Muscles of the Pectoral Region

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Questions and Answers

What is the result of paralysis of the deltoid muscle?

Flattening of the shoulder and loss of abduction. (correct)
Inability to adduct the shoulder joint.
Increased range of motion in the shoulder.
Enhanced shoulder flexion capabilities.

Which structure is NOT lodged in the deltopectoral groove?

Uppermost part of cephalic vein.
Deltoid branch of thoraco-acromial artery.
Suprascapular nerve. (correct)
Deltopectoral lymph nodes.

What action does the supraspinatus perform?

Flexes the shoulder joint.
Lateral rotation of the arm.
Steadies the head of the humerus in the glenoid cavity. (correct)
Adducts the arm from 0° to 15°.

Which of the following nerves supplies the infraspinatus muscle?

Suprascapular nerve. (B) Signup and view all the answers

What is the point of insertion for the supraspinatus muscle?

Highest impression on the greater tuberosity. (C) Signup and view all the answers

Which structure originates from the medial two-thirds of the infraspinous fossa?

Infraspinatus muscle. (A) Signup and view all the answers

What is the primary action of the pectoralis major muscle as a whole?

Adduction and medial rotation of the arm (A) Signup and view all the answers

Which muscle sends nerve supply from the medial pectoral nerve?

Pectoralis minor (D) Signup and view all the answers

Where does the pectoralis minor muscle originate?

Outer surfaces of the 3rd, 4th, and 5th ribs (A) Signup and view all the answers

What is the main function of the subclavius muscle?

Steadying the clavicle (A) Signup and view all the answers

What is the point of insertion for the pectoralis major muscle?

Lateral lip of the intertubercular groove (D) Signup and view all the answers

Which head of the pectoralis major is responsible for flexing the arm?

Clavicular head (D) Signup and view all the answers

What part of the rib does the subclavius muscle originate from?

1st costo-chondral junction (D) Signup and view all the answers

Which action is NOT attributed to the pectoralis minor muscle?

Medial rotation of the arm (B) Signup and view all the answers

What additional role does the sternocostal head of the pectoralis major play during physical activities?

It aids in climbing and swimming (D) Signup and view all the answers

Which muscles are classified as superficial layer muscles of the back?

Trapezius and Latissimus dorsi (D) Signup and view all the answers

What is the origin point of the trapezius muscle?

From the back of the skull (B) Signup and view all the answers

Which of the following is NOT included in the deep layer of back muscles?

Serratus anterior (D) Signup and view all the answers

Which nerve supplies the muscles of the back?

Anterior primary rami of spinal nerves (A) Signup and view all the answers

What forms the boundaries of the lumbar triangle?

Iliac crest, Latissimus dorsi, Oblique muscles (B) Signup and view all the answers

What muscle primarily functions to elevate the scapula?

Levator scapulae (B) Signup and view all the answers

Which of the following actions is associated with the latissimus dorsi?

Extension and internal rotation of the shoulder (A) Signup and view all the answers

What is the correct order of the muscles from superficial to deep in the back?

Trapezius, Latissimus dorsi, Rhomboideus major, Rhomboideus minor (B) Signup and view all the answers

What is the primary action of the levator scapulae muscle?

Elevates the shoulder girdle (A) Signup and view all the answers

Which back muscle is specifically responsible for the retraction of the scapula?

Rhomboideus major (C) Signup and view all the answers

Which vertebrae does the rhomboideus minor originate from?

Lower part of ligamentum nuchae and the spines of cervical and thoracic vertebrae (A) Signup and view all the answers

Which muscle is NOT considered to connect the upper limb with the vertebral column?

Pectoralis major (D) Signup and view all the answers

What is the primary nerve supply to both the rhomboideus minor and major muscles?

Dorsal scapular nerve (A) Signup and view all the answers

Which action is NOT associated with the rhomboideus major muscle?

Adducting the arm (B) Signup and view all the answers

In what anatomical region is the insertion of the levator scapulae located?

Medial border of the scapula above the spine (A) Signup and view all the answers

Which two muscles primarily work together to rotate the scapula so that the glenoid cavity faces downwards?

Rhomboideus minor and levator scapulae (C) Signup and view all the answers

Which muscles have their insertion along the medial border of the scapula?

Rhomboideus minor and major, and levator scapulae (B) Signup and view all the answers

Which of the following actions is NOT performed by the levator scapulae?

Protraction of the shoulder (B) Signup and view all the answers

What is the origin of the rhomboideus major muscle?

Spines of the second to fifth thoracic vertebrae (B) Signup and view all the answers

What is the primary action of the latissimus dorsi muscle?

Extension, medial rotation, and adduction of the arm (A) Signup and view all the answers

Which nerve is responsible for the innervation of the latissimus dorsi?

Thoraco-dorsal nerve (D) Signup and view all the answers

What structure serves as the insertion point for the latissimus dorsi?

Floor of the bicipital groove (B) Signup and view all the answers

In relation to the teres major, where does the latissimus dorsi lie at its insertion?

It lies behind, below, and in front of teres major (D) Signup and view all the answers

Which triangle is formed by the lateral border of the trapezius and the upper border of the latissimus dorsi?

Triangle of auscultation (A) Signup and view all the answers

What role does the latissimus dorsi play in violent expiration?

It assists by pulling ribs downwards (D) Signup and view all the answers

What muscles form the floor of the lumbar triangle?

Internal abdominal oblique and tranversus abdominis (C) Signup and view all the answers

Which of the following actions does the latissimus dorsi perform while climbing?

Pulling the trunk upward (C) Signup and view all the answers

What is the anatomical position of the lumbar triangle's boundaries?

Below: iliac crest, Medially: lateral border of latissimus dorsi (D) Signup and view all the answers

What is one significant aspect of the triangle of auscultation?

