1. Consists of sternum, ribs, costal cartilages and thoracic vertebrae

2. Wider from side to side than front to back

3. 12 pair of ribs with 7 true pair, 3 false pair and 2 floating

4. Ribs articulate at bodies and transverse processes of thoracic vertebrae -

nonaxial costovertebral joints

5. Movement is elevation and depression of rib cage respectively with inspiration

and expiration of lungs

Inspiration - up and out; increase in thoracic cavity with decrease pressure

in thorax, forcing air into lungs

Expiration - down and in (at the starting position); decrease in thoracic

cavity with increase pressure in thorax, forcing air out of

lungs

1. Quiet - resting or sitting quietly; diaphragm and external intercostal muscles

2. Deep - increased from resting with more O2 necessary; above muscles plus

Sternocleidomastoid, Scalene

3. Forced - very hard breathing, need great deal of O2; above muscles plus those

that elevate the shoulder girdle - levator scapula, upper trapezius, rhomboids

B. Expiration - two phases

1. Quiet - mostly passive, occurs with relaxation; no muscle action

2. Forced - depression of the thoracic cavity; rectus abdominis, external oblique,

A. Diaphragm - separates the thoracic from the abdominal cavity

O: xiphoid process, ribs, lumbar vertebrae

I: central tendon

A: Inspiration

N: Phrenic

B. External Intercostals

O: rib above

I: rib below

A: elevate

N:Intercostal branches of T1 - 11

C. Internal Intercostals

O: rib below

I: rib above

A: Depress

N: Intercostal branches of T1 - 11