Part III: Muscles of Ventilation Reference & Reading: Egan's p.158-163

 Primary Muscles  Diaphragm  Intercostal muscles  Accessory Muscles  Scalenes  Sternocleomastoid  Pectoralis Major  Abdominals

 Rises from costal margin  Connects at central tendon  Hemidiaphragms  Separates thorax from abdomen

 Resting Position  When muscle contracts, drops floor of thoracic cavity down  Pulls air in

 Located between each rib pair  External Intercostals  Internal Intercostals

 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

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

 Collection of chest wall muscles  Help to increase thoracic space, by assisting the primary muscles: Includes:  Scalene  Sternocleomastoid  Pectoralis  Trapezius

 3 muscles  Anterior  Medial  Posterior  Arise from lower 5 cervical vertebrae & connect to 2 nd rib anteriorly  Function:  Normal  With increased WOB

 Rise from manubrium & medial end of clavicle  Insert into the skull  Function:  Primary: supports head  Increased WOB: raises sternum up & out

 Rises from clavicle & anterior surface of sternum  Function:  Primary: hugging motion  With increased WOB: pulls opposite of primary function

 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

 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

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

 Arises from:  costal cartilages  Iliac crest  Part of inguinal ligament  Connects to a aponeurosis

 Arises from pubic bones  Inserts into costal cartilages 5 -7  Contraction ↓ distance from xiphoid to pubis