Anatomy of the Pectoralis Major and Minor
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Questions and Answers

Which muscle originates from the anterior surface of the medial half of the clavicle?

  • Pectoralis Minor
  • Serratus Anterior
  • Subclavius
  • Pectoralis Major (correct)

    • What is the insertion point for the bilateral tendon of Pectoralis Major?

  • Lateral lip of the intertubercular groove (correct)
  • Sternal body
  • Anterior surface of the scapula
  • Medial lip of the intertubercular groove

    • Which nerves supply the Pectoralis Major muscle?

  • Cutaneous branches of the brachial plexus
  • Lateral and medial pectoral nerves (correct)
  • Thoracic intercostal nerves
  • Supraclavicular nerves

    • Which structure is located in the deltopectoral groove?

    <p>Cephalic vein</p> Signup and view all the answers

    Where does the Pectoralis Major arise from besides the clavicle?

    <p>Upper 6 costal cartilages and external oblique aponeurosis</p> Signup and view all the answers

    What is one of the actions of the pectoralis major?

    <p>Adduction of the arm</p> Signup and view all the answers

    What is the origin of the pectoralis minor?

    <p>Front of 2nd, 3rd, 4th and 5th ribs</p> Signup and view all the answers

    Which nerve supplies the pectoralis minor?

    <p>Medial pectoral nerve</p> Signup and view all the answers

    What condition is characterized by underdeveloped pectoral muscles, usually on one side?

    <p>Poland syndrome</p> Signup and view all the answers

    What is the main function of the subclavius muscle?

    <p>Stabilizing the clavicle</p> Signup and view all the answers

    Which muscle is not supplied by the brachial plexus?

    <p>Trapezius</p> Signup and view all the answers

    What is the primary action of the upper fibers of the trapezius?

    <p>Elevation of the scapula and lateral flexion of the neck</p> Signup and view all the answers

    Which muscle originates from the spines of T6-T12?

    <p>Latissimus dorsi</p> Signup and view all the answers

    What is the main action of the rhomboideus major muscle?

    <p>Retraction of the scapula</p> Signup and view all the answers

    What nerve supplies the latissimus dorsi?

    <p>Thoraco-dorsal nerve</p> Signup and view all the answers

    Which action is NOT performed by the trapezius?

    <p>Medial rotation of the arm</p> Signup and view all the answers

    Which muscles are primarily responsible for scapula fixation?

    <p>Rhomboideus minor and major</p> Signup and view all the answers

    What happens to the breast during puberty?

    <p>Enlargement due to increase in fat</p> Signup and view all the answers

    What is the primary blood supply to the areola?

    <p>Lateral thoracic artery</p> Signup and view all the answers

    Which lymph node receives the majority of lymph drainage from the breast?

    <p>Axillary LN</p> Signup and view all the answers

    What clinical sign is associated with the invasion of the suspensory ligaments in breast carcinoma?

    <p>Skin dimpling</p> Signup and view all the answers

    What structure is responsible for the blood supply of the upper fibers of the trapezius muscle?

    <p>Superior thoracic artery</p> Signup and view all the answers

    Which of the following muscles is NOT part of the back muscles?

    <p>Pectoralis major</p> Signup and view all the answers

    Which nerve supplies the trapezius muscle?

    <p>Spinal accessory nerve</p> Signup and view all the answers

    What is the characteristic appearance associated with invasion of subcutaneous lymphatics in breast carcinoma?

    <p>Peau d'orange</p> Signup and view all the answers

    Which part of the trapezius muscle inserts at the upper lip of the spine of the scapula?

    <p>Lower fibers</p> Signup and view all the answers

    What is the primary action of the serratus anterior muscle?

    <p>Protraction of the scapula</p> Signup and view all the answers

    From which ribs does the serratus anterior muscle originate?

    <p>Ribs 1 to 8</p> Signup and view all the answers

    What happens as a result of paralysis of the serratus anterior?

    <p>Winging of the scapula</p> Signup and view all the answers

    Where does the base of the breast extend from?

    <p>2nd rib to 6th rib</p> Signup and view all the answers

    What is the primary role of the lactiferous ducts in the breast?

    <p>Transport milk to the nipple</p> Signup and view all the answers

    What is the name of the ligaments that separate the lobes of the breast?

    <p>Suspensory ligaments of breast</p> Signup and view all the answers

    What is the innervation of the serratus anterior?

    <p>Long thoracic nerve</p> Signup and view all the answers

    Which structure lies beneath the breast and separates it from underlying muscles?

    <p>Retromammary space</p> Signup and view all the answers

    Study Notes

    Pectoral Region Overview

    • The pectoral region is the soft tissue covering the anterior chest wall, connecting the upper limb to the axial skeleton.
    • It comprises various structures including skin, superficial fascia (contains nerves, blood vessels, and breast tissue), pectoral fascia, pectoralis major, pectoralis minor, clavipectoral fascia, subclavius, and serratus anterior.

    Pectoralis Major

    • Origin: Clavicular head: medial 1/2 of the clavicle. Sternocostal head: upper 6 costal cartilages, front of lateral sternal border, and aponeurosis of external oblique.
    • Insertion: Lateral lip of intertubercular groove by a bilaminar tendon. Clavicular head inserts into anterior lamina, sternocostal head into posterior lamina.
    • Nerve Supply: Lateral and medial pectoral nerves.
    • Action: Flexion, adduction, and medial rotation of the arm. Acting on the ribs, helps with deep inspiration. When the arm is fixed, it lifts the trunk upwards (pull-ups, climbing), and pulls the trunk forward during swimming.
    • Clinical Note: The lower border of the pectoralis major forms the anterior axillary fold.

