Vein skeleton of a Hydrangea leaf showing<unk>  of veins An<unk>  (, plural<unk>  is a connection or opening between two things (especially cavities or passages) that are normally diverging or branching, such as between blood vessels, leaf veins, or streams. Such a connection may be normal (such as the foramen ovale in a fetus's heart) or abnormal (such as the patent foramen ovale in an adult's heart); it may be acquired (such as an arteriovenous fistula) or innate (such as the arteriovenous shunt of a metarteriole); and it may be natural (such as the aforementioned examples) or artificial (such as a surgical<unk> . The reestablishment of an<unk>  that had become blocked is called a reanastomosis.<unk>  that are abnormal, whether congenital or acquired, are often called fistulas. The term is used in medicine, biology, mycology, geology, and geography.
Anastomosis
Hydrodissection
Surgical anastomosis
Surgical staple
Effleurage
Couching 
Craterization
Subluxation