Unit 2_Lumbosacral Plexus Flashcards
What are networks of nerves that are going to innervate not only the muscles from the waist down to provide sensory information, but also have responsibilities in our sympathetic and parasympathetic systems?
Lumbosacral Plexus
What do the following structures make up?
Two 12th Ribs
Lumbar Spine
Ilium and Iliac Crest
Iliacus muscle
Psoas Major muscle (insertion - Lesser Trochanter; Iliacus & Psoas Major are 1 degree hip flexors)
Quadratus Lumborum muscle
Posterior body wall
Where do the Lumbosacral nerves originate?
Two 12th Ribs
Lumbar Spine
What is another word for the Ilium?
Coxal bone
What is the most superior aspect of the Ilium?
Iliac Crest
Where does the posterior body wall span down to?
Ilium/Iliac Crest
What muscle lines the interior aspect of the Ilium fossa/concavity?
Iliacus muscle
What muscle runs longitudinally and comes off the vertebral bodies of the posterior body wall?
Psoas Major muscle
What muscle includes the blending of the bellies at the tendon of the Iliacus and Psoas major, which wraps around to insert on the lesser trochanter of the femur?
Iliopsoas muscle
What two muscles help to form the posterior body wall over which will lie the Lumbosacral Plexus?
Iliacus muscle
Psoas Major muscle
What muscle is the primary hip flexor?
Iliopsoas muscle
What muscle spans from the inferior aspect of the 12th rib down to grab onto the Iliac Crest and holds the pelvis in place?
Quadratus Lumborum muscle (QL)
What fascia lines the posterior abdominal wall?
Endoabdominal or transversalis fascia
*Derived from the fascia of the Transverse Abdominis
What fascia is deep to the Transversalis Fascia and supports/protects/insulates the abdominal viscera and the pelvic viscera?
Preperitoneal Fat
*Peritoneal Lining - lines the abdomen & supports the abdominal viscera
What muscle overlies the Quadratus Lumborum and the Ilium?
Psoas Major muscle
What kind of nerves make up the Lumbar Plexus?
Ventral Primary Rami
Where do the majority of the Lumbar Plexus nerves originate and lie right on top of/anterior to?
Quadratus Lumborum muscle
Where do the majority of the Lumbar Plexus nerves originate and lie deep to?
Psoas Major muscle
What is the Lumbar Plexus comprised of?
Ventral Primary Rami (L1-L4 spinal cord segments)
What nerves will network and meet up/diverge and form the peripheral nerves and the cutaneous nerves that will go on to provide information to and from our lower limb?
Ventral Primary Rami (L1-L4 spinal cord segments) of the Lumbar Plexus
What VPR nerve segment sends a slip to join L1 50% of the time?
T12
What is T12 VPR called within the Lumbar Plexus?
Subcostal Nerve (Intercostal Nerve; T12)
What does the L1 VPR bifurcate into within the Lumbar Plexus?
Iliohypogastric Nerve (L1)
Ilioinguinal Nerve (L1)
What muscles do the Iliohypogastric Nerve (L1) provide innervation to?
Abdominal muscles
*“Hypo” below the stomach
What muscles do the Iliohypogastric Nerve (L1) provide sensory information to?
Around the Iliohypogastric region
*“Ilio” around the hip
What muscles does the Ilioinguinal Nerve (L1) provide innervation to?
Deep abdominal muscles
What muscles does the Ilioinguinal Nerve (L1) provide sensory information to?
In and around the groin
What is the nerve that results from L1-L2 VPRs joining together within the Lumbar Plexus?
Genitofemoral Nerve (L1-L2)
What nerve travels on top of Psoas Major?
Genitofemoral Nerve (L1-L2)
What muscles does the Genitofemoral Nerve (L1-L2) provide sensory information to?
Adductor Region
Labia/Scrotum (depending on the sex)
What muscle does the Genitofemoral Nerve (L1-L2) provide innervation to?
Cremaster muscle (males)
*Lives in the skin surrounding the scrotum
What is the nerve that forms from the posterior divisions of L2-L3 within the Lumbar Plexus and pierces the Psoas Major muscle?
Lateral Femoral Cutaneous Nerve (L2-L3)
What area does the Lateral Femoral Cutaneous Nerve (L2-L3) provide sensation to?