    Pectoralis Minor

    • Origin: Front of the 2nd, 3rd, 4th, and 5th ribs.
    • Insertion: Medial border of the coracoid process.
    • Nerve Supply: Medial pectoral nerve.
    • Action: Protraction of the scapula, depression of the scapula, assists in deep inspiration

    Subclavius

    • Origin: Junction of the 1st rib and its costal cartilage.
    • Insertion: Subclavian groove (inferior surface of middle 1/3 of clavicle).
    • Nerve Supply: Nerve to subclavius.
    • Action: Stabilizes the clavicle during movements at the shoulder joint.

    Clavipectoral Fascia

    • Strong sheet stretched between subclavius (above) and pectoralis minor (below).
    • Structures piercing it include: cephalic vein, acromiothoracic artery, lateral pectoral nerve, and lymph vessels.

    Serratus Anterior

    • Origin: 8 upper ribs (1st and 2nd ribs).
    • Insertion: Anterior (costal) surface of medial border of scapula. (1st and 2nd digitations > superior angle, 3rd digitation > medial border, 4th-8th digitations > inferior angle).
    • Nerve Supply: Nerve to serratus anterior (long thoracic nerve).
    • Action: Main protractor, active in pushing and punching movements, rotates scapula for abduction >90 degrees, raising the hand above the head, assists in deep inspiration.

    Breast

    • Definition: Modified sweat gland.
    • Site: Superficial fascia of the pectoral region in both sexes.
    • Shape: Conical or hemispherical, with apex (nipple and areola) and base.
    • Lobes: 15-20 radiating from the nipple. Each lobe has acini (grape-like structures) which collect into lactiferous ducts.
    • Ducts: 15-20 lactiferous ducts open separately on the nipple and dilate to form lactiferous sinuses before ending.
    • Suspensory ligaments: 15-20 fibrous septa (ligaments of Cooper), separating lobes, giving the breast a smooth contour.
    • Fat tissue: Fills the space between the lobes, contributing to contour and softness.
    • Covering: Nipple is a conical projection; the areola is circular, pigmented; contains sebaceous glands; the color of the areola is pink in women who have not had children and becomes darker after pregnancy.

    Blood Supply

    • Arterial: Perforating branches of internal mammary (thoracic) artery, superior thoracic, acromiothoracic (pectoral branch), and lateral thoracic. Lateral branches of intercostal arteries.
    • Venous: Internal thoracic vein, axillary vein, and posterior intercostal veins.

    Lymph Drainage

    • 75% of lymph from the breast drains into axillary lymph nodes.
    • 20% drain into internal mammary lymph nodes.
    • 5% drain into other lymph nodes.
    • Subareolar, cutaneous, and submammary plexuses are involved

    Clinical Anatomy (Breast Carcinoma)

    • Invasion of lactiferous ducts: nipple retraction, blood discharge.
    • Invasion of suspensory ligaments: skin dimpling.
    • Invasion of subcutaneous lymphatics: peau d'orange.
    • Invasion of retromammary space: breast fixation.

    Poland Syndrome

    • Underdeveloped pectoral muscles; typically present on the right side.

    Muscles of the Back

    • Trapezius:

      • Origin: Medial 1/3 of superior nuchal line, external occipital protuberance, ligamentum nuchae, spine of C7, and spines of T1-T12.
      • Insertion: Upper fibers: posterior border of lateral 1/3 of clavicle; Middle fibers: medial border of acromion; Lower fibers: upper lip of spine of scapula.
      • Nerve Supply: Spinal accessory (11th cranial nerve).
      • Action: Upper fibers: elevate scapula, lateral flexion of the neck; Middle fibers: retrat scapula; Lower fibers: depress scapula.

    • Latissimus Dorsi:

      • Origin: Spines of T6-T12, thoracolumbar fascia, outer lip of the posterior 1/3 of the iliac crest, lower three ribs, and posterior surface of inferior angle of scapula.
      • Insertion: Floor of the intertubercular groove.
      • Nerve Supply: Thoracodorsal nerve.
      • Action: Extension, adduction, and medial rotation of the arm, draws the trunk upward in climbing.

    • Levator Scapulae:

      • Origin: Transverse processes of C1-C4.
      • Insertion: Dorsal surface of the medial border of the scapula, from the superior angle to the spine.
      • Nerve Supply: Dorsal scapular nerve.
      • Action: Elevation of the scapula, fixation of the scapula.

    • Rhomboideus Minor:

      • Origin: Lower part of ligamentum nuchae, C7, and T1 spines.
      • Insertion: Dorsal surface of the medial border of the scapula opposite the spine.
      • Nerve Supply: Dorsal scapular nerve.
      • Action: Retraction of the scapula.

    • Rhomboideus Major:

      • Origin: T2-T5 spines.
      • Insertion: Dorsal surface of the medial border of the scapula from the spine to the inferior angle.
      • Nerve supply: Dorsal scapular nerve.
      • Action: Retraction of the scapula, fixation of the scapula.

    Cutaneous Nerve Supply of the Back

    • Cutaneous branches of the dorsal rami of T1-T12.

    Male Breast Development

    • Before puberty and in males, the breast is small due to minimal fat and glandular tissue, and does not extend beyond the areola.
    • During puberty, breast size increases due to increased fat more than duct growth.
    • In early pregnancy, breast size increases due to increase in the length and branching of ducts and development of alveoli.
    • In late pregnancy and lactation, alveoli are distended with milk.

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    Pectoral Region & Breast Anatomy PDF

    Description

    Test your knowledge on the anatomy of the pectoralis major and minor muscles. This quiz covers origins, insertions, innervations, and functions of these important muscles. Perfect for students studying human anatomy or related health sciences.

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