Podcast
Questions and Answers
Which of the following muscles is considered an extrinsic muscle of the back?
Which of the following muscles is considered an extrinsic muscle of the back?
What is the primary function of the erector spinae muscle group?
What is the primary function of the erector spinae muscle group?
Which nerve primarily innervates the intrinsic muscles of the back?
Which nerve primarily innervates the intrinsic muscles of the back?
Which of these muscles is NOT part of the deep layer of intrinsic back muscles?
Which of these muscles is NOT part of the deep layer of intrinsic back muscles?
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The serratus posterior superior and inferior muscles are classified as part of which muscle group?
The serratus posterior superior and inferior muscles are classified as part of which muscle group?
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What is the role of the transversospinalis muscles?
What is the role of the transversospinalis muscles?
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Which of the following spinal column components is not a part of the back?
Which of the following spinal column components is not a part of the back?
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Which muscles are innervated by the spinal accessory nerve (CN XI)?
Which muscles are innervated by the spinal accessory nerve (CN XI)?
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Which structure is a connective tissue that attaches the spinal dural sac to the coccyx dorsum?
Which structure is a connective tissue that attaches the spinal dural sac to the coccyx dorsum?
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What type of fibers are exclusively found in the dorsal root of a spinal nerve?
What type of fibers are exclusively found in the dorsal root of a spinal nerve?
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Which of the following best describes a spinal cord segment?
Which of the following best describes a spinal cord segment?
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Where are the cell bodies of sensory neurons located in a spinal nerve?
Where are the cell bodies of sensory neurons located in a spinal nerve?
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What is the primary structure formed by the union of the dorsal and ventral roots?
What is the primary structure formed by the union of the dorsal and ventral roots?
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Through which opening(s) do spinal nerves typically exit the vertebral canal?
Through which opening(s) do spinal nerves typically exit the vertebral canal?
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Which of the following is supplied by the ventral rami of spinal nerves?
Which of the following is supplied by the ventral rami of spinal nerves?
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Which area is NOT supplied by a nerve plexus??
Which area is NOT supplied by a nerve plexus??
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What is the typical termination point of the adult spinal cord?
What is the typical termination point of the adult spinal cord?
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Which of the following best describes the 'cauda equina'?
Which of the following best describes the 'cauda equina'?
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How many pairs of spinal nerves are located in the thoracic region?
How many pairs of spinal nerves are located in the thoracic region?
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Unlike thoracic and lumbar spinal nerves, how do cervical spinal nerves exit the intervertebral foramina?
Unlike thoracic and lumbar spinal nerves, how do cervical spinal nerves exit the intervertebral foramina?
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What anatomical feature explains why spinal nerve roots in the lumbar region extend further down the vertebral canal than the spinal cord itself?
What anatomical feature explains why spinal nerve roots in the lumbar region extend further down the vertebral canal than the spinal cord itself?
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During embryonic development, at what stage does the spinal cord initially extend the entire length of the vertebral canal?
During embryonic development, at what stage does the spinal cord initially extend the entire length of the vertebral canal?
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A patient has a spinal cord injury at a level corresponding to the T12 vertebra. Which spinal nerves will still function normally?
A patient has a spinal cord injury at a level corresponding to the T12 vertebra. Which spinal nerves will still function normally?
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In the newborn, where does the conus medullaris usually terminate?
In the newborn, where does the conus medullaris usually terminate?
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Which type of nerve fibers are found in the dorsal roots?
Which type of nerve fibers are found in the dorsal roots?
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What is the primary function of the ventral roots?
What is the primary function of the ventral roots?
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Where are the cell bodies of sensory nerves located?
Where are the cell bodies of sensory nerves located?
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Which dermatome is associated with the region of the nipple on the thorax?
Which dermatome is associated with the region of the nipple on the thorax?
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Which component of the nervous system is responsible for transmitting impulses to smooth muscles and glands?
Which component of the nervous system is responsible for transmitting impulses to smooth muscles and glands?
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Which structure contains the cell bodies for general visceral afferent fibers?
Which structure contains the cell bodies for general visceral afferent fibers?
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What type of sensation do general somatic afferent fibers primarily transmit?
What type of sensation do general somatic afferent fibers primarily transmit?
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What is the primary purpose of a lumbar spinal tap?
What is the primary purpose of a lumbar spinal tap?
