lobuli

Lobuli is the plural form of lobulus, a Latin term meaning a small lobe. In anatomy, lobuli refer to small lobed subdivisions within an organ, typically delineated by connective tissue septa, ducts, or vascular and biliary structures. The exact boundaries and functional significance of a lobulus vary by organ and species, but the general idea is that a lobulus represents a discrete, locally organized unit within a larger lobe or tissue mass.

In the liver, the hepatic lobulus (the classic unit described in many texts) is a roughly hexagonal cluster of hepatocytes arranged around a central vein, with a portal triad at each corner containing a branch of the portal vein, hepatic artery, and bile duct. This microarchitecture supports liver blood flow, metabolism, and bile secretion. Alternative conceptual schemes, such as the portal lobule or the liver acinus, emphasize different functional boundaries within the liver’s vascular network.

In the lung, the pulmonary lobulus (often called the secondary pulmonary lobule) is the smallest radiologically and functionally defined unit. It is typically about 1–2.5 mm in diameter and is centered on a terminal bronchiole, with accompanying arteries and veins and septal walls that separate neighboring lobuli. This unit helps describe the pattern of gas exchange and disease spread on imaging.

In neuroanatomy and comparative anatomy, lobuli may denote small lobular subdivisions within regions such as the cerebellum or cerebral cortex, reflecting local cytoarchitectural organization.

See also lobule and lobulus for related terminology.