Breathing Mechanisms: The intercostal muscles

The intercostal muscles are located

BETWEEN the ribs

Respiratory functions of chest/shoulder muscle

Function: inspiration Sternocleidomastoid Scalene

internal intercostals action

Hold ribs steady, exhalation

Transversus Thoracis

Irregular muscles Vary in attachments Thin Fan-shaped

Internal intercostals location

Lie deep to the external intercostals 11 Extends from the anterior limits of intercostal spaces The angle to the rib posteriorly continued to the vertebral column as thin aponeuroses (posterior intercostal membranes)

Subcostals (intracostals)

Lines the back of the thorax Lateral to the tubercles of the ribs Course same as internal intercostals Not confined to one intercostal space (skip)

external intercostal location

Occupy space between the ribs Extends from the tubercles of the ribs dorsally to a region near the cartilages of the ribs ventrally (anterior intercostal membranes)

internal intercostals origin

Rib - inferior border

internal intercostals insertion

Rib - superior border

External intercostals

Stronger than internal intercostals 11 on either side Contraction "raises the ribs" (inspiration)

Scalene

coincides with diaphragm movement, constantly phasic during restful inhalation

intercostal muscles are divided into

external intercostal and internal intercostal

The external intercostal muscles responsible for _________ inhalation and __________ inhalation

forced; quiet

external intercoastal action

inhalation

Mechanics of external intercostal

inspiration ---> tends to lower ribs

External intercostals prevent

intercostal spaces from bulging in and out during breathing

external intercoastal antagonist

intercostales interni muscles (internal intercostals)

external intercoastal insertion

lower border of ribs

transverus thoracis fibers insert into the

lower borders and inner surfaces of ribs 2-6

Mechanics of internal intercostal

lower the ribs ---> muscles of expiration

Sternocleidomastoid

quiet during restful inhalation

quiet inhalation

resting

external intercostals contribute to

rigidity of the thoracic wall

external intercostal muscles control

space between ribs

active inhalation

talking

external intercoastal orgin

upper border of rib

transversus thoracis fibers course

upward and outward