unit 1: gross anatomy of the chest
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
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 2nd 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