Questions and Answers
What is the primary muscle of inspiration?
What is the action of the diaphragm during inspiration?
Pulls the central tendon down and forward, expanding the lungs
What are the accessory muscles of the thorax involved in inspiration?
The action of the external intercostal muscles is to depress the rib cage.
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What is the origin of the internal intercostal muscles?
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Which muscle helps to elevate the scapula during inspiration?
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What is the action of the serratus anterior muscle during inspiration?
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The ___ is a large, fan-shaped muscle involved in inspiration.
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The internal intercostal muscles are primarily involved in expiration.
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Where does the transversus thoracis muscle originate?
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Study Notes
Muscles of Inspiration
- The diaphragm is the primary muscle for inspiration, separating abdominal and thoracic cavities; contracts to pull the central tendon down and expand lungs vertically.
- Accessory muscles of thorax include:
- External Intercostal Muscles
- Internal Intercostal Muscles
- Levatores Costarum
- Serratus Posterior Superior
External Intercostal Muscles
- Located between ribs; elevate the rib cage.
- Originates from lower surface of each rib (except the 12th) and inserts into the upper surface of the rib below.
Internal Intercostal Muscles
- Also assists in inspiration by elevating ribs.
- Originates from the superior surface of ribs 2-12 and inserts into the inferior surface of ribs 1-11.
Levatores Costarum
- Comprises two portions—Brevis and Longus—both involved in rib cage elevation during inspiration.
- Brevis originates from transverse processes of C7 through T11; inserts into tubercle of the rib below.
- Longus originates from T7 to T11 and inserts into the rib above the origin.
Serratus Posterior Superior
- Elevates ribs 2-5 specifically.
- Originates from spinous processes of C7 and T1-T3, inserting into ribs 2-5.
Muscles of the Neck
- Includes Sternocleidomastoid and Scalenes (anterior, middle, and posterior), providing neck stability and assisting in respiration.
Sternocleidomastoid
- Elevates the sternum and rib cage.
- Originates from mastoid process of the temporal bone and inserts into the sternal head and clavicle.
Scalenes
- Elevates ribs 1-2; aids in neck stability and head rotation.
- Originates from transverse processes of C2-C7 and inserts into ribs 1-2.
Muscles of the Upper Arm and Shoulder
- Includes Pectoralis Major, Pectoralis Minor, and Serratus Anterior, which all aid in inspiration.
Pectoralis Major
- A fan-shaped muscle elevating the sternum and expanding the rib cage.
- Has two heads: sternal head and clavicular head; inserts into the greater tubercle of the humerus.
Pectoralis Minor
- Lies under Pectoralis Major; elevates ribs 2-5 when the shoulder is fixed.
- Originates from ribs 2-5 and inserts into the coracoid process of the scapula.
Serratus Anterior
- Elevates ribs 1-9 when the shoulder is fixed.
- Originates from ribs 1-9 and inserts into the scapula.
Back Muscles of Inspiration
- Comprises Levator Scapulae, Rhomboideus Major, Rhomboideus Minor, and Trapezius, all aiding in inspiration.
Levator Scapulae
- Supports the neck and elevates the scapula.
- Originates from transverse processes of C1-C4 and inserts into the medial border of the scapula.
Rhomboideus Major and Minor
- Both stabilize the shoulder girdle.
- Major originates from spinous processes of T2-T5; Minor from C7-T1, both inserting into the scapula.
Trapezius
- Large, superficial muscle of the upper back and neck; assists in inspiration.
- Originates from spinous processes of C2 to T12 and inserts into the scapula and clavicle.
Muscles of Expiration
- Includes Internal Intercostal (interosseous portion), Transversus Thoracis, Subcostals, Serratus Posterior Inferior, and Latissimus Dorsi.
Internal Intercostal (Interosseous Portion)
- Depresses ribs 1-11 during expiration; originates from the superior margin of each rib.
Transversus Thoracis
- Decreases thoracic cavity volume during expiration.
- Originates from lower third of the sternum, inserting into the inner chondral surface of ribs 2-6.
Subcostals
- Variable in number; course parallel to internal intercostals, facilitating expiration.
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Description
Explore the key muscles involved in breathing with these flashcards. This quiz covers the diaphragm and accessory muscles, detailing their functions and anatomical significance. Understand the mechanics of respiration and the role each muscle plays in inspiration and expiration.
