Медсестра наложила пластырь на рану.

Because the subject is медсестра, which is a feminine singular noun.

In the past tense, Russian verbs agree with the subject in gender and number:

• masculine: наложил
• feminine: наложила
• neuter: наложило
• plural: наложили

So:

• Медсестра наложила... = The nurse applied/put...
• If it were врач (doctor, masculine), it would be Врач наложил...

Here наложить means to apply or to put on, especially in a medical or practical sense.

In Russian, наложить is commonly used with things like:

• наложить пластырь = apply a plaster / bandage
• наложить повязку = apply a dressing/bandage
• наложить швы = put in stitches

So this is a very natural medical-style verb choice.

Because it is the direct object of the verb наложила, and for this noun, the accusative singular is the same as the nominative singular.

• nominative: пластырь
• accusative: пластырь

That happens because пластырь is an inanimate masculine noun. In Russian, inanimate masculine nouns usually have the same form in nominative and accusative singular.

Because after на, Russian uses different cases depending on the meaning:

• на + accusative = movement toward / placement onto something
• на + prepositional = location on something

Here the idea is putting the plaster onto the wound, so Russian uses accusative:

• на рану = onto the wound

Compare:

• положить пластырь на рану = put/apply a plaster onto the wound
• пластырь на ране = the plaster is on the wound

Since рана is a feminine noun ending in -а, its accusative singular becomes рану.

Yes. На is the normal choice when something is placed onto a surface or target area, including body parts or wounds.

So:

• наложить пластырь на рану
• наложить повязку на руку
• нанести крем на кожу

Using в here would sound wrong, because the plaster is not going into the wound; it is being placed on it.

It can vary by context.

Пластырь usually means an adhesive plaster or adhesive bandage. In everyday English, that might be:

• Band-Aid (common in American English, though technically a brand name)
• plaster (common in British English)
• sometimes bandage, but that is less exact

A more general non-adhesive dressing is often повязка, not пластырь.

So in this sentence, пластырь is most naturally something sticky applied over the wound.

Russian has no articles like a/an/the.

So:

• Медсестра can mean a nurse or the nurse
• рану can mean a wound or the wound

Which one is intended depends on the context. In a standalone sentence like this, English often translates it as The nurse applied a plaster to the wound or The nurse put a plaster on the wound.

Наложила is perfective.

That means the sentence presents the action as completed: the nurse finished applying the plaster.

The imperfective partner is usually накладывать:

• Медсестра накладывала пластырь... = The nurse was applying / used to apply a plaster...

So:

• наложила = completed single action
• накладывала = process, repeated action, or background action

In this sentence, perfective makes sense because the plaster was successfully applied.

Yes, but the meaning or style changes.

• приклеила пластырь = stuck the plaster on
  This focuses on the fact that it is adhesive.
• положила пластырь = put the plaster on
  This is understandable, but less medical/natural in this context.
• наложила пластырь = applied the plaster
  This sounds especially natural in medical or formal usage.

So наложила is a very good choice here.

Yes. Russian word order is more flexible than English, because the cases already show the grammatical roles.

The neutral, straightforward order here is:

• Медсестра наложила пластырь на рану.

But other orders are possible for emphasis:

• Пластырь на рану наложила медсестра.
  Emphasis on who did it.
• На рану медсестра наложила пластырь.
  Emphasis on where it was applied.

Even though the order can change, the original sentence is the most neutral and natural for basic narration.

It is accusative singular.

The noun is:

• dictionary form: рана = wound

Since it is a feminine noun ending in -а, its accusative singular changes to -у:

• nominative: рана
• accusative: рану

So на рану literally shows direction/placement onto the wound.

It is mostly neutral, with a slight medical/practical feel because of the verb наложить.

It does not sound overly technical, but it is more natural in a medical context than something very casual like:

• Медсестра приклеила пластырь на рану.

The original sentence sounds like normal standard Russian, especially in healthcare or first-aid contexts.

Normally, медсестра is grammatically and semantically female: nurse in the sense of a female nurse.

For a male nurse, Russian might use:

• медбрат = male nurse

Because the subject here is explicitly feminine, the verb is also feminine:

• Медсестра наложила...

If it were медбрат, it would be:

• Медбрат наложил...