Write two of sentences, each one containing introductory and internal participial phrases.
Example: My father's hair, streaked with gray and receding on both sides, is combed straight back to his collar.
Lets first start by remembering that a particple phrase is always used as an adjective and is uses an -ing verb or a past tense verb form to start. In your example sentence, the words streaked and receding are the participles that introduce the rest of the phrase (and illustrate both types of verb forms that can be used.)
Here are a couple more examples of each. First are two that use an introductory participle phrase to modify the subject of the sentece that immediately follows the phrase.
Ex. Running wildly for the bus, Susie barely made it on time.
Ex. Shredded beyond repair, the jeans finally had to be replaced.
Here are couple of examples of the phrase coming in the middle of the sentence (internal example).
Ex. Susie, running wildly, jumped on the bus at the last minute.
Ex. The jeans, shredded at the knees and faded, had to be replaced.
The value of learning about participle phrases is that they can easily be used to make your writing more interesting and your sentence patterns more varied. Your descriptive language can have a place of prominance at the start of the sentence, or can be regarded as less essential when it is set off with commas in the middle of a sentence. You can combine both to create an interesting and complex thought.