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Kevin K.
History, Anthropology, and Algebra
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Anatomy
TutorMe
Question:

Briefly describe how blood flows through the heart.

Kevin K.
Answer:

It is helpful to pull up a picture of a heart cross section for this answer, as I think having a visual is always helpful. If you print it out, you can draw arrows to show the blood flow! Blood enters the heart through two veins, the superior and inferior vena (vein) cava. These veins dump into the RIGHT atrium. How do you remember the right atrium? Think about it like this. In order to enter your car, you must open the door. But what side is the handle on? Its on the right of the door. Therefore, you enter through the "right" part. But how do you remember atrium? An atrium, in a house, is an entry way. So whenever you are in an atrium, you have entered from somewhere! Now, from here, the blood moves from the right atrium into the right ventricle through the TRICUSPID valve. This is not to be confused with the Mitral (or BICUSPID) valve, which separates the left Atrium and Ventricle. How do we remember this? I always think of it as the larger number is higher up, so it comes first. Its a silly way to think about it, but it helps me. Anyways, once the blood makes it into the Right Ventricle, it needs to leave (be vented) into the lungs. Remember, we are dealing with de-oxygenated blood at this point, so it must go to the lungs to get some oxygen. When the Right ventricle contracts, blood goes through the pulmonic (lung) valve into the Pulmonary artery (the only artery to carry de-oxy blood) and into the lungs. Once there, the blood gets all oxygened up and heads back into the heart via the pulmonary vein, sending oxygen rich blood to the left atrium (remember, we need to enter into an atrium). Now, why is the pulmonary artery carrying de-oxy blood and the pulmonary vein carrying oxy blood? We are normally taught that arteries carry oxygenated blood and veins carry de-oxygenated blood. But think about it this way. ANY vessel that carries blood to the heart is a vein. ANY vessel that carries blood away from the heart is an artery. Hence why the pulmonary vein and artery are the only two to not fall under the "veins are deoxygenated and veins are oxygenated" way of thought. Now, once the blood is oxygenated, it goes through the pulmonary artery into the left atrium. From there, the blood pumps through the bicuspid (or mitral) valve and into the left ventricle (remember, we need to vent out our blood!). From there, the blood is vented out through the aortic valve and into the aorta, sending oxygenated blood to the body.

Anthropology
TutorMe
Question:

What are the major features of bipedalism?

Kevin K.
Answer:

I find the best way to remember these is to work from the top down. First, we see that the foramen magnum (the hole in which the spinal cord enters the head) is located more underneath the skull when compared to chimpanzees--it is located more anteriorly in humans. Next, lets look at the spine. We see in humans our spines have 2 types of curves, with additional curves in our neck and lower lumbar region, giving us an "S" shaped curvature. Chimpanzees have a "C" shaped (easy to remember---C for chimps!) spine. This "S" shaped spine allows our spine to stay erect, shifting our center of gravity over our hips. Additionally, it allows our head to sit nicely on top of the skull, keeping our eyes forward. The pelvis perhaps the greatest changes. Our pelvis has become more bowl shaped---wider than it is tall---shifting the musculature of our hips to better help with bipedal walking. This shift helps us maintain our balance when we stand on one leg (try it!). Moving down, we see that our femur has a shorter neck and larger head for stability of the hip joint. Additionally, the femur is angled in such a way that it forces the feet to remain under the center of gravity, pulling our knees towards the midline. Its all for balance and efficient walking! Lastly, our feet have changed, too---with shorter broad toes for stability, the movement of our big toe to be in line with the others for stability and giving us a good surface from which to push off and propel ourselves, and arches in our feet to act as shock absorbers.

Algebra
TutorMe
Question:

What are the correct roots to the equation x^2 - 6x - 19 = 0 ? Use the quadratic formula.

Kevin K.
Answer:

Using the quadratic equation, we know that x = (-b±√(b²-4ac))/2a . Your "b" in this case is -6. Your "a" is 1. Your "c" is -19. Using these, we can plug them into this formula to get: x = (--6±√((-6²)-4(1)(-19)))/2(1) First, we should deal with that muddle under the radical sign. -6 squared (negative times a negative is a positive) is 36. 4*-19 is negative 76. So, 36 minus negative 76 is really 36 plus 76 which equals 112. But, we don't really like the square root of 112 (its not a pretty number) so we need to factor this out a little. At this point, sometimes the best method is trial and error, to see what you can find. However, the best way is to divide the number in question by a prime factor. So, lets factor 112 out, shall we? 112 divide 2 is 56. 56 divide 2 is 28. 28 divide 2 is 14. 14 divide 2 is 7. Let us now take the largest prime (in this case 7) and divide it into the original number (in this case 112). 7 goes into 112 16 times. 16 is a nice square! so we can reduce our problem to: x = (6±√(16*7))/2 Now, to simplify this further, lets take that 16 out of there and square root it. we know that the square root of 16 is four (4 times 4 is 16). So we can now write this x = (6±4√(7))/2 One last simplification step! Let us divide by that 2. So, we have x = 3±2√7 This problem cannot be reduced any more, so you know that the factors of the above question must be : 3+2√7 3-2√7

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