Lateral Femur (Lateral Upper Thigh)
What nerve forms from the posterior divisions of L2-L4 within the Lumbar Plexus and presents as a bigger nerve?
Femoral Nerve (L2-L4)
What muscles do the Femoral Nerve (L2-L4) provide sensory/motor information to?
Anterior Thigh muscles (Quadriceps)
What nerve forms from the anterior divisions of the L2-L4 spinal cord segments within the Lumbar Plexus?
Obturator Nerve (L2-L4)
What muscles do the Obturator Nerve (L2-L4) provide sensory and motor information to?
Medial Compartment of the Thigh/Adductor Muscles
*Muscles that bring the thigh back towards the midline
How does the Obturator Nerve (L2-L4) reach the medial compartment of the thigh?
Obturator Foramen
What is a natural opening in the pelvis that allows the Obturator Nerve (L2-L4) to reach the medial compartment of the thigh?
Obturator Foramen
What nerve exists in 9% of the population and forms from the anterior divisions of L3-L4 in the Lumbar Plexus?
Accessory Obturator Nerve (L3-L4)
What nerve provides motor/innervation to the Pectinius muscle?
Accessory Obturator Nerve (L3-L4)
What nerve forms from L4-L5 VPR within the Lumbar Plexus and travels down to the Sacral VPR and create other networks/nerves?
Lumbosacral Trunk (L4-L5)
What is made up of the L4-S4 VPR and includes nerves derived from the Anterior or Posterior Divisions (Branches)?
Sacral Plexus
What connects the L4-L5 VPR from the Lumbar Plexus to S1-S4 VPR of the Sacral Plexus to form more nerves?
Lumbosacral Trunk
What are the muscles of the pelvic floor where the Sacral Plexus nerves develop on top of?
Levator ani muscles
What muscle is deep to the S1-S4 VPR and also lies deep to gluteus maximus muscle?
Piriformis muscle
What nerves combine as a sheath to form the Sciatic nerve?
Common Fibular nerve (L4-S2)
Tibial nerve (L4-S3)
What nerve forms from the anterior divisions from L4, L5, S1-S3 VPR in the Sacral Plexus and is part of the Sciatic nerve?
Tibial nerve (L4-S3)
What nerve forms from the anterior division of the Sacral Plexus to innvervate the Quadratus Femoris muscle that lives in the inferior aspect of the buttock posteriorly?
Nerve to Quadratus Femoris muscle
What nerve forms from the anterior division of the Sacral Plexus to innervate the Obturator internus muscle that lives in the pelvis?
Nerve to Obturator Internus muscle
What nerve forms from the anterior/posterior divisions of the Sacral Plexus to deliver cutaneous information to the posterior femoral region?
Posterior Femoral Cutaneous nerve
What nerve forms from the anterior division of the Sacral Plexus to provide motor to the muscles that help us control bladder/bowel/fecal matter (potty training nerve)?
Pudendal nerve
What nerve is concerning when there’s a lesion/fracture to the sacrum/lower lumbar spine?
Pudendal nerve
What nerves develop from the anterior division of the Sacral Plexus to deliver sensory/motor information to the muscles of the pelvic floor (Levator ani muscles)? I.e., stop the flow of urine
Perineal branch of the 4th sacral nerve
Nerve to levator ani and coccygeus muscle
What nerves form from the posterior division of the Sacral Plexus to control the gluteus muscles and develop around the Piriformis?
Superior gluteal nerve (majority of the glutes)
Inferior gluteal nerve (gluteus maximus)
What nerve forms from the posterior division of the Sacral Plexus to the Piriformis muscle which originates from the anterior aspect of the sacrum to grab onto the femur (greater trochanter)?
Nerve to Piriformis muscle
What nerve forms from the posterior division of the Sacral Plexus to travel to the fibula area and is part of the Sciatic nerve?
Common Fibular nerve (L4-S2)
What is the region that the Sympathetic Nervous System and Parasympathetic Nervous System run through?
Lumbosacral Plexus
What comprises the Sympathetic Nervous System (fight or flight)?
T1-L2
Grey rami communications
White rami communications
What comprises the Parasympathetic Nervous System (rest and digest)?
Cranial and sacral segments S2-S4
