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Please any biology/biochemistry students help me

Discussion in 'Pre-Medical - MD' started by yimfong, Apr 17, 2004.

  1. yimfong

    yimfong Junior Member
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    Dear medical students, biology or related students, doctors....
    Please help me answer these questions:
    1. Other than the presence of valves in the veins, can the pumping action of the heart help to maintain the continuous flow of blood towards the heart?

    2. If you caught a common cold and got a blocked nose, will sense of smelling be affected? WHY?

    3. does sexual reproduction must involve male and female gametes? I think no because i barely remember some animal like sea horses can reproduce by fusion of two male gametes. Is this true?

    your kind help will be highly appreciated!
     
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  3. TheRussian

    TheRussian Life Size Mirror
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    1. I don't really understand what this means but I think that without valves in the veins some blood would still get back to the heart because of siphening and capillary action. Also remember that veins are very elastic and can allow the pooling of a lot of blood in the feet. For this reason I think it's necessary to have the valves in order to insure adequate blood return to the heart. I could be wrong though

    2. If you have a blocked nose the sense of smell should be effected (think of personal experience) This is because the odor receptors are located at the top of the nasal cavity and if the nose is blocked, oderants can't get to the receptors and the appropriate receptors are not activated so smell is affected.

    3. Not sure about the seahorse thing but I believe sexual reproduction must by definition involve a male and a female. My guess would be that in the case of seahorse if there are no females around one of the males will convert and become a female and then mate with the other male.
     
  4. ad_sharp

    ad_sharp Senior Member
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    Here's what I think. You can take it for what it's worth....
    1. The BP from the heart is very low in the veins in the lower limbs. Yes, I do think the blood can return w/o valves, but there will be a lot of edema associated with setting or standing in an upright position. Skeletal muscle contraction in conjuction with the valves is responsible for returning most of the blood through the leg veins. That's why so many people who suffer from paralysis have swollen feet.
    2. The site of your smell receptors is called the olfactory epithelium (the receptors regenerate which is kinda cool). As the previous poster said, it is located at the top of your nasal cavity beneath the olfactory tract and bulb (whick is a cranial nerve of the bottom surface of the brain). A lot of mucous
    blocks any molecules from gaining access to the olfactory epithelium. As a result you cannot smell (or taste well for that matter since 75% of taste is smell)
    3. Don't know about the seahorse thing, but sexual reproduction must involve the fusion of two gametes.
     
  5. Thundrstorm

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    Not sure about seahorses, but there are species that can reproduce with only female gametes. This is a phenomenon known as parthenogenesis, where there is no male contribution to the genome. One example is bees. Unfertilized eggs develop into haploid males, while fertilized eggs develop into diploid females. In other organisms, the 2nd polar body can act as a sperm to cause fertilization. I suppose that this is asexual reproduction though, so I guess the answer to your question is that reproduction is possible without both male and female gametes, but this would not be sexual reproduction.
     
  6. yimfong

    yimfong Junior Member
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    Thanks a lot, that's very kind of u!
    Moreover, regarding question 2, under same situation, will the sense of taste be affected, other than smelling?
     
  7. evines

    evines peek-a-boo
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    Depends on what you mean by "other than smelling." Sense of taste is reduced, but it is because your olfactory receptors are blocked. I can't think of a way the actual taste buds would be affected.
     
  8. draino15

    draino15 Senior Member
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    to answer #1.....there are NO valves in thie veins. The ONLY reason blood gets back to the heart is due to blood pressure buildup from the heart's pumping action on the arterial side. The last level of "valvular control" is at the Pre-Capillary sphincter which is smooth muscle right before the capillaries.
    To prove the point even further...when you stand up very quickly you get light headed....this is due to the fact that blood is not able to reach the brain at that moment...if you had valves in the veins..this would never happen. The physiology behind it is that blood is pooling in the veins due to their compliance. Eventually your HR goes up and blood is "forced" back to the heart due to the BP buildup.

    so this is really a physiology question, rather than a Biochemistry one.
    so wait for med school for more info.
     
  9. TheRussian

    TheRussian Life Size Mirror
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    I don't know where you got this notion because veins do in fact have valves.
    This is from the first website I pulled up in google:

    "It is important that the waste-rich blood keeps moving in the proper direction and not be allowed to flow backward. This is accomplished by valves that are located inside the veins. The valves are like gates that only allow traffic to move in one direction."

    http://sln.fi.edu/biosci/vessels/veins.html

    The idea is that arterial pressure is the only thing responsible for the pressure in veins is wrong because the capilaries absorb most of the pressure and the difference between arterial pressure and venous pressure is very large.

    When you stand up the reason you feel light headed is because blood rushes from your head not because it can't reach the head. This is due to inertia and the blood wanting to stay where it is while your head is moving up.
     
  10. ad_sharp

    ad_sharp Senior Member
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    There are valves in the leg veins. I've watched a few vascular surgeries. I've had human anatomy, human physiology, and dissected two cadavers. They're there.

    In addition pressure in the veins due to bp is only like 10mmGH or less (very low).
     
  11. evines

    evines peek-a-boo
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    Definitely valves in veins. I think in arterial bypass where veins are used to bypass arteries, the vein must be in the proper orientation or else the valves in the vein will not allow blood flow. Not a med student yet, but I'm sure I heard this somewhere.
     
  12. ad_sharp

    ad_sharp Senior Member
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    I one of the surgeries I watched (a femoral/popliteal bypass or fempop), they had to run a roto-rooter through the vien to clear out the valves before using it as a artery. Just cut the suckers right out of there.
     
  13. evines

    evines peek-a-boo
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    Amazing. SDN is a plethora of knowledge.
     
  14. patzan

    patzan Waiting for March 20th
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    The sense of taste would not be affected. The sense of taste from the anterior 2/3 of the tongue comes through the facial nerve (CNVII) (chorda tympani, which runs over your ear drum, actually) and the posterior 1/3 of taste comes from the glossopharyngeal nerve (CNIX).
     
  15. ad_sharp

    ad_sharp Senior Member
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    I guess that I need to clearify my first statement about #2. Your sense of taste from the taste buds themselves would not be affected, but the smelling portion of the taste sensation would be affected. Ever notice that food taste bland when your allergies are bad or you have a cold. But seriously, I think the above poster knows a lot more than I do.
     
  16. evines

    evines peek-a-boo
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    I think he's just showing off. That's what orangutans do. Or is that bigfoot??
     
  17. DrBodacious

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    In response to #1, vericose veins are the result of valves becoming non-functional in the leg veins. Muscular contractions in the leg muscles play a large role in pushing blood from the leg veins up to the heart. So, people who are very inactive are prone to getting vericose veins because the leg veins get bloated, as in they hold a larger blood volume. Blood is alway circulating however, so blood return to the heart is not so much of a problem as the distribution of blood.
     

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