Minor Calyx - Location, Anatomy, Structure, Function

The minor calyx is a funnel-shaped structure in the kidney that collects urine from a single renal papilla. It is the first part of the kidney's collecting system and channels urine into a larger major calyx. Each kidney contains multiple minor calyces, typically 7 to 14, each of which receives urine from one renal pyramid.

Structure

The minor calyx is lined by transitional epithelium (urothelium) and consists of a thin muscular wall that is continuous with the rest of the renal pelvis and ureter. At the tip of the renal papilla, small openings (area cribrosa) allow urine to drain directly into the minor calyx.

Shape: Cup-like or funnel-shaped
Epithelium: Transitional epithelium for stretch resistance
Connection: Joins one or more other minor calyces to form a major calyx

Location

Minor calyces are located in the renal sinus and surround the apex of each renal pyramid. They lie between the renal papillae and the major calyces:

Structure	Relative Location to Minor Calyx
Renal papilla	Directly drains into the minor calyx
Major calyx	Receives urine from minor calyces
Renal pelvis	Receives urine downstream of major calyces

Function

The minor calyx serves as the initial conduit in the urinary drainage pathway:

Urine collection: Receives freshly produced urine from a renal papilla
Urine transport: Channels urine into a major calyx, then to the renal pelvis
Passive conduit: No absorptive or secretory function — simply a drainage chamber

Clinical Significance

Obstruction or stenosis: Narrowing at the calyceal outlet may impede urine flow and cause upstream pressure or dilation (hydronephrosis)
Kidney stones: Calculi often form or lodge in minor calyces, potentially causing pain or hematuria
Calyceal diverticulum: A congenital outpouching of a minor calyx that may harbor stones or infection
Imaging: Calyces are visible on contrast-enhanced imaging like IV pyelograms or CT urography and help assess renal drainage patterns

The minor calyx is a small but vital structure in the renal collecting system, serving as the first anatomical chamber where urine is collected before being passed through the renal pelvis and into the ureter. Its health is essential for unimpeded urine flow and overall kidney function.