---
title: "Recurrent Laryngeal Nerve Course - Why is it different on both sides?"
description: "Understand the embryological and anatomical reasons behind the asymmetric course of the Recurrent Laryngeal Nerve - an important short question in ENT exams."
source: "The ENT Resident"
author: "Dr. Mausumi Das"
canonical_url: "https://www.theentresident.com/ent-notes-lectures/recurrent-laryngeal-nerve-different-course"
categories: ["Larynx and Trachea", "Short Questions in ENT"]
video: "https://www.youtube.com/watch?v=SDCFfkLBNIY"
image: "https://media.theentresident.com/og-images/recurrent-laryngeal-nerve-different-course.png"
---

# Recurrent Laryngeal Nerve Course - Why is it different on both sides?

Understand the embryological and anatomical reasons behind the asymmetric course of the Recurrent Laryngeal Nerve - an important short question in ENT exams. Watch the full video lecture on YouTube: https://www.youtube.com/watch?v=SDCFfkLBNIY

## Why Does the Recurrent Laryngeal Nerve Have a Different Course on Each Side?

The **recurrent laryngeal nerves (RLNs)** — branches of the vagus nerve (cranial nerve X) — are essential for **motor and sensory innervation** of the larynx. Interestingly, they follow **asymmetrical paths** on the right and left sides. Let's understand why.

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### 📍 Origin of the Recurrent Laryngeal Nerve

- **Right RLN**:
  - Arises from the right vagus nerve at the **root of the neck**, near the **T1 vertebral level**.
  - Loops around the **first part of the right subclavian artery**.

- **Left RLN**:
  - Arises from the left vagus nerve in the **thorax**, at the **T3 vertebral level**.
  - Loops around the **arch of the aorta**, **posterior to the ligamentum arteriosum**.

---

### 🛣 Course of the Nerve

After looping around their respective arteries:

- Both nerves ascend in the **tracheoesophageal groove**.
- Pass deep to the **inferior constrictor muscle**.
- Enter the larynx **behind the cricothyroid joint**.
- Divide into **motor and sensory branches**.

---

### 🧬 Embryological Explanation

The asymmetry is explained by the **development of aortic arches**:

#### Left Side:
- The **dorsal part of the 6th aortic arch** persists as the **ductus arteriosus** in fetal life and becomes the **ligamentum arteriosum** after birth.
- The **left RLN** gets "hooked" beneath the arch of the aorta due to this persistent ligament.
- The **4th aortic arch** contributes to the arch of the aorta.

#### Right Side:
- The **5th and 6th aortic arches** regress completely.
- The **4th aortic arch** forms the **proximal part of the right subclavian artery**.
- The **right RLN** loops around this artery instead of a structure in the thorax.

As a result:
- The **left RLN has a longer and deeper course** in the thorax.
- The **right RLN** takes a **shorter course in the neck**.

---

### 🧠 Summary Table

| Feature | Right RLN | Left RLN |
| --- | --- | --- |
| Origin | Root of neck (T1) from right vagus | Thorax (T3) from left vagus |
| Loops Around | Right subclavian artery (from 4th arch) | Arch of aorta (near ligamentum arteriosum) |
| Embryological Arch | 4th arch only | 4th and persistent 6th arch |
| Relative Course | Shorter, in neck | Longer, in thorax |
| Enters Larynx | Behind cricothyroid joint | Behind cricothyroid joint |

---

### 📝 Viva Tip

When asked _"Why is the RLN course different on both sides?"_ — always link your answer to **embryological arch derivatives** and **anatomical development** for full marks.

---

## About This Note

This free ENT note on Recurrent Laryngeal Nerve Course - Why is it different on both sides? was written by Dr. Mausumi Das and is paired with a corresponding video lecture.

Canonical page of this note: https://www.theentresident.com/ent-notes-lectures/recurrent-laryngeal-nerve-different-course

When citing or referencing this content, please credit The ENT Resident and link to the canonical page above.

## Related Notes by Category

- Larynx and Trachea: https://www.theentresident.com/ent-notes-lectures/category/larynx-and-trachea.md
- Short Questions in ENT: https://www.theentresident.com/ent-notes-lectures/category/short-questions-in-ent.md

## About The ENT Resident

The ENT Resident is an educational website and resource library created by Dr. Mausumi Das (MS ENT) for ENT residents, ENT postgraduates preparing for exams, and MBBS students.

Dr. Mausumi Das writes the notes, draws the diagrams, and records the lectures herself.

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