Lobules

A lobule is a small division or subdivision of an organ that can function as a unit within the tissue. The term is used across anatomy to describe parts bounded by connective tissue, ducts, vessels, or other structural features. Size and boundaries vary by organ, but the concept serves to describe a modular organization within a larger organ system.

In the liver, the hepatic lobule is the classic microanatomical unit. It is roughly hexagonal and organized around a central vein, with portal triads located at the corners. Blood flows from the portal tracts through sinusoids toward the central vein, and hepatocytes are arranged in plates between these vessels. This arrangement supports metabolic processing, detoxification, and bile production.

In the lung, the pulmonary lobule is the smallest clearly defined unit visible in histology and radiology. It is typically 1–2 cm in diameter and bounded by connective tissue septa. Each lobule contains a small bronchiole, accompanying artery and vein, lymphatics, and the surrounding alveolar ducts and sacs where gas exchange occurs.

In the breast, the gland is organized into lobes and further subdivided into lobules, which contain milk-producing alveoli lined by secretory cells. Ducts from the lobules drain toward the nipple, with hormonal signals regulating lactation.

Pancreatic tissue is likewise divided into lobules of exocrine tissue containing acini, separated by connective tissue; the endocrine islets of Langerhans are interspersed among the lobules.

The term lobule is also used in neuroanatomy to describe small lobes or subdivisions within certain brain areas, such as the cerebellar lobules, reflecting a similar modular concept.