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Questions and Answers
Which artery primarily supplies the iliacus and psoas major muscles?
Which artery is considered the largest branch of the anterior trunk and supplies the buttock and posterior thigh?
What is the correct anatomical relationship of the superior gluteal artery?
Where does the obturator artery primarily travel within the pelvis?
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Which statement accurately describes the location of the internal pudendal artery in relation to the inferior gluteal artery?
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Which muscles are part of the Levator Ani?
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What is the primary action of the Levator Ani muscles?
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Which of the following nerves innervates the Levator Ani muscles?
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Where does the Sciatic nerve originate?
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The (Ischio) Coccygeus muscle plays which role?
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Which artery is the terminal branch of the common iliac artery?
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What does the pudendal nerve primarily supply?
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Which of the following muscles is NOT part of the pelvic diaphragm?
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Which artery is most likely to be located closer to the ischial spine than the inferior gluteal artery?
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Which artery passes medially in front of the sacral ventral rami and provides spinal branches through the sacral foramina?
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What is the largest branch of the posterior trunk that supplies the gluteal muscles?
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Which artery runs alongside the obturator nerve and vein through the obturator foramen?
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Which statement correctly describes the innervation of the pelvic diaphragm?
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What is the main function of the pelvic diaphragm?
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Which nerves specifically innervate the ischio coccygeus muscle?
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What are the three muscles that comprise the Levator Ani?
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What role does the pudendal nerve play in pelvic functioning?
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Which branch arises from the lumbosacral trunk?
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What is the primary action of the ischio coccygeus muscle?
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Which artery is the terminal branch of the internal iliac artery?
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Which structure does NOT penetrate the pelvic diaphragm?
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Study Notes
Pelvic Diaphragm
- The pelvic diaphragm is also known as the pelvic floor, made up of two levator ani muscles and two (ischio) coccygeus muscles.
- It supports the abdominal viscera and separates the pelvic cavity from the perineum.
- The rectum, urethra, and vagina penetrate the diaphragm.
Levator Ani Muscles
- The levator ani muscle is made of three muscles:
- Puborectalis
- Pubococcygeus
- Iliococcygeus
- Innervated by the perineal branches of the S3 and S4 ventral rami.
- Actions: Supports pelvic viscera, resists increased intra-abdominal pressure (coughing, lifting).
Ischiococcygeus Muscle
- Forms the pelvic diaphragm with the levator ani muscles.
- Innervated by branches of the S4 and S5 ventral rami.
- Actions: Supports the coccyx, pulls it anteriorly, assists levator ani muscles.
Nerves of the Pelvis
- The lumbosacral plexus is formed by the descending portion of the L4 ventral ramus joining with the L5 ventral ramus.
- The lumbosacral trunk passes anterior to the ala of the sacrum and joins the ventral rami of S1, S2, S3, S4.
Branches of Lumbosacral Plexus
- Sciatic nerve: Ventral rami L4-S3. Supplies the posterior thigh muscles, lower leg, and foot.
- Pudendal nerve: Ventral rami S2-S4. Exits the greater sciatic foramen, reenters through the lesser sciatic foramen. Supplies the external urethral sphincter, anal sphincter, and partially the levator ani. It provides sensation to the external genitalia.
Arteries of the Pelvis
- The internal iliac artery is a terminal branch of the common iliac artery.
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Branches of the internal iliac artery:
- Iliolumbar artery: Ascends laterally, supplying the iliacus, psoas major, and quadratus lumborum muscles.
- Superior gluteal artery: Largest branch, runs between the lumbosacral trunk (L4,5) and S1. Supplies the piriformis, obturator internus, and gluteal muscles.
- Lateral sacral artery: Runs medially, anterior to the sacral ventral rami, giving off spinal branches through the sacral foramina.
- Obturator artery: Runs on the lateral wall of the pelvis, with the obturator nerve and vein, through the obturator foramen.
- Inferior gluteal artery: Largest branch of the anterior trunk, supplying the buttock and posterior thigh.
- Internal pudendal artery: Usually closer to the ischial spine than the inferior gluteal artery.
Pelvic Diaphragm
- The pelvic diaphragm, also known as the pelvic floor, is comprised of two levator ani muscles and two (ischio)coccygeus muscles.
