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Questions and Answers
What is the nerve supply for the latissimus dorsi muscle?
Which of the following is an action of the levator scapulae muscle?
Which structure does the rhomboideus major muscle primarily affect?
The trapezius is affected by an injury to which nerve?
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What is the primary insertion point of the latissimus dorsi muscle?
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Which muscle primarily contributes to the retraction of the scapula along with the middle fibers of the trapezius?
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The lumbar triangle is closely associated with which muscle?
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Which muscles are involved in violent expiration?
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Which muscles of the back are primarily supplied by the brachial plexus?
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What is the primary action of the upper fibers of the trapezius muscle?
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Which statement is true regarding the insertion points of the trapezius muscle?
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What is the nerve supply for proprioception to the trapezius muscle?
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Which muscle specifically acts on the shoulder joint rather than the shoulder girdle?
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What part of the trapezius muscle originates from the external occipital protuberance?
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What structure is specifically related to the actions of the rhomboid muscles?
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Which muscle does NOT originate from the back of the trunk?
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Study Notes
Back Muscles
- Muscles of the back originate from the back of the trunk (origin)
- All muscles insert into the scapula except latissimus dorsi, which inserts into the humerus
- All act on the shoulder girdle except latissimus dorsi, which acts on the shoulder joint
- All are supplied by the brachial plexus except trapezius, which is supplied by the spinal accessory nerve (cranial nerve)
Back Muscle Layers
- First layer: Trapezius, Latissimus dorsi
- Second layer: Levator scapulae, Rhomboidus minor, Rhomboidus major
Trapezius Muscle
- Composed of occipital, cervical, and thoracic parts
Origin
- Occipital part: External occipital protuberance, medial 1/3 of the superior nuchal line
- Cervical part: Ligamentum nuchae, spine of C7
- Thoracic part: All thoracic spines, supraspinous ligaments
Insertion
- Upper fibers: Posterior border of the lateral 1/3 of the clavicle
- Middle fibers: Medial border of the acromion and upper lip of the crest of the spine of the scapula
- Lower fibers: Tubercle of the crest of the spine of the scapula
Nerve Supply
- Spinal accessory nerve (motor)
- C3 & C4 (proprioception)
Action
- Upper fibers: Elevate the scapula
- Middle fibers: Retract the scapula
- Lower fibers: Elevation of the glenoid cavity
Trapezius Injury
- Injury to the spinal accessory nerve leads to drop shoulder
Latissimus Dorsi
Origin
- Lower 6 thoracic spines
- Thoraco-lumbar fascia
- Posterior part of the outer lip of the iliac crest
- Lower 4 ribs
- Back of the inferior angle of scapula
Insertion
- Floor of the bicipital groove
Nerve Supply
- Nerve to dorsi (thoracodorsal nerve)
Action
- Extension, adduction, and medial rotation of the arm
- Climbing
- Violent expiration
Relations
- Triple relation with Teres major
- Related to the triangle of auscultation and the lumbar triangle
Levator Scapulae
Origin
- Transverse processes of upper 4 cervical vertebrae
Insertion
- Back of the medial border of scapula from the superior angle to the root of the spine
Nerve Supply
- C3 & C4
- Nerve to Rhomboideus (C5)
Action
- Elevates the shoulder girdle
- Glenoid down
- Retract scapula
Rhomboideus Minor
Origin
- Lower part of the ligamentum nuchae
- Spines of C7 and T1
Insertion
- Back of the medial border of scapula opposite the root of the spine
Rhomboideus Major
Origin
- Spines of T2, 3, 4, and 5
- Supraspinous ligaments
Insertion
- Back of the medial border of scapula from the root of the spine to the inferior angle
Nerve Supply
- Nerve to Rhomboideus (dorsal scapular nerve - C5)
Action
- Downward rotation of the glenoid cavity
- With the middle fibres of trapezius: Retraction of the scapula
Lumbar Triangle & Triangle of Auscultation
- Both are regions of the back related to the latissimus dorsi muscle
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Description
This quiz covers the anatomy and functions of back muscles, including their origins, insertions, and innervations. It focuses on key muscles like the trapezius and latissimus dorsi and classifies them by layers. Test your knowledge of how these muscles interact with the shoulder girdle and joint.