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Which spinal nerve component has its cell bodies located in the ventral horn?
Which spinal nerve component has its cell bodies located in the ventral horn?
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Which of the following spaces is considered a 'potential space' in relation to the spinal meninges?
Which of the following spaces is considered a 'potential space' in relation to the spinal meninges?
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What type of neurons transmit impulses from the central nervous system to smooth muscles, cardiac muscle, and glands?
What type of neurons transmit impulses from the central nervous system to smooth muscles, cardiac muscle, and glands?
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In which region of the vertebral column is it important to perform a lumbar spinal tap below the conus medullaris?
In which region of the vertebral column is it important to perform a lumbar spinal tap below the conus medullaris?
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What is a common indication for performing a lumbar spinal puncture?
What is a common indication for performing a lumbar spinal puncture?
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Where are the cell bodies of presynaptic neurons located in the autonomic nervous system?
Where are the cell bodies of presynaptic neurons located in the autonomic nervous system?
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What primary function does the epidural block serve?
What primary function does the epidural block serve?
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Which part of the meninges is the most outer layer of spinal meninges?
Which part of the meninges is the most outer layer of spinal meninges?
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What do the general visceral afferent (GVA) fibers primarily transmit?
What do the general visceral afferent (GVA) fibers primarily transmit?
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Which structure is crucial for performing caudal epidural anesthesia?
Which structure is crucial for performing caudal epidural anesthesia?
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Which space is the potential space between the dura mater and the arachnoid mater?
Which space is the potential space between the dura mater and the arachnoid mater?
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Where are the cell bodies of sensory neurons located in relation to the spinal cord?
Where are the cell bodies of sensory neurons located in relation to the spinal cord?
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The spinal dural sac is formed by which layer of the meninges?
The spinal dural sac is formed by which layer of the meninges?
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Which of the following best describes the subarachnoid space?
Which of the following best describes the subarachnoid space?
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What is detected by proprioceptive sensations transmitted by general somatic afferent neurons?
What is detected by proprioceptive sensations transmitted by general somatic afferent neurons?
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What is the primary function of the epidural space?
What is the primary function of the epidural space?
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Study Notes
Back I: Muscles, Spinal Cord, Meninges
- The back is comprised of skin, subcutaneous tissue, muscles, vertebral column, joints, ligaments, intervertebral discs, vertebral canal, spinal cord and meninges
- Back muscles are categorized into superficial and deep groups
- Superficial muscles include latissimus dorsi, trapezius, rhomboids, and levator scapulae. These muscles connect upper limbs to the trunk, and control limb movements
- Intermediate muscles include serratus posterior superior and inferior. These are accessory respiratory muscles, lying deep to the rhomboid and latissimus dorsi muscles.
Back Muscles: Intermediate Layers
- Erector spinae muscles include iliocostalis, longissimus, and spinalis, acting as chief trunk extensors.
- They are divided into three columns: iliocostalis (lateral), longissimus (median), and spinalis (medial)
- Deep back muscles consist of semispinalis muscles (extend and rotate), multifidus (stabilize), and rotators (stabilize, extend, rotate).
Deep Back Muscles
- The superficial layer includes splenius capitis and cervicis muscles, holding and covering deep neck muscles in position.
- The intermediate layer contains erector spinae muscle group which is a chief extensor of the trunk and divided into 3 columns: iliocostalis (lateral), longissimus (median), spinalis (medial)
- Deep layer includes transversospinalis muscles: semispinalis (extend and rotate), multifidus (stabilize), and rotators (stabilize, extend and rotate).
- All intrinsic back muscles are innervated by dorsal rami of spinal nerves. They maintain posture, control movements of the vertebral column and work with the muscles of the anterolateral abdominal wall to produce movements of the trunk.
Spinal Cord
- The spinal cord continues into the medulla oblongata.
- The end of the spinal cord is called the conus medullaris, situated at the level of L1-L2 vertebrae in adults.
- The spinal cord has enlargements for the upper (cervical) and lower (lumbosacral) limbs.
- The cervical enlargement (C4-T1) supplies nerves to the upper limb.
- The lumbosacral enlargement (T11-S1) supplies nerves to the lower limb.
- There are 31 pairs of spinal nerves.
- Cauda equina (horse tail) refers to the nerve roots branching off from the lumbosacral part of the spinal cord that continue inferiorly within the lumbar cistern.
