Defining the pelvic region Flashcards
What are the four bones that make the pelvis together?
2 innominate bones formed by ilium, ischium + pubis.
Sacrum (formed by fusion of 5 sacral vertebrae)
Coccyx (formed by fusion of 4 coccygeal vertebrae)
Describe the location of the ligaments of the pelvis
Sacroiliac: between sacrum and ilium, has anterior and posterior components.
Sacrococcygeal: between sacrum to coccyx.
Sacrospinous: between ischial spine and sacrum/coccyx.
Sacrotuberous: posterior to sacrospinous; between lateral aspect of sacrum + coccyx onto medial margin of ischial tuberosity.
What is the perineum?
space located at pelvic outlet and inferior to pelvic diaphragm - narrow region between thighs.
Diamond-shaped surface extending from mons pubis (in females) to medial surface of thighs and posteriorly to gluteal folds.
How is the perineum divided?
A transverse line joining the two ischial tuberosities splits the perineum into two triangles: urogenital and anal triangles.
mid point of line defines perineal body which sees convergence of several sphincter and perineal pouch muscles.
Which structures does the deep perineal pouch enclose?
Urethra, vagina
Bulbourethral (Cowper) glands in males
Perineal muscles that act as sphincters e.g. compressor urethrae or urethrovaginal sphincter in females.
Which structures does the superficial perineal pouch enclose?
Urethra, vagina
root of penis
Bartholin glands in females
Perineal muscles that provide support to external genitalia e.g. bulbospongiosus or ischiocavernosus muscles.
What is the pelvic brim formed by?
Promontory + ala of sacrum
Right + left linea terminalis: arcuate line & pectineal line.
What are the borders of the true pelvic cavity?
Posterior – sacrum/coccyx Anterior – pubic symphysis Inferior – pelvic floor Superior – pelvic brim Lateral – obturator internus m
What are the contents of the true pelvic cavity?
Reproductive organs/tracts, bladder, rectum
What is the pelvic musculature composed of?
muscles that line the wall: piriformis and obturator internus.
line the floor: coccygeus, levator ani (iliococcygeus, pubococcygeus and puborectalis).
What are the pelvic floor muscles?
Coccygeal: from ischial spine to inferior end of sacrum and coccyx.
Iliococcygeus: from tendinous arch to annococcygeal body.
Pubococcygeus: from posterior aspect of pubic bone and inserting to coccyx (lateral fibres) or merging with contralateral fibres of the same named muscle (medial fibres).
Puborectalis: a continuous muscle that originates from posterior aspect of pubic bone and slings behind rectum.
What is the blood supply and drainage of the pelvic region?
Arteries - branches of anterior division of internal iliac artery: uterine - uterus vesical - bladder internal pudendal - perineum gonadal from abdominal aorta - gonads obturator – adductor region of thigh Veins: Internal iliac to common iliac veins Gonadal to IVC or L renal vein
What is the innervation to the pelvic region?
Somatic plexuses (L4-Co) subdivided into: lumbosacral (L4-S4) and coccygeal (S4-Co). they function as motor or sensory e.g. sciatic nerve, sup/inf gluteal, pudendal nerve. (L4-5 - femoral and obturator nerves).
Visceral plexuses: paravertebral / prevertebral,
sympathetic / parasympathetic / visceral fibres,
erection / ejaculation - e.g. inferior hypogastric plexus.
What does the lumbosacral trunk consist of?
Superior gluteal, inferior gluteal, sciatic, pudendal
What are the visceral plexuses?
Parasympathetic flow: pelvic splanchnic nerves (S2-4).
Sympathetic flow: sacral sympathetic trunk, superior and inferior hypogastric plexuses.
