Form+Follows+Function


 * __How does the cardiovascular System demonstrate how 'Form Follows Function' in the human body?__**

Form follows function in the heart of a fetus. Because the lungs are still developing, they are very fragile and would be damaged if blood flowed through them. Therefore, an alternate system is needed to ensure that the fetus gets the oxygen it needs, and is able to get rid of the carbon dioxide it doesn't need. This is done through **umbilical circulation**. The umbilical vein forms and allows blood to transport the oxygen from the placenta to the fetal body. Two other structures also form in the heart to allow umbilical circulation. The **Ductus Arteriosus**, allows blood to bypass the lungs and go directly from the pulmonary trunk to the aorta. The **Foramen Ovale**, also contributes because it is a small passageway for blood to flow directly from the right atrium to the left. The formation of the umbilical vein, ductus arteriosus, and foramen ovale follows their function, which is to allow umbilical circulation and prevent damage to the lungs. =)

Form Follows Function in regard to the body capillaries. Gaseous Exchange needs to occur between the cells and blood in the body capillaries. If the carbon dioxide produced in the cells from cellular respiration was left in the cells, the cells would die. Also, the cells need to get oxygen from the blood in order to be able to perform necessary cellular respiration. The epithelial tissue found in the capillaries, simple squamous cells, is perfect for diffusion of gases. Diffusion is further facilitated in that a strong diffusion gradient is present for both oxygen and carbon dioxide; there is high concentration of oxygen in the blood and low concentration of oxygen in the body cells as well as high concentration of carbon dioxide in the body cells and low concentration of carbon dioxide in the blood. Therefore, the body cells and tissues are made of simple squamous cells to allow for this vital diffusion of oxygen and carbon dioxide.

The function of the human heart is to pump deoxygenated blood to the lungs to receive oxygen and pump oxygenated blood to the rest of the body cells for nourishment. To accomplish this, the heart has two pumps to transport blood to different locations. The right side pumps the blood to the lungs and the left side of the heart pumps blood to the body cells that need oxygen. Because most of the body is farther away from the heart than the lungs are, the left side of the heart must work harder to pump blood. Therefore, the left side of the heart is larger and more muscular than the right side of the heart.

Form follows function in regard to the veins and arteries. As blood vessels, veins and arteries need to transport blood throughout the heart and body. **Arteries** transport blood away from the heart to the body cells. Because arteries work so closely with the heart, they must consist of more elastin and collagen fibers so they can stretch to best accommodate the pressure changes in the heart. Smaller arteries, called **arterioles**, branch off the main arteries so blood can be transported to more places. However, in certain conditions (when it is very cold), it is better for the body to keep blood centered by the major organs. As a result, **sphincter** **muscles** are developed to stop blood flow to smaller arteries. **Veins** carry blood back to the heart. Because veins start so far away from the heart, there is not alot of pressure to help them return blood to the heart. Since they need some way to transport blood back up to the heart, and have no pressure of their own, the veins are situated next to or inside muscles. Muscles are always contracting and relaxing to allow movement. When a muscle contracts, the vein gets squeezed, and the blood can go in only two directions. Since the blood is already deoxygenated, and of no use to the body cells, the veins have **one way valves** to stop the backflow of blood. These force the blood to return to the heart when the muscles contract, thus allowing the process of circulation to continue.

Form follows function in respect to red blood cells (RBC's). The main function of red blood cells is to transport oxygen through the bloodstream to the rest of the body. In order to carry as much oxygen as possible, all other organelles in the red blood cells have been shed. Therefore, red blood cells differ from other body cells in that they are **anucleate,** meaning they do not have a nucleus. This allows for more room within the red blood cells to carry **hemoglobin.** Hemoglobin is a protein that contains iron that binds to oxygen and helps transport it through the blood. In order to hold as much oxygen as possible, red blood cells are shaped like dimpled disks **(biconcave disks),** which increases surface area to volume ratio. This makes them ideal for gaseous exchange. The red blood cells produce energy through **anerobic respiration**, which doesn't use the oxygen that must be transported to the rest of the body. The **flexible** biconcave disk shape also makes it easier for RBC's to flow through the bloodstream.

Form follows function in white blood cells. The white blood cell's primary function is to fight against infections in the body's cells. Therefore it must be responsive and efficient at locating and destroying infected cells. The white blood cells move through the blood with **amoeboid** motion via pseudopods. As the white blood cell moves through out the blood it senses prostoglandins secreted by infected body cells. The white blood cells continue to remain in the blood until the cells find an area where there is the highest diffusion gradient of prostoglandins. The white blood cells respond to the chemicals secreted by the infected body cells in a process called **positive chemotaxis**. The white blood cells then moves out of the blood through blood vessels in a process known as **diapedesis**. When the white blood cell finally arrives to the location where the infected cell has released the prostoglandis the white blood cells will begin phagocytosis. **Phagocytosis** is the process in which white blood cells engulf and eventually destroy the infected cell. Once the infected cell is engulfed in the white blood cell the **lysosomes** breakdown the infected cell. Für Deutschland