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Questions and Answers
What is the primary action of the pectoralis major muscle?
What is the primary action of the pectoralis major muscle?
From which structure does the clavicular head of the pectoralis major arise?
From which structure does the clavicular head of the pectoralis major arise?
Which nerve supplies the pectoralis minor muscle?
Which nerve supplies the pectoralis minor muscle?
Which muscle is responsible for depressing the shoulder girdle?
Which muscle is responsible for depressing the shoulder girdle?
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What action does the sternocostal head of the pectoralis major perform?
What action does the sternocostal head of the pectoralis major perform?
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Where does the subclavius muscle insert?
Where does the subclavius muscle insert?
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What is the origin of the pectoralis minor muscle?
What is the origin of the pectoralis minor muscle?
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What role does the subclavius muscle play in shoulder movement?
What role does the subclavius muscle play in shoulder movement?
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Which muscle is considered part of the superficial layer of the back muscles?
Which muscle is considered part of the superficial layer of the back muscles?
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Which of the following muscles is located in the deep layer of the back muscles?
Which of the following muscles is located in the deep layer of the back muscles?
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What is the origin of the trapezius muscle?
What is the origin of the trapezius muscle?
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Which statement correctly describes the relationship between the levator scapulae and the vertebral column?
Which statement correctly describes the relationship between the levator scapulae and the vertebral column?
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Which muscles are included in the deep layer of muscles connecting the upper limb with the vertebral column?
Which muscles are included in the deep layer of muscles connecting the upper limb with the vertebral column?
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What is the nerve supply for the back muscles?
What is the nerve supply for the back muscles?
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How many muscles constitute the superficial layer of the back muscles?
How many muscles constitute the superficial layer of the back muscles?
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What action is primarily associated with the latissimus dorsi muscle?
What action is primarily associated with the latissimus dorsi muscle?
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What is the origin of the trapezius muscle?
What is the origin of the trapezius muscle?
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Where do the middle fibers of the trapezius insert?
Where do the middle fibers of the trapezius insert?
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Which nerve supplies motor function to the trapezius muscle?
Which nerve supplies motor function to the trapezius muscle?
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What action does the upper fibers of the trapezius perform?
What action does the upper fibers of the trapezius perform?
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What condition may occur due to paralysis of the trapezius muscle?
What condition may occur due to paralysis of the trapezius muscle?
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What is the function of the lower fibers of the trapezius muscle?
What is the function of the lower fibers of the trapezius muscle?
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What structure surrounds the insertion of the trapezius muscle?
What structure surrounds the insertion of the trapezius muscle?
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What do the middle fibers of the trapezius muscle do in conjunction with the rhomboids?
What do the middle fibers of the trapezius muscle do in conjunction with the rhomboids?
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What is one of the primary actions of the latissimus dorsi muscle?
What is one of the primary actions of the latissimus dorsi muscle?
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Which nerve supplies the latissimus dorsi?
Which nerve supplies the latissimus dorsi?
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Where does the latissimus dorsi insert?
Where does the latissimus dorsi insert?
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What anatomical feature is medial to the lower part of the scapula?
What anatomical feature is medial to the lower part of the scapula?
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Which structure assists in violent expiration such as in coughing?
Which structure assists in violent expiration such as in coughing?
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What is one of the boundaries of the lumbar triangle?
What is one of the boundaries of the lumbar triangle?
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In relation to the teres major, how does the latissimus dorsi position itself at its insertion?
In relation to the teres major, how does the latissimus dorsi position itself at its insertion?
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What forms the floor of the triangle of auscultation?
What forms the floor of the triangle of auscultation?
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What is a clinical consequence of paralysis of the deltoid muscle?
What is a clinical consequence of paralysis of the deltoid muscle?
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Which structure is NOT found in the deltopectoral groove?
Which structure is NOT found in the deltopectoral groove?
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Where does the supraspinatus muscle originate?
Where does the supraspinatus muscle originate?
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What action does the supraspinatus muscle perform?
What action does the supraspinatus muscle perform?
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Which nerve supplies the infraspinatus muscle?
Which nerve supplies the infraspinatus muscle?
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What is the action of the infraspinatus muscle?
What is the action of the infraspinatus muscle?
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Which of the following statements about the deltopectoral groove is true?
Which of the following statements about the deltopectoral groove is true?
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The insertion of the supraspinatus muscle is located at which specific area?
The insertion of the supraspinatus muscle is located at which specific area?
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Study Notes
Pectoral Region Muscles
-
Pectoralis Major:
- Superficial muscle of the pectoral region.
- Forms the anterior axilla wall.
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Origin:
- Clavicular head: medial 1/2 of clavicle's anterior surface.
- Sternocostal head: anterior sternum, upper 6 costal cartilages, external abdominal oblique aponeurosis.
- Insertion: Lateral lip of the intertubercular (bicipital) groove.
- Nerve supply: Lateral and medial pectoral nerves.
-
Action:
- Adduction and medial rotation of the arm.
- Clavicular head: arm flexion.
