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Unit 1: Gross Anatomy of the Chest

Unit 1: Gross Anatomy of the Chest. Part III: Muscles of Ventilation Reference & Reading: Egan's p.158-163. Muscles of Ventilation. Primary Muscles Diaphragm Intercostal muscles Accessory Muscles Scalenes Sternocleomastoid Pectoralis Major Abdominals. Diaphragm.

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Unit 1: Gross Anatomy of the Chest

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  1. Unit 1: Gross Anatomy of the Chest Part III: Muscles of Ventilation Reference & Reading: Egan's p.158-163

  2. Muscles of Ventilation • Primary Muscles • Diaphragm • Intercostal muscles • Accessory Muscles • Scalenes • Sternocleomastoid • Pectoralis Major • Abdominals

  3. Diaphragm • Rises from costal margin • Connects at central tendon • Hemidiaphragms • Separates thorax from abdomen

  4. Diaphragm - Function • Resting Position • When muscle contracts, drops floor of thoracic cavity down • Pulls air in

  5. Intercostal Muscles • Located between each rib pair • External Intercostals • Internal Intercostals

  6. Intercostal Muscles - Function • Active during quiet breathing • Elevates ribs, ↑ thoracic volume - occurs closer to exhalation • At increased lung volumes, ribs are lowered • Stabilizes chest wall during large pressure changes Quiet Breathing – from www.gettyimages.com

  7. Retractions • Also called intercostal retractions • There is increased amount of negative pressure generated • Clinical sign of increased WOB; look at suprasternal notch • Retractions on infant

  8. Collection of chest wall muscles Help to increase thoracic space, by assisting the primary muscles: Includes: Scalene Sternocleomastoid Pectoralis Trapezius Accessory Muscles - Inspiration

  9. Scalene Muscles • 3 muscles • Anterior • Medial • Posterior • Arise from lower 5 cervical vertebrae & connect to 2nd rib anteriorly • Function: • Normal • With increased WOB

  10. Sternocledomastoids • Rise from manubrium & medial end of clavicle • Insert into the skull • Function: • Primary: supports head • Increased WOB: raises sternum up & out

  11. Pectoralis Muscles • Rises from clavicle & anterior surface of sternum • Function: • Primary: hugging motion • With increased WOB: pulls opposite of primary function

  12. Trapezius Muscles • Arise from the occipital bone in the skull & all thoracic vertebrae; insert into clavicle • Function: • Primary: shrug shoulders; raise or lower arms • Increased WOB: Raises rib cage

  13. Accessory Muscles - Exhalation • Used to forcibly exhale (cough, sneeze, etc) • Muscles used are the abdominal muscles • Collectively compress abdominal contents to push diaphragm up • Includes: • External & internal obliques • Transverse abdominals • Rectus abdominus

  14. Internal & External Oblique • External Oblique: arise from lower 8 ribs • Internal Oblique: Arise from iliac crest& inguinal ligament • Fibrous aponeurosis

  15. Transverse Abdominis • Arises from: • costal cartilages • Iliac crest • Part of inguinal ligament • Connects to a aponeurosis

  16. Rectus Abdominis • Arises from pubic bones • Inserts into costal cartilages 5 -7 • Contraction ↓ distance from xiphoid to pubis

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