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17 votes
Accepted

Which type of test tube should not be used for blood collection?

Your reasoning is sound and correct. The answer key is wrong. An unclotted blood sample needs something to prevent clotting. Extracellular calcium is required for both the coagulation cascade and ...
De Novo's user avatar
  • 8,791
8 votes
Accepted

How does increased resistance to flow decrease blood pressure?

There is not enough information in the question to solve it. The answer key from the original question makes a logical error: Viscosity is directly proportional to resistance. This is true. An ...
Bryan Krause's user avatar
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7 votes
Accepted

Why are veins not blocked by plaques?

Atherosclerosis can develop in high pressure systems, such as arteries, and not in low pressure systems, such as veins. It is high blood pressure that can damage the lining of the blood vessel and ...
Jan's user avatar
  • 8,079
6 votes
Accepted

How to understand the biophysics and math behind a 0.2 second delay between the pulse in my arm and my ankle?

So it turns out that your estimate is not bad, by simple velocity calculation, I get it to be a little over 50% out (see below), but as you say, there is some error in your measurement. However, it ...
bob1's user avatar
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6 votes
Accepted

How are monocytes larger than capillaries?

They aren't completely rigid and can change shape to squeeze through (see Downey et al). If they are activated, monocytes can get stuck in capillaries and block them, which contributes to poor ...
Bryan Krause's user avatar
  • 45.7k
5 votes
Accepted

Question regarding circulatory system of the body

No. An individual blood cell will complete the whole loop but can take any route through the circulatory system to do this. For example, a blood cell leaving the left ventricle may immediately pass ...
Rory M's user avatar
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4 votes
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Do fat people have more chances of developing nitrogen bends?

Well, you're right! First of all, Nitrogen Bends or Decompression sickness (DCS) is a disease that arises as a consequence of bubbles forming within tissues. Inert gases, such as nitrogen and ...
kartlad's user avatar
  • 265
3 votes

Why did the requirement for coronary circulation arise?

Oxygen and nutrients diffuse out of capillaries into surrounding tissue. If you don't have sufficient density of capillaries, diffusion distances are too long, and tissue becomes anoxic and dead. See ...
Bryan Krause's user avatar
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3 votes
Accepted

Why do veins contain lower concentration of proteins as compared to arteries?

lower concentration of proteins/amino acids/fatty acids/other named nutrient This answer key wants to allow an answer that the blood at Y has fewer nutrients than the blood at X because you should ...
Bryan Krause's user avatar
  • 45.7k
3 votes

renal portal system

Excellent question! The book is right, but ... well, biology has a hard time with the word because. We read causes and effects into evolutionary designs to make them easier to remember, much as the ...
Mike Serfas's user avatar
  • 2,465
3 votes
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Is dextrocardia congenital?

As the comments pointed out, this is not a hard question to answer with some research, but I'll add a few more details. Dextrocardia is congenital. The human heart normally actually isn't so much on ...
YviDe's user avatar
  • 2,258
2 votes

Arteries used for inserting catheter

Those arteries are (a) big enough for the catheters, (b) superficial enough (close enough to the surface of the skin) for catheterization. It would be quite a challenge to use the renal arteries, for ...
Bryan Krause's user avatar
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2 votes
Accepted

How does vasodilation slow blood flow?

The measurement that decreases during vasodilation is flow velocity, $v$, or a change in distance over change in time $\frac{\Delta x}{\Delta t}$. Prior to a reflex response, the same rate of flow, $Q$...
De Novo's user avatar
  • 8,791
2 votes

In adverse effects of Heparin, why is bleeding from deeper organs more common?

Skin is extraordinarily tough compared to much of our internal tissues; it has to be to protect us. To bleed, skin integrity must be breached, which usually involves sharp objects. Think for a moment ...
anongoodnurse's user avatar
2 votes
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Why does higher venous volume increase atrial pressure?

Imagine the circulatory system is an amusement park ride. The ride is the left ventricle and the arterial system. After riding, people go around and get back in line to go again. The line and the ...
Willk's user avatar
  • 2,964
1 vote
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Is there a term for the entire system of moving oxygen around?

Short answer "Oxygen homeostasis" is the best I can think of. Longer answer Don't forget the other half of the oxygen equation: carbon dioxide is an important waste gas and failing to remove ...
Bryan Krause's user avatar
  • 45.7k
1 vote

Why does atheroma contain thromplastin/tissue factor?

Tissue factor is present in subendothelial tissue and leukocytes - in this case this would be within the atheroma since the atheroma consists of damaged endothelium. Tissue factor's presence in the ...
Anderson's user avatar
1 vote
Accepted

How does the blood of the veins in the legs get to the heart?

The veins in your legs have one way valves. These prevent blood from flowing down, but do not actively push it up. However, normal muscle movement from walking etc will squeeze the veins to push blood ...
ovid's user avatar
  • 46
1 vote
Accepted

Is there any evidence of causation for breathing rate to affect blood pressure in a human?

Interesting question, it has been studied because sleep apnea is associated with hypertension in humans. It's not my field of research, so I read a few sources to give you an answer. There is a open-...
Akwajejou's user avatar
1 vote
Accepted

How does LDL leave the circulatory system and enter the interstitial fluid to deliver cholesterol to cells?

Many biologists had the same question for a number of years. In the 1950s, Nobel Laureate George Palade identified small vesicles in endothelial cells and postulated a mechanism whereby these vesicles ...
De Novo's user avatar
  • 8,791
1 vote

What's so special about Chassaignac tubercle?

The reason massaging the carotid artery can relieve symptoms of supraventricular tachycardia is because by massaging the artery, as you point our yourself, you artificially increase BP within the ...
Tobias Knudsen's user avatar

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