How Long is YOUR Digestive System?

1. First, I cut some black yarn that stretched from the front to the back of my mouth to represent my mouth. Then, I measured and cut burgundy yarn that stretched from the back of my jaw to just below my rib cage to represent my esophagus. To represent my stomach, I measured a piece of green yarn that extended from my thumb to my little finger when my fingers were stretched. I measured my height, multiplied it by four, and cut a piece of white yarn of that length to be my small intestine. Finally, I cut a piece of purple yarn that was my height to be my large intestine. Once all the pieces were tied together, the length of yarn was 853 cm (8.53 m) which is approximately the length of my actual digestive system. My main take away from this lab was how extensive, intricate and lengthy our digestive system really is. I also learned how the flow of food through our body is a system of tubes and food is passed from one tube to the next until it exits the body.

2. My height --> 5 ft 2 in = 62 in x 0.0254 m/in = 1.5748 m
    Length of my digestive system = 8.53 m
Although the digestive system is almost six times the length of my body, it's able to fit inside my abdomen because of how intricately it's folded. The large and small intestines of the digestive system, especially, are folded very precisely to save space and allow them to more compactly fit into the abdomen.

3. I think it takes about half a day (12 hours) for food to move all the way through the digestive system. According to the Mayo Clinic's website, it takes about six to eight hours for food to pass through the digestive system and small intestine, after which it goes to the large intestine (colon). and awaits further absorption of water. To go through your entire body, however, it takes an average of 53 hours Factors that affect the time it takes for food to be digested include how thoroughly the food is chewed, how much liquid is consumed with the meal (liquids dilute the digestive enzymes in the stomach and increase the digestion time), condiments and flavors that are consumed, and the frequency of meals as if food is consumed before the previous meal has been digested, the mixture of the two meals will take longer to digest.

4. Digestion includes the breaking down of food in the alimentary canal through enzymatic and mechanical methods to make energy that the body can use. This is what occurs in the first half of the digestive system. Absorption, on the other hand, is the process by which small molecules are absorbed by the small intestine and deposited into the bloodstream which transports it to various locations throughout the body. This generally occurs in the second half of the digestive system as the body begins to absorb nutrients from the digested food.

5. How does the formation of an ulcer affect how the digestive system processes food? Does the digestive system function differently depending on what foods you consume? What causes a person to throw up due to food poisoning? Is it different if they have the stomach flu?

New Year, New Me

This semester, as college interviews start and I prepare for college next year, I want to improve on being a more confident person when it comes to how I present myself. I recently watched a Tedtalk by Amy Cuddy about how your body language can influence your mind and self-esteem, which I found pretty interesting. According to Cuddy, when a person takes a high-power position (as opposed to a slouched, low-power position), their testosterone levels increase and their cortisol levels decrease, causing the person to behave more confidently. This can be really important when it comes to making first impressions or approaching situations when someone is evaluating me. A sloucher due to bad-habits, I want to start sitting straighter and not slouching to improve my mood and confidence when I speak to other people.

In addition, I will improve my sleep schedule. Due to the stress of my classes, the tennis season, and college apps last semester, I often found myself sleeping very late at night, leading to my being very lethargic and unable to concentrate in class the next day. If I can start finishing my work earlier and sleeping by 11 rather than 2, I will be more productive and attentive during the day. As I no longer have tennis practice every day after school and college applications have started wrapping up, there's no excuse for me to sleep any later than 11. And as school ends at 2:10, I should have plenty of time to finish my school work by 2 as long as I stay focused and don't procrastinate.

Wellness Day Presentation: Stretching

Because we are both athletes involved in multiple sports throughout the year, Maxine and I chose to explore Warm Up and Cool Down Stretches for our wellness day presentation. I'm on the Varsity tennis team for SHS and as the season continued, we became lazy and stopped warming up and stretching before practicing. As a result, many people on the team started getting injured - spraining their ankles and getting tennis elbow. I wanted to explore why this was and how not stretching played a role in the injuries. Maxine had some similar experiences with her softball team, which is why we chose this topic. We began our project by asking classmates to post a couple sentences on the canvas discussion board about why certain stretches/exercises are used to warm up for one sport while different ones are used for another sport? We also asked classmates to write about how the stretches used to warm up for a particular sport help to warm up for that sport. 

Most people posted that stretching prepares the muscles that are used in the activity, so people who play upper body intensive sports tend to stretch out the arms and shoulders more, while those who play lower body intensive sports tend to stretch out the legs. For example, basketball players stretch out their legs and arms before playing, gymnasts do toe touches to improve their flexibility, and runners warm up with a light jog so not to run with cold muscles and get injured. Warming up before a sport is extremely important because it increases a body's internal temperature and stretches out the muscles around joints, making one less prone to injury. This increase in body temperature is crucial as it makes it easier for the lungs to gather oxygen, lowers the rate of metabolic reactions, increases the blood flow to muscles, reduces muscle viscosity, and increases nerve impulses. 

