pinnae

Pinnae, the plural of pinna, refers to the external ear, or auricle, of mammals, including humans. The pinna is a cartilage-supported structure covered by skin, with landmarks such as the helix, antihelix, tragus, antitragus, and lobule. It functions to capture and funnel sound into the external auditory canal and contributes to sound localization, particularly in the vertical plane and in shaping higher-frequency sounds. The size and shape of pinnae vary among individuals and species.

Anatomically, the pinna is supplied by blood vessels such as the posterior auricular and superficial temporal arteries and is innervated by sensory nerves, notably the great auricular nerve (C2–C3) and the auriculotemporal branch of the trigeminal nerve (V3). In humans, the pinna has no dedicated muscles of its own for movement, though surrounding muscles can produce limited motility. Developmentally, the pinna arises from the first and second pharyngeal arches during embryogenesis and continues to mature after birth.

In botany, pinnae are the leaflets of pinnate leaves. They are arranged along the rachis and may be simple or subdivided into pinnules. The term is commonly used for fern fronds, where pinnae are the primary divisions of the frond and can vary in size, shape, and margin. The concept helps describe the overall architecture and photosynthetic surface of compound leaves.