Sacral Plexus Anatomy Quiz
18 Questions
1 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

Which nerve is directly responsible for innervating the piriformis muscle?

  • Nerve to Obturator Internus
  • Nerve to Quadratus Femoris
  • Nerve to Piriformis (correct)
  • Inferior gluteal nerve
  • What is the primary path of the nerve to Obturator Internus after it exits the pelvis?

  • It exits through the lesser sciatic foramen.
  • It loops around the iliolumbar ligament.
  • It passes under the piriformis muscle.
  • It directly innervates the obturator internus muscle. (correct)
  • From which spinal segments does the Nerve to Quadratus Femoris originate?

  • L3 to L5
  • S1 to S3
  • L4 to S1 (correct)
  • L5 to S2
  • What distinguishes the second course of nerves from the sacral plexus?

    <p>Nerves remain within the pelvis to innervate pelvic structures.</p> Signup and view all the answers

    Which course of nerves involves traveling through the lesser sciatic foramen?

    <p>Third Course</p> Signup and view all the answers

    What is the primary function of the sacral plexus?

    <p>Supplies the skin and muscles of the pelvis and lower limb</p> Signup and view all the answers

    Which spinal nerves contribute to the formation of the sacral plexus?

    <p>S1, S2, S3, S4, and lumbar L4, L5</p> Signup and view all the answers

    Which nerve is primarily responsible for innervating the gluteus maximus?

    <p>Inferior Gluteal Nerve</p> Signup and view all the answers

    What components make up the sciatic nerve?

    <p>Common fibular and tibial components</p> Signup and view all the answers

    Which nerve provides sensory innervation to the perineum?

    <p>Pudendal Nerve</p> Signup and view all the answers

    Which of the following muscles is NOT innervated by the tibial component of the sciatic nerve?

    <p>Biceps femoris (short head)</p> Signup and view all the answers

    Which nerve originates from the S2 and S3 spinal roots and innervates the inferior gluteal region?

    <p>Perforating Cutaneous Nerve</p> Signup and view all the answers

    What structure is the sacral plexus located anterior to?

    <p>Piriformis muscle</p> Signup and view all the answers

    Which of the following nerves emerges anteriorly from the psoas major muscle?

    <p>Genitofemoral nerve</p> Signup and view all the answers

    From which spinal roots does the ilioinguinal nerve originate?

    <p>L1 only</p> Signup and view all the answers

    Which of the following statements regarding the lumbar plexus is incorrect?

    <p>All nerves emerge laterally from the psoas major muscle.</p> Signup and view all the answers

    Which mnemonic helps identify the originating roots for the nerves of the lumbar plexus?

    <p>2 from 1, 2 from 2, 2 from 3</p> Signup and view all the answers

    Which of the following nerves primarily innervates the anterior compartment muscles of the thigh?

    <p>Femoral nerve</p> Signup and view all the answers

    Study Notes

    Sacral Plexus Anatomy

    • The sacral plexus is a network of nerve fibers supplying the skin and muscles of the pelvis and lower limb.
    • Located on the posterior pelvic wall, anterior to the piriformis muscle.
    • Formed from the anterior rami of sacral spinal nerves S1, S2, S3, and S4.
    • Receives contributions from lumbar spinal nerves L4 and L5, forming the lumbosacral trunk.
    • Spinal nerves S1 to S4 form the sacral plexus's foundation.
    • Each nerve branches into anterior and posterior rami.
    • Anterior fibers of S1, S2, S3, and S4 emerge through anterior sacral foramina.
    • Joining the fourth and fifth lumbar roots forms the lumbosacral trunk, descending into the pelvis.
    • The sacral plexus is located on the anterior surface of the piriformis muscle.

