--- title: "Anatomy of External Ear" description: "ENT notes on the Anatomy of Pinna and External Auditory canal - relations, blood supply, nerve supply, and clinical aspects." source: "The ENT Resident" author: "Dr. Mausumi Das" canonical_url: "https://www.theentresident.com/ent-notes-lectures/external-ear-anatomy" categories: ["Otology"] video: "https://www.youtube.com/watch?v=W6ZDGBtmOZw" image: "https://media.theentresident.com/og-images/external-ear-anatomy.png" --- # Anatomy of External Ear ENT notes on the Anatomy of Pinna and External Auditory canal - relations, blood supply, nerve supply, and clinical aspects. Watch the full video lecture on YouTube: https://www.youtube.com/watch?v=W6ZDGBtmOZw ## Anatomy of the External Ear ### 🌬 Divisions of the Ear The ear can be divided into three main parts: 1. **External Ear**: Auricle (Pinna) and External Auditory Canal (EAC), ending at the Tympanic Membrane. 2. **Middle Ear**: From the Tympanic Membrane medially, containing the middle ear cleft and ossicles. 3. **Internal Ear**: Containing the labyrinth, responsible for hearing and balance. In this post, we'll focus on the **External Ear**. --- ### ✨ The External Ear: Pinna and EAC ### 👂 Anatomy of the Auricle (Pinna) The auricle, or pinna, is the visible projecting part of the external ear. Its primary function is **collecting sound waves**. - **Surfaces**: Has a lateral surface (visible) and a medial (cranial) surface. **📍 Lateral Surface Anatomy:** The lateral surface has distinct prominences and depressions: - **Helix**: The curved outer rim. >What is Darwin's Tubercle? - **Antihelix**: A curved rim anterior to and parallel to the helix. - Divides superiorly into **two crura**. - **Triangular Fossa**: Enclosed between the two crura of the antihelix. - **Scaphoid Fossa**: Lies superior to the two crura. - **Concha**: The large, deep cavity anterior to the antihelix, partly encircled by it. - Divided by the **Crus of the Helix** (anterior superior portion of the helix). - **Cymba Concha**: The smaller, superior portion (lateral relation to the suprameatal triangle). - **Cavum Concha**: The larger, inferior portion. - **Tragus**: A small, blunt, triangular cartilaginous prominence anterior to the EAC opening, pointing posteriorly. - **Antitragus**: Lies opposite the tragus, at the inferior limit of the antihelix. - **Intertragic Notch**: The notch separating the tragus from the antitragus. - **Lobule**: The soft, fleshy part below the antitragus (the **earlobe**). _**Clinical Note**_: The unique pattern of the lateral surface is comparable to fingerprints and can aid in identification. **📍 Medial (Cranial) Surface Anatomy:** The medial surface has elevations corresponding to the lateral depressions (e.g., Eminentia Concha). --- ### Structure of Pinna **1- 🔬 Skin of the Pinna:** - Very thin. - **Lateral Surface**: Closely attached to the perichondrium. - **Medial Surface**: Slightly loose due to **subdermal adipose tissue**, which facilitates dissection (e.g., during pinnaplasty). - Covered with fine hair, mostly in the **concha** and **scaphoid fossa**. Thick, coarse hair grows over the **tragus** and **intertragic notch** in older males. - Sebaceous glands open into hair root canals. **2- 🦴 Cartilage of the Pinna:** - Composed of **elastic fibrocartilage**. - Forms the entire pinna except for the **lobule**, which is made of fibrous and adipose tissue. - Continuous with the cartilage of the external auditory canal. >What is Incisura Terminalis? What is the clinical importance of Incisura Terminalis? **🩸 Perichondrium:** - Covers the cartilage. - Provides **blood supply** to the avascular cartilage. >What is Boxer's Ear? >What are the different grafts for Tympanoplasty that can be harvested from the pinna? --- ### 🦾 Ligaments of the Pinna: - **Extrinsic Ligaments**: Connect the auricular cartilage to the temporal bone. - **Anterior**: From tragus/crus of helix to zygomatic arch root. - **Posterior**: From medial concha to mastoid prominence. - **Intrinsic Ligaments**: Connect various parts of the auricular cartilage to each other. --- ### 💪 Muscles of the Pinna: - **Extrinsic Muscles**: Three muscles radiating from the auricle to the epicranial aponeurosis. - **Auricularis Anterior**: Smallest. - **Auricularis Superior**: Largest, fan-shaped. - **Auricularis Posterior**: Has 2-3 fleshy slips, inserts on the ponticulus. >What is the blood supply and nerve supply of the Extrinsic muscles of pinna? >What are the actions of Extrinsic muscles of pinna? - **Intrinsic Muscles**: Six small muscles passing between cartilaginous parts (Helices Major/Minor, Tragicus, Antitragicus, Transversus/Obliquus Auriculae). - Responsible for very minimal shape changes. >What is the blood supply and nerve supply of the Intrinsic muscles of pinna? --- ### 🩸 Blood Supply of the Pinna: Mainly from the **External Carotid Artery** via: - **Posterior Auricular Artery** (dominant supply): Supplies most of the medial surface, concha, middle/lower helix, lower antihelix. - **Anterior Auricular Branches