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Pelvis and Vulva Anatomy — Transcript Study Notes

Six parts of the vulva

  • Labia majora and labia minora
    • Labia minora (the thinner lips) are smaller than the labia majora; the speaker notes this as a memory aid: minor is smaller than major.
    • Labia majora are the larger outer lips.
  • Clitoris
  • Urethral opening (where urine is expelled)
  • Vestibule
    • The vestibule is described as the opening of the vagina.
  • Note: The speaker refers to “six parts” of the vulva but only lists five items (labia minora, labia majora, clitoris, urethral opening, vestibule). There may be an omitted item in the transcript.

Bony pelvis: key bones and layout

  • The bony pelvis consists of four bones in total (two innominate bones per side plus the sacrum and coccyx):
    • Two innominate bones (each is a fusion of pubic bone, ilium, and ischium)
    • Sacrum (posterior, behind the pelvic cavity; near the tailbone)
    • Coccyx (tailbone)
  • Each side has one innominate bone, so there are two innominate bones in the pelvis.
  • Visual cue: the innominate bone is the composite of the pubic, iliac, and ischial bones all in one unit.

True pelvis vs. false pelvis

  • The pelvis is divided into two regions:
    • True pelvis (below the ileopectineal line): contains pelvic organs such as the uterus and bladder.
    • False pelvis (above the ileopectineal line): lies superior to the true pelvis.
  • The ileopectineal line is an imaginary diagonal line used to separate the true and false pelvis; it’s described as an imaginary line that would be visible if someone were cut in a midsagittal (longitudinal) plane.
  • Note: The speaker emphasizes that the bladder lies in the true pelvis and mentions the uterus as located in the true pelvis.

Muscles of the pelvis: overview and key examples

  • Relational anatomy emphasis: Many exam questions test your ability to describe where muscles are located in relation to other structures (anterior to bladder, lateral to others, etc.).
  • Rectus abdominis
    • Runs from the xiphoid process down to the pubic bone
    • Forms part of the anterior wall of the pelvis
    • Also described as contributing to the anterior abdominal wall; the speaker notes it as a key anterior muscle of the pelvis in this slide, though it is primarily an abdominal wall muscle.
  • Psoas major and iliacus (forming the iliopsoas)
    • The psoas major runs from the vertebrae, and it joins with the iliacus to form the iliopsoas muscle.
    • The iliopsoas enters the pelvis and extends toward the femur (toward the greater trochanter), exiting the true pelvis.
    • Important clinical note: in ultrasound, the iliopsoas is often mistaken for an ovary because it sits in the pelvic region but is not inside the true pelvis.
    • The iliopsoas is located in the false pelvis and does not pass into the true pelvis.
    • Ultrasound tip: if you’re looking in transverse, a true muscle will lengthen when the probe is rotated; an ovary tends to stay more oval/circular.
  • Piriformis
    • A true muscle of the pelvis running from the sacrum to the lateral wall of the pelvis.
  • Obturator internus
    • Another lateral pelvic muscle; described as lateral and anterior in some views.
  • Pelvic floor muscles (levator ani group)
    • Function: maintain intra-abdominal pressure and support pelvic organs; help prevent descent of organs during bearing down or coughing.
    • Key components of the levator ani group:
    • Pubococcygeus
      • Origin: pubis to coccyx
    • Puborectalis
      • Origin: pubis around the rectum
    • Iliococcygeus (iliococcygeus)
      • Origin: iliac bone to coccyx
  • General note on pelvic floor anatomy:
    • The pelvic floor muscles form a supportive sling across the bottom of the pelvic cavity and are essential for continence and organ support.
    • The slide being discussed includes pelvic floor muscles in a view that resembles the pelvis with no organs drawn, to emphasize the muscles themselves.

How to distinguish ovary from muscle in ultrasound (practical tip)

  • In transverse view of the pelvis:
    • Ovaries are typically circular/oval in cross-section.
    • Iliopsoas muscle may appear more elongated or elongated when the patient is rotated; a muscle will lengthen when rotated, whereas an ovary tends to maintain its circular/oval cross-section.
  • This distinction helps prevent misidentifying the iliopsoas as the ovary during ultrasound scanning.

Orientation and relational anatomy for exams

  • The slides emphasize relational anatomy: describe where structures are in words (e.g., anterior to the bladder, lateral to a reference structure).
  • The pelvis includes structures from both the true and false pelvis; the coronary landmarks discussed include the bladder, uterus, rectum, sacrum, coccyx, pubic bone, and iliac/ischial structures.
  • In lectures, this relational approach is a common focus for registry and major exams.

Quick reference: key terms and their connections

  • Labia minora = minor lips; smaller/thinner set of vaginal lips.
  • Labia majora = major lips; larger outer lips.
  • Clitoris = erectile structure located at the anterior end of the vulva.
  • Urethral opening = external opening for urine.
  • Vestibule = opening region of the vagina.
  • Innominate bone = the fused pubis, ilium, and ischium that form each half of the pelvis; there are two (one per side) in the pelvis; total of 2 innominate bones.
  • Pelvic bones total = 4 bones in the pelvis (two innominate bones, sacrum, coccyx).
  • Sacrum = the large, triangular bone at the base of the spine, forming the posterior wall of the pelvis.
  • Coccyx = tailbone.
  • Ileopectineal line = the imaginary line that divides true and false pelvis; indicates anatomical division.
  • Psoas major + iliacus = iliopsoas (muscle group in the false pelvis; can be mistaken for ovaries on ultrasound).
  • Piriformis and obturator internus = lateral pelvic muscles.
  • Levator ani = major component of the pelvic floor; includes:
    • Pubococcygeus
    • Puborectalis
    • Iliococcygeus
  • Functions to remember: support pelvic organs; maintain intra-abdominal pressure; prevent organ descent during coughing or bearing down.

Summary takeaways for exam preparation

  • Be able to name and describe the six parts of the vulva as given (noting the transcript lists five and mentions a sixth that isn’t explicitly described).
  • Memorize the four main bony components of the pelvis and how they come together: two innominate bones, sacrum, coccyx.
  • Understand the division of true vs false pelvis and the role of the ileopectineal line and midsagittal plane in defining the boundary.
  • Know the major pelvic muscles and their approximate locations, origins/insertions, and functional roles, especially the levator ani group.
  • Be able to explain why the iliopsoas can be confused with an ovary on ultrasound and how to differentiate it using transverse views and rotation.
  • Practice relational anatomy phrasing (e.g., “X is anterior to Y”) as this is stressed for exams.