Podcast
Questions and Answers
How many pairs of spinal nerves are present in the human body?
How many pairs of spinal nerves are present in the human body?
Which spinal nerves are categorized as lumbar?
Which spinal nerves are categorized as lumbar?
What type of fibers do the ventral roots contain?
What type of fibers do the ventral roots contain?
Which rami form nerve plexuses in the spinal cord?
Which rami form nerve plexuses in the spinal cord?
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What is the primary function of dorsal roots?
What is the primary function of dorsal roots?
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Which of the following accurately describes the effect of damage to one spinal segment?
Which of the following accurately describes the effect of damage to one spinal segment?
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How are spinal nerves named?
How are spinal nerves named?
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Which plexus is not found in the lumbar region?
Which plexus is not found in the lumbar region?
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What structure do each spinal nerve use to connect with the spinal cord?
What structure do each spinal nerve use to connect with the spinal cord?
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Where do dorsal roots arise from?
Where do dorsal roots arise from?
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Which spinal nerves are involved in the formation of the intercostal nerves?
Which spinal nerves are involved in the formation of the intercostal nerves?
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What is the primary function of the phrenic nerve?
What is the primary function of the phrenic nerve?
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Which plexus is responsible for the innervation of the upper limb?
Which plexus is responsible for the innervation of the upper limb?
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What structure in the brachial plexus serves the front and back of the upper limb?
What structure in the brachial plexus serves the front and back of the upper limb?
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Which nerve in the brachial plexus is responsible for innervating essentially all extensor muscles?
Which nerve in the brachial plexus is responsible for innervating essentially all extensor muscles?
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Which nerve supplies the flexor carpi ulnaris muscle?
Which nerve supplies the flexor carpi ulnaris muscle?
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The cervical plexus is formed by the ventral rami of which spinal nerves?
The cervical plexus is formed by the ventral rami of which spinal nerves?
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Which of the following nerves is NOT a major branch of the brachial plexus?
Which of the following nerves is NOT a major branch of the brachial plexus?
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What does the musculocutaneous nerve primarily innervate?
What does the musculocutaneous nerve primarily innervate?
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Which structure in the brachial plexus is formed from five ventral rami?
Which structure in the brachial plexus is formed from five ventral rami?
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Which spinal nerves are involved in the formation of the lumbar plexus?
Which spinal nerves are involved in the formation of the lumbar plexus?
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What is the primary function of the lumbar plexus?
What is the primary function of the lumbar plexus?
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Which nerve is the major nerve of the sacral plexus?
Which nerve is the major nerve of the sacral plexus?
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What two nerves comprise the sciatic nerve?
What two nerves comprise the sciatic nerve?
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Which spinal nerve does not participate in dermatomes?
Which spinal nerve does not participate in dermatomes?
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What is a dermatome?
What is a dermatome?
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Which area is not served by the sacral plexus?
Which area is not served by the sacral plexus?
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The obturator nerve is primarily associated with which plexus?
The obturator nerve is primarily associated with which plexus?
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Which statement about dermatomes is true?
Which statement about dermatomes is true?
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Which nerves innervate the thigh and abdominal wall?
Which nerves innervate the thigh and abdominal wall?
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Study Notes
Spinal Nerves
- 31 pairs of mixed nerves arising from the spinal cord
- Supply all parts of the body except the head.
- Named according to their point of issue:
- 8 cervical (C1-C8)
- 12 thoracic (T1-T12)
- 5 Lumbar (L1-L5)
- 5 Sacral (S1-S5)
- 1 Coccygeal (C0)
- Connect to the spinal cord via two medial roots
- Each root forms a series of rootlets that attach to the spinal cord
- Ventral roots arise from the anterior horn and contain motor (efferent) fibers
- Dorsal roots arise from sensory neurons in the dorsal root ganglion and contain sensory (afferent) fibers
Nerve Plexuses
- Ventral rami, except those of T2-T12, form interlacing nerve networks called plexuses
- Found in the cervical, brachial, lumbar, and sacral regions
- Each resulting branch of a plexus contains fibers from several spinal nerves
Spinal Nerve Innervation: Back, Anterolateral Thorax, and Abdominal Wall
- The back is innervated by dorsal rami
- The thorax is innervated by ventral rami T1-T12 as intercostal nerves
- Intercostal nerves supply muscles of the ribs, anterolateral thorax, and abdominal wall
Cervical Plexus
- Formed by ventral rami of C1-C4
- Most branches are cutaneous nerves of the neck, ear, back of head, and shoulders
- Most important nerve is the phrenic nerve
- The phrenic nerve is the major motor and sensory nerve of the diaphragm
Brachial Plexus
- Formed by C5-C8 and T1 (C4 and T2 may also contribute)
- Gives rise to nerves that innervate the upper limb
- Four major branches:
- Roots – five ventral rami (C5-T1)
- Trunks – upper, middle, and lower, which form divisions
- Divisions – anterior and posterior serve the front and back of the limb
- Cords – lateral, medial, and posterior fiber bundles
Brachial Plexus: Nerves
- Axillary – innervates the deltoid and teres minor
- Musculocutaneous – sends fibers to the biceps brachii and brachialis
- Median – branches to most of the flexor muscles of the arm
- Ulnar – supplies the flexor carpi ulnaris and part of the flexor digitorum profundus
- Radial – innervates essentially all extensor muscles
Lumbar Plexus
- Arises from L1-L4 and innervates the thigh, abdominal wall, and related muscles
- Major nerves are the femoral and the obturator
Sacral Plexus
- Arises from L4-S4 and serves the buttock, lower limb, pelvic structures, and related sacral areas
- Major nerve is the sciatic, the longest and thickest nerve of the body
- The sciatic is actually composed of two nerves: the tibial and the common fibular nerves
Dermatomes
- A dermatome is the area of skin innervated by the cutaneous branches of a single spinal nerve
- All spinal nerves except C1 participate in dermatomes
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Description
Test your knowledge on spinal nerves and their networks with this quiz. Explore the anatomy and functions of the 31 pairs of spinal nerves, their connections, and the various plexuses formed by the ventral rami. This quiz is ideal for biology and anatomy students.
