Sheep Heart Dissection Video Tutorial

After we finished our sheep heart dissection, we made a video explaining the parts of the heart, their functions, how the blood flows through the heart, and how the heart beats. The video is below and can also be found on YouTube here and here:

2015.11.01 Sheep Heart Dissection

Today we dissected a sheep's heart. We were able to observe all the structures on the outside and inside the heart. As we studied the heart we answered questions that our teacher gave to us. The answers are below, and the question numbers are in parentheses ().

On the outside of the heart is the pericardium, a two-layered membrane sac that protects the heart and secretes a fluid that lubricates the heart to reduce friction. It also keeps the heart together as it continuously contracts and relaxes (1).

There are many blood vessels that connect to the heart. Blood vessels that take blood from the heart to the body are called arteries. Blood vessels that take blood from the body to the heart are called veins. Arteries are more elastic than veins, and their walls are thicker and contain more smooth muscle than the walls of veins. This lets the arteries expand and contract under the pressure that the heart exerts against the artery walls as it pumps blood (2).

The inside of the heart is divided into four chambers, two atria and two ventricles. The four chambers are divided into left and right. Each side (left or right) has one atrium and one ventricle. The right side of the heart pumps blood only to the lungs, so it is not as large and muscular as the left side of the heart, which pumps blood to the whole body. The right side of the heart contains deoxygenated blood, while the left side of the heart contains oxygenated blood (12).

The atria are the superior chambers that receives blood from the veins and pumps it into the ventricles. On top of each atrium is a dogear-like pouch that increases the blood volume of the atria so they can receive more blood from the veins (3). Since the atria only have to pump blood to the ventricles, their walls are not as thick and muscular as the walls of the ventricles, which have to pump blood to the lungs or to the whole body (4).

The atria are separated from the ventricles by atrioventricular valves, which prevent blood in the ventricles from flowing back into the atria when the ventricles contract. The atrioventricular valves, which are the tricuspid and bicuspid (mitral) valves, are "anchored" by the chordae tendinae, which are long fibers that trail off the valve, and the papillary muscle, which attach the chordae tendinae to the wall of the ventricle. This makes sure the valves close properly and keeps the valves from swinging backwards into the atria so that blood does not leak backwards into the atria. If valves are not anchored properly, blood could leak backwards instead of going where it needs to go, which could cause health problems like fatigue, swelling, or heart palpitations (irregular heartbeat) (7).

drawing of the tricuspid valve, showing the chordae tendinae and papillary muscle (6)

drawing of the bicuspid (mitral) valve, showing the chordae tendinae and papillary muscle (8)

The semilunar valves are the valves that separate the ventricles from the arteries that leave the heart. Just like the atrioventricular valves, they prevent blood from flowing backwards. The semilunar valves prevent blood flow back into the ventricles and keeps the blood flowing in the arteries away from the heart (9).

drawing of aortic semilunar valve (11)

Valve failure on different sides of the heart has different effects. If valvular heart disease occurs on the right side of the heart, swelling in the feet and ankles occurs because blood that is pumped into the right ventricle by the right atrium does not stay in the right ventricle. Instead, it flows back into the right atrium, backing up the blood flow and not letting blood from the body flow into the right atrium. As a result, blood collects in the feet and ankles, causing them to swell up (10a).

If valvular heart disease occurs on the left side of the heart, the body would not be able to get as much blood. Body cells would not get as much oxygen, which would cause fatigue. This is because blood in the aorta that is supposed to be pumped to the body by the left ventricle instead flows back into the left ventricle and does not go to the body (10b).

At the very end of the dissection, we made a frontal cut through the heart to separate the anterior (front) and posterior (back) sides. This way we were able to see all the structures inside the heart.

drawing of interior of heart (13)

Unit 3 Reflection: The Circulatory System

Unit 3 was about the circulatory system and the respiratory system. The essential questions of this unit included:

• What are the major features of the circulatory system?
• What are the structures of the heart and their functions?
• What are the (dys)functions of the blood vessels?
• What are the different components of blood and what are their functions?
• What are heart attacks and strokes? What causes them, how are they identified, and how are they treated?
• What are the functions of the respiratory system?

