why can’t limbs be transplanted to the needy just like heart, eyes etc ?
Sowing a limb into someone is difficult, but it can certainly be done.
The issue is that just sewing a limb on doesn’t mean the new owner can control the limb. That’s because there are thousands of tiny nerve cells that run up and down your limbs, each connecting muscles and sensory organs to the brain. These allow the brain to both sense and control the limb.
Nerves are extremely small. So small the individual cells can only be seen under a microscope, and for a successful transplant to be done, thousands of nerves in the new limb would need to be connected to each corresponding nerve in the host, and unfortunately that’s beyond our medical capability at the moment.
If you look up Robert J. White, you’ll see that we have the power. The problem with doing it is tissue compatibility.
The biggest issue is connecting all the nerves/tendons/muscles for the limb to be worth transplanting, since heart and eyes are more of a “priority” than a missing arm for example leads the scientists to develop that procedures first.