Useful+Information


 * __Useful Information you will need to know for the end of unit evaluation__**

__[|Try watching this video on the circulatory system first]__:


 * 1.** **__Structure of the Heart__**


 * The heart consists of two pumps; the right, which pumps deoxygenated blood to the lungs, and the left, which pumps oxygenated blood to the rest of the body.
 * The lining of the inside of the heart is made up of epithelial tissue, which provides a smoother passageway for the blood rather than having it exposed to cardiac muscle.


 * __**The right side**__ consists of the right atrium which is supplied with deoxygenated blood from the **superior vena cava** and **inferior vena cava**. Once filled with blood, the **right atrium** contracts, pushing the blood through the **tricuspid valve** and into the **right ventricle** . The tricuspid valve then closes, making the "lub" sound of our heartbeat, as the right ventricle contracts. This pushes the blood through the **pulmonary semi-lunar valve** and into the **pulmonary trunk** . As the pulmonary semi-lunar valve closes, in order to prevent the blood from flowing back into the right ventricle, it makes a "dub" sound. The pulmonary trunk then splits off into the **pulmonary arteries** which travel to the **capillaries in the lungs** to allow the blood to release carbon dioxide and pick up oxygen.
 * __**The left side**__ of the heart is made up of the **left atrium** and the **left ventricle**. Oxygenated blood, coming from the lungs via the **pulmonary veins**, rushes into the left atrium. The **bicuspid valve**, which separates the atrium from the ventricle, opens and lets this pool of blood enter the left ventricle. This valve is also known as the **mitral valve**. As the blood fills the ventricle, the walls of the ventricle expand, causing the mitral valve to close and prevent any more blood from entering. Then, as the mitral valve closes, it makes a "lub" sound. Then the left ventricle contracts and forces blood through the **aortic semi-lunar valve** and out into the **aortic arch**. Since the left side of the heart pumps blood to the entire body, and not just the lungs, the cardiac muscle surrounding the left ventricle is drastically thicker than its right counterpart. As the aortic semi-lunar valve closes, it emits a "dub" sound.



The **cardiac cycle** is the process that occurs as the heart contracts and relaxes as it pumps blood to either the lungs or the cells and tissues all over the body. During **diastole**, the muscles of the heart are relaxed, allowing blood to enter, by way of the pulmonary veins into the left side of the heart or the vena cavas into the right side of the heart, and fill up the atria. Once the atria are filled with blood, the atrioventricular (AV) valves are pushed open in order to allow this blood to enter the ventricles. In the left side of the heart this valve is known as the bicuspid valve and in the right side of the heart, the tricuspid valve. The ventricles fill themselves with blood by pressure caused by contraction in the atria and also by suction from the relaxed ventricular walls. Once the ventricles are full and stretched with blood, the atrioventricular valves close and the semilunar valves are forced open. The pressure that forces the semilunar valves open (the pulmonary semilunar valve in the right side of the heart and the aortic semilunar valve in the left side of the heart) is known as systolic pressure. **Systole** occurs when heart muscle and the ventricle contracts forcing blood out of the heart and pumping it to where ever it has to go.
 * 2. __Cardiac cycle__**

There are two types of circulation in the human body: **Pulmonary circulation** and **Systemic** **circulation**.
 * 3. __Circulation__**


 * Pulmonary circulation** is the circulation of blood to and from the lungs. De-oxygenated blood travels from the right side of the heart to the lungs via the pulmonary trunk and arteries. Once it delivers carbon dioxide and picks up oxygen in the lungs, this blood travels back from the lungs to the left side of the heart by way of the pulmonary veins. During pulmonary circulation, a //gaseous exchange// occurs when the blood arrives at the lungs. As blood travels through the lung capillaries, carbon dioxide diffuses from the blood into the air of the lung alveoli and is expelled with exhalation. At the same time the oxygen diffuses from the air inhaled into the alveoli into the blood flowing through the lung capillaries.


 * Systemic circulation** is the circulation of blood to and from all areas of the body except the lungs. Oxygenated blood travels from the left side of the heart to the body cells and tissues, and then back to the right side of the heart. The oxygenated blood is sent to the cells around the body through the aorta. As the blood travels through the body, glucose and other nutrients diffuse into the blood from the **small intestine**. When the blood arrives at the body cells, a gaseous exchange occurs here as well. **Oxygen** and **glucose** diffuse into the **body cells** from the blood**,** and carbon dioxide diffuses into the blood from the body cells. Oxygen and glucose are needed for cells to carry out cellular respiration and create //ATP energy//. The **carbon dioxide** is a waste product of **cellular respiration** and diffuses into the blood so that it can be expelled from the body. **Urea** and **uric acid**, which are by-products of the **cellular metabolic processes,** also diffuse into the blood to be expelled. Most blood travels through the kidneys at least once every five minutes at which time urea and uric acid leave the blood and are passed through the kidneys into the bladder where they will eventually be released in urine.

[|Good Diagrams of Systemic and Pulmonary Circulation] <--Click Here!!


