hmm...so i guess it just depends on the verb, and if it can be "continued"..hmm...i think i understand a bit better. Thanks!
The problem is that you're trying to explain Japanese sentences with English grammar.
With te-iru forms, my first bit of advice would be to drop the idea of a "present tense" as it doesn't exist as neatly in Japanese as it does in English.
So let's look at your sentence:
When the te-form of a verb is used in the middle of a sentence before another verb or clause, it often carries the meaning of "do X and".
So for the above sentence, we could literally translate it as:
Yamashita got married and is.
So he got married and continues in his current state (of being married). So what the above text reveals is that he got married and is still married.
You can apply this line of thinking to undrentide's examples as well.
Yamada sat down and is.
(Yamada sat down and continues to be sitting.)
山田さんはリンゴを食べています。
Yamada eats an apple and is.
(Yamada eats an apple and continues to eat it.)