Sunday, November 6, 2016

Unit 3 Reflection

For the first half of this Unit we discussed the structure of the human heart (including the layers of the heart wall and the 4 chambers of the heart), the function of valves, the cardiac cycle, the circulatory system and its components, blood pressure, the different types of blood vessels, the different types of blood cells, and heart attacks. For a more detailed discussion of these topics, please click here to view my Mid-Unit SummaryThe second half of this unit, we discussed how problems in the circulatory system (as we went over in the Heart Chalk Walk Activity) can lead to various cardiovascular diseases, specifically heart attacks and strokes. As I already detailed how heart attacks occur in my mid-unit summary, in this blog-post I will focus on strokes (shown in the picture below) and the respiratory system. 
A stroke is a brain injury that occurs when the blood supply to part of the brain is interrupted by a blood clot (also known as an thrombus, if it's made in a blood vessel and stays there, or an embolus, if it forms in one part of the body and then travels to another). It is sometimes referred to as a "brain attack," as it is essentially the same as a heart attack, except that it occurs in the brain. There are two main types of strokes: ischemic strokes and hemorrhagic strokes. An ischemic stroke occurs when an artery that supplies blood to the brain is blocked - a condition often caused by atherosclerosis. The picture below shows how in an ischemic stroke, a blood clot (in this case, an embolus) formed in the heart during atrial fibrillation can travel through the aorta, common carotid artery, and internal carotid artery, settle in a branch of the internal carotid artery, and stop blood flow. A hemorrhagic stroke, on the other hand, occurs when an artery taking blood to the brain bursts, which can be caused by high blood pressure or excess cholesterol, and blood leaks out of the blood vessel and into the brain. The brain tissue that had its blood supply cut off by the stroke dies and other parts of the brain must be trained to take over the functions that the dead tissue was responsible for (also shown in the diagram below). A transient ischemic attack (or TIA) is a "warning stroke" that only lasts a couple minutes, but foreshadows that a larger stroke is probably in the near future. When someone is having a stroke, the signs to check if he or she is really having a stroke and to minimize the effects of the stroke are to check the acronym FAST - Face (ask the person to smile), Arms (ask the person to lift up both of their arms), Speech (ask the person a question and see if they can respond properly), and record the Time since their symptoms (this will make it much easier for doctors to determine the proper course of treatment). Often times, doctors use the tissue plasminogen activator (tPA) to bust the clot formed, stent insertion to open up the artery, or MERCI to retrieve the clot via a "corkscrew" method.
Cardiovascular health is extremely important in order for blood to consistently and properly flow throughout your body. Cardiovascular diseases like heart attacks and strokes hinder the flow of blood and are generally caused by atherosclerosis of the coronary arteries. Atherosclerosis is chronic inflammation caused by the excess consumption of sugars, polyunsaturated fats, or Omega-6, and it can severely damage the blood vessels. Other factors that can lead to cardiovascular disease are lack of exercise, being overweight, smoking, diabetes, metabolic syndromes, high blood pressure (caused by atherosclerosis), and high cholesterol. Thus, to promote cardiovascular health and reduce the chances of cardiovascular disease, one should try to control their blood pressure and cholesterol, stop smoking, eat a healthy diet, consume alcohol in moderation, control weight and diabetes, manage stress, and be aware of family genetic history. I still wonder about the role that genetic history plays in our cardiovascular health: if all of my grandparents and many of my uncles have had diabetes or cardiovascular diseases, what are the chances that I will get it too? In addition, how do the lungs of the respiratory system work with the circulatory system to oxygenate blood before returning it to the heart?

In addition, we discussed how the respiratory system works in conjunction with our circulatory system by oxygenating the blood that the circulatory system then pumps throughout the body. The main functions of the respiratory system are to deliver oxygen, remove carbon dioxide, filter the air we breath in, and regulate the pH of the blood. The respiratory involves many organs that work together. The nose (nasal cavity) is a large open chamber lined with mucus that contains the sinuses. The pharynx (throat) also lined with a mucous membrane is a passageway for food and air that sends air to the larynx and food to the esophagus. The tonsils, which are also located in the pharynx, trap bacteria from the air we breathe in. The larynx (voice box) is made of 9 cartilage rings, contains our vocal chords, and contains a flap called the epiglottis which directs food into the esophagus and keeps food out of the lungs. The trachea (wind pipe) is an organ made of cartilage and lined with a mucous membrane that is hard in the front and soft in the back to allow the esophagus to expand when a person swallows. The lungs (air sacs) are surrounded by a pleural membrane and contain a bronchiole tree and an alveolar sac, which is very thin and easily damaged but is responsible for gas exchange in the capillaries. The image below shows how these organs function together to help us breathe:

We also did a sheep heart dissection towards the end of this unit that helped us visualize the different parts of the heart by identifying them on a real heart. It made me realize that a diagram of the heart is a simplified representation of the heart. Many of the structures in the heart are much harder to identify in a real heart, but are generally in the same locations that diagrams show them in, which was pretty amazing to see. Click here to read my previous blog post about our Sheep Heart Dissection

