I have a mutiple choices homework, but I understand NOTHING From it.. please hel - (Aug/04/2012 )

Which of the following would occur the earliest in the development of a human fetus?
<*>Nervous system begins to control body functions
<*>Organs in the digestive system form.
<*>Bone replaces cartilage in the skeleton
<*>The lungs begin rhythmic movement


How does the timing of meiosis in humans differ in males and females?
<*>In females it begins prior to birth, while in males, it begins after birth.
<*>In females it ends at the end of puberty, while in males, it ends at birth.
<*>In females it is completed as puberty begins, while in males, it starts at puberty.
<*>In females it continues throughout life, while in males, it stops at puberty.



Which of the following best describes an example of a nonspecific internal response to pathogens?
<*>Fever increases metabolism, speeding up the body’s reaction to the pathogens.
<*>Mucus traps the pathogens and prevents them from invading the body.
<*>Lymphocytes recognize the pathogens and destroy them.
<*>Dead skin cells provide a barrier between the pathogens and the body.



During a cell-mediated immune response, which of the following describes how infected cells are detected by the immune system?
<*>The infected cell’s membrane shows some of the antigens of the invading pathogen.
<*>The pathogen engulfs and destroys healthy cells, leaving antigens behind.
<*>Antibodies bind with the pathogen’s antigens, causing inflammation and swelling.
<*>Memory B cells recognize the cell shape that results from infection by specific pathogens.

If you provide some guesses and explanation for your answers, we will be much more likely to help - you need to learn, not have us tell you the answers...

I know this isn't my homework, but I'm interested in the answers. Could someone please check if these are correct?

raimelgarcia on Sat Aug 4 22:11:57 2012 said:

I have no idea on this one... But I guess it is either number 2 or 3 as the lungs shouldn't be required if the foetus is gaining oxygenated blood from the mother, and it can't be number 1 if the answer to number 2 is referring to the formation of the digestive system, as surely the development of the digestive system comes before the functioning of the organs.

raimelgarcia on Sat Aug 4 22:11:57 2012 said:

I know sperm production occurs throughout life in males, and I read somewhere about females being born with all oocytes made.

raimelgarcia on Sat Aug 4 22:11:57 2012 said:

I think it's either 1/2, but seeing as it says internal I will go for number 1.

raimelgarcia on Sat Aug 4 22:11:57 2012 said:

I'm not sure on #1 but I would have guessed that the nervous system would develop pretty early so I would go for the first answer.
#2 Correct, however, you reasoning is a little off - sperm production in males is only from puberty onwards. There is also some evidence that females may not be born with all the eggs pre-made, however this is being scientifically debated at the moment.
#3 Correct - mucus is also internal usually, but is present all the time, so isn't a response to an infection. Fever is a response to any type of infection - therefore non-specific.
#4 Correct, though this isn't always the case with intracellular pathogens - most pathogens are extracellular and can be recognised by the antigens on their surface, then phagocytosed by the immune cells. Intracellular pathogens are much more difficult for the body to recognise, as the pathogens hide inside the cells, which is why these types of infections are more dangerous generally.

#1 is the nervous system;
Organs in the digestive system form: why would you need a full digestive system as early as possible when your mommy gives you everything throught the ombilical cord?
Bone replaces cartilage in the skeleton: starts around the end of the first trimester
The lungs begin rhythmic movement: why would you need lungs? you cannot breath under water (in utero)
You have to think more in terms what do you need first and foremost and how long would it take to develop (complex vs simple) then it all makes sense.

Here is a list of the step by step development. took my 5 min to google it: http://www.nlm.nih.gov/medlineplus/ency/article/002398.htm

<*>Week 5 of pregnancy (gestational age)

<*>The brain, spinal cord, and heart begin to develop.
<*>The gastrointestinal tract begins to develop.
<*>Weeks 6 - 7 of pregnancy (gestational age)

<*>Arm and leg buds become visible.
<*>The brain develops into five areas and some cranial nerves are visible.
<*>The eyes and ear structures begin to form.
<*>Tissue forms that develops into the vertebra and some other bones.
<*>The heart continues to develop and now beats at a regular rhythm.
<*>Rudimentary blood moves through the main vessels.
<*>Week 8 of pregnancy (gestational age)

<*>The arms and legs have grown longer, and foot and hand areas can be distinguished.
<*>The hands and feet have fingers and toes (digits), but may still be webbed.
<*>The brain continues to form.
<*>The lungs begin to form.
<*>Week 9 of pregnancy (gestational age)

<*>Nipples and hair follicles form.
<*>Elbows and toes are visible.
<*>All essential organs have begun to form.
<*>Week 10 of pregnancy (gestational age)

<*>The eyelids are more developed.
<*>External features of the ear begin to take their final shape.
<*>Facial features continue to develop.
<*>The intestines rotate.