bio study

The major function of the shoulder girdle is flexibility. What is the major function of the pelvic girdle? Relate these functional differences to anatomical differences seen in these girdles.

The major function of the pelvic girdle is attaching the lower limb to the axial skeleton. This distributes the weight exerted on the upper body to the lower limbs. As an adaptive feature, the bones of the pelvic girdle are large and strong. The functionality of the pelvic girdle is similar to other girdles like the shoulder girdle. For instance, both offer flexibility. They are also a ball and socket type of joints. However, the shoulder girdle has weaker bones compared to the pelvic girdle, and the former is more flexible than the latter.

Compare a young adult skeleton to that of an extremely aged person relative to bone mass in general and the bony structure of the skull, thorax, and vertebral column in particular.

1. Bones of a young adult’s skeleton are strong and dense, while those of an older adult is weak and thin.
2. The cortical bone is generally thicker in young adults, but the outer and inner tables of the frontal, occipital, and parietal bones of females reduce in thickness significantly with an increase in age.
3. A young adult has a less rigid thoracic region compared to an older adult, who have a very rigid thoracic region, caused by ossification of costal cartilage.
4. The vertebral column of a young adult is strong compared to that of an older adult.

Mr. Wright had polio as a boy and was partially paralyzed in one lower limb for over a year. Although no longer paralyzed, he now has a severe lateral curvature of the lumbar spine. Explain what has happened and identify his condition.

During the paralysis at his childhood, Wright’s muscles on one side of his back malfunctioned. The functional muscles on the other side of the back could then stretch without balance (opposing force), causing misalignment of the spine. It is the misalignment of the spine that has caused severe lateral curvature of the lumbar spine, and the condition is called scoliosis. It is an abnormal lateral curvature of the spine of more than 10 degrees.

Question

Since some dancers stretch their legs to gain flexibility, does it mean that the pelvic girdle is as flexible as the pectoral girdle, but its flexibility reduces due to inactivity?