    Major Nerves of the Sacral Plexus

    • Superior Gluteal Nerve: originates from L4, L5, and S1; innervates gluteus minimus, gluteus medius, and tensor fasciae latae.
    • Inferior Gluteal Nerve: originates from L5, S1, and S2; innervates gluteus maximus.
    • Sciatic Nerve: the largest nerve; derived from L4 to S3; composed of common fibular and tibial components.
      • Common Fibular Component: formed from dorsal divisions of L4 to S2; innervates the short head of biceps femoris, anterior and lateral leg muscles, and extensor digitorum brevis.
      • Tibial Component: formed from ventral divisions of L4 to S3; innervates all posterior thigh muscles except the short head of biceps femoris, hamstring portion of adductor magnus, and posterior leg and foot muscles.
    • Posterior Femoral Cutaneous Nerve: originates from S1, S2, and S3; innervates skin of the posterior thigh and leg, and perineum.
    • Pudendal Nerve: originates from S2, S3, and S4; innervates perineal skeletal muscles (external urethral sphincter, external anal sphincter, and levator ani), and provides sensory innervation to the penis/clitoris and perineal skin.

    Smaller Branches of the Sacral Plexus

    • Perforating Cutaneous Nerve: originates from S2 and S3; innervates inferior gluteal skin; pierces the sacro-tuberous ligament.
    • Nerve to Piriformis: formed from S2 (sometimes S1); innervates the piriformis muscle directly.
    • Nerve to Obturator Internus: originates from L5 to S2; exits the pelvis via greater sciatic foramen, loops around sacrospinous ligament, re-enters via the lesser sciatic foramen to innervate obturator internus and superior gemellus.
    • Nerve to Quadratus Femoris: originates from L4 to S1; exits the pelvis via greater sciatic foramen inferior to the piriformis; innervates quadratus femoris and inferior gemellus.

    Nerve Courses

    • Nerves from the sacral plexus follow three courses:
      • First Course: leave the pelvis through the greater sciatic foramen, entering the gluteal region of the lower limb.
      • Second Course: remain within the pelvis, innervating pelvic muscles, organs, and perineum.
      • Third Course: leave the greater sciatic foramen, loop around the sacrospinous ligament, re-entering via the lesser sciatic foramen to supply lateral pelvic and perineal structures.

    Lumbar Plexus

    • The lumbar plexus is formed from the anterior rami of L1 to L4 and receives fibers from T12.
    • Formed within the psoas major muscle.
    • Mnemonic "I twice get laid on Fridays" helps remember six main nerves:
      • Iliohypogastric
      • Ilioinguinal
      • Genitofemoral
      • Lateral Femoral Cutaneous
      • Obturator
      • Femoral
    • All nerves except genitofemoral and obturator emerge from the lateral aspect of the psoas major muscle.
    • The genitofemoral nerve emerges anteriorly from the psoas major muscle, splitting into genital and femoral branches.
    • The obturator nerve emerges medial to the psoas major muscle.

    Nerve Roots

    • Mnemonic "2 from 1, 2 from 2, 2 from 3" helps determine nerve root origins:
    • "2 from 1": Iliohypogastric nerve originates from L1, Ilioinguinal nerve originates from L1.
    • "2 from 2": Genitofemoral nerve originates from L1 and L2, Lateral femoral cutaneous nerve originates from L2 and L3.
    • "2 from 3": Femoral nerve originates from L2, L3, and L4, Obturator nerve originates from L2, L3, and L4.

    Other Points:

    • The subcostal nerve (branch of T12) contributes to the lumbar plexus.
    • The accessory obturator nerve is not always present, originating from L3 and L4.
    • Muscular branches of the femoral nerve innervate the psoas and iliacus muscles.

    Innervation

    • Obturator nerve: Innervates the medial compartment muscles of the thigh.
    • Femoral nerve: Innervates the anterior compartment muscles of the thigh.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Description

    Test your knowledge on the anatomy of the sacral plexus, including its formation, location, and major nerves. This quiz covers details on the nerve fibers that supply the pelvis and lower limb. See how well you understand the intricate network vital for movement and sensation in these areas.

    More Like This

    1. Lower Limb Overview
    15 questions

    1. Lower Limb Overview

    DedicatedTurkey avatar
    DedicatedTurkey
    Pneumonectomy Elisha 18
    70 questions
    Lumbar and Sacral Plexus - L3
    44 questions
    Anatomía Plexo Braquial y Lumbosacro
    42 questions
    Use Quizgecko on...
    Browser
    Browser