isya ga watasi no sinzou wo mimasita.

A natural reading is:

いしゃ が わたし の しんぞう を みました。

A smooth pronunciation would sound like:

Isha ga watashi no shinzou o mimashita.

Notes:

• 医者 = いしゃ
• 心臓 = しんぞう
• を is written を but pronounced like お
• 診ました comes from 診る（みる）

が marks the grammatical subject of the sentence: the person who performed the action.

So in this sentence:

• 医者が = the doctor is the one who examined
• 私の心臓を = my heart is what was examined

If you changed it to 医者は, the nuance would be different. は introduces or contrasts the topic, while が more directly identifies the subject.

So:

• 医者が私の心臓を診ました。 = The doctor examined my heart.
• 医者は私の心臓を診ました。 = As for the doctor, he/she examined my heart or possibly the doctor (as opposed to someone else) examined my heart, depending on context

For a simple neutral sentence, が is very natural here.

の connects nouns and often shows possession or relation.

So:

• 私 = I / me
• 私の = my
• 心臓 = heart

Therefore:

• 私の心臓 = my heart

This is one of the most basic uses of の: A の B = B of A or A's B.

Examples:

• 私の本 = my book
• 先生の車 = the teacher’s car

を marks the direct object, meaning the thing directly affected by the verb.

In this sentence:

• 心臓を診ました = examined the heart

So:

• 医者が = the doctor did the action
• 心臓を = the heart received the action
• 診ました = examined

This is a very common pattern:

• subject が
• object を
• verb

Great question. They are pronounced the same here, but the kanji tells you the meaning.

• 見ました = looked / saw
• 診ました = examined medically

Because the sentence is about a doctor and a heart, 診ました is the correct verb. It specifically means a doctor examined a patient, checked a condition, or performed a medical examination.

So although both can be read みました, the kanji changes the meaning.

Japanese normally puts the verb at the end of the sentence.

So instead of English order:

• The doctor examined my heart

Japanese uses:

• Doctor + subject marker + my heart + object marker + examined

That gives:

• 医者が私の心臓を診ました。

This verb-final pattern is one of the most important differences between Japanese and English.

Japanese usually does not have articles like a and the.

So 医者 can mean:

• a doctor
• the doctor

Which one sounds best depends on context.

In English, if the listener already knows which doctor you mean, you would often translate it as the doctor. If not, a doctor may also be possible.

Japanese leaves that kind of detail to context rather than using articles.

Yes, it could be omitted if the meaning is already clear from context.

Japanese often leaves out information that both speaker and listener already understand.

So these are both possible:

• 医者が私の心臓を診ました。
• 医者が心臓を診ました。

However, if you just say 心臓を, it may sound less clear unless everyone already knows whose heart is being discussed. So 私の is included here to make it explicit: my heart.

Because 私 is not the direct object of the verb here. The doctor did not examine me as the object in this sentence; the doctor examined my heart.

So the noun relationship is:

• 私の心臓 = my heart

Then the whole noun phrase becomes the object:

• 私の心臓を = my heart as the thing examined

If you said 私を診ました, that would mean examined me.

So compare:

• 医者が私を診ました。 = The doctor examined me.
• 医者が私の心臓を診ました。 = The doctor examined my heart.

診ました is polite past tense.

It comes from the dictionary form:

• 診る = to examine medically

Its polite past form is:

• 診ました = examined

So the sentence describes a completed action in the past:

• The doctor examined my heart.

Yes. The verb ending -ました makes it polite.

• 診る = plain dictionary form
• 診ました = polite past form

This is a normal polite style used in everyday conversation, reports, and classroom examples.

A plain version would be:

• 医者が私の心臓を診た。

That sounds less polite and more casual.

Yes, Japanese word order is more flexible than English as long as the particles stay attached to the right words.

For example, these can all be grammatical:

• 医者が私の心臓を診ました。
• 私の心臓を医者が診ました。

The particles tell you each word’s role:

• が = subject
• を = object

Even so, the most neutral and easy-to-follow order is often:

• subject + object + verb

So the original sentence is a very standard pattern.

心臓 means the actual organ, heart.

• 心臓 = heart as a body organ
• 胸（むね） = chest

So if the doctor examined the heart specifically, 心臓 is the precise word. If the sentence were about the chest area more generally, 胸 might be used instead.

Not really. This sentence specifically says the doctor examined my heart.

Because the object is:

• 私の心臓を = my heart

If you want to say the doctor examined you generally, you would say something like:

• 医者が私を診ました。 = The doctor examined me.

So the current sentence is narrower and more specific.

The pattern is:

noun + が + noun + の + noun + を + verb

More specifically:

• 医者 = doctor
• が = subject marker
• 私 = I / me
• の = my / of
• 心臓 = heart
• を = object marker
• 診ました = examined

So structurally it is:

[subject] が [possessor] の [object] を [verb]

or more naturally:

The doctor examined my heart.