Why do the fibers of external oblique and internal oblique(toad)run in different direction?
112685
Isn't this something they're trying to teach you at school? Think of the origins and insertions of these muscles, and of the movements achieved when each muscle layer contracts. Look at the pictures in any good Comparative Anatomy book and check the difference between the muscles of fishes and tetrapods (hint: new feature- lungs).
434302
diff muscle types have diff shapes and characteristics\n1. Cardiac muscle - spindle shape, nuclei are centrally located, involuntary muscle, branching, primarily found in the heart\n\n2. Smooth muscle - spindle shape, involuntary, not branching, primarily found in the gastrointestinal tract\n\n3. Skeletal muscle - branching, voluntary, multi-nucleited, straited, found all over the body
164015
If it is what I'm thinking it is, let me put it into simple words.\n\nImagine a heart. The electric waves that make it beat go down ( from the upper to the bottom side) and leftwards\n \nA rightward axis would mean that the elecrical waves take an alternate way, upper to bottom plus left to right\n\nThat doesn't mean much, for it may be caused by several conditions. This is a finding that can be interpreted only  with clinical examination of your husband.
103089
Tell it to go in the other direction
985047
They don't all have a left and a right side.   Those that do are called bilaterally symmetrical.   But some others, like certain jellyfish and many flowers,  are radially symmetrical and still others, --amoebae, for example-- are irregular & not symmetrical at all.
786481
Basically you have groups of muscles that control your eyes.  Each group is controlled by a Cranial Nerve.  There are three Cranial Nerves that move the eyes.  CN IV-->lateral rectus, \nCN VI -->superior oblique and CN III--> medial rectus, inferior oblique, inferior rectus, and superior rectus.  So there is coordination between the muscles to move the eyes together.  Cross eyes is when the lateral rectus and the medial rectus which move your eyes left and right don't quiet communicate properly.  in a nut shell
59344
A mirror preserves absolute direction, both horizontally and vertically.  Say you're facing west; the reflection of your north hand is on the same side of the room as your real north hand -- namely the north side.  And the reflection of the top of your body is toward the ceiling, just like the real top of your body.  That's because north vs. south and up vs. down are the same for everybody.  But right and left are not absolute directions.  Your north hand is on the right because you're facing west.  If someone were facing east, their north hand would be on the left.  And your reflection in this example _is_ facing east because you are facing west, and the reflection is looking back at you.  So, your reflection's north hand, which is the same as your north (that is, right) hand, is its left hand.
1155102
As we come to the vertebrates, we begin to find real efficiencies with the closed system. Fish possess one of the simplest types of true heart. A fish's heart is a two-chambered organ composed of one atrium and one ventricle. The heart has muscular walls and a valve between its chambers. Blood is pumped from the heart to the gills, where it receives oxygen and gets rid of carbon dioxide. Blood then moves on to the organs of the body, where nutrients, gases, and wastes are exchanged. However, there is no division of the circulation between the respiratory organs and the rest of the body. That is, the blood travels in a circuit which takes blood from heart to gills to organs and back to the heart to start its circuitous journey again.\n\nFrogs have a three-chambered heart, consisting of two atria and a single ventricle. Blood leaving the ventricle passes into a forked aorta, where the blood has an equal opportunity to travel through a circuit of vessels leading to the lungs or a circuit leading to the other organs. Blood returning to the heart from the lungs passes into one atrium, while blood returning from the rest of the body passes into the other. Both atria empty into the single ventricle. While this makes sure that some blood always passes to the lungs and then back to the heart, the mixing of oxygenated and deoxygenated blood in the single ventricle means the organs are not getting blood saturated with oxygen. Still, for a cold-blooded creature like the frog, the system works well. Humans and all other mammals, as well as birds, have a four-chambered heart with two atria and two ventricles. Deoxygenated and oxygenated blood are not mixed. The four chambers ensure efficient and rapid movement of highly oxygenated blood to the organs of the body. This has helped in thermal regulation and in rapid, sustained muscle movements.
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>>>What happens when the air is pumped into the lungs? \n\nThe lungs expand.\n\n>>Compare the walls of the atria and the ventricle?\n\nThe atria walls are thin and flexible. The ventricle wall is  thick and more rigid.\n\n>>>Describe the movement of the leg muscles as the leg is bent and straightened.\n\nWhen the leg is straightened the muscle on the opposite side of the joint expands. You really do need some detailed digrams or a frog carcasse to explain this properly.\n\n>>>>How is the location of the nares an adaptation to living water? \n\nThe nares are located high on the snout and towards the front. That allows the frog to breathe while keeping almost all of its body beneath the atwer line. \n\n>>>How does the length of the small intestine relate to its function in absorbing digested food?\n\nThe longer the intestine the more time food has to digest and the more thorough digestion will be.\n\n>>>Explain why the frogs hearts has a thicker wall than the atrium.\n\n\nHuh? The atrium is part of the heart. Part of the heart can't have a thicker wall than the heart.
1044770
Your most advanced animals have what is called bilateral symmetry.  This simply means they have two sides to their body.  The right and the left.  They also have what is called cephalization where most of the organisms sense organs are located in the area of the head.  It is a body plan that seems to work in the scheme of evolution.  It helps the animal adapt to a new environment since the head is the firs body part to enter it.
71932
Answers provided so far a basically correct except they have the primary functions of xylem and phloem reversed. See links below.
1013680
Torsion (spiral process of gastropods) can happen in either direction, but most are counterclockwise. They compare these kinds of snails by calling them either left or right handed snails! i.e. the Laksmi conch is a left handed conch.
912779
I suspect it's something simple.  I think because of the way your arm joints work, when you release the board with your right hand, for example, the board will have a very slight horizontal inclination to the left, which will eventually cause it to turn in the air and veer to the left.\n\nIt will be interesting to hear what someone with a knowledge of biology or physics will say though.  :)
239106
Gravity,it is often diffacult to tell which direction you are faceing, the teory is to whatch the saliver to see which way it goes.so you digg in the opposite direction and not bury your self ferther
192182
It's because left and right are relative terms, while up and down refer more to absolutes.  If were facing east looking into a mirror, our right hand would be south, and our left hand north.  Referred to north and south, there is no inversion--move your "north hand" and the image's "north hand" moves; move your south hand and the images south hand moves.  The problem is that left/right is a special sort of orientation that is centered from ourselves and distinguishes from two symmetrical sides of ourselves.  You right hand looks like the reflection of you left hand, but when you look at the reflection of your left hand, that reflect is still on *your* left.  If you imagine that the image reflected is some different person, and you try to set up a left/right orientation with resepct to the person in the mirror, it will be backwards--but that's only because it is erroneous to think that the reflection of your right hand is your reflection's left hand.  It isn't; it just looks like a left hand because our bodies display left/right symmetry.  If your head looked like the mirror image of your feet, you might make the same mistake, but the body does not display any manner of top/bottom symmetry.
767503
Snail shells can be either right-handed (as you\nhave described) or left-handed, although the\nright-handed ones are much more common.  Even\nin the same species of snail an occasional one\nwill come out with handedness opposite to the\nusual.  The handedness seems to be fixed by\nthe tilt of the spindle during the earliest cell\ndivisions of the embryo.  If the spindle leans one\nway the result is a right-handed shell, if it leans the\nother way, left-handed.  Why right-handed is more\ncommon no one seems to know.  It may be just\na historical accident.
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http://ajpregu.physiology.org/cgi/content/full/280/5/R1388