Differential Growth of Vertebral Column vs. Spinal Cord
- During fetal development, the vertebral column grows faster than the spinal cord which results in the spinal cord ending at vertebrae levels L1-L2 in adults.
- Nerve roots (lumbar, sacral, coccygeal) extend to reach their appropriate vertebral levels.
- In newborns, the conus medullaris is at around L2-L3, but can vary.
- In adults, the conus medullaris ends opposite the intervertebral disc between the L1-L2 vertebrae.
Spinal Nerves
- Spinal nerves exit the vertebral column through intervertebral foramina.
- Cervical spinal nerves (C1-C8) usually exit above their corresponding vertebrae (except C8)
- Spinal nerves below the cervical region (thoracic through sacral) exit below their corresponding vertebrae..
Spinal Meninges
- The spinal meninges are three membranes that surround the spinal cord: dura mater, arachnoid mater, and pia mater.
- Dura mater is the outermost tough, fibrous, and elastic membrane that encloses the spinal dural sac.
- Arachnoid mater is a delicate, avascular membrane between the dura mater and pia mater. It's characterized by a potential subdural space.
- Subarachnoid space lies between the arachnoid and pia mater; contains cerebrospinal fluid (CSF), and the enlargement of this space between L1 and S2 is called lumbar cistern.
- Pia mater is the innermost layer, directly covering the spinal cord. Lateral extensions form denticulate ligaments. The inferior extension of this membrane is the filum terminale.
Spinal Cord and Spinal Nerves: Components
- Spinal nerves contain both sensory and motor fibers.
- General somatic afferent (GSA): Transmit sensory information (pain, temperature, touch, pressure, proprioception) from the body to the CNS. Cell bodies lie in the dorsal root ganglia (DRG) and enter the spinal cord through dorsal roots.
- General somatic efferent (GSE): Transmit motor impulses from CNS to skeletal muscles. Cell bodies are in the ventral horn of the spinal cord.
- General visceral afferent (GVA): Transmit subconscious sensory information (stretch, pain, etc.) from visceral organs to the CNS. Cell bodies are in the dorsal root ganglia (DRG).
- General visceral efferent (GVE): Transmit motor impulses from CNS to smooth muscles, cardiac muscle, and glands. These nerve fibers are part of the autonomic nervous system. Presynaptic fibers are in the lateral horn of the spinal cord, and postsynaptic fibers are in an autonomic ganglion.
- Spinal nerves divide into a dorsal primary ramus and ventral primary ramus. The dorsal ramus usually supplies the deep muscles, and the skin of the back. The ventral primary ramus typically provides innervation to the lateral body wall, limbs and associated structures.
Dermatomes
- Dermatomes are specific segments of skin supplied by a single spinal nerve, showing relatively consistent patterns throughout the body.
- Dermatomes are often used in clinical examinations to assess nerve function or damage.
Important Clinical Procedures
- Spinal needle insertion, for example when performing a lumbar spinal tap (spinal puncture): this is done at a specific level usually the lumbar region (between the L3-L4 vertebrae) to avoid the spinal cord.
- Epidural blocks, given for pain control e.g., in the lumbar region (trans-sacral area): local anesthetic is injected for pain management purposes.
Additional Information (based on questions from the listed questions)
- Nerves connected to the erector spinae muscles: dorsal rami of spinal nerves.
- Two superficial back muscles: latissimus dorsi, and trapezius.
- Cell bodies located in the DRG: sensory neurons.
- Cauda equina: nerve roots branching off from the spinal cord in the lumbar and sacral regions
- Spinal nerves that form the brachial plexus: C5-T1.
- Motor/efferent nerves utilize two neuron pathways (one pre-synaptic and postsynaptic).
- Denticulate ligament: fibrous tissue supporting and anchoring the spinal cord within the duralsac.
- Ventral roots contain motor neurons.
- Spinal cord ending level: L1-L2.
- Potential meningeal space: epidural, subdural, and subarachnoid.
- Filum terminale parts: internum and externum
- How spinal nerve C5 leaves the vertebral canal: intervertebral foramen associated with the nerve root.
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Description
Test your knowledge on the anatomy of back muscles and the spinal nerve system. This quiz covers extrinsic and intrinsic muscle groups, innervation, and spinal cord components. Perfect for students in anatomy or health sciences.
