tubulus

Tubulus is a Latin term meaning "little tube" that has been adopted into biological and medical vocabulary to describe small, tube-shaped structures. In anatomy and histology, the word is used as a generic descriptor for tubular ducts or conduits and for subunits within organs that carry fluids, gases, or cells. The plural form is tubuli.

In the kidney, the renal tubules, or tubuli renales, are the microscopic ducts that modify the filtrate produced by the glomerulus into urine. They include segments commonly termed proximal and distal tubules. These tubules reabsorb water, ions, and nutrients and participate in secretion and acid–base balance. The proximal tubule epithelium features a brush border of microvilli to increase surface area for absorption.

In the testes, the tubulus seminiferus (plural tubuli seminiferi) refers to the seminiferous tubules, long coiled tubes where spermatogenesis takes place within the germinal epithelium, supported by Sertoli cells.

Outside these well-known examples, tubulus and tubuli are broadly used in Latinized anatomy to name other small tubular structures throughout the body. The term functions as a descriptive label rather than a strict anatomical unit, with its exact meaning depending on the organ and context.