1. Respiratory Anatomy

2. Muscles of Expiration
Unlike inspiration: expiration is an interaction between passive & active forces
active: rib cage and abdominal muscles (opposition to diaphragm)
passive: recoil forces, gravity
3 relatively independent forces:
Passive forces
Active diaphragm-abdomen forces
Active rib cage forces

3. Internal Intercostals
Fill spaces between ribs (except in back) on the inside of the chest
Connect ribs at opposite angles to external intercostals
Work in opposition to each other (external/internal)
Internal: pull down from the pelvis through connection with abdominal muscles
External: Pull upward from the spine, skull, neck and fixate upper ribs

4. Transversus Thoracis
Upward & outward from lower sternum to insert into 2nd-6th ribs
Flat muscle lying along inside front wall of the chest
Upper fibers run obliquely & assist in pulling the chest downward

5. Subcostal Muscles Along lower inside back wall of the thorax
Originate from lower ribs near the vertebral attachment
Run outward and up to insert into ribs one or more higher
Pull lower ribs (bucket handle) inward & downward

6. Internal Rib Cage Muscles of Exhalation
Outside view
of back wall
of lower six
ribs
Transversus
Thoracis
Inside view
of front wall
of upper six
ribs
Internal
Intercostals
Subcostals

7. Serratus Posterior Inferior
Slants upward & outward from lower thoracic and upper lumbar vertebrae
Inserts into the lowest four ribs
Size, angle of pull & leverage to depress the lower ribs with strong force

8. Quadratus Lumborum Strongly pulls down on the lowest floating rib
Pulls from its attachment along the upper border of the hip (coxal bone)
Flat vertical muscle in the posterior abdominal wall

9. External Rib Cage Muscles of Exhalation
Serratus
Posterior
Inferior
Quadratus
Lumborum

10. Abdominal Muscles of Expiration
Abdominal wall muscles provide major active force in exhalation
Contribution to breathing is compression of viscera that push up on diaphragm
Pushing displaces 60-80% of the exhaled volume
Function as rib cage depressors (pull down on thorax) & abdominal compressors

11. Rectus Abdominus Large, vertical ribbon muscle
Runs from front of pelvis along midline of belly to the sternum & lower ribs
Limited in amount of compression it applies (Pulls in a straight line)
Downward pull on sternum provides powerful exhalatory force

12. External Oblique
Originates from the lower 8 ribs and sweeps down and forward
Posterior fibers descend vertically to crest of coxal bone
Other fibers slant obliquely forward toward midline
Insert into tendinous sheath called abdominal aponeurosis (covers rectus abdominus)
Contribute to exhalation by pulling down on the thorax while compressing viscera

13. Internal Obliques Thinner muscle, middle layer of abdominal wall
Course of fibers opposite to external obliques
Originate along upper border of coxal bone, fan out and up
Fan out at right angles to the external obliques
Insert at the midline into the abdominal aponeurosis & cartilages of the lower ribs
External & Internal pull down on the thorax and squeeze the viscera

14. Transversus Abdominus
Deepest layer of abdominal muscle
Horizontal fibers sweep from the vertebrae in the back of the abdomen
Insert into abdominal aponeurosis
Attaches above to the lower border of the ribs (the cartilages of the lower 6 ribs)
Attaches below to the upper border of the pelvis (coxal bone)- Like a corset (compress viscera)
Corset action- Ext. & Int. obliques add
Paired muscle- Tug of war

15. Abdominal Muscles of Exhalation
Rectus Abdominus
Transverse Abdominus
Internal
Oblique
External
Oblique

16. Passive forces Inspiration- raises rib cage against gravity
cartilage are twisted
viscera compressed
alveolar sacs inflated against surface tension
greater the inhalation= greater resistance (muscles)
Muscles relax= passive forces
Untorquing
Gravity
Elastic recoil of lungs

17. Relaxation Pressure Ribs Exhaled Raised Torqued cartilage
Elastic Recoil
Inhaled
Gravity

18. Assignments Reading: Seikel: Ch.3 (Pgs. 99-109)
Maue-Dickson: Ch.3 ( )