27-10-09 Biomed Hw 5

Tejada 1 Edgar Tejada Intro to Biomedical Engineering 8 October 2009 HW 5 1. Muscles are not working in mechanical advantage because the joints are rotary (and deal with torque), and the muscle setup itself is a third-class lever, which means that the fulcrum is acting in opposition to both forces. This setup requires almost 10 times as much input for a given output, it also increases resistances and allows for greater control. 2. [Refer to attached sheet] 3. [Refer to attached sheet] 4. Crossbridge cycle: I. Hydrolisis, the process in which water is split up into OH+ and OH- ions, occurs while myosins, motor proteins, are detached. II. Hydrolisis of ATP (most of life's energy currency) attatches myosisns. III. The products of ATP Hydrolosis is released, generating the force of 'powerstroke.' IV. Myosins detatch from actins, ending one cycle of actomyosin ATPase. 5. Diaphysis is the long midsection of longbone; it contains the marrow and adipose tissue and is composed of cortical bones. Epiphysis is the curved ends of long bone, which contain red bone marrow (the producers of red-blood cells), and connects the long bones to the joins and articular cartilage. 6. One method of helping those with knee problems, which usually deals with issues with the cartilage, is the use an autograph. We can gather a small amount of the cartilage tissue from the portions of the joint that do not receive much stress, and then grow cultures of it in dishes. We

Tejada 2 then graph this native tissue to the area where the cartilage is either thining or becoming fibrous, allowing for better joint movement, The issue with this process is that cartilage cultures quickly disassociate into a different type of cartilage cells, the process is time consuming and expensive, and donor sites of the tissue often die. 7. Cartilage is composed mostly of water but is held together by a collagen matrix with the additional components of proteoglycans and other proteins. 8. Starting from the bone: I. Enthesis: the point at which the muscle and tendons attach to the bone using collagen, II. Tendons are the fibrous connective tissue that connect bones to bones. They usually also work with ligaments and muscles for movement. III. Ligaments are similar in structure to tendons, but connect muscle to bone. They work with disks of fibrocartilage at joins (miniscus). 9. [Refer to attached sheet] 10. Mechanical testing is a key component of materials engineering in that one must test a structure or material against different stresses to have an idea of it's limits. One example is Charpy Impact testing, usually done with a pendulum axe that puts strain on a given material or component. The amount of pressure (strain) is quantitative, but the strength at fracture can only be relative to other materials. 11. MicroCT is the use of a small, x-ray device to produce isotropic images. The use of MicroCT allows for the production of better 3-D models of bones and soft tissue, but usually requires contrast agents, such as iodine, to be used to improve the image quality. We can even use mico-particles in micro-structures to appear as different 'colors' (refracted wavelengths) in the resulting images. This is extremely useful for orthopedic treatments because it allows for a

Tejada 3 better look at bone structures and any possible complications, such as tumors.