There are four main kinds of stretching: ballistic, static, dynamic, and proprioceptive neuromuscular facilitation. Ballistic movements involve repetitive bouncing movements, static movements stretch the muscles to the point of slight discomfort and is held for long periods of time. Dynamic movements challenge the muscles but in a comfortable range. Lastly, proprioceptive neuromuscular facilitation uses alternating contractions of the muscles. The stretches in each of these categories are separated even further into passive stretches, both of which are equally beneficial to the warm up process. 

From this project, I learned the importance of stretching and especially, how that warms up one's body temperature before doing strenuous physical activity. This topic is extremely important for health and wellness because without stretching, athletes would be more likely to get injured if they play a sport when their muscles are cold. On a scale of 1 to 10 for this project, I would definitely give myself a 9.5-10. Maxine and I put a lot of thought and effort into this project and tried our best to make it personal by reflecting on our own experiences. Maxine and I worked really well together as a team; we worked on the presentation together, had a video chat to go over the details of the presentation, and really thought through what information we wanted to go over with the class. I'm really proud of the presentation we made and will start thinking twice before I play tennis or go running without stretching and warming up.

For more details about this topic, see the powerpoint presentation we used here.

Unit 4 Reflection

This unit focused on the integumentary system. We explored the various layers of the skin (which are shown and labelled in the diagram below) and the purposes that the skin serves, for example, maintaining homeostasis and protecting the body. We also discussed how accessory organs like cutaneous glands, hair, and nails are formed and how they all work together with the skin to protect our bodies. 

We also touched on the Immune System, which consists of many different factors varying from nonspecific to specific that work together to defend the body against pathogens. The human body's first line of defense against invaders is non-specific resistance, which mainly involves the skin and mucous membranes, but also includes the epiglottis, urine flow, defecation and vomiting, tears, and saliva. Various chemical methods of nonspecific resistance like sebum, perspiration, lysozyme, and gastric juice work alongside the skin and mucous membranes to protect the body. If the pathogens somehow evade this first line of defense, eosinophils, basophils, neutrophils, and macrophages, which make up the second line of defense, work to inhibit the pathogens. Both the first and second lines of defenses are non-specific and will attack all pathogens. If the pathogen still manages to get by these two lines, the third line of defense - the specific response - will take place with the help of lymphocytes that differentiate into B cells and T cells and react to a particular antigen (a part of a pathogen). B cells and the antibodies they produce go on to neutralize pathogens or trigger complement proteins to cause cell lysis or attract phagocytes that take in the pathogen. T cells, on the other hand, release toxic substances that directly trigger apoptosis (programmed cell death). A comparison of how B cells and T cells work to defend the body against pathogens is depicted in the image below. We also discussed how benign and malignant cancers come about and can result from genetic and environmental factors. 

I almost fully understood most of this unit as it was a reinforcement of the most recent unit in AP Biology. I'm still a little bit confused as to how tumors arise and how they manage to evade the three lines of defense in our immune response. I still wonder as to how the glands in the integumentary system work and how nerve fibers get signals to the brain when we touch something and what, if any, role does the tactile corpuscle play in this process.

This unit solidified what I've learned about myself and my studying habits all through high school: I most definitely am a visual and verbal learner. As I was reading the textbook and filling out the reading guides for this unit, I found myself constantly drawing and labelling diagrams of the layers of the epidermis, the different types of white blood cells, and how T cells and B cells reacted differently when they encountered a pathogen. I've learned that diagrams really help me understand what we are learning about by making the material more tangible and "real" rather than theoretical. It really helps me to relate concepts we learn in class to everyday life; for example, using a hypothetical scenario of someone getting the flu or cancer and talking through or drawing out what that would potentially look like in the person's body on a cellular level. I think this is one of my major strengths, especially when it comes to science classes like biology and anatomy, as much of what we learn can be drawn or mapped out, making it easier to understand the bigger picture. A major weakness of mine is definitely memorizing specific details and applying them to that big picture, but I think my strength of visualizing and drawing out diagrams really helps me remedy this weakness. 

