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

DiaphragmDiaphragm

Vertebral Attachment

Sternum

Central Tendon

Diaphragm

Central Tendon

Position whenContracted

Sternum

Central Tendon

VertebralColumn

Diaphragm

CentralTendon

Right Crusof VertebralAttachment

Left Crusof VertebralAttachment

Diaphragm

EsophagealHiatus

L3L4

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

ExternalIntercostals

Accessory: External intercostals

Internal Intercostals

Accessory: External intercostals

External intercostals

Accessory: Levator Costarum & Serratus Posterior Superior

LevatoresCostarum Serratus Posterior

SuperiorLatissimus Dorsi

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 (by passes next rib down to insert into 2nd rib down from insertion)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 & T1-T3 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

LevatorCostarum Serratus

PosteriorSuperior

SerratusPosteriorInferior

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 (Anterior)

Scaleni (Posterior)

Scaleni (Middle)

Subclavius

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

PectoralisMinor

PectoralisMajor

SerratusAnterior

Accesory: Pectoralis Major & Minor

PectoralisMinor

PectoralisMajor

Sternocleidomastoid

Accessory: Serratus Anterior

SerratusAnterior

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)