Male Pelvis and Perineum Flashcards
Describe the distinctive characteristics of the female pelvis
Pelvic inlet- oval/round
Sub pubic angle- wide >80 degrees
Ischial spines DO NOT project medially
Greater false pelvis- shallow
Lesser true pelvis- wide, shallow and cylindrical
distance between symphysis pubis and anterior margin of acetabulum equal to or greater than the diameter of the acetabulum
Describe the distinctive characteristics of the male pelvis
Pelvic inlet- narrow/heart-shaped Sub pubic angle- narrow (50-60 degrees) Ischial spines- project medially Greater pelvis- deep Lesser pelvis- narrow, deep and tapering distance between symphysis pubis and anterior margin of acetabulum less than the diameter of the acetabulum
Summarise the Peritoneum & Pelvic Fascia
Parietal peritoneum continues into pelvic cavity but does not reach the pelvic floor.
Pelvic viscera (except uterine tubes) are not completely covered by peritoneum.
Several folds and pouches are formed
Space between pelvic wall and peritoneum not occupied by viscera contains pelvic fascia
Pelvic fascial condensations form “ligaments” supporting viscera like cervix, vagina, prostate
List the contents of the male pelvic cavity
Ureter, bladder, urethra
Prostate, ductus deferens, seminal vesicles, bulbourethral glands
Rectum
Some of the abdominal GI tract spills into the greater pelvis- Caecum, appendix, parts of sigmoid colon and ileum
Vessel, nerves and lymphatics
Describe the peritoneum
Continuous at the pelvic inlet with the peritoneum of the abdomen- the peritoneum drapes over the viscera in the midline, forming:
pouches between adjacent viscera
folds and ligaments between viscera and pelvic walls
Anteriorly, median and medial umbilical folds of peritoneum cover the embryological remnants of the urachus and umbilical arteries respectively
These folds ascend out of the pelvis and onto the anterior abdominal wall
Posteriorly, peritoneum drapes over the lateral aspects of the upper third of the recutm, the anterior surface of the middle third: the lower third is not covered
Describe the peritoneum in males
The visceral peritoneum drapes over the top of the bladder onto the superior poles of the seminal vesicles and then reflects onto the anterior and lateral surfaces of the rectum- a rectovesical pouch occurs between the the bladder and the rectum
Posteriorly and superiorly it becomes the sigmoid mesocolon
The testicular vessels and lymphatics lie in a retroperitoneal position and course to and from the deep inguinal ring. At the ring, you can see the retroperitoneal pathway of the vas deferens as it courses toward the seminal vesicle
Describe the consequences of the retroperitoneal course of the ureters
They course beneath the testicular vessels but over the iliac vessels- they then pass deep to the vas deferens as they approach the bladder
Surgeons operating in the abdominopelvic cavity must be careful as the extraperitoneal ureters can easily be damaged, leading to the extravasation of urine into adjacent retroperitoneal and intraperitoneal spaces
What is the length of the ureter and urethra in males
Ureter- 25cm
Urethra - 20cm
What structures in the male pelvis can be felt on a digital rectal examination (DRE) of a healthy man?
Can palpate the prostate gland, and perhaps seminal vesicles if they are calcified
Anorectal ring is posterior
Normal prostate is smooth with a palpable sulcus between lateral lobes- loss of groove is indicative of cancer
Benign prostatic hypertrophy- common over 50 and may lead to obstruction of urinary outflow and distension of the bladder
Cancer of prostate- begins in posterior portion of organ and so can be palpated
Which of the two (1 or 2) bends of the male urethra can be straightened before passing a catheter?
