---
title: "Infrahyoid Muscles | Anatomy and Physiology I"
description: "Infrahyoid muscles are the neck muscles below the hyoid that depress the hyoid and larynx, shaping swallowing, speech, and airway control in A&P I."
canonical: "https://fiveable.me/anatomy-physiology/key-terms/infrahyoid-muscles"
type: "key-term"
subject: "Anatomy and Physiology I"
unit: "Unit 11"
---

# Infrahyoid Muscles | Anatomy and Physiology I

## Definition

Infrahyoid muscles are the strap muscles below the hyoid bone in Anatomy and Physiology I. They depress the hyoid and larynx during swallowing, speech, and breathing.

## What It Is

In Anatomy and Physiology I, the infrahyoid muscles are the four strap muscles on the front of the neck that sit inferior to the hyoid bone: sternohyoid, sternothyroid, thyrohyoid, and omohyoid. Their main job is to pull the hyoid bone and larynx downward after they have been lifted for swallowing or speaking.

Think of them as the counterbalance to the suprahyoid muscles. The suprahyoids elevate the hyoid and help start the swallowing motion, while the infrahyoids bring everything back down to a resting position. That back-and-forth is what lets the throat stay coordinated for moving a bolus of food, protecting the airway, and making normal speech sounds.

These muscles are called strap muscles because they are long and thin rather than bulky. They lie in the anterior neck and attach to structures like the sternum, scapula, thyroid cartilage, and hyoid bone. That positioning matters because the larynx and hyoid need to shift as a unit during swallowing and voice production.

Their nerve supply is the ansa cervicalis, a loop from the cervical plexus. In A&P, that detail matters because it separates them from many other head and neck muscles, which often get cranial nerve innervation. If a question asks how the infrahyoids are controlled, the answer is not a cranial nerve but the cervical plexus via ansa cervicalis.

A simple way to picture their action is this: when you swallow, the hyoid rises first, then the infrahyoid muscles help lower it again so the neck can reset. If they are weak, injured, or disrupted, the timing of swallowing and laryngeal movement can feel off, which is why these muscles show up in discussions of dysphagia, speech changes, and airway protection.

## Why It Matters

Infrahyoid muscles show up any time Anatomy and Physiology I connects the muscular system to swallowing, breathing, or voice production. They are a clean example of how a muscle group does not just move one bone, but coordinates with nearby structures to keep the airway and digestive tract working smoothly.

This term also helps you compare muscle groups in the neck. If you can tell infrahyoid muscles from suprahyoid muscles, you can reason through which direction the hyoid is moving and what phase of swallowing is happening. That kind of cause-and-effect thinking is common in lab IDs, lecture questions, and diagrams of the anterior neck.

The term matters for innervation too. The ansa cervicalis is a classic A&P detail, and infrahyoid muscles are one of the main places you use it. When a question asks which nerve loop supplies the strap muscles, or which muscles might be affected by cervical nerve damage, this is the group you should think of.

They also connect anatomy to function in a very practical way. A person with weakness in these muscles may have trouble clearing the throat, coordinating speech, or managing a swallow. That makes the infrahyoid muscles a good bridge between structure, movement, and clinical symptoms.

## Connections

### [Hyoid Bone](/anatomy-physiology/key-terms/hyoid-bone)

The infrahyoid muscles attach to or act on the hyoid bone, so you need the hyoid’s position to understand what these muscles move. The hyoid is unusual because it does not articulate with other bones, which makes its muscle attachments especially important. When the hyoid rises and falls during swallowing, the infrahyoids help bring it back down.

### Larynx

These muscles also depress the larynx, not just the hyoid. That matters because the larynx has to shift position during swallowing and speech. If you are tracing a neck diagram, the larynx is the lower structure being stabilized and repositioned as the suprahyoids and infrahyoids work together.

### Strap Muscles

Infrahyoid muscles are a subset of the strap muscles, the thin anterior neck muscles that lie like bands over the throat. This label helps you spot them on diagrams and remember their shape and location. If a question uses the broader term, infrahyoids are usually the group below the hyoid.

### [anterior scalene](/anatomy-physiology/key-terms/anterior-scalene)

The anterior scalene is also a neck muscle, but it belongs to a different functional region. It helps with neck movement and assists inspiration by lifting the first rib, while infrahyoid muscles act on the hyoid and larynx. Confusing them can lead you to pick the wrong action or attachment on an anatomy question.

## On the AP Exam

A diagram question may ask you to identify the strap muscles below the hyoid, trace their line of pull, or name the muscle group that depresses the hyoid after swallowing. A labeling lab can also test the four members by name, especially sternohyoid, sternothyroid, omohyoid, and thyrohyoid. When you see a case about dysphagia, voice changes, or neck surgery, think about how infrahyoid weakness could affect hyoid and larynx movement. For innervation questions, match them with the ansa cervicalis rather than a cranial nerve.

## infrahyoid muscles vs Suprahyoid Muscles

These two groups work in opposite directions and are easy to mix up on a neck diagram. Suprahyoid muscles sit above the hyoid and elevate it, while infrahyoid muscles sit below the hyoid and depress it. If you remember the prefix, supra means above and infra means below, the movement becomes much easier to sort out.

## Key Takeaways

- Infrahyoid muscles are the strap muscles below the hyoid bone in the anterior neck.
- Their main action is depressing the hyoid and larynx after they have been lifted during swallowing and speech.
- They work opposite the suprahyoid muscles, so the two groups help coordinate airway and swallowing mechanics.
- The four infrahyoid muscles are sternohyoid, sternothyroid, thyrohyoid, and omohyoid.
- They are innervated by the ansa cervicalis, a branch of the cervical plexus, which is a common anatomy detail to recognize.

## FAQs

### What is infrahyoid muscles in Anatomy and Physiology I?

Infrahyoid muscles are the four muscles in the front of the neck that sit below the hyoid bone. They depress the hyoid and larynx, which helps reset the throat after swallowing and supports speech and breathing. In A&P I, they are usually taught as a strap muscle group.

### What muscles are in the infrahyoid group?

The infrahyoid group includes the sternohyoid, sternothyroid, thyrohyoid, and omohyoid muscles. These muscles all run in the anterior neck and share the job of helping lower the hyoid or larynx. On diagrams, they are often shown as long, thin bands.

### How are infrahyoid muscles different from suprahyoid muscles?

Suprahyoid muscles sit above the hyoid and lift it, while infrahyoid muscles sit below the hyoid and lower it. They work as a team during swallowing, with one group elevating the structures and the other bringing them back down. Prefixes help here, supra means above and infra means below.

### What nerve innervates the infrahyoid muscles?

Most infrahyoid muscles are innervated by the ansa cervicalis, a loop of nerves from the cervical plexus. That detail is a common way to identify them in anatomy questions because many other head and neck muscles have cranial nerve supply instead. If you see ansa cervicalis, think strap muscles below the hyoid.

## Related Study Guides

- [11.3 Axial Muscles of the Head, Neck, and Back ](/anatomy-physiology/unit-11/3-axial-muscles-head-neck/study-guide/T18iHjO6luAZ0pd7)

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