of the Superficial Temporal Artery**: Supply upper helix/antihelix, triangular fossa, tragus, lobule. - **Superior Auricular Artery**: Connects STA and Posterior Auricular networks. - Small auricular branch from the Occipital Artery (sometimes assists PA in supplying medial surface). --- ### Nerve Supply of the Pinna: Crucially supplied by branches from multiple cranial and cervical nerves: - Greater Auricular Nerve - Lesser Occipital Nerve - Auricular Branch of Vagus Nerve (Arnold's nerve) - Auriculotemporal Nerve(Branch of Mandibular division of Trigeminal Nerve) - Facial Nerve >What are the areas of supply of the above mentioned nerves in the pinna? --- ### 🦠 Lymphatic Drainage of the Pinna: - **Posterior/Medial Surface**: Drains to **Postauricular (Mastoid) lymph nodes**. - **Tragus & Upper Anterior Surface**: Drains to **Preauricular lymph nodes**. - **Rest of the Auricle**: Drains to **Upper Deep Cervical lymph nodes**. --- ### 🕳️ Anatomy of the External Auditory Canal (EAC) The EAC is a tube extending from the concha to the tympanic membrane. - **Length**: Approximately **2.4 cm**. - **Parts**: - **Outer One-Third (Cartilaginous)**: ~8 mm long. - **Inner Two-Thirds (Bony)**: ~16 mm long. - The anterior wall and floor are about **6 mm longer** than the posterior wall and roof. **📏 Direction & Straightening:** - The EAC is **S-shaped**. - **Cartilaginous Part**: Directed upwards, backwards, and medially. - **Bony Part**: Directed downwards, forwards, and medially. - **To straighten the EAC for examination**: - **Adults**: Gently pull the auricle **upwards and backwards**. - **Neonates**: The bony EAC is undeveloped; the TM is more horizontal. Pull the auricle gently **downwards and backwards**. #### 🦴 **Parts of the EAC:** - **Cartilaginous EAC (Outer 1/3)**: - Continuous with the auricular cartilage. - Medial border attached to the bony canal rim by fibrous bands. - Contains **Fissures of Santorini**: Two horizontal fissures anterior-inferiorly. - **Hair follicles are present ONLY here**. >Why do furuncles occur only in the cartilaginous part of EAC? >What infections spread through **Fissures of Santorini**? - **Bony EAC (Inner 2/3)**: - Lined by very thin skin, continuous with the skin of the tympanic membrane. - Devoid of hair and ceruminous/sebaceous glands. - Medial end marked by the **Tympanic Sulcus** (a groove for the TM, absent superiorly). - Contains suture lines: **Tympanosquamous suture** (anteriorly) and **Tympanomastoid suture** (posteriorly). - May have the **Foramen of Huschke**: A deficiency in the anterior-inferior bony canal wall (common in children up to age 4, sometimes persists in adults). >What infections spreads through the Foramen pf Huschke? >What are the 2 constrictions of the EAC? #### 🧭 **Relations of the EAC:** - **Laterally**: Opens to the outside world (at the concha). - **Medially**: The Tympanic Membrane and Middle Ear. - **Posteriorly**: Mastoid bone. - **Anteriorly**: Temporomandibular Joint (TMJ), Superficial Temporal Artery & Vein, Auriculotemporal nerve, Parotid gland, Preauricular lymph nodes. - **Superiorly**: Middle Cranial Fossa. - **Inferiorly**: Jugular bulb, Carotid artery, Facial nerve, Styloid process, Parotid gland, Digastric muscle. **🔬 Lining Epithelium of EAC:** - Lined with **keratinizing stratified squamous epithelium**. - Unique property: **Outward and oblique growth/migration** of the epidermis (approx. **0.1 mm/day**). - Short hair projects laterally at the opening. **🧬 Appendages:** Located in the **cartilaginous EAC only**: - **Ceruminous glands**: Modified sweat glands, secrete **cerumen**. - **Pilo-sebaceous glands**: Secrete **sebum**. - **Wax (Cerumen)**: Mixture of desquamated cells, cerumen, and sebum. - *Varieties*: Dry (yellowish/grey) and Wet (yellowish-brown, sticky). --- ### 🩸 Blood Supply of the EAC: Derived from the **External Carotid Artery**: - **Auricular branches of the Superficial Temporal Artery**: Supply the roof and anterior part. - **Deep Auricular Branch of the Maxillary Artery**: Supplies the anterior meatal wall skin and the outer surface epithelium of the TM. - **Auricular branches of the Posterior Auricular Artery**: Supply the posterior part. - *Veins*: Drain into the External Jugular Vein, Maxillary veins, and Pterygoid plexus. --- ### Nerve Supply of the EAC: - **Auriculotemporal Nerve** (Branch of Mandibular division of Trigeminal Nerve): Supplies the anterior wall and roof. - **Auricular Branch of Vagus Nerve** (Arnold's Nerve): Supplies the posterior wall and floor. - **Facial Nerve**: Supplies a small portion of the posterior wall (via communicating branches, often reaching via the auricular branch of the Vagus). >What is **Hitzelberger Sign**? >Which nerve stimulation in EAC causes **Vasovagal Reflex**? >What findings in EAC do you find in **Ramsay-Hunt Syndrome** and why? --- ## About This Note This free ENT note on Anatomy of External Ear was written by Dr. Mausumi Das and is paired with a corresponding video lecture. 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