From this Unit, I realized how much of a visual learner I am. The various heart diagrams at the end of the heart dissection packet, diagrams like the ones I have inserted in my blog posts, and the sheep heart dissection all helped me visualize what we were learning much better - it made these cardiovascular diseases more relatable rather than just theoretical/textbook knowledge. I realized that these diseases are real and happening to people every single day, making the material more interesting to learn due to its relevancy. It also made me realize how much these diseases can affect me in the future, which is why I need to be more careful with my eating and exercise habits to ensure I don't get diabetes or cardiovascular diseases early in life. I also learned that I need to spend more time memorizing details that cannot be visualized, as it has always been hard for me to memorize facts. I think I'm definitely a better student after this unit, as I learned the importance of collaboration and working together, especially when it comes to labs like the dissection. In regards to the Unit 2 health goals, I think I'm doing much better with exercise as I have tennis practice everyday and have started running on the weekends. In addition, I've been more conscious of my eating and have been trying to consistently eat 3 meals a day. Lastly, I'm still pretty stressed out and sleep-deprived due to my class load and college applications, but am working on my time management so I can finish my work faster and sleep earlier. And if I find myself feeling too tired at the end of a day, I take a nap before starting my work. Though I still have a long way to go before my health is where I want it to be, I think I've made a lot of progress already and just need to work on it more.

Sheep Heart Dissection




Here is the link to our Sheep Heart Dissection Video Tutorial

Lab Questions: 
1. The pericardium consists of an outer fibrous layer and an inner double layer of serous membrane. It's purpose is to surround the heart, protect it, and help keep it in place as it's beating.

2. The veins have thinner walls than the arteries but store most of the blood volume in our bodies. They are responsible for carrying blood back to the heart and they have valves that ensure the blood flows in one direction. On the other hand, arteries are elastic and contractile blood vessels that have much thicker walls as they carry blood away from the heart and to the rest of the body.

3. The auricles, which felt rough when we touched them, are elastic ear-shaped appendages that are external parts of the atria and increase the blood capacity of the heart's atria, allowing the atria to expand and hold a greater volume of blood. 

4. The atria have auricles on the outside and are much smaller in size than the ventricles, which appear to be completely covered in fat. 

5. The coronary sinus is a wide channel that collect deoxygenated blood from the coronary veins and empties into the right atrium of the heart. The inferior vena cava is a large vein that brings deoxygenated blood from the lower body to the right atrium of the heart. Lastly, the tricuspid valve, ensures that blood flowing from the right atrium to the right ventricle flows in one direction with no back flow. 

6. Picture of the tricuspid valve, including the chordae tendinae and the papillary muscle:

7. When the right ventricle contracts, the pressure of the blood in the ventricle increases and the blood pushes up against the tricuspid valve, which keeps the blood from flowing back into the right atrium. The chordae tendinae attach to papillary muscles that pull the chordae tendinae to open and shut the valve.

8. The bicuspid valve lies between the left atrium and left ventricle and, like the tricuspid valve, it ensures that the blood flows in one direction.

9. The semilunar valves keep blood in the arteries from re-entering the ventricles of the heart during ventricular diastole and ensures that blood is consistently traveling into the arteries and to the rest of the body. There are two types of semilunar valves: the aortic semilunar valve, which is situated where the left ventricle empties into the aorta, and the pulmonary semilunar valve, which lies at the opening where the pulmonary trunk leaves the right ventricle. 

10. Valvular heart disease:
a) An abnormal amount of blood is flowing to the feet and ankles in an uncontrolled manner because the ventricles are unable to pump blood up against the flow of gravity, and thus, back flow occurs.
b) If valve disease were to occur on the left side of the heart, an insufficient amount of blood would be pumped throughout the body, causing swelling. 

11. The coronary arteries supply blood to the heart muscles. The aortic semilunar valve keeps blood in the arteries from re-entering the ventricles. The chordae tendinae are stringy structures that attach the cusps of valves to papillary muscles. Lastly, the papillary muscles provide the "muscle power" that pull the chordae tendinae to open and shut the valve.

12. The right side of the heart has thinner walls than the left side of the heart and mainly deals with deoxygenated blood. Deoxygenated blood enters the right atrium through the inferior and superior vena cavas. The blood then travels through the tricuspid valve and into the right ventricle, which pumps the blood through the pulmonary semilunar valve and into pulmonary veins. The pulmonary veins then take that blood to the left and right lungs to be oxygenated. The left side of the heart, on the other hand, has thicker walls because it is responsible for pumping blood to the entire body and it mainly deals with oxygenated blood. Oxygenated blood from the lungs enters the left atrium via pulmonary arteries. The blood is then pumped through the bicuspid valve and into the left ventricle. The left ventricle (the largest chamber of the heart) pumps the blood through the aortic semilunar valve and into the descending aorta, which takes oxygenated blood to the lower body, and the ascending aorta (aortic arch), which branches into three other arteries that all take blood to the upper body. 

13. Drawing of the interior of the cross section: