory duct.
How much of the secretions in the ductus deferens are from the seminal vesicles and the prostate gland?
Seminal vesicles - 60%
Prostate gland - 40%
Form the semen alongside sperm from the epididymis.
Where can it be difficult to pass a catheter through in the male?
There are three narrowing in the male urethra at:
- External urethral orifice (narrowest)
- Prostatic part of the urethra
- Near the bulbourethral gland (90 degrees angle)
- Can also get caught in the navicular fossa (fossa terminals) at the head of the penis
How are the testis supplied with blood?
Supplied via the testicular artery which is a branch off of the abdominal aorta. Unlike the rest of the pelvis which is perfuse via the internal iliac artery.
What does the inferior vesicle artery?
Prostate, bladder and ductus deferens - it is a branch of the internal iliac artery. The superior vesicle arteries also supply the bladder and the ductus deferens.
How is the gluteal region perfused?
Via the superior and inferior gluteal arteries/
What is the perineum?
A diamond-shaped area between the pubic symphysis, ischial tuberosities and the coccyx. It is divided into the anterior urogenital and the posterior anal triangles.
How can the urogenital triangle be further divided?
Divided into superficial and posterior parts by the perineal membrane.
What is the anal triangle composed of?
Composed of fat-filled spaces which separate the anal canal and levator ani from the pelvic walls. These are the same in both genders.
What is the perineal membrane?
Thick, triangular fascial structure that is attached to the pubic arch. It fills the urogenital triangle and erectile tissues are anchored to it.
What is the deep perineal space?
Above the perineal membrane and below the fascia of the pelvic diaphragm.
What is the superficial perineal space?
Space below the perineal membrane and perineal fascia (subcutaneous tissue).
What is the ischio-anal fossae?
Fat-filled spaces in the anal triangle that allow recto-anal and vaginal expansion. In their lateral wall is the pudendal neurovascular bundles which supplies the perineum and lower rectum.
How does the erectile tissue develop in males?
Forms the bulb of the penis (corpus spongiosum)
How does the erectile tissue develop in females?
Divides around the vestibule to form vestibular bulbs.
What two tissues meet to form the shaft and head of the penis (or clitoris in females)?
- Corpus spongiosum (internal)
- Corpora cavernosae
How is the rectum perfused?
One pair of arteries from inferior mesenteric artery and two from the internal iliac artery.
How is blood drained from the rectum?
Has similar venous drainage to the arteries that supply it so there is an important portal-systemic venous anastomosis around the lower rectum and anal canal.
What are the contents of the spermatic cord?
- External spermatic fascia (external oblique aponeurosis)
- Internal spermatic fascia (trasversali fascia)
- Cremasteric fascia (from internal oblique muscle)
- Testicular artery and pampiniform plexus of veins
What tissues is the penis made up of?
- Corpus cavernous (bi-lobed)
- Corpus spongiosum (smaller and runs on the underside of the penis)
What is the glans of the penis formed from?
Corpus spongiosum
How is the corpus cavernosum attached to the ischiopubic rami?
Via the left and right crus
How is the penis supplied with blood?
- Mainly supplied by the pudendal artery (branch of the internal iliac artery)
- Deep artery supplies corpora cavernosum
- Dorsal artery supplies the skin and connective tissue
- Artery of the bulb supplies the bulb, corpus spongiosum, glans and urethra
- Helicine arteries (coiled) supply the cavernous spaces
What causes blood to flow to the penis in an erection?
Parasympathetic stimulation, causing the helicon arteries to relax.
What does parasympathetic innervation of the penis result in?
- Blood flow (vasodilation of arterioles in erectile tissue)
- Secretions from the prostate and bulbourethral glands
What does sympathetic innervation of pelvic organs result in?
- Contraction of smooth muscle of epididymis, vas deferens, seminal vesicles and prostate causing emission
- Contraction of internal urethral sphincter to prevent reflux of semen and no urine from passing through the urethra
Where is visceral pain referred to from the pelvic region?
Pelvic sensation is visceral and poorly localised so it is often referred to the suprapubic region and perineum.
How are perineal skeletal muscles innervated?
Via somatic nerves by the pudendal nerve (S2-4).
How do the pudendal nerve/somatic nerves leave the pelvis?
Via the lumbosacral plexus.
What do the sensory somatic nerves supply?
Penis (penile skin and glands 0 dorsal nerve)
What do the motor somatic nerves supply?
- Perineal msucles
- Bulbospingiosus and ischivacernosus tissue
This cause ejaculation and contraction of the external urethral sphincter.
What innervation is involved in an erection?
- Central parasympathetic pathway that is activated by psychic stimulation
- Pudenal artery and arterioles (as well as helicine arteries) relax to allow blood flow into he cavernous spaces of erectile tissue
What stimulates secretion from the prostate, seminal vesicles and other glands?
Sympathetic innervation.
What stimulates emission?
- Central sympathetic pathway activates smooth muscle contraction of vas deferens, prostate nad seminal vesicles
- Internal urethral sphincter contracts and bladder muscle contraction is prevented by sympathetic inhibitory action so there is no urine flow
What stimulates ejaculation?
Entry of semen into the urethra triggers a somatic reflex via the pudendal nerve, causing the contraction of the bulbospongiosus skeletal muscle.
How is detumescence stimulated?
Selective sympathetic nerves supplying the pudendal arterioles are activated, causing arteriole construction to restrict blood flow to the cavernous spaces.