The circulatory system is a fluid-filled network of tubes throughout the body. It is made of several major components: the heart, which pumps the fluid through the system; the blood vessels, which carry the fluid through the system; and the blood, which is the actual fluid. There are also several accessory organs to the circulatory system: the lungs, which exchange carbon dioxide in the blood for oxygen; the kidneys, which remove excess waste and water from the blood; and the intestines, which absorb nutrients and water from digested food into the blood.

We learned about different parts of the heart in detail in this unit. To help us learn about the heart's structure, we went outside, drew a diagram of the heart on the ground, and made a video explaining the path a red blood cell takes through the heart.

Our diagram (top) and video (left) of the heart

I also drew a diagram of the heart by myself to help me learn about the heart. This was after we had learned more about the structures of the heart and their functions, so it is more accurate (the papillary muscle in the above diagram is incorrectly labeled).

my diagram of the heart

All this drawing of the heart helped us prepare for our sheep's heart dissection, which was very interesting and let us see what an actual heart looked like. There was some fat on the heart, which we did not really expect because diagrams of the heart don't really depict fat, and the anatomy of the heart was a little bit different since it wasn't a human heart.

anterior (front) view of sheep's heart (where's the inferior vena cava!?)

heart cut lengthwise (the way most heart diagrams are drawn)

We also learned about blood vessels. There are three main kinds of blood vessels: arteries, which take blood from the heart to the body; veins which take blood from the body to the heart; and capillaries, which connect the two. Arteries are the ones that expand and contract as the heart beats (this is how you feel you pulse). Veins have valves in them that prevent blood from flowing backwards (e.g. blood in your leg has to flow against gravity to get back to your heart). The capillaries are where the exchange of nutrients, wastes, and gasses actually occur.

In the blood vessels flow the blood, which is made of plasma and cells. Plasma itself is made of water and dissolved solutes. Blood cells include red blood cells, which carry oxygen, and white blood cells, which are part of our immune system and help fight infections. There are many different kinds of white blood cells, including neutrophils, basophils, eosinophils, lymphocytes (B-cells and T-cells), and monocytes (which mature into macrophages). Blood also contains platelets, which help the blood clot if you get cut.

What we learned about heart diseases tied into our past unit about health. Mostly we learned about atherosclerosis (the buildup of plaque, or fatty material, in the blood vessels) and aneurysms (the weakening of a blood vessel wall due to blood getting in between the layers of the wall and making it swell up). Atherosclerosis is caused by chronic inflammation; excess sugars, omega-6, and LDL ("bad") cholesterol; and too little HDL ("good") cholesterol. When little microtears form in the blood vessel wall, this excess LDL becomes stuck in the wall. If there is too little HDL to clean it up, white blood cells think that the body is under attack, come to engulf the LDL, and become stuck as well. This forms a plaque in the artery that restricts blood flow. A blood clot can form around the plaque and cut off blood flow entirely. If this happens in a coronary artery that provides blood to the heart muscle, it is called a heart attack. If this happens in the brain, it is called a stroke (strokes can also be caused by aneurysms). Good nutrition lowers your risk of atherosclerosis (since atherosclerosis is caused by excess sugars, omega-6, and LDL) and therefore the diseases associated with it. Exercising, managing stress, and controlling your weight also prevents atherosclerosis.

We also learned about the respiratory system, since it is connected to the circulatory system (oxygen-poor blood is pumped from the heart to the lungs to exchange carbon dioxide for oxygen, then returns back to the heart to be pumped to the rest of the body). Air enters the respiratory system through the nose, then travels down the pharynx (throat), larynx (voice box), trachea (windpipe), bronchus, broncial branches, and finally into the lungs. The lungs themselves are made of tiny air sacs called alveoli, which are covered with capillaries and are where the actually gas exchange takes place. Breathing in occurs when the diaphragm contracts and flattens out from its relaxed, curving-upward state (this is interesting; I didn't know about how the diaphragm actually moved down before), and the intercostals (muscles between the ribs) contract and pull the ribcage out.

