ANATOMY: FEMALE PELVIS
See Male Pelvis Anatomy Chapter Notes for concepts common to females
Bony pelvis
- Females have a wider diameter and a more oval inlet compared to males
Female-specific Ligaments
- Broad ligament
- Contains the fallopian tube and ovary
- Divided into mesometrium, mesosalpinx, and mesovariaum
- Mesometrium of the broad ligament contains the gonadal vessels and nerves
- Lies on the posterolateral surface of the uterus attaching it to the pelvic wall
- Round ligament
- Present within the broad ligament
- Attaches the lateral walls of the uterine body to the pelvic sidewalls, enters at the internal inguinal ring and crosses over the external iliac artery, passes through inguinal canal, and terminates in the mons pubis of the labium majus
- Homologous to the gubernaculum of the male
- Lateral cervical ligament and uterosarcal ligaments
- Within the parameterium
- Lateral cervical ligament
- Also known as transverse cervical ligament and cardinal ligament
- Contains uterine vessels
- Clinical implication
- Blood vessels, nerves, smooth muscle, adipose, and connective tissue lie near these ligaments; nerves from the inferior hypogastric/pelvic plexus travel through the cardinal and uterosacral ligaments with the vessels, and damage to these during a hysterectomy can result in bladder dysfunction.
- Suspensory ligament of ovary
- Also known as infundibulo-pelvic ligament
- Contains the gonadal vessels
Female-specific Pelvic Vasculature
- Uterine artery
- Source: anterior trunk of the internal iliac artery
- Enters the broad ligament and lateral sacral ligament.
- Passes anterior to the ureter
- Clinical impliacion: ureter is vulnerable to iatrogenic injury during division of the uterine pedicle
- Ovarian artery
- Source: abdominal aorta, inferior to the renal arteries
- Location: most frequently identified at the infundibulo-pelvic ligament
- Structures that may be injured during a sacrospinous ligament vault suspension (3):
- Lateral sacral artery (from the posterior division of the internal iliac)
- Sacral plexus (see below)
- Pudendal nerve (see below)
- The venous drainage of the pelvis parallels the arteries but contains an intricate network of plexuses (uterine, vaginal, retropubic, vesical, rectal).
Female-specific Innervation
- Sacral plexus (L4-S3)
- Exits the pelvis through the greater sciatic foramen immediately posterior to the sacrospinous ligament
- Supplies motor and sensory innervation to the posterior thigh and lower leg
- Can be injured during a sacrospinous ligament vault suspension
- Caverous nerve
- Derived from the pelvic/inferior hypogastric plexus
- Responsible for clitoral engorgement during sexual activity
- Pudendal nerve (S2-4) is also vulnerable to injury during a sacrospinous culdosuspension.
Lymphatics
- The vulva, clitoris, and labia minora drain to the inguinal nodes.
Perineum
- Perineal membrane (previously called the urogenital diaphragm)
- A sheet of fascia that lies between the two sides of the pubic arch.
- Divides the urogenital hiatus into:
- Superficial perineal space
- Contains the superficial perineal muscles, clitoris, vestibular bulbs (bulbospongiosus), and Bartholin glands
- Deep perineal space
- Contains the external urethral sphincter, urethrovaginalis, compressor urethrae, and deep transverse perineal muscles
- The urethra and vagina pass through the urogenital hiatus of the perineal membrane to exit at the vestibule.
External female genitalia
- Clitoris
- Bounded by the labia minora laterally, the prepuce dorsally, and the frenulum ventrally
- Composed of a root, body, and glans
- There are 2 corpora cavernosa that split as crura proximally to attach to the inferior ischiopubic rami and are surrounded by the ischiocavernosus. They fuse distally and terminate as the glans, which is composed of spongy erectile tissue and is connected to the bulbs by bands of erectile tissue
- Labial fat pad
- Used in Martius flap
- Blood supply derives from:
- Superiorly from the external pudendal artery
- Laterally from the obturator artery
- Inferiorly from the posterior labial vessels (branch of the Internal pudendal artery)
- Bartholin/vestibular glands
- At the end of each bulb and travel 2 cm to empty through the groove between the hymen and labia minora.
- These glands can become obstructed and present as Bartholin gland cysts.
