A brief about anatomy, physiology and functions of skin

1. Biomechanics of respiration

2. Introduction
• The movement of the rib cage is an amazing
combination of the types and angles of the
articulations, the movement of the
manubriosternum, and the contribution of the
elasticity of the costal cartilages.

3. Principle 1
1. Each rib may be regarded as a lever, the fulcrum of
which lies just lateral to the tubercle.
• Because of the disproportion in the length of the
two arms of the lever, the slight movements at the
vertebral end of the rib are greatly magnified at the
anterior end.

4. Principle 2
• The anterior end of the rib is lower than the
posterior end.
• Therefore during elevation of the rib, the
anterior end also moves forwards.
• This occurs mostly in the vertebrosternal ribs.

5. Continued…
• In this way the anteroposterior diameter of
the thorax is increased.
• Along with the up and down movements of
the 2nd to 6th rib, sternum also moves up and
down called pump – handle movement

6. Principle 3
• The middle of the shaft of the rib lies at a
lower level than the plane passing through the
two end.
• Therefore during elevation of the rib, the shaft
also moves outwards.

7. Continued…
• This causes increase in transverse diameter of
the thorax.
• Such movements occurs in a vertebrochondral
rib known as bucket handle movement

8. Principle 4
• The thorax resembles a cone, tapering upwards.
• As a result each rib is longer than the next higher
rib.
• On elevation the larger lower rib comes to occupy
the position of the smaller rib.
• This also increases the diameter of the thorax

9. First rib
• The anterior articulation of rib 1 is larger and
thicker than that of any other rib.
• The first costal cartilage is stiffer than the
other costocartilages.

10. Continued…
• Posteriorly, the CV joint of the first rib has a
single facet, which increases the mobility at
that joint.
• During inspiration, the CV joint moves
superiorly and posteriorly, elevating the first
rib

11. Sternum
• During inspiration, the ribs elevate.
• The costocartilage become more horizontal.
• The movement of the ribs pushes the sternum ventrally
and superiorly.
• The excursion of the manubrium is less than that of the
body of the sternum because the first rib is the shortest,
with the caudal ribs increasing in length until rib 7.

12. Pump handle movement
• The discrepancy in length causes movement at the MS
joint.
• The motion of the upper ribs and sternum has its greatest
effect by increasing the anteroposterior (A-P) diameter of
the thorax.
• This combined rib and sternal motion that occurs in a
predominantly sagittal plane has been termed the
“pumphandle” motion of the thorax

13. Bucket handle movement
• Elevation of the lower ribs occurs about the axis of
motion lying nearly in the sagittal plane.
• The lower ribs have a more angled shape (obliquity
increases from rib 1 to rib 10) and an indirect
attachment anteriorly to the sternum.
• These factors allow the lower ribs more motion at the
lateral aspect of the rib cage.

14. Continued…
• The elevation of the lower ribs has its greatest
effect by increasing the transverse diameter of
the lower thorax.
• This motion that occurs in a nearly frontal
plane has been termed the “bucket-handle”
motion of the thorax

15. 11 and 12th rib
• The 11th and 12th ribs each have only one
posterior articulation with a single vertebra
and no anterior articulation to the sternum.
• therefore, they do not participate in the
closed-chain motion of the thorax.

16. Muscles
• Inspiration: diaphragm, sternocleidomastoid,
scalene, SA, pect min, erector spinae
• Expiration: abdominals. Latissimus dorsi