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.