Female Pelvic Anatomy

Learning Outcomes

• Describe the anatomy of the bony pelvis and male/female differences

• Describe the obturator internus and piriformis muscles, including attachments and nerve supply

• Describe the pelvic diaphragm muscles, including attachments, parts and nerve supply and their role in supporting pelvic organs and the role the pelvic diaphragm plays in supporting the organs of the pelvis
• Describe the anatomy of the female genital organs

• Identify the uterus and vagina on radiological imaging

• Describe some of the main clinical conditions that may affect the cervix and uterus
• Describe the iliac vessels and the somatic & autonomic nervous structures of the pelvis in a practical session

Female Reproductive Organs

• Pelvic organs have an ovary and uterine tubes, a uterus, and the proximal half of the vagina

Ovaries

• The shape is ovoid and mesovarium
• Ligaments that support the ovaries include the ovarian ligament proper and the suspensory ligament
• The ovarian fossa is located at the angle between the internal and external iliac vessels and the obturator nerve runs along it

Uterine Tubes

• Mesosalpinx is a part of the broad ligament that surrounds the uterine tubes
• The ovarian ligament is proper
• Sections include; histology, outer longitudinal muscle, inner circular muscle
• The histology is columnar epithelium (ciliated & non-ciliated)

Uterus

• Consists of the body and the cervix
• The body: fundus, isthmus of uterus, cornu (uterine horns)
• The body lies between the layers of the broad ligament
• Cervix: internal os, external os

Uterus Body Position and Layers

• Body of the uterus typically arches forward (anteflexed; approx 170°) over the superior surface of the emptied bladder
• Cervix is angled forward (anteverted) on the vagina which is approximately 90°
• The wall has layers of perimetrium, serous outer coat (peritoneum), the myometrium, middle muscular layer, and the endometrium, inner mucous layer

Vagina

• Vagina is a fibromuscular collapsable tube that opens into the vestibule
• The cervix bulges into the vagina, and its surrounding recesses are the fornices: anterior, posterior (related to the pouch of Douglas), lateral (ischial spine, uterine artery & ureter)

Cervical Examination and Cytology

• Used to gather cellular material from the supravaginal cervical mucosa
• Uterus is lined by the columnar epithelium
• The upper vagina is lined with stratified squamous-non-keratinized
• At the external cervical os, stratified squamous epithelium changes to columnar mucinous epithelium, which is a squamocolumnar junction called the transformation zone

Pelvic Fascia

• In females, the anterior is pubocervical ligament, the lateral is transverse cervical or cardinal ligament (The uterine artery can be found here) and posterior is uterosacral ligament
• In males, puboprostatic ligament, prostatic fascia and rectovesical septum

Peritoneal Reflection

• The superior surface of the bladder is covered by the parietal peritoneum
• Reflections of peritoneum (from the bladder to surrounding viscera) create peritoneal pouches; rectovesical pouch, rectouterine pouch, and vesicouterine pouch

Broad Ligament

• Double layer of peritoneum that "drapes” over the uterus and tubes (like a rain poncho)
• The mesosalpinx and the mesometrium are within the broad ligament and close to the ovaries

Lymphatics

• Ovaries, uterine tubes, and fundus of the uterus drain to the lumbar/para-aortic nodes
• Cornu of the uterus drains to the superficial inguinal
• Body of the uterus drains to external iliac lymph nodes
• Cervix and superior and middle parts of the vagina drain into the internal iliac nodes
• External vagina, labia majora, and labia minora drain to superficial inguinal nodes

Clinical Conditions

• Uterine fibroids, Endometrial carcinoma, Cervical carcinoma, Uterine prolapse remember the structures that support the uterus
• Ectopic pregnancy, uterine tube bleeding +++, Ovarian Cyst, Ovarian Carcinoma

Organization

• False pelvis (greater pelvis) is superior to (above) the pelvic inlet and is considered part of the abdominal cavity
• True pelvis (lesser pelvis) is inferior to (below) the pelvic inlet where the floor is bounded by the pelvic diaphragm

Pelvic Bones

• Pelvic bones are irregular in shape and made of the ilium, pubis, and ischium

Sacrum

• Features include alae, sacral canal, sacral hiatus and promontory

Ligaments of the Pelvic Wall

• Convert notches into foramina: greater and lesser sciatic foramen
• Stabilizes the sacrum and prevents its rotation

Joints

• Sacroiliac joints (synovial joints that may fibrose or ossify) transmit forces from the lower limbs to the vertebral column
• Joints are stabilized by anterior, posterior, and interosseous sacroiliac ligament
• Pubic Symphysis, secondary cartilaginous joint, joint surfaces are covered by hyaline cartilage and are linked across the midline to adjacent surfaces by fibrocartilage
• The joint is surrounded by interwoven layers of collagen fibers with superior & inferior pubic ligament

Apertures and Getaways

• Subinguinal hiatus contains the iliopsoas, femoral vessels, and femoral nerve
• Greater sciatic foramen includes; Above piriformis, superior gluteal vessels, superior gluteal nerve and Below piriformis, inferior gluteal vessels, inferior gluteal nerve and sciatic nerve ,Posterior femoral cutaneous nerve, Nerve to quadratus femoris, Pudendal nerve and internal pudendal vessels and Nerve to obturator internus
• The obturator foramen contains the obturator nerve and obturator vessels
• Lesser Sciatic foramen contains the pudendal nerve, internal pudendal vessels, Nerve to obturator internus and the Obturator internus muscle

Pelvic Cavity

• The pelvic cavity includes the Pelvic inlet, walls, floor (muscles), and pelvic outlet

Pelvic Walls

• Obturator internus is on the deep surface of the obturator membrane to the greater trochanter, which is innervated by a nerve running to it
• The action is lateral rotation of the extended hip joint and abduction of flexed hip
• The Piriformis is on the anterior surface of the sacrum to the greater trochanter, innervated by S1 & S2
• The action is lateral rotation of the extended hip joint and abduction of flexed hip

Pelvic Floor

• The pelvic floor separates the pelvic cavity and the perineum that consists of Levator ani (innervated by branches from S2-4), Coccygeus (innervated by branches from S3-4), Perineal membrane & Muscles of the deep perineal pouch
• The Levator ani originates from a line that extends from the pubic bone to the ischial spines and inserts into the muscle from the other side, the Innervation: S2-4 via direct branches and pudendal nerve and includes Puborectalis, Pubococcygeus and the Iliococcygeus
• The Coccygeus extends From the ischial spine to the coccyx and sacrum with an Innervation: S3-4

Pelvic Inlet and Outlet

• The pelvic inlet features include promontory, alae, Sacro-iliac joint. linea terminalis (pubic crest, pecten pubis, arcuate line), Pubic symphysis
• The pelvic outlet features include Pubic symphysis, Body of the pubis, Inferior ramus of the pubis, Ramus of the ischium, Ischial tuberosity, Sacrotuberous ligament & Coccyx

Sexual Difference in Pelves

• Females have a circular pelvic inlet, and males have a heart-shaped inlet
• Females have an indistinct sacrum and males has a distinct one
• Female angle is greater (80-85 degrees)
• The male angle is narrow (50-60 degrees)
• Female has less medial projection into the pelvic cavity and males have more projection

Pelvic Measurements

• Obstetric Measurements: Conjugate = AP or diagonal or Oblique, Transverse, Interspinous diameter (narrowest) outlet, and AP diameter of the pelvic outlet
• Used to determine the fixed size of the birth canal and the likelihood of a safe vaginal delivery

Inlet and Outlet Diameters

• Transverse is the widest part of the brim
• Interspinous outlet