- It plays a crucial role in supporting abdominal viscera and separates the pelvic cavity from the perineum.
- The rectum, urethra, and vagina pass through the pelvic diaphragm.
Levator Ani Muscles
- The levator ani muscle is made up of three individual muscles:
- Puborectalis: This muscle helps control defecation by constricting the rectum.
- Pubococcygeus: This muscle supports the pelvic organs and helps with urinary control.
- Iliococcygeus: This muscle helps to support the pelvic viscera and helps with defecation.
- The levator ani muscles are innervated by the perineal branches of the S3 and S4 ventral rami.
- Their functions include supporting pelvic viscera, resisting increased intra-abdominal pressure during activities like coughing and lifting heavy objects.
- The action of the levator ani is directly related to maintaining continence and supporting pelvic organs.
(Ischio)Coccygeus Muscle
- The (ischio)coccygeus muscle contributes to the pelvic diaphragm along with the levator ani muscles.
- It receives innervation from branches of the S4 and S5 ventral rami.
- Its primary function is to support the coccyx, pulling it anteriorly, and assisting the levator ani muscles in maintaining pelvic floor integrity.
Lumbosacral Plexus
- The lumbosacral plexus is a network of nerves that originates in the lumbar and sacral regions.
- It plays a vital role in innervating the lower limbs and pelvic region.
- The descending portion of the L4 ventral ramus combines with the L5 ventral ramus to form the lumbosacral trunk.
- This trunk travels anterior to the ala of the sacrum and joins the ventral rami of S1, S2, S3, and S4 to form the lumbosacral plexus.
Branches of the Lumbosacral Plexus
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Sciatic Nerve: This nerve originates from the ventral rami of L4-S3 and supplies the posterior thigh muscles, lower leg, and foot.
- The sciatic nerve has two main branches:
- Tibial nerve: Innervates muscles in the posterior compartment of the leg and plantar muscles of the foot.
- Common peroneal nerve: Innervates muscles in the anterior and lateral compartments of the leg.
- The sciatic nerve has two main branches:
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Pudendal Nerve: This nerve originates from the ventral rami of S2-S4 and is responsible for innervating the external urethral sphincter, anal sphincter, and levator ani muscles.
- It also provides sensation to the external genitalia.
- This nerve exits through the greater sciatic foramen, then re-enters through the lesser sciatic foramen.
Arteries of the Pelvis
- Internal Iliac Artery: This is a terminal branch of the common iliac artery, the other terminal branch being the external iliac artery.
- Iliolumbar Artery: This artery ascends laterally and supplies the iliacus, psoas major, and quadratus lumborum muscles.
- Superior Gluteal Artery: This is the largest branch of the internal iliac artery and runs between the lumbosacral trunk (L4, L5) and S1. It supplies the piriformis, obturator internus, and gluteal muscles.
- Lateral Sacral Artery: This artery courses medially, anterior to the sacral ventral rami, and provides spinal branches through the sacral foramina.
- Obturator Artery: This artery runs along the lateral wall of the pelvis, accompanying the obturator nerve and vein, and passes through the obturator foramen.
Arteries of the Pelvis (Continued)
- Inferior Gluteal Artery: This artery is the largest branch of the anterior trunk of the internal iliac artery, supplying the buttock and posterior thigh muscles.
- Internal Pudendal Artery: This artery runs closer to the ischial spine compared to the inferior gluteal artery and is involved in blood supply to the perineum and external genitalia.
- The internal pudendal artery supplies the levator ani and other muscles related to the pelvic floor.
Summary
- The levator ani muscles (puborectalis, pubococcygeus, iliococcygeus) are the major components of the pelvic diaphragm, which acts as a supportive structure for pelvic organs and contributes to continence.
- The lumbosacral plexus branches (sciatic nerve and pudendal nerve) innervate the muscles of the pelvic floor and lower limbs, allowing for coordinated movement and sensation.
- The internal iliac artery branches provide the pelvic floor muscles and surrounding structures with blood supply, ensuring their proper function.
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Description
Explore the anatomy and functions of the pelvic diaphragm, including the levator ani and ischiococcygeus muscles. This quiz covers their structure, innervation, and roles in supporting pelvic organs. Test your knowledge on the critical functions these muscles perform!
