What is the difference between the auricle and the pinna?

The Auricle and Pinna: Understanding the Terminology

The terms "auricle" and "pinna" are synonymous and refer to the visible portion of the external ear that projects from the side of the head.

Anatomical Definition and Function

The external ear consists of two main components:

1. Auricle/Pinna: The visible cartilaginous structure projecting from the side of the head
2. External Auditory Canal: The canal that extends from the auricle to the tympanic membrane (eardrum)

According to multiple clinical practice guidelines, these terms are used interchangeably in medical literature 1. As clearly illustrated in Figure 1 of the tympanostomy tubes guideline, the pinna (outer ear) is labeled as the external visible portion of the ear 1.

Anatomical Structure

The auricle/pinna has several important characteristics:

• Composed of elastic cartilage covered by skin (except for the earlobe) 2
• Contains a small amount of subcutaneous fat 2
• The skin covering the cartilaginous canal contains:
  • Hair cells
  • Sebaceous (lipid-producing) glands
  • Apocrine (ceruminous) glands 2

Clinical Significance

The auricle/pinna serves several important functions:

• Sound collection and funneling toward the middle ear 3
• Protection of the external auditory canal
• Exposed location makes it vulnerable to:
  • Ultraviolet light damage
  • Trauma
  • Various dermatologic conditions 2

Common Conditions Affecting the Auricle/Pinna

Several conditions can affect the auricle/pinna:

• Acute Otitis Externa: Inflammation often involving the pinna with tenderness that is "often intense and disproportionate to what might be expected based on visual inspection" 1
• Dermatologic Conditions: Including eczema, seborrheic dermatitis, contact dermatitis, and psoriasis 1, 2
• Congenital Malformations: Collectively termed microtia, ranging from mild structural abnormalities to complete absence (anotia) 4
• Traumatic Injuries: Including auricular hematomas 5

Terminology in Medical Literature

In medical literature and clinical practice guidelines, the terms are used as follows:

• In otolaryngology guidelines, both terms appear, sometimes within the same document 1
• When describing ear anatomy, some sources use "pinna (outer ear)" or "auricle (or pinna)" showing their equivalence 1
• The terms are used interchangeably in both research and clinical contexts 3

Common Misconceptions

A common misconception is that these terms refer to different structures. However, the evidence clearly shows they are synonymous terms for the same anatomical structure. This is consistently demonstrated across multiple clinical practice guidelines and research papers in otolaryngology.

In summary, there is no anatomical or functional difference between the auricle and the pinna - they are different names for the same structure of the external ear.