biomechanics of respiration, anatomy and physiology

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 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 2 nd to 6 th 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 12 th 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