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)