Ok, barring our posable thumb and their lengthy tailsl, I’ve heard it said that canine anatomy is very similar to human anatomy…just laid out horizontally. Is this more-or-less correct? And, if so, how are dogs any more similar to human anatomy than, say, cats? Just hit the highlights, if you would please…no need for a hundred page dissertation.
Thanks,
Dogs have plenty of features that are homologous with human anatomy. This is no different than any other mammal. And in fact there are homologies with reptiles, and all tetrapods, etc. They get fewer the farther away you get on the evolutionary tree. Chimps are closer to humans, dogs less so. Dogs and cats are equally similar, I’d guess. But it’s not exactly a matter of change-the-opposable-thumb-and-remove-the-tail. Dogs have a pelvis, for example, but it’s layed out a bit differently due to their four-legged posture. And dogs have a lot of similar bones in their head, but a dog skull still looks very different from a human’s skull. This is unsurprising, since there’s serious selective pressure on skull shape for an animal that catches prey in its mouth.
But my knowledge of this matter is largely from hanging around folks who were busily cutting up dog cadavers in their gross anatomy labs. I don’t have direct knowledge, so you probably don’t want to take my word for it. 
I would expect that a dog’s digestive system would be more like a human’s than a cat’s would be, due to similarities in diet. Humans and dogs are both omnivores (though dogs tend more towards meat than do humans), while cats are exclusively carnivores. So, for instance, dog intestines are probably longer than cat intestines, but similar (for a given body size) to human intestines.
Dogs are really no more similar to humans than are a host of other mammals (each of which differs from humans, and from dogs, in a different way). They might be marginally more similar than cats, but this is only because cats are very highly specialized for a carnivorous diet.
Primates in general are relatively unspecialized mammals, except for those adaptations related to an arboreal life style. Primates probably have the greatest anatomical similarities to tree shrews, and then to insectivores, flying lemurs, and bats. Dogs and other carnivores are pretty distant.
In some ways, pigs, because of their size and omnivorous diet, provide some of the strongest similarities to humans among groups that are not closely related; certainly they would be more similar than dogs.
That’s opposable, as in “able to move in the opposite direction of the rest of the digits”, not posable, as in “able to be posed” (if there is such a word - it’s not in my dictionary).
I know you didn’t ask, but it was driving me crazy. Sorry.
As said, not really much similar overall than most mammels, though certain features are very close to a human’s, the renal system (kidneys, essentially) is very close, and as such is used in many tests for dialysis machines. Sometimes dental applications use canine tests as well.