Pelvic Muscles: Gemelli Superior and Inferior Quiz

Gemellus Muscles

• The Gemelli are two small muscles in the pelvis that function as accessories to the tendon of the obturator internus.
• Gemellus superior arises from the outer surface of the ischial spine and blends with the upper part of the tendon of the obturator internus.
• Gemellus inferior arises from the ischial tuberosity and blends with the lower part of the tendon of the obturator internus.
• Both muscles help rotate the thigh laterally.

Levator Ani Muscle

• The levator ani is a broad, thin muscle situated on the side of the pelvis.
• It is attached to the inner surface of the side of the lesser pelvis and unites with its fellow of the opposite side to form the greater part of the floor of the pelvic cavity.
• It supports the viscera in the pelvic cavity and surrounds the various structures that pass through it.
• It helps maintain urinary and fecal continence.

Pelvic Floor

• The pelvic floor is made up of several muscles, including the levator ani, which is divided into three parts: iliococcygeus muscle, pubococcygeus muscle.
• The pubococcygeus muscle controls urine flow and contracts during orgasm.

Pelvis Functions

• The pelvis serves several functions, including:
  • Transferring weight from the upper axial skeleton to the lower appendicular components of the skeleton, especially during movement.
  • Providing attachment for a number of muscles and ligaments used in locomotion.
  • Containing and protecting the abdominopelvic and pelvic viscera.

Pelvis Structure

• The pelvis is composed of three bones: ilium, ischium, and pubis, which fuse together during growth and development.
• The ilium is the largest of the three bones, with the iliac crest, ASIS, PSIS, and sciatic notch.
• The ischium is the strongest of the three bones, with the ischial spine, ischial tuberosity, and ischial ramus.
• The pubis includes the inferior ramus, pubic tubercle, superior ramus/pubic crest, and pubic symphysis (PS).

Bony Pelvis

• The bony pelvis has three parts: the ilium, ischium, and pubis.
• The anterior view of the pelvis includes the ischiopubic rami, obturator foramen, anterior superior iliac spine, iliac crest, iliac fossa, ischial spine, pubic tubercle, pubic crest, pubic symphysis, and sacro-iliac joint.

Characteristic Differences in Pelvic Structure

• Female pelvis:
  • Smoother and lighter
  • Wider pubic arch (subpubic) angle
  • Flared iliac wings
  • Enlarged pelvic outlet
  • Less curvature of the sacrum/coccyx
• Male pelvis:
  • Stronger and heavier
  • Narrower pubic arch (subpubic) angle
  • Iliac wings less flared
  • Designed for strength and speed

Ischial Tuberosity and Ischial Spine

• The ischial tuberosity is a large swelling on the posterior surface of the ischium.
• It marks the lateral boundary of the pelvic outlet, along with the ischial spine.
• The gluteus maximus muscle covers the ischial tuberosity in the upright posture, but leaves it free in the seated position.
• The ischial spine is a triangular eminence that extends backward from the posterior border of the body of the ischium.
• The coccygeus muscles, levator ani, and pelvic fascia attach to the ischial spine.

Greater Sciatic Foramen

• The greater sciatic foramen is a major foramen of the pelvis, bounded by the greater sciatic notch, sacrotuberous ligament, sacrospinous ligament, and anterior sacroiliac ligament.
• The piriformis muscle exits through the greater sciatic foramen.