2- during erection
What does the ductus deferens join
The seminal vesicles (found behind the prostate)
Summarise the male pelvic organs
Prostate gland surrounds 1st (prostatic) part of urethra
Ductus deferens from testis passes through inguinal canal, then over, and behind ureter to enter the urethra through the prostate
Seminal vesicles on back of bladder - open into ductus deferens between ampulla and ejaculatory duct
Outline the different regions of the male urethra
preprostatic- 1cm long- extends from base of bladder to the prostate- associated with a circular cuff of smooth muscle fibres (internal urethral sphincter)
prostatic- 3-4cm long- surrounded by the prostate- the lumen of the urethra is marked by a longitudinal midline fold of mucosa- the urethral crest
membranous part- narrow and passes through the deep perineal pouch- during its transit- the urethra is covered by the skeletal muscle of the external urethral sphincter
spongy part- surrounded by the erectile tissue of the penis (corpus spongiosum)- enlarged to form a bulb at the base of the penis and again at the end to form the navicular fossa. The two bulbo-urethral glands in the deep perineal pouch are part of the male reproductive system and open into the bulb of the spongy urethra- the external urethral orifice is the saggital slit at the end of the penis
Describe the location of the prostate
Unpaired accessory structure of the male reproductive system that surrounds the urethra in the pelvic cavity- it lies immediately inferior to the bladder, posterior to the pubic symphysis, and anterior to the rectum
Describe the prostate gland
Shaped like an inverted, rounded cone with a larger base- which is continuous above with the neck of the bladder and a narrower apex which rests below on the apex floor- the inferolateral surfaces of the prostate are in contact with the levator ani muscles
The ejaculatory ducts pass almost vertically in an anteroinferior direction through the posterior aspect of the prostate to open into the prostatic urethra.
What constitutes the secretions of the ductus deferens
The secretions of the ductus deferens, seminal vesicles (60% ) & prostate (40%) empty into the prostatic urethra to form the semen
Describe the seminal vesicles
Accessory gland of the male reproductive system- that develops as a blind-ended tubular outgrowth from the ductus deferens
The tube is coiled with numerous pocket-like outgrowths and is encapsulated by connective tissue to form an elongate structure situated between the bladder and rectum
The gland lies lateral to the ductus deferens in contact with the posterior wall of the bladder base- with its upper end just below the point of entrance of the ureter into the bladder- the very short duct leaves the lower end to join the ductus deferens at the edge of the prostate and form the ejaculatory duct
What do the seminal vesicles secrete
Produces much of the seminal fluid (rich in fructose)
Describe the bulbo-urethral glands
Small, pea-shaped mucous glands situated within the deep perineal pouch and lateral to the membranous part of the urethra- the duct from each gland passes inferomedially through the perineal membrane, to open into the bulb of the spongy urethra at the root of the penis
Together with the small glands positioned along the length of the spongy urethra- the bulbo-urethral glands contribute to lubrication of the urethra and pre-ejaculatory emission from the penis
Describe the Prostatic Urethrawhere urinary & reproductive tracts meet
Midway along the length of the urethral crest it is enlarged to form a somewhat circular elevation (the seminal colliculus)- which can be used to determine the position of the prostate gland during transurethral transection of the prostate
a small- blind ended pouch- the prostatic utricle- opens onto the centre of the seminal colliculus
on each side of this are the openings of the ejaculatory ducts
What can the tip of a catheter get lodged in
The tip of a urethral catheter can also become lodged in the prostatic utricle
Describe the internal urethral sphincter
Smooth muscle, well organized in males (not in females)
Closed during ejaculation by sympathetic stimulus- to prevent retrograde movement of semen into bladder during ejaculation
(Parasympathetic stimulation relaxes the sphincter)
Describe the arterial blood supply to the male pelvis
Testis receives arterial supply from testicular artery arising form the abdominal aorta. (not from internal iliac artery)
Inferior vesical artery- to prostate, bladder
& ductus deferens
prostatic branch of inferior vesical artery- prostate
superior vesical arteries- to bladder & ductus deferens
Describe the importance of the pampniform venous plexus
found in spermatic cord- it surrounds the testicular artery and drains blood from the testes into the testicular vein
Acts as a countercurrent cooling mechanism that cools the arterial blood flowing in the testicular artery.
