Benny Jeong, bennyjeong218@gmail.com
Tuesday, March 15, 2011
Bones, bones, bones
On page 30, Shubin tells of a discovery that Owen had made on the number of bones in limbs. He tells us that a common pattern in all limbs is that it starts off with one bone then the number of bones increases. For example, in a human arm there is "one bone in the upper arm, two bones in the forearm, a bunch of nine little bones in the wrist, then a series of five rods that make the fingers". Using the theme of structure and function and evolution, why is it that all limbs follow this common pattern?
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The arm has 1 large bone in the upper arm, followed by 2 little bones in the forearm, followed by little bones in the hand. This is because of the fact that different parts of the arm have different functions. The upper arm is mainly for strength and support. Thus, to support a whole arm with strength a large bone is present. A large bone is able to handle tough work as compared to tiny bones scattered everywhere. Comparing the upper arm to a human hand, the human hand is much more precise. The hand performs functions that are requiring more delicacy and flexibility. Made up of tendons, muscles, and phalanges, the hand is able to flex more than the upper arm, which is made up of one bone, whose primary function is support.
ReplyDeleteLimbs must follow this pattern because every arm and leg must have a strong support system. In the legs, the femur is the large bone in the human upper leg. Its large size is for “support and body posture” (Campbell 1114). The femur must be able to support the body weight of the human during locomotion and while standing without moving. The lower leg is comprised of the tibia and fibula which also play a large role in body posture and support. The foot is comprised of many tarsals and metatarsals. These provide flexibility in the feet. Thus, you are able to stand on your toes because the tarsals are very flexible. Also, the flexibility within the foot allows for balance and proper locomotion.
Campbell
http://library.thinkquest.org/5777/ske4.htm
Matt Micucci (coochqbk@sbcglobal.net)
Following the theme of structure and function of ALL limbs, we can go into a more generalized analyzation of bones. The human skeleton consists of both fused and individual bones supported by ligaments, tendons, muscles and cartilage. Bones act as a scaffold which supports organs, anchors muscles and protects organs such as the brain, lungs and heart. The biggest bone in the body is the femur in the thigh and the smallest is the stapes bone in the middle ear. In an adult, the skeleton comprises around 30-40% of the total body weight, and half of this weight is water.
ReplyDeleteFurthermore, relating back to the immunity unit, blood cell production occurs in bone marrow, which is present in long bones ie. legs. Also, bones release a hormone called osteocalcin which regulates blood sugar levels. Overall, on a molecular scale the bones are important to our bodies extremities as the source of nutrition/energy and defense mechanisms are far away. Also, bones store calcium and iron which are both major components in metabolism. The bones not only help with support and posture, rather with endocrine regulation, metabolism and blood cell production.
As Matt stated above, there are many parts to limbs because each have different functions. When comparing a limb the center of the body, a limb is an extremity that needs extra support and flow of blood because it's so far from the heart and spinal cord. The reason why the legs, hands and feet are comprised of many bones is because they each have very specific functions that have to make up for the distance they are away from the center of the body. The arch bones in our feet help hold our foot bones firmly while still giving us springiness. There is a plethora of functions that each bone serves in human and animal limbs and it relates right to its structure.
Eryk Fundakowski- arthur2446@comcast.net
http://www.bbc.co.uk/science/humanbody/body/factfiles/handsandfeet/hand.shtml
http://www.mananatomy.com/basic-anatomy/types-bone