- Sternocostal head: extension of flexed arm, used in activities like swimming, rowing, and climbing.
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Pectoralis Minor:
- Lies deep to the middle pectoralis major.
- Origin: Outer surfaces of the 3rd, 4th, and 5th ribs near their costal cartilages.
- Insertion: Medial border and the upper surface of the coracoid process.
- Nerve supply: Medial pectoral nerve.
-
Action:
- Shoulder girdle protraction.
- Shoulder depression.
- With fixed scapula, it can raise ribs during forceful inspiration.
-
Subclavius:
- Slender muscle located just below the clavicle.
- Origin: Upper surface of the 1st costo-chondral junction.
- Insertion: Groove on the lower surface of the middle third of the clavicle.
- Nerve supply: Nerve to subclavius (C5).
- Action: Stabilizes the clavicle, preventing excessive movement of the shoulder girdle.
Muscles of the Back
-
Muscles connecting the upper limb to the vertebral column:
- Supplied by anterior primary rami of spinal nerves.
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Superficial layer:
- Trapezius
- Latissimus dorsi
-
Deep layer:
- Levator scapulae
- Rhomboideus major
- Rhomboideus minor
-
Trapezius:
- Large triangular muscle covering the upper back.
- Forms the outline of a trapezium when paired with its counterpart.
-
Origin:
- Skull: External occipital protuberance and the medial third of the superior nuchal line.
- Neck: Ligamentum nuchae and the spine of the 7th cervical vertebra.
- Thorax: Spines of all thoracic vertebrae and their supraspinous ligaments.
-
Insertion:
- V-shaped insertion.
- Upper fibers: Posterior border of the lateral third of the clavicle.
- Middle fibers: Medial border of the acromion and the upper lip of the spine of the scapula.
- Lower fibers: Rough tubercle on the crest of the spine of the scapula.
-
Nerve supply:
- Motor: Accessory nerve.
- Sensory: C3 and C4.
-
Action:
- Maintains shoulder level.
- Upper fibers: Elevate the shoulder girdle.
- Upper and lower fibers: Rotate scapula, elevating the arm above the head.
- Middle fibers: Retract the scapula and stabilize the posterior shoulder with the rhomboids.
-
Latissimus Dorsi:
- Large triangular muscle covering the lower back down to the iliac crest.
- Wide origin and narrow insertion tendon.
-
Origin:
- Fleshy fibers: Posterior third of the iliac crest's outer lip, spines of the lower 6 thoracic vertebrae (under the trapezius), thoraco-lumbar fascia, outer surface of the lower 4 ribs, a few fibers from the inferior angle of the scapula.
- Insertion: Bicipital groove floor.
- Nerve supply: Thoracodorsal nerve (nerve to latissimus dorsi).
-
Action:
- Extension, medial rotation and adduction of the arm (rowing and swimming).
- Pulls the trunk upwards in climbing, working from its insertion.
- Assists in forceful expiration (coughing).
-
Triangle of Auscultation:
- Located medial to the scapula's lower part.
- Allows clear auscultation of breath sounds.
-
Boundaries:
- Above: Trapezius' lateral border
- Below: Latissimus dorsi's upper border.
- Laterally: Scapula's medial border's lower part.
- Floor: Rhomboideus major, 6th and 7th ribs, and the space between them.
-
Lumbar Triangle:
- Located above the iliac crest.
- Potential site for lumbar hernia.
-
Boundaries:
- Below: Iliac crest.
- Medially: Latissimus dorsi's lateral border.
- Laterally: Vertical posterior border of the external abdominal oblique muscle.
- Floor: Internal abdominal oblique and transversus abdominis muscles.
Shoulder Region Muscles
-
Deltoid
- Large triangular muscle covering the shoulder region.
-
Origin:
- Clavicular head: Lateral third of the clavicle.
- Acromial head: Acromion.
- Spinal head: Spine of the scapula.
- Insertion: Deltoid tuberosity on the lateral surface of the humerus.
- Nerve supply: Axillary nerve (C5,6).
-
Action:
- Abduction of the arm (up to 90 degrees).
- Anterior fibers: Medial rotation of the arm.
- Posterior fibers: Lateral rotation of the arm.
-
Supraspinatus:
- Origin: Medial two-thirds of the supraspinous fossa.
- Insertion: Highest impression on the greater tuberosity of the humerus.
- Nerve supply: Suprascapular nerve (C5,6).
-
Action:
- Stabilizes the humerus head in the glenoid cavity.
- Initiates arm abduction (0-15 degrees).
-
Infraspinatus:
- Origin: Medial two-thirds of the infraspinous fossa.
- Insertion: Middle impression on the back of the greater tuberosity.
- Nerve supply: Suprascapular nerve (C5,6).
-
Action:
- Stabilizes the humeral head.
- Lateral arm rotation.
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Description
Test your knowledge on the muscles of the pectoral region, focusing on the Pectoralis Major and Minor. This quiz covers their origins, insertions, nerve supply, and actions. Perfect for students studying anatomy and physiology.
