Tubulusok

Tubulusok, or tubules, are elongated, tube‑like structures found in many organisms that transport fluids, and in which absorption, secretion, or both processes take place. The term comes from the Latin tubulus, meaning “little tube.” In anatomy and physiology, tubules are a common organizational motif for moving substances through a system while maintaining surface area for interaction with the lumen.

In vertebrates, the most prominent examples are the renal tubules. They form the tubular portions of the nephron, including the proximal tubule, the loop of Henle, and the distal tubule, which together reabsorb most of the filtered water, electrolytes, and nutrients and secrete waste products. The cells lining renal tubules are specialized for selective transport and often feature microvilli to increase surface area. Another well‑known example is the seminiferous tubules in the testes, where sperm cells are produced within a germinal epithelium.

Tubules also occur in invertebrates. For instance, insects possess Malpighian tubules, excretory organs that extract waste from the hemolymph and regulate osmotic balance before waste is eliminated with the gut contents.

Glandular and epithelial tissues frequently form tubular units, enabling organized secretion and transport in organs such as glands and the digestive tract. Structure and specialization of tubules vary by organism and tissue, but their fundamental role is to provide a conducing channel with a large surface area for selective exchange.

Disruption of tubule function can lead to organ‑level pathology, such as tubular damage in the kidneys, which can impair reabsorption and waste handling.