In anatomy, the medullary ray (Ferrein's pyramid) is the middle part of the cortical lobule or renal lobule, consisting of a group of straight tubes to the collecting ducts.
Their name is potentially misleading — the "medullary" refers to their destination, not their location. They travel perpendicular to the capsule and extend from the cortex to the medulla.
This article incorporates text from a public domain edition of Gray's Anatomy.
— "Urinary System: kidney, H&E, cortex and medullary ray"
— "Urinary System: neonatal kidney"