The V&A explains the exhibit theme and Leonardo's thinking "The dominant theme is the mathematical operation of all the powers of nature. Every small part of nature mirrors the action of the whole, and the human body is specifically a “lesser world” – lesser in scale but not in wonder and complexity. Everything is related to everything else. Leonardo saw connections where we see only differences."
As an example, here is the commentary that accompanies this exhibit drawing. "This is Leonardo’s supreme, composite demonstration of the irrigation systems of the body in terms of the microcosm or 'lesser' world. It is the culmination of his thinking after the dissection of a 100-year-old man in the winter of 1507-8. Some forms are shown in three dimensions, others sectioned and others rendered as if transparent. Traditional knowledge (for example, the two-chambered heart and "horned" uterus) is synthesised with observation and theory. To clarify the spatial disposition of the organs, Leonardo reminds himself to 'make this demonstration from the side'. Other notes discuss reproduction, birth, death and rebirth."