Female Pelvic Anatomy

Female Pelvic Anatomy

• The presentation covers female pelvic anatomy.
• Topics covered include: uterus, fallopian tubes, surrounding spaces, ligaments, bony pelvis, ovaries, ultrasound appearance, and pelvic vasculature.

Uterus

• The uterus is a pear-shaped muscular organ.
• It has 4 regions: fundus, corpus, isthmus, and cervix.
• The uterus has three tissue layers: serosa (perimetrium), myometrium, and endometrium.
• Serosa (Perimetrium) is the outermost layer.
• Myometrium is the middle layer.
• Endometrium is the inner mucous membrane, glandular portion of the uterine body.
• Shape and size varies with age and obstetric history.
• Prior to menarche, the uterus is cylindrical and narrow.
• In a mature uterus, the corpus and fundus enlarge.
• After menopause, the uterus regresses in size.
• Premenarchal uterus measures 1.0 to 3.0 cm long by 0.5 to 1.0 cm wide.
• Menarchal uterus measures 6.0 to 8.0 cm long by 3.0 to 5.0 cm wide.
• With multiparity, the uterus increases in size by 1.0 to 2.0 cm.
• Postmenopausal uterus measures 3.5 to 5.5 cm long by 2.0 to 3.0 cm wide.

Variants in Uterine Position

• Anteflexion is the bending of the fundus toward the abdominal wall.
• Anteverted uterus is tipped toward the anterior abdominal wall and is the usual position when the bladder is empty.
• Dextroflexed uterus is flexed to the right.
• Dextroposition is the displacement to the right.
• Levoflexed uterus is flexed to the left.
• Levoposition is displacement to the left.
• Prolapse is the dropping of the uterus into the vaginal canal.
• Retroflexed bending of the fundus toward the rectum.
• Retrocession is the backward displacement of the entire uterus.
• Retroverted uterus is tipped toward the sacrum.
• Retroversioflexion is a combination of retroversion and retroflexion.
• All positions are in relation to the pelvic axis.

Ultrasound Appearance: Uterus

• Uterus myometrium appears with mid gray or medium level echoes.
• It has an even homogeneous texture and pattern.
• It has a smooth even contour.
• The endometrial cavity varies in thickness and shape in relation to the menstrual phase.
• The vagina displays mid gray to medium level echoes.
• The vaginal canal is a hyperechoic line.

Fallopian Tubes

• The fallopian tubes have 4 portions:
• Interstitial (intramural): the narrowest part, nearest the cornua
• Isthmus: slightly wavy and longer
• Ampulla: tortuous and longest part
• Infundibulum: Lateral, trumpet shaped with fimbriae

Pelvic Spaces

• Anterior cul de sac (vesicouterine pouch): is the reflection of peritoneum over anterior surface of uterus and bladder.
• Posterior cul de sac (rectouterine pouch, Pouch of Douglas): is the reflection of peritoneum over posterior surface of uterus and rectum.
• Space of Retzius (retropubic space): can be identified between the anterior bladder wall and the pubic symphysis

Uterine Ligaments

• Broad: lateral aspect of uterus to pelvic sidewall.
• Mesovarium: posterior fold of broad ligament that encloses the ovary.
• Mesosalpinx: the upper fold of the broad ligament that encloses the fallopian tube.
• Mesometrium: name of the ligament
• Round: extends from uterine cornua to anterior pelvic sidewalls and holds the uterus forward.
• Cardinal: extend across pelvic floor laterally and firmly support the cervix.
• Cardinal ligaments house the vasculature of the uterus.
• Uterosacral: extend from the uterine isthmus downward, lying alongside the rectum and attaching to the sacrum.
• These firmly support the cervix.

Bony Pelvis

• The pelvic girdle consists of four bones: two innominate (coxal) bones, the sacrum, and the coccyx.
• It is divided into two continuous compartments (true and false pelvis) by an oblique plane that passes through the pelvic brim.
• Linea Terminalis is also known as Iliiopectineal Line
• The muscles of the false pelvis include the psoas major and iliacus muscles.
• In the false pelvis, psoas muscles join with iliacus muscles to form iliopsoas muscles.
• Muscles of the True Pelvis include:
  • Piriformis muscles.
  • Obturator internus muscles.
  • Muscles of the pelvic diaphragm: Levator ani (Pubococcygeus muscles, iliococcygeus muscles, puborectalis muscles), and Coccygeus muscles

Ovaries

• The ovaries are located lateral to the uterus in the adnexa, in the posterior fold of the broad ligament.
• They may be superior or posterior to the uterine fundus and may be in the posterior cul de sac.
• The size of the ovaries are as follows:
  • SAG = 2.5-5.0 cm.
  • TRV = 1.5-3.0 cm.
  • AP = .6-2.2 cm.
• The ovaries are anchored by the mesovarian ligament (anchors to posterior surface of broad ligament), ovarian ligament (anchors to uterine cornu), and infundibulopelvic ligament (anchors to pelvic brim).
• Abdominal organ not covered by peritoneum (nude ovary).
• Ovaries produce hormones and gametes.
• Ovaries are composed of two parts: cortex (outer) & medulla (inner).
• Ovaries cortex contains primordial follicles.
• Ovaries medulla contains connective tissue, nerves, blood supply, lymphatics & smooth muscle tissue.
• Tunica albuginea is surrounded by a single, thin layer of cells known as germinal epithelium.

Ovarian Follicles

• Millions of primordial follicles are present at birth.
• Between 300-400 mature in a lifetime
• Graafian Follicle is the follicle that matures each month
• Graafian Follicle ruptures with ovulation at approximately 1.8 TO 2.5 cm
• After rupture, the follicular cavity becomes the corpus luteum of menstruation
• If ovum is fertilized, the corpus luteum remains, if not it resolves

Ultrasound Appearance of Ovaries

• Similar to myometrium in echogenicity
• Follicles give "swiss cheese appearance"
  • Post menopausal ovaries are difficult to visualize
• Some tips for better visualization
  • Turn down gains
  • Look for posterior enhancement
  • Ovary may be anterior to internal iliac vessel

Pelvic Vascular Supply

• Hypogastric Artery (Internal Iliac)
• Uterine Artery
• Ovarian Artery
• Veins have similar pattern
• Veins are distensible and vary in size with certain conditions