This unit was a pretty good unit for me, since I understood what was taught in class. I felt more comfortable with this unit's material than with last unit's on health; I suppose I am better at learning about the larger things that I can see and feel than I am at learning about the little things that I can't really see for myself. The active studying method that we discussed in class also helped, especially relating concepts to each other by drawing concept maps.

active studying

 Last unit we made a chart of health goals. My goals were to:

• eat seafood at least three times a week.
• exercise at least three times a week.
• sleep at least eight hours every day.

So far, I have achieved the eating and the exercise goals. These were pretty easy since my whole family likes to eat seafood, and whenever I wanted to exercise I would just go run with my friends on the cross-country team. However, now that the cross-country season is over, I need to find time during the weekends to exercise with my family or convince some friends to run with me after school (most of them don't really want to run after the season is over), since I don't like to exercise alone. I also have to work harder on getting eight hours of sleep daily. I get eight hours of sleep during the weekends now, but sometimes during the weekdays I stay up later doing homework. I can manage my time better and spend less time lying around so that I can finish my homework earlier and go to sleep earlier.

Monday Wellness Reflection: Tea

Our Monday Wellness was on tea. The presentation can be found here.

We chose to do my Monday Wellness project on tea because we had heard that teas had a lot of health benefits. However, I did not know why exactly teas had such health benefits. Also, I knew that there are thousands of different blends of tea and had heard that different teas have different health benefits. We had also heard of how antioxidants in tea were good for the body, but we did not know what antioxidants actually were; we also heard that tea was a good substitute for coffee, but beyond "because it is more healthy," we did not know exactly why.

When researching for my Monday Wellness, I found it interesting that all "true" teas (white, green, oolong, black, pu'er) are made from the same plant, Camellia sinesis. I had previously thought that different teas came from different plants (e.g. green tea came from green tea plants, black tea came from black tea plants, etc.). The different teas and their distinct characteristics come from the different ways the plant is processed.

We also finally learned how exactly antioxidants and caffeine affect our bodies. We always hear that antioxidants are good and that caffeine is bad, but many people do not understand why this is so. Antioxidants actually work by keeping harmful particles in our body, called "free radicals," from being harmful. Caffeine is actually a naturally occurring chemical compound in some plants that is a stimulant drug in humans. It was very interesting to find out that caffeine in moderation is actually good for the body, since it increases mental alertness, improves memory, and reduces the risk of certain diseases.

The most important theme of our Monday Wellness was moderation. We also talked about moderation and balance in class during our health unit. Sure, drinking tea is good, but drinking too much for too long may result in side effects. In fact, drinking too much of anything, even water, which is essential for life, is harmful. Furthermore, "too much" is different for everyone depending on their age, gender, body weight, and many, many other factors; it is not a concrete number. We frequently want to hear numbers so that we know what we should or should not do -- I saw this when people started asking me about how many cups of tea they should drink and how many cups was too much -- but we should keep in mind that there are not really any clearly set limits that fit everyone.

On a scale of 1 to 10, I would give us an 8. Since we did not practice our presentation together before actually presenting it in class, our timing was a little off. It took more time than we expected to set up and clean up our activity, so in the end I did most of the presentation while my partner set up and cleaned up the activity, since she brought the supplies for it. We also wanted to do the activity before most of the presentation to wake up the students and get them more involved in the presentation. However (as stated before), it took longer than we expected to set up the activity, so we got through half of our presentation first before we did the activity. As expected, the activity did wake up the students and get them more involved: during the half of the presentation before the activity, I felt like the students were just staring at me talk and not engaging; after the activity, the students seemed much more lively and asked a lot more questions.

2015.10.13 Measuring Blood Pressure and Pulse

Today we learned how to take blood pressure and pulse and practiced doing so on each other.

Blood pressure is the pressure blood exerts on the walls of arteries when the ventricles of the heart contract and send blood into the body. There are two parts of blood pressure, systolic pressure and diastolic pressure. Systolic pressure is the pressure that the blood exerts on the walls of the arteries when the ventricles contract, so it is higher. Diastolic pressure is the pressure that the blood exerts on the walls of the arteries when the ventricles relax, so it is lower.

