---
title: "Teres Major | Anatomy and Physiology I"
description: "Teres major is a thick shoulder muscle that moves and rotates the arm, running from the scapula to the humerus in Anatomy and Physiology I."
canonical: "https://fiveable.me/anatomy-physiology/key-terms/teres-major"
type: "key-term"
subject: "Anatomy and Physiology I"
unit: "Unit 11"
---

# Teres Major | Anatomy and Physiology I

## Definition

Teres major is a thick muscle of the upper limb that runs from the lower scapula to the humerus. In Anatomy and Physiology I, you learn it as a muscle that helps move, extend, adduct, and internally rotate the arm.

## What It Is

Teres major is a muscle of the posterior shoulder in Anatomy and Physiology I. It sits on the back of the upper limb, starting on the lower lateral border of the scapula and attaching to the humerus. Because it crosses the shoulder joint, it can move the arm rather than the forearm or hand.

Its main actions are extension, adduction, and medial rotation of the arm at the shoulder. That means it helps you bring the arm backward, pull it toward the body, and turn it inward. If you picture a rowing motion, a climbing pull, or the downward phase of a forceful tug, teres major is one of the muscles contributing to that movement.

This muscle is thick and powerful, which fits its job. It does not work alone, though. Shoulder motion usually comes from a group of muscles working together, so teres major often teams up with nearby posterior shoulder and upper back muscles to produce a smooth movement. In lab diagrams, it may be shown near the lower part of the scapula, close to the latissimus dorsi region, because the two muscles share a similar line of pull.

A useful way to think about teres major is to connect its location with its action. Muscles generally pull toward where they attach, so a muscle on the back of the scapula that inserts on the humerus tends to help move the arm backward and inward. That pattern is a big clue in A&P when you are identifying an unlabeled structure or predicting what a muscle does from an origin and insertion.

Do not confuse teres major with teres minor just because the names sound alike. Teres minor is part of the rotator cuff, while teres major is not. They sit near each other on the scapula, but they do different jobs and show up in different movement patterns.

## Why It Matters

Teres major matters because it connects anatomy landmarks to shoulder movement. In Anatomy and Physiology I, you are constantly matching a muscle’s position with the motion it creates, and teres major is a good example of that pattern. If you know where it starts and where it inserts, you can predict how it changes arm position during pulling, lifting, and rotating actions.

It also helps you organize shoulder muscles by function. The upper limb has a lot of overlapping muscles, and many of them can contribute to similar motions. Teres major is one of the muscles that gives the shoulder power for movements like adduction and medial rotation, which makes it useful when you are comparing muscles in the pectoral girdle and upper limb unit.

This term also shows up in visual identification. On a diagram, you may need to spot a muscle near the inferior scapula and explain how it differs from nearby structures such as the rotator cuff muscles. That kind of recognition is a common skill in A&P lab, quizzes, and practicals.

## Connections

### Scapula

The scapula is the bone where teres major begins. When you learn the lower lateral border of the scapula, you can use that landmark to place the muscle correctly in shoulder diagrams. The bone matters because a muscle’s action depends on the direction it pulls from the scapula to the humerus.

### Humerus

Teres major inserts on the humerus, so that bone is the lever it moves at the shoulder joint. In A&P, this helps you explain why the muscle affects arm movement rather than the forearm. If you can trace the line from scapula to humerus, the muscle’s action becomes easier to remember.

### [Rotator Cuff](/anatomy-physiology/key-terms/rotator-cuff)

Teres major is often discussed near the rotator cuff muscles because it sits in the same shoulder region, but it is not part of the cuff. The rotator cuff stabilizes the shoulder joint, while teres major is better known for power movements like adduction and medial rotation. That distinction shows up a lot in comparison questions.

### [anterior compartment of the arm](/anatomy-physiology/key-terms/anterior-compartment-of-the-arm)

The anterior compartment of the arm is a different region with different muscle actions, mostly focused on flexion at the elbow. Comparing it with teres major helps you separate shoulder movers from elbow movers. That kind of regional sorting is useful when a lab question asks you to identify what part of the limb a muscle controls.

## On the AP Exam

A lab practical might show you a shoulder model or cadaver image and ask you to name the muscle, give its attachment points, or predict the motion it creates. A written quiz may describe an arm movement, like pulling the arm down and back, and ask which muscle is involved. You should be ready to connect teres major with the scapula, the humerus, and the actions of extension, adduction, and medial rotation.

Short-answer questions often test whether you can separate teres major from teres minor or from the rotator cuff muscles. If you are given a movement and a location, use both clues together instead of memorizing a single word match.

## teres major vs teres minor

Teres major and teres minor are close in name and location, but they are not the same muscle. Teres minor is part of the rotator cuff and helps with lateral rotation, while teres major is a stronger mover that helps with adduction, extension, and medial rotation of the arm. If you remember function, the difference gets much easier.

## Key Takeaways

- Teres major is a thick muscle on the posterior shoulder that runs from the lower scapula to the humerus.
- Its main actions are extension, adduction, and medial rotation of the arm at the shoulder joint.
- The muscle helps with pulling motions because it brings the arm backward and inward.
- It is near the rotator cuff region, but it is not one of the rotator cuff muscles.
- In Anatomy and Physiology I, you usually identify teres major by combining its location, attachments, and movement.

## FAQs

### What is teres major in Anatomy and Physiology I?

Teres major is a posterior shoulder muscle that connects the scapula to the humerus. It helps move the arm at the shoulder, especially with extension, adduction, and medial rotation. In A&P, it comes up when you study the muscles of the pectoral girdle and upper limb.

### What does teres major do?

It helps pull the arm backward, toward the body, and inward. Those actions are useful in movements like rowing, climbing, and forceful pulling. Because it crosses the shoulder joint, it affects the arm at the shoulder rather than the elbow or hand.

### Is teres major part of the rotator cuff?

No, teres major is not part of the rotator cuff. It sits near the same region of the shoulder, which is why it gets confused with those muscles, but its main job is movement rather than stabilization. Teres minor, on the other hand, is a rotator cuff muscle.

### How do you identify teres major on a diagram?

Look for a thick muscle near the lower part of the scapula that attaches to the humerus. It is usually shown on the back of the shoulder, below or near teres minor and close to the latissimus dorsi area. Its location helps you link it to arm adduction and medial rotation.

## Related Study Guides

- [11.5 Muscles of the Pectoral Girdle and Upper Limbs ](/anatomy-physiology/unit-11/5-muscles-pectoral-girdle-upper-limbs/study-guide/vmMeyxnPvtI7ludS)

## About This Document

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- [llms-full.txt](https://fiveable.me/llms-full.txt): complete subject and unit listing
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