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Questions and Answers
Which structure serves as the nerve supply for the latissimus dorsi muscle?
What is one of the primary actions of the latissimus dorsi muscle?
Which of the following muscles acts with the latissimus dorsi for trunk elevation?
In which triangle does the rhomboideus major form the floor?
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What anatomical landmarks define the boundaries of the lumbar triangle?
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Where does the trapezius muscle originate from?
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Which of the following is an action of the trapezius muscle?
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What type of nerve supplies motor function to the trapezius muscle?
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Which part of the trapezius inserts into the posterior border of the lateral third of the clavicle?
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What is the function of the rhomboids when acting with the trapezius muscle?
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Study Notes
Trapezius
- Large triangular muscle covering the upper back
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Origin:
- External occipital protuberance and medial third of the superior nuchal line (back of skull)
- Ligamentum nuchae and spinous process of the 7th cervical vertebra (back of neck)
- Spines of all thoracic vertebrae and their supraspinous ligaments (back of thorax)
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Insertion:
- V-shaped insertion:
- Upper fibers: posterior border of lateral third of the clavicle
- Middle fibers: medial border of the acromion and upper lip of the spine of the scapula
- Lower fibers: tubercle on the crest of the spine of the scapula
- V-shaped insertion:
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Nerve Supply:
- Motor: spinal root of accessory nerve
- Sensory: Cervical nerves 3 and 4 (C3 and C4)
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Action:
- Maintains shoulder level
- Upper fibers elevate shoulder girdle
- Upper and lower fibers rotate scapula to allow arm to move above head
- Middle fibers retract scapula and support shoulder with rhomboids
Latissimus Dorsi
- Large triangular muscle covering the lower back, extending to the iliac crest
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Origin:
- Posterior third of the outer lip of the iliac crest
- Spines of the lower six thoracic vertebrae
- Underneath the trapezius
- Thoracolumbar fascia
- Outer surface of the lower four ribs
- Dorsal aspect of the inferior angle of the scapula
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Insertion:
- Floor of the bicipital groove
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Nerve Supply:
- Thoracodorsal nerve
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Action:
- Extends, medially rotates, and adducts the arm
- Works with pectoralis major to pull the trunk upwards
- Assists in forceful exhalation (coughing)
Triangle of Auscultation
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Boundaries:
- Lateral border of the trapezius (above)
- Upper border of the latissimus dorsi (below)
- Lower part of the medial border of the scapula (laterally)
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Floor:
- Rhomboideus major and sixth and seventh ribs
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Clinical Significance:
- Allows for clear auscultation of breath sounds
Lumbar Triangle
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Boundaries:
- Iliac crest (below)
- Lateral border of the latissimus dorsi (medially)
- Vertical posterior border of the external abdominal oblique muscle (laterally)
-
Floor:
- Internal abdominal oblique and transverse abdominis muscles
-
Clinical Significance:
- Potential site for lumbar hernia
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Description
Explore the intricate details of the trapezius muscle, including its origin, insertion, nerve supply, and actions. This quiz will enhance your understanding of this essential muscle in the upper back and its role in shoulder movement and stability.
