Normal Anatomy and Physiology of the Female Pelvis

Transabdominal Pelvic Ultrasonography

• 3.5 to 5 MHz transducer

• wider field of view

• requires distended urinary bladder

  • pushes uterus posteriorly

  • moves bowel out of pelvic cavity

Endovaginal Pelvic Ultrasonography

• 7.5 to 10 MHz

• more detailed

• limited field of view & depth of penetration

• depends on age & sexual status

Bony Pelvis

• composed of four bones:

  • two innominate (coxal) bones forming the anterior and lateral walls,

  • sacrum & coccyx forming the posterior wall.

False Pelvis

• Muscles

  • psoas major

  • iliacus

• create the iliopsoas muscle

True Pelvis

• piriformis muscles

• obturator internus muscles

• pelvic diaphram muscles

  • coccygeus muscles

  • levator ani (group of 3 closest to vaginal level)

    • pubococcygeus

    • iliococcygeus

    • puborectalis

Bladder

• apex = posterior to pubic bones

• base = anterior to vagina

• neck = rests on upper surface of urogenital diaphragm

Ureters

• transport urine from kidneys to bladder

• don’t typically see unless something is wrong w/ them

Vagina

• collapsed muscular tube

  • approx. 9 cm in length

  • 90-degree angle w/ the cervix

Cervix

• Endocervix

  • cervical canal

    • communicates w/ the uterine cavity

    • via internal os

    • vagina via the external os

• Exocervix

  • outer portion of the cervix

  • protrudes into the upper vaginal canal

  • archlike recesses (fornices)

Uterus

• hollow, pear shaped

• Consists of:

  • fundus

    • widest (most superior)

  • body (corpus)

    • largest portion

  • Isthmus

    • point between body of uterus & cervix

    • bends anteriorly or posteriorly

  • Cervix

    • most inferior portion

Uterize Sizes

• premenarchal

  • 1.0 - 3.0 cm long by 0.5 - 1.0 cm wide

• Menarchal

  • 6.0 - 8.0 long by 3.0 - 5.0 cm wide

• Multiparity

  • increases size by 1.0 - 2.0 cm

• Postmenopausal

  • 3.5 - 5.5 cm long by 2.0 - 3.0 cm wide

Perimetrium

serous outer layer of uterus (serosa)

Myometrium

• thick middle layer of smooth muscle/connective tissue

• bulk of the uterine wall

Endometrium

• mucosal inner lining of the uterine body

• Consists of:

  • superficial functional layer (zona functionalis)

    • sheds w/ menses

  • deep basal layer (zona basalis)

    • regenerates new endo. after menses

Broad Ligaments

• Double folds of peritoneum

• drapes over the fallopian tubes, uterus, and ovaries

• lateral uterus to the pelvic sidewalls

Round Ligaments

• Fibrous cords originating in front of and below the fallopian tubes

• holding the uterine body in a forward position

Anteverted Uterus

• most common uterine position

• fundus & body bent forward toward cervix

Anteflexed Uterus

body & fundus are curved forward on the cervix

Retroverted Uterus

entire uterus tilted posteriorly

Retroflexed Uterus

fundus & body bent backward toward the cervix

Uterine Prolapse

• abnormal downward displacement of the uterus

• caused by weakness in pelvic floor muscles & ligaments

Fallopian tubes (oviducts)

• coiled, muscular tubes

• approx. 10-12 cm long & 1-4mm diameter

• blood supply from ovarian arteries & veins

• divided into 4 portions

  • infundibulum, ampulla, isthmus, interstitial portion

Infundibulum

• lateral, widest portion

• contains fimbriae

Ampulla

• middle, longest, most coiled

• most common site of ovum fertilization

Isthmus

located lateral to the uterus.

Interstitial Portion

• narrowest portion

• passes through uterine wall at the cornua

Ovary

• almond-shaped organ

• approx. 3 cm long in menarcheal women

• responsible for ovum development

• produces 2 hormones:

  • estrogen - secreted by follicles

  • progesterone - secreted by corpus luteum

• Dual blood supply

  • receives blood from ovarian artery & uterine artery

• Blood drained

  • ovarian vein into IVC on right

  • renal vein on left

Blood Supply

• Iliac arteries

  • anterior & medial to psoas muscles

  • bifurcate into

    • external iliac artery & internal iliac artery

• Ovarian veins

  • left → drains into left renal vein

  • right → drains directly into IVC

Uterine Artery

• Anastomose anteriorly & posteriorly within myometrium

• form arcuate vessels that encircle uterus

Arcuate Arteries

Anechoic tubular structures in outer third of myometrium

Radial Arteries

• arising from the arcuate vessels

• penetrate deep into the myometrium to supply the base of the endometrium.

Spiral Arteries

• Coiled terminal branches of radial arteries

• supply functional layer of the endometrium

• shed during menses

Polymenorrhea

• irregular

• less than 21 days

Oligomenorrhea

• short & light menses

• extending beyond 35 days

Amenorrhea

absence of menses

Dysmenorrhea

Painful menstruation

Premenarche

prepuberty (before onset of menses)

Menarche

regular menstrual cycles (approx. every 28 days)

Menopause

cessation of menses (typically occurring around age 50)

Ovulation

• occurs at day 14 of a 28-day cycle

• ovum released once a month by one of two ovaries

• some will mature & be released while other degenerate

Follicular Phase

• first phase of the ovarian cycle (days 1–14) driven by FSH

• follicles grow/fill w/ fluid

• secrete estrogen

• select a dominant Graafian follicle

  • 2 cm before ovulation

• LH increases 24-36 hours before ovulation

• Mittelschmerz = middle pain (dull ache on either side)

Luteal Phase

• second phase (day 14 - 28)

• FSH decreases due to LH surge

  • egg is either fertilized or degenerates

• corpus luteum formation

• progesterone secretion 9-11 days after

Menstrual Phase

• 1-5 days (1-5mm)

• begins w/ declining progesteron levels

• decreased blood flow → causes spiral arteries to shed

• coincides with follicular phase of ovarian cycle (days 1-14)

Proliferative Phase

• days 5-14

• rising estrogen regenerates the functional layer

• prepares endometrium for implantation

• producing a characteristic 'three-line' (trilaminar) appearance

  • early = 4-8mm

  • late = 6-10mm

Secretory Phase

• days 15–28

• Corresponds with luteal phase of ovarian cycle

• thick endometrium (7-14mm)

Menorrhagia

abnormally heavy or long periods (luteal phase affected)

Vesicouterine Pouch

• anterior cul-de-sac

• anterior to fundus between the bladder & uterus

Rectouterine Pouch

• posterior cul-de-sac or pouch of Douglas,

• posterior to uterus between uterus & rectum

• inferior & most posterior region of peritoneal cavity

• most common for fluid

Retropubic

• Space of Retziusan

• anterior bladder wall & pubic symphysis

• contain subcutaneous fat