Medicinska sestra uzima krv.

Medicinska sestra is a noun phrase:

• sestra = the noun, literally sister
• medicinska = an adjective meaning medical

Together, medicinska sestra is the normal Serbian expression for nurse.

Grammatically:

• sestra is feminine singular
• medicinska has to match it in gender, number, and case, so it also appears in the feminine singular form

So medicinska sestra literally means medical sister, but idiomatically it means nurse.

Because the adjective must agree with the noun it describes.

Here:

• sestra is feminine singular
• so the adjective must also be feminine singular
• that gives medicinska

Compare:

• medicinski brat = male nurse
• medicinska sestra = female nurse

So the ending -a is there because of agreement with sestra.

It is in the nominative case because it is the subject of the sentence — the person doing the action.

You can ask:

• Who is taking blood?
• Medicinska sestra.

That tells you it is the subject, so nominative makes sense.

Krv is in the accusative case because it is the direct object of uzima.

You can ask:

• What is the nurse taking?
• Krv.

The reason it looks unchanged is that some Serbian nouns do not show a visible difference between nominative and accusative singular.

So here:

• nominative: krv
• accusative: krv

Even though the form looks the same, the function is accusative.

Uzima is the 3rd person singular present tense of the imperfective verb uzimati.

It matches the subject:

• medicinska sestra = she
• so the verb form is uzima = she takes / is taking

This form is natural when describing:

• an action happening now
• a general or repeated action
• a simple statement of what someone does

So uzima krv can mean something like:

• is taking blood
• takes blood depending on context.

Because uzme comes from the perfective verb uzeti, while uzima comes from the imperfective verb uzimati.

Very roughly:

• uzimati / uzima = ongoing, repeated, or uncompleted action
• uzeti / uzme = completed, single whole action

In a simple present-time description like this, Serbian normally prefers the imperfective:

• Medicinska sestra uzima krv.

Using uzme would not fit as naturally in this kind of plain descriptive sentence.

It is both grammatical and idiomatic in a medical context.

In this sentence, uzima krv naturally means:

• takes blood
• draws blood
• takes a blood sample

So even if the literal words are simple, the phrase is commonly understood in the medical sense.

If someone wanted to be more explicit, they could say something like:

• uzima uzorak krvi = takes a blood sample

Because Serbian does not have articles like English the and a/an.

So:

• medicinska sestra can mean the nurse or a nurse
• krv can mean blood or the blood, depending on context

The listener understands the intended meaning from the situation, not from an article.

Serbian word order is more flexible than English word order.

The neutral, straightforward order here is:

• Medicinska sestra uzima krv.

But other orders are possible if you want different emphasis, for example:

• Krv uzima medicinska sestra.
  This emphasizes blood
• Uzima krv medicinska sestra.
  This can sound marked or stylistic, depending on context

So the original sentence is the most neutral and beginner-friendly version.

Sometimes, yes, but it depends on context.

By itself, sestra most basically means:

• sister

But in hospitals or clinics, people may also use sestra to mean:

• nurse

Still, the full expression medicinska sestra is clearer, especially for learners, because it removes ambiguity.

Krv is one of those Serbian words where r can act like the center of the syllable.

So it is pronounced approximately like:

• krv
• with a rolled or tapped r
• and without a full vowel between k and r

That can feel strange to English speakers, because English usually expects a vowel there.
The word is short, compact, and perfectly normal in Serbian.

Yes, krv is singular, but it behaves like a mass noun, similar to blood in English.

So it does not usually mean one blood or a countable unit. It means the substance in general.

In this sentence, it usually means:

• the nurse is drawing some blood
• the nurse is taking a blood sample

If you wanted to be more precise, you might mention:

• uzorak krvi = a blood sample