---
title: "Intercostal Nerve | Anatomy and Physiology I"
description: "Intercostal nerve is a thoracic spinal nerve branch that carries motor and sensory signals between the ribs, linking the spinal cord to the chest wall."
canonical: "https://fiveable.me/anatomy-physiology/key-terms/intercostal-nerve"
type: "key-term"
subject: "Anatomy and Physiology I"
---

# Intercostal Nerve | Anatomy and Physiology I

## Definition

An intercostal nerve is a branch of a thoracic spinal nerve that runs between the ribs. In Anatomy and Physiology I, it supplies the chest wall and helps you trace how the nervous system reaches the rib cage.

## What It Is

An intercostal nerve is a peripheral nerve that travels in the intercostal space, the gap between adjacent ribs. In Anatomy and Physiology I, you usually meet it as one of the branch pathways coming from the thoracic spinal nerves, especially T1 through T11, as those nerves leave the spinal cord and head into the body wall.

These nerves are called intercostal because they run with the ribs and the muscles between them. That route matters: the nerve does not float randomly through the chest. It follows a fairly predictable path along the underside of each rib, where it can supply the muscles and skin of the thoracic wall. The lower thoracic nerves also continue beyond the ribs to reach parts of the abdominal wall.

Intercostal nerves are mixed nerves, so they carry both motor and sensory information. Their motor fibers help control the intercostal muscles, which move the rib cage during breathing. Their sensory fibers carry touch, pain, and temperature information from the chest wall, so if you feel a bruise, cut, or rib injury, those signals can travel back through an intercostal nerve.

A useful way to picture this is to separate the body region from the spinal level. The thoracic spinal nerve is the source, while the intercostal nerve is the branch that serves the rib space. That is why the term shows up in diagrams of the thoracic cage, dermatomes, and spinal nerve branching, not just in nervous system charts. If a lab model asks you to trace the path of innervation to the chest wall, intercostal nerves are the pathway you are looking for.

Because they sit under the ribs and near the intercostal muscles, these nerves are also easy to connect to real anatomy. When you breathe, move, cough, or feel pressure along the chest wall, intercostal nerves are part of the wiring that makes those sensations and movements possible.

## Why It Matters

Intercostal nerves connect nervous system anatomy to a body region you can actually see and palpate: the rib cage. That makes them useful for learning how spinal nerves branch, how peripheral nerves distribute function, and how sensory and motor pathways are organized in the trunk.

They also help you separate the thoracic wall from the abdominal wall. The lower intercostal nerves continue into the abdominal musculature, so they show that body regions do not always stop neatly at one textbook boundary. If you are tracing innervation on a diagram, this term helps you follow where a thoracic spinal nerve goes after it leaves the spinal cord.

In lab and lecture, intercostal nerves often show up when you study breathing mechanics, chest wall sensation, or nerve pathways associated with dermatomes. If a question asks why someone can still feel pain along the ribs or why the intercostal muscles receive neural input from thoracic levels, this is the structure that ties the answer together. It is a small term with a big job in linking the nervous system to the musculoskeletal anatomy of the thorax.

## Connections

### Peripheral Nervous System

Intercostal nerves belong to the peripheral nervous system because they branch off spinal nerves and travel out to body tissues. That connection is useful when you compare central versus peripheral pathways. The spinal cord sends the signal origin, but the intercostal nerve is part of the outgoing route that reaches the chest wall and carries sensation back.

### Thoracic Spinal Nerves

Intercostal nerves come from thoracic spinal nerves, mainly T1 through T11. The relationship matters because the spinal nerve is the source, while the intercostal nerve is the branch that runs in the rib spaces. If you are tracing innervation on a diagram, start at the thoracic spinal level and then follow the nerve outward.

### Sensory Innervation

One job of intercostal nerves is sensory innervation of the chest wall. That means they carry information about touch, pain, and temperature from the skin and deeper tissues between the ribs. This is the part to focus on when a question asks where chest wall sensations travel or how pain from a rib injury reaches the nervous system.

### [Anterior Cavity](/anatomy-physiology/key-terms/anterior-cavity)

The intercostal nerves serve the thoracic wall, which borders the anterior cavity and protects organs in the thoracic portion of that cavity. This connection is useful when you are organizing body regions by cavity and wall. The nerves themselves do not fill the cavity, but they supply the muscles and skin around it.

## On the AP Exam

A quiz item might show a diagram of the rib cage and ask you to identify which nerve runs between the ribs and supplies the intercostal muscles. On a lab practical, you may need to point to the nerve path under a rib or explain which spinal levels give rise to it.

If the question is case based, look for chest wall pain, reduced sensation between ribs, or trouble with intercostal muscle control during breathing. Then connect the symptom to the nerve pathway, not just the rib bones. That shift from structure to function is the move instructors are usually testing in Anatomy and Physiology I.

## Key Takeaways

- An intercostal nerve is a thoracic spinal nerve branch that runs between the ribs.
- It carries motor signals to the intercostal muscles and sensory signals from the chest wall.
- These nerves are part of the peripheral nervous system, not the central nervous system.
- The lower thoracic intercostal nerves can continue into the abdominal wall.
- If you are tracing chest wall innervation, follow the thoracic spinal nerve to the intercostal nerve route.

## FAQs

### What is an intercostal nerve in Anatomy and Physiology I?

It is a nerve that runs in the space between the ribs and comes from a thoracic spinal nerve. In A&P I, you study it as part of the pathway that supplies the chest wall with both motor and sensory innervation.

### Are intercostal nerves sensory or motor?

They are mixed nerves, so they do both. Their motor fibers help the intercostal muscles move the rib cage, and their sensory fibers carry information from the skin and tissues between the ribs.

### Which spinal nerves form the intercostal nerves?

They arise from thoracic spinal nerves, especially T1 through T11. That is why they are tied to the rib cage and thoracic wall rather than the limbs or neck.

### How is an intercostal nerve different from an intercostal muscle?

The nerve is the signal pathway, while the muscle is the tissue that contracts. The intercostal nerve supplies the intercostal muscles, so the nerve controls the muscle but is not the muscle itself.

## About This Document

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