Breath sounds are clearly heard during auscultation (C) Signup and view all the answers

Study Notes

Pectoral Region Muscles

Pectoralis Major:
- Superficial muscle of the pectoral region
- Forms the anterior wall of the axilla
- Origin:
  - Clavicular Head: Anterior surface of the medial 1/2 of the clavicle
  - Sternocostal Head:
    - Anterior surface of the sternum
    - Front of the upper 6 costal cartilages
    - Aponeurosis of external abdominal oblique muscle
- Insertion: Lateral lip of the intertubercular (bicipital) groove
- Nerve Supply: Lateral and medial pectoral nerves
- Action:
  - Adducts and medially rotates the arm
  - Clavicular head flexes the arm
  - Sternocostal head extends the flexed arm
  - Used in swimming, rowing, and climbing
Pectoralis Minor:
- Deep to the middle part of the pectoralis major
- Origin: Outer surfaces of the 3rd, 4th, and 5th ribs near their costal cartilages
- Insertion: Medial border and upper surface of the coracoid process
- Nerve Supply: Medial pectoral nerve
- Action:
  - Protracts the shoulder girdle
  - Depresses the shoulder
  - With fixed scapula, raises the ribs during forced 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 (C5,6)
- Action: Steadies the clavicle, preventing excessive movements of the shoulder girdle

Muscles of the Back

Muscles Connecting the Upper Limb with Vertebral Column
- Superficial Layer:
  - Trapezius:
    - Large triangular muscle covering the upper half of the back
    - Origin:
      - Back of the skull: External occipital protuberance and medial third of the superior nuchal line
      - Spines of the lower 6 thoracic vertebrae
      - Thoraco-lumbar fascia
      - Outer surface of lower 4 ribs
      - Inferior angle of scapula
    - Insertion: Floor of the bicipital groove
    - Nerve Supply: Thoraco-dorsal nerve (nerve to latissimus dorsi)
    - Action:
      - Extends, medially rotates, and adducts the arm (rowing and swimming)
      - Pulls the trunk upwards during climbing
      - Assists in violent expiration (coughing)
  - Latissimus Dorsi:
    - Origin:
      - Posterior third of the outer lip of the iliac crest
      - Spines of the lower 6 thoracic vertebrae
      - Thoraco-lumbar fascia
      - Outer surface of lower 4 ribs
    - Insertion: Floor of the bicipital groove
    - Nerve Supply: Thoraco-dorsal nerve (nerve to latissimus dorsi)
    - Action:
      - Extends, medially rotates, and adducts the arm (rowing and swimming)
      - Adducts and internally rotates the arm; pulls the shoulder downward and backward (climbing)
- Deep Layer:
  - Levator Scapulae:
    - Origin: Transverse processes of upper 4 cervical vertebrae
    - Insertion: Dorsal surface of medial border of scapula above the root of the spine
    - Nerve Supply: Nerve to rhomboids (dorsal scapular nerve, C5)
    - Action:
      - Elevates shoulder girdle
      - Rotates the scapula so that the glenoid cavity looks downwards
      - Retracts the scapula
  - Rhomboideus Minor:
    - Origin: Lower part of ligamentum nuchae, spines of the 7th cervical and 1st thoracic vertebrae
    - Insertion: Dorsal surface of the medial border of the scapula opposite the root of the spine
    - Nerve Supply: Nerve to rhomboids (dorsal scapular nerve, C5)
    - Action:
      - Rotates the scapula so that the glenoid cavity looks downwards
      - Retracts the scapula
  - Rhomboideus Major:
    - Origin: Spines of the 2nd, 3rd, 4th, and 5th thoracic vertebrae and their supraspinous ligaments
    - Insertion: Dorsal surface of the medial border of the scapula from the root of the spine to the inferior angle
    - Nerve Supply: Nerve to rhomboids (dorsal scapular nerve, C5)
    - Action: Same as the rhomboideus minor

Clinical Importance

Lumbar Triangle:
- Situated just above the iliac crest
- Boundaries:
  - Below: Iliac crest
  - Medially: Lateral border of latissimus dorsi
  - Laterally: Vertical posterior border of external abdominal oblique muscle
- Floor: Internal abdominal oblique and transversus abdominis muscles
- Potential site for lumbar hernia
Triangle of Auscultation:
- Located medial to the lower part of the scapula
- Boundaries:
  - Above: Lateral border of the trapezius
  - Below: Upper border of the latissimus dorsi
  - Laterally: Lower part of the medial border of the scapula
- Floor: Rhomboideus major, 6th and 7th ribs, and the space in between
- Provides clear auscultation of breath sounds
Paralysis of Deltoid:
- Results in flattening of the shoulder and loss of abduction between 15° and 90°
- Deltoid: Abducts the arm from 15° to 90°

Shoulder Region Muscles

Supraspinatus:
- Origin: Medial two-thirds of the supraspinous fossa
- Insertion: Highest impression on the greater tuberosity
- Nerve Supply: Suprascapular nerve (C5,6)
- Action:
  - Helps steady the head of the humerus in the glenoid cavity
  - Abducts the arm from 0 to 15° (initiates abduction)
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:
  - Helps steady the head of the humerus
  - Laterally rotates the arm
Teres Minor:
- Origin: Lateral border of the scapula
- Insertion: Lower impression on the greater tuberosity
- Nerve Supply: Axillary nerve (C5,6)
- Action:
  - Laterally rotates the arm
  - Adducts the arm
  - Helps to keep the humerus close to the glenoid cavity

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Description

This quiz covers the anatomy of the pectoral region muscles, primarily focusing on the pectoralis major and minor. You'll learn about their origins, insertions, nerve supplies, and actions. Test your knowledge on how these muscles contribute to movements such as swimming, rowing, and climbing.