 * 4. __Artery and Vein Structure__**
 * Arteries and veins need to have very specific structure to help blood flow through the entire body. Both arteries and veins are made of three parts, **the tunica externa** (external section), **tunica media** (middle section), and **tunica intima** (section most intimate with blood. TY Mr. Keaney).
 * Arteries** branch off into **arterioles** and then into **small capillaries.** Arteries have a thicker tunica media to allow them to expand and recoil as the blood, under **a lot of pressure** due to the forceful contractions of the heart, travels through them.
 * Capillaries** have only a **single layer of squamous cells** to allow the diffusion of materials into and out of the blood and body cells.
 * After blood travels through the capillaries it will flow into a **venule** and then into a **vein.** The blood is now under **low pressure**, as it does not have any major force pushing it to return to the heart.To help blood return to the heart, veins usually pass through, or next to, **skeletal muscles** that when they contract squeeze the blood through the vein. They also have **one way valves** to prevent blood backflow (Arteries do not have one way valves). Another thing the body does to help the veins move blood is by **constantly breathing**. As we breath pressure changes in the thoracic cavity 'pull' blood back towards the heart . SM

Blood is composed of white blood cells, red blood cells, plasma, and platelets. The cycle of blood is a complex one and the list of where it travels could begin at any place. However, the easiest place to begin is at the heart. When the blood is in the left side of the heart, it contains oxygen. It is then pumped through the aorta to body tissues, organs, and cells; (Systemic Circulation) where oxygen is "exchanged" for carbon dioxide by following a diffusion gradient (they are not really //exchanged// because the blood would be able to supply the body cells with oxygen without the presence of carbon dioxide, and vice versa). Carbon dioxide is a waste product created by **Cellular Respiration.** Before returning to the heart however, the blood makes stops at two very important body organs: the small intestine and the kidneys. As blood passes through the small intestine, it absorbs glucose from digested food. From that point on, any body cell the blood comes in contact with absorbs the glucose and in return gives the blood the waste products formed during **cellular metabolism**; **urea** and **uric acid**. This "exchange" is also done by diffusion. As blood passes through the kidneys, it deposits the urea and uric acid there so that they can be excreted at a later time. After the blood circulates around the body it returns to the right side of the heart through either the inferior (if coming from the lower regions of the body) or superior (if coming from the upper regions of the body) vena cava. From there blood is pumped through the pulmonary artery to the lungs. At the lungs gaseous exchange in the form of diffusion takes place. The air in the lungs exchanges oxygen for carbon dioxide in the blood and vice versa. From there blood is pumped through the pulmonary veins back to the left side of the heart, where the process begins all over again. , The blood contains platelets, white blood cells and red blood cells. **Platelets** are irregularly shaped bodies in blood. Their sticky surface, and other substances, help to form clots to stop bleeding. When bleeding from a wound occurs, the platelets gather at the wound and attempt to block the blood flow. The mineral calcium, vitamin K, and a protein called fibrinogen helps the platelets form a clot. **White blood cells** are always on the look out for signs of disease. White blood cells use positive chemotaxis to detect prostoglandins from injured cells around the body. Once they detect these chemicals, the white blood cell moves with ameboid motion, by using pseudopods, to the area of the body. The white blood cells are also able to use diapedesis or the ability to move out of the cappilary walls into the tissues. Once the white blood cell finds the foreign body, it engulfs it and uses lysosomes to break it down. Some white blood cells use powerful protective antibodies that will overpower the foreign body. **Red blood cells** are constantly moving throughout the body delivering oxygen and removing waste. Red blood cells are biconcave disks in order to give them a larger surface area so they are able to diffuse a lot of oxygen. To help transport the oxygen, red blood cells are filled with hemoglobin which binds to the oxygen. Red blood cells are anucleate and have no major organelles to make room for as much hemoglobin as possible so they can transport as much oxygen as possible. Red blood cells use anerobic ways to produce atp so they do not use up their oxygen supply. They are also very flexible so they can fit through tiny capillaries. The life span of a red blood cell is about 120 days and they are continually being produced by the bones.
 * 5. __Blood__**




 * 6. Heart Attack**
 * A heart attack (also known as a **myocardial infarction**) is the death of heart muscle from the sudden blockage of a coronary artery by a blood clot. Coronary arteries are blood vessels that supply the heart muscle with blood and oxygen. Blockage of a coronary artery deprives the heart muscle of blood and oxygen, causing injury to the heart muscle. Injury to the heart muscle causes chest pain and pressure. If blood flow is not restored within 20 to 40 minutes, death of the heart muscle will begin to occur. Muscle continues to die for six to eight hours at which time the heart attack usually is "complete." The dead heart muscle is replaced by scar tissue.
 * **Atherosclerosis** is a gradual process in which plaques (collections) of cholesterol are deposited in the walls of arteries. Cholesterol plaques cause hardening of the arterial walls and narrowing of the inner channel (lumen) of the artery. Arteries that are narrowed by atherosclerosis cannot deliver enough blood to maintain normal function of the parts of the body they supply. For example, atherosclerosis of the arteries in the legs causes reduced blood flow to the legs. Reduced blood flow to the legs can lead to pain in the legs while walking or exercising, leg ulcers, or a delay in the healing of wounds to the legs.
 * While heart attacks can occur at any time, more heart attacks occur between **4:00 A.M. and 10:00 A.M.** because of the higher blood levels of adrenaline released from the adrenal glands during the morning hours. Increased adrenaline, as previously discussed, may contribute to rupture of cholesterol plaques.





Interactive tour of the heart and heart disease - GOOD ANIMATION [|http://www.nationalgeographic.com/human-heart/index.html] Article on the mending broken hearts: [|**http://ngm.nationalgeographic.com/ngm/0702/feature1/index.html**] Sights and Sounds from the article: [|**http://ngm.nationalgeographic.com/ngm/0702/sights_n_sounds/index.html**] Photos from the article: [|**http://ngm.nationalgeographic.com/ngm/0702/feature1/gallery1.html**] Movie on an artificial heart transplant: [|http://ngm.nationalgeographic.com/ngm/0702/feature1/multimedia.html]
 * __7. Helpful Websites__**
 * __Check out these links from National Geographic__**