Вытянутый, like many other words in the Russian language, can be classified as a participle. Participles are not considered to be a separate part of speech in Russian, but are rather considered to be verb forms that can function as adjectives. In general, participles are created by adding an affix to the infinitive form of a verb, which changes the verb into an adjective that can be used to modify a noun.
In the case of вытянутый, the affix -ут- has been added to the infinitive вытянуть (to stretch). This creates a past passive participle, which can be translated into English as «stretched» or «pulled.» Participles can be used to create complex verb tenses, such as the present perfect progressive, by combining the auxiliary verbs with the participle.
In addition to being used as adjectives, participles can also be used to form gerunds or participial phrases. For example, Вытянув руку, я смог ухватиться за ствол дерева (Stretching out my arm, I was able to grab onto the trunk of the tree).
Overall, the participle form of вытянутый allows speakers and writers to express a wide range of complex ideas in a concise and elegant manner. Whether used as an adjective or as part of a more complex grammatical construction, participles are an essential part of the Russian language and its rich and expressive vocabulary.