Week Two
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Page Two
Page Three
Welcome to Day Eleven!
The pelvic bone is at the base of the torso and is made up of three bones. We have the left and right sides of the pelvis itself, and the Sacrum which helps to create the back surface of this bone structure. The pelvis's main purpose is to help support the weight and structure of upper half of the the body and skeleton.
There are many ways in which a pelvis can differ from one person to another, but the major differences, are seen when looking at both a male and female pelvis. In fact, the right person with an understanding of these differences can determine the sex of the skeleton at a 100% accuracy rate, as stated by this article on pubmed.gov, by the pelvis. Do keep in mind, however, that these changes occur after puberty, meaning that when looking at a child's pelvis, they are largely indistinguishable before this point.
The main, and possibly obvious, reason is that the female pelvis is generally designed to be able to cary and give birth to a child. The female pelvis is much more round, shallow, and open, compared to a male's, to provide a good structure to support a fetus within the pelvic cavity during gestation. The pelvic outlet, or the opening at the bottom of the pelvis, is much wider to allow for the passage of a child's skull through the pelvic outlet during a natural child birth. For the same reason, the sacrum and coccyx in the female tend to be straighter and more out of the way to widen the over all size of the pelvic outlet. With all of this put together, women end up with a much wider, flatter pelvis which leads to women inevitably having much wider hips.
This means that a male pelvis has no concern at all for bearing children, so it can stand up a little more vertically, it can be thinner and more narrow, with a more curved sacrum and coccyx, leading to a smaller pelvic outlet. Similarly, men tend to have a skinnier, taller pelvis, leading to men having skinnier hips when compared to women.
You might notice by looking at the two examples here, that there is one other measurement that is pretty accurate in helping to differentiate between a male or female pelvis, which is known as the subpubic angle. This is a measure of the angle that is at the very base of the pelvis and the male pelvis almost always has a measurement that is less than 90°, while the female pelvis has a measurement that is almost always greater than 90°.
Today we discussed the differences between the pelvis of a male and female person. In general, men have a more narrow, but tall pelvis while their pelvic outlet is smaller in part to the sacrum and coccyx being more round. Women have a wider pelvis more designed to carry and give birth to children with a wider pelvic outlet to help natural childbirth be a bit easier. To aid in this, the sacrum and coccyx are straighter.
The pelvic bone can be tricky to wrap your head around as it is a rather strange structure, so looking at 3D models is one way to get a better grasp of the form. I suggest looking up other resources to continue your learning to expand your understanding of this structure, as it will probably take some time to become more familiar with it.
ASSIGNMENT ONE
Armed with this knowledge, meaning the major differences between male and female pelvis, your first assignment is to sketch out two pelvises, one that is more typically male, and one that is more typically female.
Assignment Two
As you might imagine, we are going to view the other four examples from today and draw out the pelvis in four different views. The first from the front, the second in 3/4th view, the third from the side, and the fourth from the back. Feel free to use the 3D model to aid your efforts.