lobule

Lobule is a term used in anatomy to denote a small subdivision of a lobed organ, roughly equivalent to a miniature lobe. In anatomy, many glands and organs are described as being divided into lobules by connective tissue septa, with each lobule containing the tissue elements responsible for the organ's function. The term originates from Latin lobulus, a diminutive of lobus.

Hepatic lobule: In the liver the classic hepatic lobule is a hexagonal unit with a central vein at its core and a portal triad at each of its six corners. Hepatocytes are arranged in plates radiating from the central vein, and sinusoids allow blood flow from the portal triads toward the central vein. Bile produced by hepatocytes drains into bile canaliculi and ducts located in the portal triads.

Mammary lobule: In the mammary gland, lobules are glandular units containing milk-secreting acini. These lobules drain through a network of ducts that converge on the nipple. They enlarge during puberty and pregnancy in many species.

Pulmonary lobule: In the lung, the pulmonary lobule is the smallest clearly defined unit, bounded by connective tissue septa. It contains a terminal bronchiole, accompanying respiratory bronchioles, alveolar ducts and multiple alveoli, together forming the functional gas-exchange unit.

Exocrine glands such as the pancreas and salivary glands also show lobular organization, with lobules composed of acini or secretory units separated by septa, each unit designed to release enzymes or fluids.

See also: Lobe, Lobule (anatomy)