Here's why:

* Bean-shaped: Kidneys are indeed bean-shaped, with a concave medial border where blood vessels and the ureter connect.

* Efferent and Afferent Vessels:

* Afferent arterioles carry blood *into* the kidneys.

* Efferent arterioles carry blood *out* of the kidneys. These vessels are essential for filtering waste products from the blood and producing urine.

Let me know if you have any other questions!