pinna

Pinna refers to the external part of the ear in humans and many other mammals, also known as the auricle. The pinna is composed largely of flexible cartilage covered by skin, with a characteristic rim called the helix and a central fold known as the antihelix, along with features such as the lobule, tragus, and concha. Its primary function is to collect sound waves and funnel them into the ear canal, aiding in sound localization, particularly in the vertical plane. The shape and size of the pinna vary among individuals and can influence auditory cues. Blood supply comes from branches of the posterior auricular and superficial temporal arteries, and sensory innervation is provided by several nerves, including the auriculotemporal and greater auricular nerves. The pinna develops from the first pharyngeal arch and surrounding mesenchyme, and congenital anomalies can affect its size or shape. Trauma or infection can lead to cosmetic or functional issues; cauliflower ear is a common consequence of repeated ear trauma.

In botany, pinna is a primary division of a pinnate leaf, consisting of a single leaflet attached to the rachis. Multiple pinnae are arranged along the rachis, and each pinna may be subdivided into pinnules. The term helps describe the overall architecture of compound leaves found in many plants, including ferns and some flowering species. Etymologically, pinna comes from Latin, meaning feather or wing, a reflection of its shape in many species.

Other uses of the term exist in descriptive language, referring to feather-like or wing-like structures in various organisms or objects, though the botanical and anatomical senses are the most common.