According to the VARK Questionnaire, I have a multimodal learning preference, meaning using visual aids, diagrams, and writing things down generally helps me learn. My scores from the VARK Questionnaire were visual: 9, aural: 8, read/write: 9, and kinesthetic: 11. I've been experimenting with studying strategies in some of my other classes and I think I agree. When studying for AP Biology, for example, I take notes from the textbook and then add in details from class lectures and try to incorporate diagrams or flowcharts to make sense of what the chapter discussed. The results from the VARK Questionnaire are generally what I thought they would be because I prefer using spatial diagrams and images, words (both written and spoken), and using my body, hands, and sense of touch to help me learn. I will definitely incorporate these techniques when studying for the upcoming Unit 4 Test, by actively studying: drawing out diagrams, taking notes from the textbook by hand, and maybe explaining the unit to a friend or classmate verbally to help me make sense of all the information.

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 Summary. The 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:

Mid-Unit Summary: The Heart

The human heart is about the size of a first and weighs less than a pound. It is located in a cavity of the thorax called the mediastinum and is covered by the pericardium, a double sac of membranes that releases fluids to lubricate the heart and reduce friction. The three layers of the heart (as shown in the image below) are the epicardium which is the visceral pericardium, the myocardium which is the contractile part of the heart, and the endocardium which lines the chambers of the heart. 

The heart has four chambers that help regulate the blood: the right and left atria, which receive blood, and the right and left ventricles, which discharge blood. The valves of the heart - labelled in the image below - keep blood moving in one direction and prevent the back flow of blood. When listening to a heart beat, the "lub" sound happens when the tricuspid valve (between the right atrium and right ventricle) and the bicuspid valve (between the left atrium and left ventricle) contract. The "dub" sound is heard when the aortic and pulmonary valves close as the heart relaxes. The nodal system of the heart is composed of the SA (sinoatrial) node which is found in the right atrium and the AV (artrioventricular) node which is found where the atria and ventricles meet. This nodal system is made up of special tissue that causes the heart to beat uniformly at about 75 beats per minute. The cardiac cycle is the heat's rotation between systole (contraction) and diastole (relaxation) of both the atria and both the ventricles that work together to push blood through the body. For more information on how blood is circulated through the chambers of the heart, see my previous blog post from our heart chalk walk activity here

The circulatory system is a fluid-filled network of vessels through which materials move between the environment and cells of a multicellular animal. It's major components are the heart which continuously circulates blood, the arteries which take blood away from the heart, the veins which bring blood back to the heart, and blood which is the fluid being circulated. The image below depicts the structural differences between arteries and veins. The specific parts of the circulatory system are pulmonary veins and arteries, the aortic arch and trunk, the common carotid artery, the renal vein and artery, and the mesenteric arteries. Some accessory organs that aid in the circulation of blood are the lungs, kidneys, small intestine, large intestine, liver, spleen, and bone marrow. Blood pressure is measured by the systolic pressure, which results from the contraction of the ventricles, and diastolic pressure from the relaxation of the heart. To learn more about blood pressure, see my last blog post from our blood pressure lab here

Many blood vessels work together to aid in the circulation of blood through the circulatory system as shown in the diagram above. Veins are thin vessels that carry blood from the tissues to the heart. Arteries are elastic and contractile vessels that carry blood away from the heart and to the tissues. Capillaries are tiny vessels that connect arterioles (small arteries) to venules (small veins). Blood - the main material pumped through the circulatory system - has three components (depicted below): red blood cells, a buffy coat made up of white blood cells and platelets, and plasma. Blood's main functions are transportation, regulation, and protection. Different types of white blood cells in peripheral blood include neutrophils, basophils, eosinophils, lymphocytes, and monocytes, each of which has different responsibilities in the body. 

One of the main cardiovascular diseases is a heart attack, which is caused when blood supply to the myocardium is severely reduced or blocked and is usually due to atherosclerosis. Atherosclerosis is a disease that occurs when fatty material deposits on the inside of blood vessels, making it harder for blood to flow - the chronic inflammation is generally caused by excess polyunsaturated fats, omega-6, and damaged blood vessels that cause LDL (bad cholesterol) to stick to damaged cells causing plaque to develop, as shown in the image below. Another cardiovascular injury, an aneurysm occurs when a thin weakened portion of the blood vessel wall droops, and they are life threatening, especially if they burst. Cholesterol, a cause of atherosclerosis, comes in two types: LDL which sticks to arteries and HDL which cleans up the build up of LDL in arteries. A major effect of a heart attack which is often confused with a heart attack is cardiac arrest, which occurs when the heart stops beating entirely. Signs of a heart attack include chest pain/pressure, arm pain, nausea, shortness of breath, and pale/sweaty skin. Methods to diagnose a cardiovascular disease include an angiogram, an echocardiogram, an electrocardiogram (EKG/ECG), a stress test, or nuclear scanning. Factors that increase the risk of a heart attack are a lack of exercise, obesity, smoking, diabetes, high blood pressure, and high cholesterol. Thus, it's important to maintain good health to prevent a heart attack from occurring.