UNIX for Advanced & Expert Users

OK so I wanted to know how does grep outputs to the pipe and how sort reads from it. So I run a strace over "grep blah myfile | sort" and this is what I got:

open("myfile", O_RDONLY|O_LARGEFILE) = 3
fstat64(3, {st_mode=S_IFREG|0600, st_size=84, ...}) = 0
read(3, "blah blah and blah cause of blah"..., 32768) = 84
fstat64(1, {st_mode=S_IFIFO|0600, st_size=0, ...}) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7fe8000
read(3, "", 32768) = 0
close(3) = 0
write(1, "blah blah and blah cause of blah"..., 85) = 85
close(1) = 0
munmap(0xb7fe8000, 4096) = 0
exit_group(0) = ?
Process 14533 detached
blah blah and blah cause of blah
find blah myfile blah grep it.
this is my blah file

I know that grep nor sort are aware of the pipe, they just input/output to the stdin/stdout... the pipe just connect them, that's how pipes works as far as I know... but what I don't see in this code is how grep is outputing to the pipe (stdout) and how is sort reading from the pipe (stdin). Is there anyway to check that relation? All I can tell from the code I bolded is:

MyFile -> Grep --------------------------> stdout

Unless "read(3, "", 32768)" has anything to do with the sort process.
Thanks in advance.