ANAT 1625 Lecture Notes - Pelvis

ANAT 1625 Lecture Notes - Pelvis - 1 Pelvis Pelvic floor Is...

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Pelvis Pelvic floor Is formed by the funnel – shaped pelvic diaphragm , which consists of two muscles, levator ani, coccygeus and the fascia covering the superior and inferior surfaces of the muscles Levator ani Is attached to the internal surface of the lesser pelvis, forms most part of the pelvic floor It consists of three parts 1. pubococcygeus is the main part, arises from the posterior aspect of the body of the pubis and passes horizontally 2. puborectalis is the medial most part of the pubococygeus, forms a U shaped muscular sling that passes posterior to the anorectal junction 3. iliococygeus is the posterior part, poorly developed Functions of levator ani 1. forms a muscular sling for supporting abdominopelvic viscera 2. resists increases in intra – abdominal pressure 3. helps to hold the pelvic viscera in position Levator ani Origin 1. body of the pubis 2. tendinous arch of obturator fascia 3. ischial spine Insertion 1. perineal body 2. coccyx 3. anococcygeal ligament 4. walls of the prostate ( in male ) 5. walls of the vagina ( in female ) 6. rectum 7. anal canal Nerve supply 1. nerve to leavator ani ( branches of S4 2. inferior rectal nerve 3. coccygeal plexus Actions 1
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1. helps to support the pelvic viscera 2. resists increases in intra – abdominal pressure Coccygeus Origin – ischial spine Insertion – inferior end of sacrum Nerve supply – branches of S4 and S5 nerves Actions 1. forms small part of the pelvic diaphragm that supports the pelvic viscera 2. flexes the coccyx Obturator internus Origin 1. pelvic surface of ilium and ischium 2. obturator membrane Insertion – greater trochanter of femur Nerve supply – nerve to obturator internus from sacral plexus ( L5, S1, S2 ) Action – rotates the thigh laterally, assists in holding the head of femur in acetabulum Piriformis Origin 1. pelvis surface of sacrum 2 nd , 3 rd , 4 th segments 2. superior margin of greater sciatic notch 3. sacrotuberous ligament Insertion – greater trochanter of femur Nerve supply – nerve to piriformis from sacral plexus ( ventral rami of S1, S2 ) Actions 1. rotates the thigh laterally 2. abducts the thigh 3. assists in holding the head of femur in acetabulum Pelvic nerves 1. sacral nerves 2. cocygeal nerves 3. pelvic part of autonomic nervous system Lumbosacral trunk 2
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Is thick and corlike, formed by the descending part of L4 unites with the ventral ramus of L5 nerve and joins the sacral plexus Sacral plexus Is located on the posterior wall of the lesser pelvis, closely related to the anterior surface of piriformis muscle The main nerves are 1. sciatic nerve 2. pudendal nerve Sciatic nerve Is the largest and broadest nerve in the body, formed by the ventral rami of L4, L5, S1, S2, S3 It passes through the greater sciatic foramen, inferior to piriformis, to enter the gluteal region It then descends along the posterior aspect of the thigh to supply the back of thigh muscles Pudendal nerve Is the main nerve of the perineum and the chief sensory nerve of the external genitalia
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ANAT 1625 Lecture Notes - Pelvis - 1 Pelvis Pelvic floor Is...

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