- Analogous to bulbourethral/Cowper’s glands in men
- Lymphatic drainage of the vulva, clitoris, and labia minora is to the inguinal nodes
- Parasympathetic stimulation results in:
- Increased vaginal secretion
- Erection of the clitoris
- Engorgement of the erectile tissues
Female pelvic organs
- Uterus
- Composed of the uterine body and the cervix and is normally anteverted and anteflexed
- Areterial supply: uterine artery
- Branch off the anterior branch of the internal iliac artery
- Crosses the ureter close to the cervix and also provides a small branch to the ureter
- Passes through the broad ligament and feeds the fallopian tube, and then runs laterally and joins the ovarian artery
- Cervix
- The base of the bladder lies directly in front of cervix on the anterior vaginal wall
- Ovaries
- Supported by the mesovarium and are in the ovarian fossa in the posterior peritoneum, which is bordered by the obliterated umbilical artery, ureter, and internal iliac artery
- Attached to the posterior aspect of the broad ligament and suspended by the infundibulopelvic ligament, which contains the ovarian vessels. It is also attached to the uterus by the ovarian ligament.
- Arterial supply: ovarian artery
- Arises directly from the aorta
- Passes in the infundibulopelvic ligament into the hilum of the ovary. It then passes through the broad ligament supplying the fallopian tube and joins the uterine artery.
- Crosses the iliac vessels anterior and lateral to the ureter
- Venous drainage: ovarian vein
- A pampiniform plexus drains the ovary and merges into the ovarian vein
- The right vein drains drains directly into the vena cava below the renal vein and the left drains into the left renal vein, similar to the testicle
- Fallopian (uterine) tubes
- ≈10 to 12 cm in length
- Draped in the broad ligaments
- Vagina
- The vaginal muscle is lined by non-keratinized stratified squamous epithelium.
- The anterior wall is ≈7.5 cm on average, and the posterior wall is ≈9 cm
- The ureters pass close to the lateral fornices of the vagina and are anterior to the vagina as they enter the bladder.
- The lower 1/4th of the vagina also has somatic innervation from the pudendal nerve and is sensitive to touch and to temperature changes.
- Ureter
- Vulnerable to injury
- Crosses the infundibulopelvic ligament
- Posterior to the ovarian artery
- Posterior and medial to the uterine artery
- Passes near the cardinal ligament and lies in close proximity to the cervix
- Travel for short time on anterolateral aspect of proximal vaginal wall
- Covered by pelvic peritoneum
Pelvic organ support
- The anterior vagina provides support to the urethra through its lateral attachment to the pubococcygeus and ATFP
- The parametrium and paracolpium provide support to the vagina and uterus. The cardinal ligaments and uterosacral ligaments also provide additional support to the uterus, cervix, and upper vagina. This is level I support.
- Level II support is from the paravaginal attachments to the ATFP and to the arcus tendineus rectovaginalis
Urethra
- Length of the female urethra is ≈4 cm from the internal to the external urethral meatus
- Lining changes from transitional to non-keratinized squamous
- There are many periurethral glands around the urethra that, when obstructed, can give rise to diverticula. The most prominent are Skene glands, which open distally just inside the external urethral meatus
- The anterior vagina provides support to the urethra
- No internal urinary sphincter identified in females
- The external urethral sphincter invests the distal 2/3 of the female urethra.
- Blood supply to the urethra comes from the inferior vesical, vaginal, and internal pudendal arteries.
- Somatic and autonomic innervation of the urethra travel on the latera walls of the vagina near the urethra
- Clinical significance: to avoid denervation of the striated urethral sphincter, incisions through the vaginal wall to enter the retropubic space should be made far lateral in the vaginal wall, parallel to the urethra
Radiographic anatomy
- Pelvic MRI is the best imaging technique to visualize and localize urethral diverticula and to differentiate them from cystic lesions in the vagina and urethra.
- Some benign vaginal cysts include müllerian cysts, epidermal inclusion cysts, Gartner duct cysts, Bartholin gland cysts, and Skene gland cysts.
Questions
Answers
References
- Wein AJ, Kavoussi LR, Partin AW, Peters CA (eds): CAMPBELL-WALSH UROLOGY, ed 11. Philadelphia, Elsevier, 2015, chap 67