Question

place a single word into each sentence to make it correct in describing the repair of a pns axon.

1. a damaged (click to select) axon may regenerate if its cell body is intact and some neurilemma remains.
2. when an axon is cut, the axon distal to the injury (click to select) survive.
3. near the site of injury, the basal lamina and the neurilemma form a (click to select) tube.
4. the tube guides the growing sprout back to the original target cells, reestablishing (click to select) contact.
5. when contact is established, the (click to select) shrinks, and reinnervated muscle fibers regrow.

Explanation:

1. In the PNS (peripheral nervous system), axons have the potential for regeneration under certain conditions. If the cell body is intact and some neurilemma (Schwann - cell membrane) remains, a damaged peripheral axon can regenerate.
2. When an axon is cut, the axon distal to the injury does not survive. This is because the axon depends on the cell body for metabolic support. Without the connection to the cell body (which is proximal to the injury), the distal part cannot maintain its functions and degenerates.
3. Near the site of injury, the basal lamina (a layer of extracellular matrix) and the neurilemma form a regeneration tube. This tube acts as a physical guide for the regenerating axon sprout.
4. The regeneration tube guides the growing sprout back to the original target cells, re - establishing nerve contact. This is crucial for the restoration of function, as the axon needs to reconnect with the appropriate target (such as a muscle fiber or another neuron) to transmit signals.
5. When contact is established, the regeneration tube shrinks. Once the axon has successfully reconnected with its target, the regeneration tube, which was a temporary structure for guiding regeneration, is no longer needed and undergoes atrophy. And the reinnervated muscle fibers (if the target was a muscle) can regrow as the normal nerve - muscle interaction is restored.

Answer:

1. peripheral
2. does not
3. regeneration
4. nerve
5. regeneration tube