Summarise the perineum
Diamond-shaped area between pubic symphysis, ischial tuberosities and coccyx
Living anatomy: diamond shaped area between the thighs when the person lies on the back with thighs flexed and abducted
Divided into anterior (urogenital) and posterior (anal) triangles
Posterior compartment: there is ischio-anal fossae - fat-filled spaces separating anal canal and levator ani from pelvic walls
Anterior triangle divided into superficial and deep parts (or pouches) by the perineal membrane
What is the perineal membrane
A thick fascial, triangular structure attached to the bony framework of the pubic arch. It is orientated in the horizontal plane and has a free posterior margin.
Anteriorly, there is a small gap between the membrane and the inferior pubic ligament
The perineal membrane is related above to a thin space called the deep perineal pouch, which contains a layer of skeletal muscle and various neurovascular elements
Describe the margins of the perineum
Anterior point- inferior border of the pubic symphysis
posterior point- tip of coccyx
lateral points- ischial tuberosities
the lateral margins are formed by the ischipubic rami anteriorly and the sacrotuberous ligaments posteriorly
Describe the two divisions of the perineum
Divided into two triangles by an imaginary line joining the two ischial tuberosities- anterior to the line is the urogenital triangle and posterior to the line is the anal triangle
Significantly, the two are not in the same plane- in the anatomical position, the urogenital triangle is orientated in the horizontal plane, whereas the anal triangle is tilted upward at the trantubecular line so that it faces more posteriorly
Describe the structure of the perineum
roof- formed by the levator ani muscles- these muscles , one on each side, form a cone- or funnel- shaped pelvic diaphragm, with the anal aperture at its inferior apex in the anal triangle
Anteriorly, the urogenital triangle, a U-shaped defect in the muscles, the urogenital hiatus, allows the passage of the urethra and vagina
Describe the structures found in the anal triangle
Structures in the anal triangle are same in both sexes
contains the external anal sphincter (surrounds the anal canal and formed by skeletal muscle)
Describe the structure of the anal canal
ceiling is the pelvic diaphragm, which is formed by the levator ani and coccygeous muscles.
The anal aperture occurs centrally in the anal triangle and is related on either side to an ischio-anal fossa- the major muscle in the anal triangle is the external anal sphincter
Describe the external anal sphincter
Surrounds anal canal and consists of 3 parts (deep, superficial and subcutaneous)- aligned sequentially along the canal from superior to inferior
deep -thick-ring shaped- blends with fibres of levator ani muscle
superficial- surrounds muscle but is anchored anteriorly to the perineal body and posteriorly to the coccyx and anococcygeal ligament
subcutaneous- horizontally flattened disc that surrounds the anal aperture just beneath the skin
Summarise the Perineal Spaces (or Pouches)
Perineal membrane (PM): Thick triangular fascial structure attached to pubic arch. Posterioly free margin. Anteriorly a small gap.
Deep perineal space: is above the PM and below the fascia of pelvic diaphragm.
Superficial perineal space: is below PM and perineal fascia (subcutaneous tissue)
These spaces are potential spaces and they become real only when for eg: fluid leaks into them
Which membrane fills the urogenital triangle
Perineal membrane fills the urogenital triangle. The erectile tissues and associated skeletal muscles are anchored to this.
