Types of Skeletal Systems

Free Response

What are the major differences between the male pelvis and female pelvis that permit childbirth in females?


The female pelvis is tilted forward and is wider, lighter, and shallower than the male pelvis. It also has a pubic angle that is broader than the male pelvis.

What are the major differences between the pelvic girdle and the pectoral girdle that allow the pelvic girdle to bear the weight of the body?


The pelvic girdle is securely attached to the body by strong ligaments, unlike the pectoral girdle, which is sparingly attached to the ribcage. The sockets of the pelvic girdle are deep, allowing the femur to be more stable than the pectoral girdle, which has shallow sockets for the scapula. Most tetrapods have 75 percent of their weight on the front legs because the head and neck are so heavy; the advantage of the shoulder joint is more degrees of freedom in movement.

Both hydrostatic and exoskeletons can protect internal organs from harm. Contrast the ways the skeletons perform these functions.


Hydrostatic skeletons protect internal organs from harm by cushioning them from external shock. However, these skeletons do not provide protection from external trauma. Exoskeletons are hard structures that protect the organs from damage caused by their environment. However, since they are rigid, they provide little shock absorption, so the animal will need to have other ways of cushioning its internal organs.

Scoliosis is a medical condition where the spine develops a sideways curvature. How would this change interfere with the normal function of the spine?


Normal vertebral columns are stacked in a vertical line. If the spine were to curve to the side instead this would disrupt the support and cushioning functions of the vertebrae. When the spine is out of alignment, it cannot absorb shock as well so normal activities can become painful and cause back problems later in life. The curvature also disrupts posture and structure, even disrupting lung expansion in severe cases due to changes to rib location.