La esterilización y el examen clínico aparecen en el historial veterinario.

Because the subject is actually two things joined by y:

• la esterilización
• el examen clínico

Together, they form a plural subject, so Spanish uses the 3rd person plural verb:

• aparecen = they appear / are listed / show up

If there were only one item, you would use aparece:

• La esterilización aparece en el historial veterinario.

In Spanish, it is very common to repeat the article before each noun in a list when each noun is separate and clearly identified:

• la esterilización y el examen clínico

This sounds natural and standard. English often says the sterilization and clinical exam, but Spanish prefers to mark each noun with its own article when needed.

You might sometimes see article omission in other contexts, but here repeating the articles is the most normal choice.

Because esterilización is a feminine noun, while examen is a masculine noun.

So the articles and adjectives must agree with each noun:

• la esterilización → feminine singular
• el examen clínico → masculine singular

The adjective clínico matches examen, not esterilización.

In Spanish, most descriptive adjectives normally come after the noun:

• examen clínico
• historial veterinario

This is one of the biggest differences from English, where adjectives usually come before the noun:

• clinical exam
• veterinary record

So examen clínico is the standard Spanish word order.

Because Spanish accent marks show where the stress goes when it does not follow the default stress rules.

• clínico has stress on the first syllable: CLI-ni-co, so it needs an accent mark.
• examen is stressed as e-XA-men, which follows normal spelling/stress patterns, so it does not need an accent mark.

Also notice:

• esterilización has an accent because the stress falls on the last syllable: -ción

Not necessarily in a visual, dramatic sense. In this kind of sentence, aparecer en often means:

• to appear in
• to show up in
• to be listed in
• to be included in
• to be recorded in

So here it has an administrative or documentary sense, not a literal suddenly appear meaning.

Because Spanish uses en for the idea of something being in a document, record, file, list, or report.

So:

• aparecen en el historial veterinario = they are found/listed in the veterinary record

This is very similar to English uses such as in the report, in the file, or in the record.

This is a very common question.

• historia often means story or history
• historial often means a record, file, or case history

In medical and veterinary contexts, historial is commonly used for a patient’s record or background information.

So historial veterinario sounds like veterinary record / veterinary history rather than a story about a vet.

Here it is an adjective modifying historial:

• historial veterinario = veterinary record

The word veterinario can also be a noun meaning vet / veterinarian, but in this sentence it is clearly adjectival because it describes the type of historial.

Yes. Spanish word order is flexible, and both versions are natural:

• La esterilización y el examen clínico aparecen en el historial veterinario.
• En el historial veterinario aparecen la esterilización y el examen clínico.

The second version puts more focus on where the information appears. The original version puts more focus on what items appear.

You could, but it would usually sound more like headings, notes, labels, or a telegraphic style.

The full version with articles:

• La esterilización y el examen clínico aparecen...

sounds more complete and natural in a normal sentence.

Without articles, Spanish can sound more abstract, general, or list-like.

Because with A y B, Spanish normally treats the subject as plural:

• La esterilización y el examen clínico aparecen...

A singular verb would usually sound wrong here.

Spanish does sometimes use singular with coordinated ideas in very special cases when they are treated as one unit, but that is not the normal interpretation in this sentence. Here, they are simply two separate entries in the record.

Yes, it is very common and natural, especially in general or formal contexts.

In veterinary usage, esterilización can refer broadly to procedures that prevent reproduction. Depending on context, Spanish may also use more specific words such as:

• castración
• ovariohisterectomía in technical contexts

But esterilización is a very common, understandable choice in everyday veterinary language.

Adding clínico makes the type of exam more specific.

• examen by itself can mean many kinds of examination
• examen clínico specifically refers to a clinical examination

So the adjective helps narrow the meaning and makes the sentence sound more precise, especially in a medical or veterinary record.

It sounds neutral to formal, which fits a medical or veterinary record well.

Words like:

• esterilización
• examen clínico
• historial veterinario

are standard and professional. This is not especially casual spoken Spanish, but it is very natural in administrative, medical, or veterinary contexts.