Questions and Answers
What is the origin of the nerve that innervates the latissimus dorsi muscle?
Which muscle is innervated by the dorsal scapular nerve?
What is the source of the arterial supply to the intermediate back muscles?
What is the primary function of the ventral rami of spinal nerves?
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What is the term for the area of skin supplied by a particular spinal nerve segment?
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Which nerve innervates the serratus posterior superior muscle?
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Which muscle is innervated by the thoracodorsal nerve?
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Which of the following nerves does NOT supply the rhomboid muscles?
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What is the source of the arterial supply to the superficial back muscles?
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What is the term for the area of skin supplied by a single spinal nerve?
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Which muscle is not innervated by the dorsal scapular nerve?
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What is the term for the branches of spinal nerves that supply the skin?
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Which of the following statements is TRUE about the dorsal rami of spinal nerves?
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What is the term for a network of nerves formed by the union of ventral rami of spinal nerves?
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Which of the following spinal nerves DOES NOT contribute to the formation of the brachial plexus?
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What is the primary function of the sensory/afferent neurons in spinal nerves?
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Which artery supplies the trapezius muscle?
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What is the innervation of the latissimus dorsi muscle?
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Which nerve plexus innervates the superficial back muscles such as rhomboids?
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What is the source of arterial supply to the serratus posterior superior and inferior muscles?
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Which artery changes its name to the axillary artery?
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What is the venous drainage of the back muscles?
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Which nerve innervates the skin of the back?
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Which muscle is supplied by the thoracodorsal artery?
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Which muscle is supplied by the dorsal scapular artery?
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Which nerve supplies the latissimus dorsi muscle?
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Which intercostal space is the triangle of auscultation located at?
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What is the function of the serratus posterior inferior muscle?
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What is the origin of the dorsal scapular nerve?
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Which reference line is used to locate the triangle of auscultation?
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What is the boundary of the triangle of auscultation?
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What is the direction of rotation produced by the rhomboids on the scapula?
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Which nerve supplies the trapezius muscle?
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What is the source of innervation for the superficial back muscles?
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What is the function of the anterior rami of spinal nerves in relation to the trapezius muscle?
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What is the relationship between the levator scapulae and rhomboid muscles to the trapezius?
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What is the consequence of atrophy of the right trapezius muscle?
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How many pairs of spinal nerves are there?
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What is the origin of the accessory nerve that innervates the trapezius muscle?
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Study Notes
Innervation of Extrinsic Back Muscles + Skin
- Spinal nerves (SN) originate from the spinal cord and contain both motor (efferent) neurons and sensory/afferent neurons.
- SN divides into dorsal and ventral rami.
Key Concept: Spinal Nerves
- Ventral rami innervate skin, mm, joints of limbs, and anterolateral trunk.
- Dorsal rami innervate skin and deep mm of back (excluding superficial back mm).
Innervation of Superficial Back Muscles
- Latissimus dorsi is innervated by thoracodorsal n. (C6, 7, 8).
- Levator scapulae, rhomboid major, and rhomboid minor are innervated by dorsal scapular n. (C5).
Innervation of Intermediate Back Muscles
- Intercostal nerves originate from ventral rami of thoracic spinal nerves.
- Serratus posterior superior is innervated by T2-T5 intercostal nerves.
- Serratus posterior inferior is innervated by T9-T12 intercostal and subcostal nerves.
Dermatomes
- A dermatome is the area of skin supplied by a particular spinal nerve segment.
- Cutaneous branches (touch, pain, etc.) vary and overlap.
Arterial Supply to Superficial Back
- Superficial back muscles are supplied by branches from the subclavian artery.
- Intermediate back muscles are supplied by branches directly from the aorta.
Arterial Supply to Superficial Back Muscles
- Trapezius is supplied by a superficial branch of the transverse cervical artery.
- Rhomboids + levator scapulae are supplied by the dorsal scapular artery.
- Latissimus dorsi is supplied by the thoracodorsal artery (branch of subscapular artery).
Key Concept: Supply to Superficial Back Muscles
- Trapezius is innervated by the accessory nerve (CN XI) and supplied by a superficial branch of the transverse cervical artery.
- Latissimus dorsi is innervated by the thoracodorsal nerve (C6-C8) and supplied by the thoracodorsal artery.
Venous Drainage
- Posterior intercostal or regional veins drain into the IVC or SVC.
- Lymph vessels and nodes parallel veins.
Surface Anatomy
- The triangle of auscultation is located just medial to the inferior angle of the scapula at the 6th intercostal space.
- Borders: trapezius (medially), latissimus dorsi (inferiorly).
Neurovasculature: Check-In
- The trapezius muscle is innervated by the accessory nerve (CN XI).
- Skin of the back is innervated by dorsal or ventral rami of SN.
- Superficial back muscles are innervated by nerves from the brachial plexus.
- The subclavian artery changes names to the axillary artery.
- Posterior intercostal arteries travel with the ribs.
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Description
This quiz covers the innervation of extrinsic back muscles and skin, including the formation and branches of spinal nerves and their functions in motor and sensory neurons.