Summarise the contents in the superficial perineal pouch
Median erectile tissue mass (corpus spongiosum) - bulb of penis
In females it divides round the vestibule to form vestibular bulbs
Lateral erectile tissue masses (corpora cavernosae) attached to ischiopubic rami
These meet to form shaft and head of penis or clitoris (in female)
Erectile tissue within perineum surrounded by skeletal muscles
Describe the function of the perineal membrane and deep perineal pouch
provide support for the external genitalia, which are attached to its inferior surface. Also the parts of the perineal membrane and deep perineal pouch inferior to the urogenital hiatus in the levator ani provide support for the pelvic viscera above
the urethra leaves the pelvic cavity through the deep perineal pouch and perineal membrane- in women, the vagina also passes posterior to these structures
Describe the structure of the urogenital triangle
roof= levator ani
unlike the anal triangle, the urogenital triangle has a strong fibromuscular support platform, the perineal membrane and deep perineal pouch, which is attached to the pubic arch
anterior extensions of the ischio-anal fossae occur between the deep perineal pouch and the levator ani on each side
between the perineal membrane and the membranous layer of superficial fascia is the superficial perineal pouch- whose principal structures are the erectile tissues and associated skeletal muscles
Describe the structures in the superficial perineal pouch
erectile structures that join together to form the penis and clitoris
skeletal muscles that are associated with parts of the erectile structures attached to the perineal membrane and adjacent bone
Each erectile tissue consists of a central core of expandable vascular tissue and its surrounding connective tissue capsule
Describe the root of the penis
consists of two crura, which are the proximal parts of the corpora cavernosa attached to the pubic arch, and the bulb of the penis which is the proximal part of the corpus spongiosum anchored to the perineal membrane
Describe the body of the penis
Covered entirely by skin, is formed entirely by the tethering of the two proximal free parts of the corpora cavernosa and the related free part of the corpus spongiosum.
Describe the ligaments that support the penis
The base of the body of the penis is supported by two ligaments: the suspensory ligament of the penis (attached superiorly to the pubic symphysis) and the more superficially positioned fundiform ligament of penis (attached above to the linea alba of the anterior abdominal wall and split below into two bands that pass on each side of the penis and unite inferiorly)
Describe the anatomical position of the penis
erect
paired corpora are dorsal and spongiosum is ventral
Positions reversed when penis is flaccid
Describe the expansion of the corpus spongiosum
Expanded proximally (bulb attached to urogenital diaphragm) and at distal end (glans penis) over the distal ends of the corpora cavernosa
Describe the ischiocavernous muscle of the superficial perineal pouch
Cover the crura of the penis
Each muscle is anchored to the medial margin of the ischial tuberosity and related ischial ramus and passes forwards to attach to the sides and inferior surface of the related crus
forces the blood from the crus into the body of the erect penis
Describe the bulbospongious muscle of the superficial perineal pouch
Associated with the attached part of the corpus spongiosum in men
In men, the bulbospongious muscles are joined in the midline to a raphe on the inferior surface of the bulb of the penis
the raphe is anchored posteriorly to the perineal body
Muscle fibres course anterolaterally on each side from the raphe and perineal body to cover each side of the bulb and attach to the perineal membrane and connective tissue of the bulb- others extend anterolaterally to associate with the crura and attach anteriorly to the ischiocavernous muscles
Describe the functions of the bulbospongious muscle
Compress attached parts of the corpus spongiosum and force blood to the more distal regions, mainly the glans
facilitate emptying of the bulbous part of the penile urethra following micturition
Their reflex contraction during ejaculation is responsible for the pulsatile emission of semen
Describe the superficial transverse perineal muscles
The paired superficial transverse perineal muscles follow a course parallel to the posterior margin of the inferior surface of the perineal membranes
These flat, band-shaped muscles, which are attached to the ischial tuberosities and rami extend medially to the perineal body in the midline and stabilise the perineal body
Summarise the structure of the penis
Each corpus is surrounded by muscle, which are bound together in a tubular sheath of skin and connective tissue (deep fascia of the penis; Buck’s fascia), The fold of the skin covering the glans is the prepuce (foreskin)
The urethra runs through the corpus spongiosum to open at the tip of the glans
Describe the deep perineal pouch in men
Anteriorly, a group of muscle fibres surround the urethra and collectively form the external urethral sphincter
Deep transverse perineal muscle on each side parallels the free margin of the free margin of the perineal membrane and joins with its partner in the midline (perineal body) and originate from the medial aspect of the ischial ramus
stabilise the perineal body
Where doe the bulbourethral glands open
Bulbourethral glands and ducts open into the urethra below the perineal membrane
