Если рана неглубокая, её сначала промывают водой, а потом заклеивают пластырем.

Неглубокая is an adjective agreeing with рана.

• рана = feminine singular nominative
• so the adjective must also be feminine singular nominative: неглубокая

That ending -ая is the normal feminine singular nominative ending for many adjectives.

Also, не- is written together here because неглубокая means a single idea: shallow / not deep. If you wrote не глубокая, it would usually sound more contrastive, like not deep, but...

Yes. Both are possible, but they feel a little different.

• рана неглубокая = the full adjective form; very neutral and common
• рана неглубока = the short form; a bit more concise, sometimes more bookish or formal

In everyday explanatory or instructional language, неглубокая is very natural.

Because the wound is the object of the verbs промывают and заклеивают.

• она = she/it in the nominative case, used for the subject
• её = her/it in the accusative/genitive form

Here, the wound is not doing the action; something is being done to it, so Russian uses её.

This is a very common Russian pattern for instructions, general procedures, and habitual actions.

Literally, it looks like they rinse it / they cover it with a plaster, but the real meaning is more like:

• one rinses it
• people rinse it
• it is rinsed
• you should rinse it

Russian often uses 3rd person plural with no stated subject to express general instructions. It sounds very natural here.

Because the sentence gives a general rule or standard procedure, not a single specific future event.

Russian often uses the present tense for this kind of meaning:

• Если рана неглубокая, её... промывают...
  = If the wound is shallow, they/you first rinse it...

This is similar to English general-condition sentences like If the wound is shallow, you wash it first...

Also, the verbs are imperfective because the sentence describes the normal process or recommended action, not just one completed result.

They are both in the instrumental case.

Russian often uses the instrumental for the means, tool, or material used to do something.

• водой = with water
• пластырем = with a plaster / bandage strip

So:

• промывают водой = rinse with water
• заклеивают пластырем = cover/seal with a plaster

This is a very common use of the instrumental case.

Мыть means to wash in a general sense.

Промывать usually means something more like:

• to rinse
• to wash through
• to flush out

So промывают водой is especially suitable for a wound, because the idea is not just ordinary washing, but rinsing/cleaning it with water.

Заклеивать means to stick over, to seal up, or to cover by sticking something onto it.

Here it means that the wound is covered with an adhesive plaster/bandage.

The prefix за- adds the idea of covering up / closing over, so заклеивают пластырем is more specific than just клеят.

Сначала means at first / first, and потом means then / afterwards.

Together they mark the order of steps:

• сначала = first
• а потом = and then / and after that

The conjunction а often links two stages or two contrasting parts of a statement. Here it helps separate the two actions clearly:

1. first rinse
2. then cover with a plaster

Using а sounds very natural in Russian for this kind of step-by-step sequence.

There are two commas for two different reasons.

1. Если рана неглубокая, ...
   A clause introduced by если (if) is a subordinate clause, so it is separated by a comma.

2. ..., а потом заклеивают пластырем.
   Russian normally puts a comma before а.

So the punctuation is standard Russian syntax.

Not always exactly, so it is worth being careful.

In this medical context, пластырь means an adhesive plaster, like:

• a Band-Aid
• a sticking plaster
• a small adhesive dressing

So it is not just the building material plaster. In medical Russian, пластырь is the thing you stick onto the skin.

In careful writing, её shows the correct pronunciation, with ё.

• её is pronounced roughly ye-YO
• the ё is stressed

In many Russian texts, especially less formal ones, writers omit the dots and write ее, but the word is still understood as её. For learners, the version with ё is very helpful.