Pelvis

Bony pelvis Composition: formed by paired hip bones, sacrum, coccyx, and their articulations Two portions Greater pelvis Lesser pelvis Terminal line ( pelvic inlet): formed by promontory of sacrum, arcuate line, pectin of pubis, pubic tubercle, upper border of pubic symphysis Pelvic outlet: formed by tip of coccyx, sacrotuberous ligament, ischial tuberosity, ramus of ischium, inferior ramus of pubic symphysis

Identify the bony walls and ligamentous landmarks of the pelvis. Iliopectineal Line Sacrotuberous Ligament Greater Sciatic Foramen Sacrospinous Ligament Lesser Sciatic Foramen Sacrospinous Ligament Sacrotuberous Ligament Pubic Symphysis Pubic Arch Ischial Tuberosity Sacrotuberous Ligament Pelvic Outlet Tip of Coccyx Ant. Sup. Iliac Spine Pubic symphysis Coccyx 1

Sacrotuberous Ligament Piriformis Muscle Greater Sciatic Foramen Muscular Walls Sacrotuberous Ligament Piriformis Muscle Greater Sciatic Foramen Piriformis Muscle Sacrospinous Ligament Sacrotuberous Ligament Ischial Tuberosity Lesser Trochanter Greater Trochanter Gemellus Superior & Inferior Obturator Internus

Muscles of pelvic wall Piriform Obturator internus Iliacus

Piriform muscle Arise from the ant surface of the lateral mass of the sacrum and enter the gluteal region by passing through the greater sciatic notch to be inserted on to the upper border of the greater trochanter of the femur. It’s a lateral rotator of the hip Receives nerve supply from sacal plexus.

Obturator internus Arises from the pelvic surface of the obturator membrane and the adjoining part of the hip bone. Muscle fibres from a tendon which exit the pelvis through lesser sciatic foramen and gets inserted on to the greater trochanter.

Iliacus The iliacus arises from the iliac fossa on the interior side of the hip bone, and also from the region of the anterior inferior iliac spine (AIIS). It joins the psoas major to form the Iliopsoas and gets inserted on to the lesser trochanter of the femur.  The iliopsoas is innervated by the femoral nerve and direct branches from the lumbar plexus.

Muscles of the Pelvic Floor (Pelvic Diaphragm) The pelvic diaphragm is composed of two paired muscles – levator ani and coccygeus These muscles: Close the inferior outlet of the pelvis Support the pelvic floor Elevate the pelvic floor to help release feces Resist increased intra-abdominal pressure PD is is pierced by the rectum and urethra and vagina in females Region inferior to the pelvic diaphragm is the perineum

Muscles of the Pelvic Floor: Pelvic Diaphragm Figure 10.12a

Levator ani 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 The levator ani is divided into three parts: Iliococcygeus muscle Pubococcygeus muscle Puborectalis muscle

Iliococcygeus The Iliococcygeus arises from the inner side of the ischium and from the posterior part of the tendinous arch of the obturator fascia, and is attached to the coccyx and anococcygeal raphé.

Pubococcygeus stretches from the pubic bone to the coccyx.

Puborectalis The fibers which form a sling for the rectum are named the Puborectalis or Sphincter recti. They arise from the lower part of the pubic symphysis, and from the superior fascia of the urogenital diaphragm. They meet with the corresponding fibers of the opposite side around the lower part of the rectum, and form for it a strong sling. Relaxation reduces the angle between rectum and anus, allowing defecation in conjunction with relaxation of the internal and external sphincters.

Coccygeus The Coccygeus is a muscle of the pelvic wall (i.e. peripheral to the pelvic floor), located posterior to levator ani and anterior to thesacrospinous ligament. It is a triangular plane of muscular and tendinous fibers, arising by its apex from the spine of the ischium and sacrospinous ligament, and inserted by its base into the margin of the coccyx and into the side of the lowest piece of the sacrum.

Muscles Inferior to the Pelvic Floor: The Urogenital Diaphragm Stretches between two sides of the pubic arch in the anterior half of the perineum Contains Deep transverse perineal muscle Extrnal urethral sphincter muscle The ischiocavernosus and bulbospongiosus assist in erection of the penis and clitoris; lie superficial to the urogenital diaphragm

Muscles of the Pelvic Floor

Muscles of the Pelvic Floor

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