What is the pinna?

The Pinna: Anatomy and Clinical Significance

The pinna (or auricle) is the visible part of the external ear that extends from the side of the head, functioning to collect and funnel sound waves into the ear canal toward the middle ear. 1

Anatomical Structure and Function

The pinna is an osseous-cartilaginous structure that forms the outermost part of the external ear. It has several key characteristics:

• Composed primarily of elastic cartilage covered by skin, except for the earlobe which lacks cartilage 2
• Contains a small amount of subcutaneous fat 2
• Works in conjunction with the external auditory canal to form the complete external ear 3
• Serves as a sound-collecting apparatus that helps direct sound waves into the ear canal 4

Clinical Significance

The pinna has important clinical relevance in several contexts:

Diagnostic Value

• Abnormalities in pinna appearance may indicate underlying middle ear anomalies 5
• Careful examination of the pinna can serve as a simple diagnostic sign of potentially surgically correctable hearing loss 5
• Pinna abnormalities are more frequently associated with middle ear anomalies than with other congenital malformations 5

Common Pathologies

1. Infections:

   • The pinna can be affected in acute otitis externa (AOE)
   • A hallmark sign of diffuse AOE is tenderness of the tragus, pinna, or both that is often intense and disproportionate to visual appearance 1

2. Dermatologic conditions:

   • Due to its exposed location, the pinna is particularly vulnerable to ultraviolet light damage and subsequent preneoplastic and neoplastic skin lesions 2
   • Can be affected by various dermatoses including eczema, seborrhea, and other inflammatory conditions 2

3. Congenital abnormalities:

   • Pinna defects are observed in several craniofacial syndromes, including Lacrimo-auriculo-dento-digital (LADD) syndrome 6
   • FGF10 signaling is essential for normal pinna extension during development 6

Clinical Examination of the Pinna

When examining the pinna, clinicians should assess:

• Tenderness (when pushed or pulled) - a key sign in diagnosing otitis externa 1
• Visual appearance for signs of inflammation, trauma, or congenital abnormalities
• Presence of lesions that may indicate dermatologic conditions or neoplasms

Relationship to Other Ear Structures

The pinna works in conjunction with other ear structures:

• It connects to the external auditory canal, which extends to the tympanic membrane (eardrum) 1
• Together with the ear canal, it forms the complete external ear, which is separate from the middle and inner ear structures 1

Understanding the pinna's anatomy and function is essential for proper diagnosis and management of various ear conditions, particularly those affecting the external ear.