Complex sentence: Koalas are unable to clean out their pouches since they face backwards, so just prior to giving birth to the young koala joey, a self-cleaning system is activated, secreting droplets of an anti-microbial liquid that cleans it out.
Split into simpler sentences: Koalas are unable to clean out their pouches since they face backwards. So just prior to giving birth to the young koala joey, a self-cleaning system develops, secreting droplets of an anti-microbial liquid that cleans it out.