Blood pressure can be measured using a digital sphygmomanometer (blood pressure cuff), or using a manual one and a stethoscope. In class we learned how to use a manual sphygmomanometer and a stethoscope to measure blood pressure:

1. Put the patient's arm palm up on a flat surface. Make sure the patient's arm is level with his heart.
2. Wrap the blood pressure cuff around the patient's upper arm, at least 1 inch above his elbow.  The tubes that connect the pressure gauge and the pump to the cuff should be pointing down, in line with the patient's arm. Secure the cuff.
3. Put on the stethoscope. Put the flat part of the stethoscope on top of the brachial artery, on the inside of the patient's arm a little above his elbow. You will not be able to hear anything yet.
4. Make sure the valve on the pump is closed. Start pumping air into the cuff until the pressure gauge reaches about 150 mmHg.
5. Slowly release air from the cuff by opening the valve on the pump slowly. The needle on the gauge should fall about 2 mmHg every time you open the valve.
6. Note the number on the gauge when you hear a very faint tapping sound through the stethoscope. This is the systolic pressure.
7. Keep releasing air from the cuff until you stop hearing anything through the stethoscope. The number on the gauge at which this occurs is the diastolic pressure.
8. Blood pressure is written as a fraction, systolic pressure/diastolic pressure.

We tried taking blood pressure using a sphygmomanometer and a stethoscope on each other:

Blood Pressure Results

	Subject 1	Subject 2
Trial 1	90/50	110/80
Trial 2	100/60	105/70

Pulse is the number of times the heart beats over a certain amount of time. It can be measured by using a stethoscope over the heart, or just with 2 fingers (index and middle) over the radial artery (in the wrist) or over the common carotid artery (in the neck). Count the number of times the heart beats for 15 seconds, then multiply that number by 4. We do not use the thumb to measure pulse because there is also a pulse in thumb, which may throw off how many times we count the heartbeat. We tried taking pulses at different locations on each other:

Pulse Results

	Subject 1	Subject 2	Average for All Subjects
Radial	70	70	70
Carotid	68	70	69
Heart (stethoscope)	72	86	79
Average of Individual Subjects	70	76	73

Unit 2 Reflection: Health

Unit 2 was about health. The essential questions of this unit included:

• What is health? What are the five pillars of health?
• How do nutrients in foods affect our physiology?
• What exercise is needed to realize physiological benefits?
• Why is sleep important?
• What are the physiological effects of stress?

Health is not simply one thing or condition, though good or bad health may manifest itself in illnesses or lack thereof. It is a combination many different factors that work together to make a healthy lifestyle and a healthy body that functions optimally. Good health may be distilled into five basic "pillars:" as the questions above hinted, four of the five pillars of health are nutrition, exercise, sleep, and stress; the fifth is social health.

the five pillars of health

I had always thought that I lived a pretty healthy lifestyle, since I try to get enough sleep, eat healthy foods, and not get too stressed because I don't like feeling unwell. After learning about this unit, I found areas in which I could still improve and learned about how to improve in those areas. Normally I sleep for 7 to 8 hours everyday, but in class I learned that most teenagers need 9 to 10 hours of sleep daily. I learned even more about what foods are good for the body, such as in-season produce and ruminant meat (beef, lamb, goat, etc.). I could also exercise more.

my goals to live a healthier life

However, I feel like the students at my school as a whole could be more healthy. I think part of the reason may be because we are such a academically competitive school, so many students try to push themselves to be the best. I frequently hear students say they get 3 to 4 hours of sleep each night because they have such a heavy homework load from all their high-level classes. This puts a lot of stress on them as well. Also because of this, many students do not exercise enough because they "do not have enough time." I also hear many students say that they did not eat breakfast or see people who only eat a slice of pumpkin pie from the cafeteria for lunch, which is not good nutrition. These problems could be remedied if teachers do not give so much homework or try not to give too many exams on the same day (I know a teacher who asks students if they have a lot of exams on a certain day to determine if that day is a good day to give a test). The cafeteria can also provide more healthy, balanced meals rather than just pizza and burritos to help promote proper nutrition.

typical cafeteria pizza: not very healthy (Flickr)

The most important theme of this unit was balance. Balance is extremely important in all aspects of life. This unit applied it especially to nutrition, but it can also apply to daily life, such as work vs. recreation or having a treat vs. gorging oneself. If you apply the simple principal of balance to your life, you will live a healthy, fulfilling life.