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Respiratory Anatomy Muscles of Inspiration • Inspiration is a graded activity – quiet – forced • How does inspiration take place? – All Muscular – Thorax expansion (vertical expansion)Diaphragm Primary Muscle of Inspiration • Diaphragm: – Completely separates abdominal and thoracic cavities – Large inverted bowl – Attach at inferior boundary of rib cage, xiphoid process & posterior vertebral column – Intermediate region- central tendon (aponeurosis) – Muscle contracts muscle fibers shorten diaphragm pulls central tendon down & forward Diaphragm Sternum Diaphragm Vertebral Attachment Diaphragm Central Tendon Diaphragm Central Tendon Vertebral Column Central Tendon Sternum Position when Contracted Diaphragm Diaphragm Central Tendon Esophageal Hiatus Right Crus of Vertebral Attachment L3 L4 Left Crus of Vertebral Attachment Diaphragm (Superficial) Primary Muscle of Inspiration • Diaphragm: – Innervation (nerves): • phrenic nerves (from cervical plexus; C3, C4, C5) • primary control by the autonomic nervous system (no choice) • voluntary control (holding breath) • bilateral innervation Accessory Muscles of Inspiration • Anterior Thoracic – External intercostals – Interchondral portion, internal intercostals • Posterior Thoracic – Levatores costarum (brevis & longis) – Serratus posterior superior • Muscles of Neck – Sternocleidomastoid – Scalenus – Trapezius Accessory Muscles of Inspiration • Muscles of the Thorax, Back, and Upper limb –Pectoralis major –Pectoralis minor –Serratus anterior –Subclavius Accessory: External Intercostals • Run from lower border of one rib to the upper border of the rib below. • Fills the outside of the 11 spaces between the ribs (spareribs) • Pull all lower ribs toward the first rib-elevates rib cage • Second most important muscle of inspiration • Function to increase cavity size • Account for the A-P dimensional change in thorax Accessory: Internal Intercostal (Interchondral Portion) • Mostly muscle of expiration BUT… • Chondral portion (parasternal) active during forced inspiration • Protective barrier for lungs & heart Accessory: External intercostals Internal Intercostals External Intercostals Accessory: External intercostals External intercostals Accessory: Levator Costarum & Serratus Posterior Superior Levatores Costarum Latissimus Dorsi Serratus Posterior Superior Accessory: Levator Costarum • Rib elevators • Series of 12 small muscles • Each insert into rib just below the vertebrae from which it originates • Pulls up on ribs-weak (size, points of insertion gives poor leverage) – Brevis- “brief” originate transverse process of C7-T11 (12 total) (Inserts into next rib down) – Longis- originate transverse process of T7-T11 (by passes next rib down to insert into 2nd rib down from insertion) • Both course obliquely down & out Accessory: Serratus Posterior Superior • Flat muscles, slanting down from neck • Originate from spinous process of C7 & T1T3 and insert into 2nd-5th ribs • Course down & laterally • Larger than levatores, better angle of insertion • Lifts upper ribs • Stabilizes thorax for pull of external intercostals Accessory: Latissimus Dorsi • Doubted involvement in respiration • Large flat muscle from upper arm to insert into lower back vertebrae • Some fibers insert into lower ribs • humerous movement contracts rib fibers & assists in expanding lower thorax Accessory: Levator Costarum & Serratus Posterior Superior & Inferior Levator Costarum Serratus Posterior Superior Serratus Posterior Inferior Accessory Neck Muscles: Sternocleidomastoid • Broad, thick muscle • Lies superficially in the lateral part of neck • Two head origination: anterior surface of manubrium sternum, sternal end of clavicle • Extends posteriorly & superiorly to insert in skull behind ear (mastoid process & temporal bone) • Function: Balance head & elevate sternum and raise anterior rib cage Accessory: Sternocleidomastoid Sternocleidomastoid Scaleni (Posterior) Subclavius Scaleni (Anterior) Scaleni (Middle) Accessory: Scaleni • Originate from cervical vertebrae & insert into 1st and 2nd ribs • Head balance, major force for raising & stabilizing the upper chest (ribs) of inhalation • Facilitate neck rotation, potential to increase superior-inferior dimensions of thorax Accessory: Upper Arm & Shoulder: Pectoralis Major • Major- Fan-shaped muscle • Originates from 2 heads: sternal head (attached to sternum); Clavicular head (attached to front of clavical) • Inserts into the humerous of the upper arm • When fixed it assists in drawing sternum & ribs upward • Increases transverse dimension of rib cage Accessory: Upper Arm & Shoulder: Pectoralis Minor • Fan shaped • Lies deep to the pectoralis major • Courses superiorly & laterally • Originates from scapula; inserts into 2nd-5th ribs • Function is to elevate the rib cage Accessory: Serratus Anterior • Large; originates from scapula & inserts into the upper nine ribs • Elevates ribs • Serratus= “sawlike” • Coursing upward Accesory: Pectoralis Major & Minor Pectoralis Minor Pectoralis Major Serratus Anterior Accesory: Pectoralis Major & Minor Pectoralis Major Sternocleidomastoid Pectoralis Minor Accessory: Serratus Anterior Serratus Anterior Accessory: Subclavius • Courses under the clavicle obliquely & medially • Originates from inferior margin of the clavicle & inserts into superior surface of the first rib • Small muscle • Elevate first rib during inspiration Accessory: Subclavius Subclavius Accessory: Trapezius • Massive muscle; Upper back & neck • Originating from spinous process of C2 to T12 and insert into scapula and superior surface of clavicle • Function to elongate the neck and head control • Respiratory function; stability & balance for respiratory system Accessory: Trapezius Trapezius Reading/Assignments • Seikel: Ch.3 (Pgs. 80-98) • Dickson: Ch.3 (Pgs. 90-115)
