In anatomy, a medullary ray (Ferrein's pyramid) is the middle part of a cortical lobule (or renal lobule).
Each consists of a group of nephrons in the renal cortex.
[1] Their name is potentially misleading, as "medullary" refers to their destination, not their location.
They travel perpendicular to the capsule, and extend from the cortex to the medulla.
[1] This article incorporates text in the public domain from the 20th edition of Gray's Anatomy (1918) This article related to the genitourinary system is a stub.