Triceps brachii muscle

Author: Scott A. Sheffield MS

Last update:

The triceps brachii is a three-headed arm muscle and the primary extensor of the elbow joint. It consists of a long head, a medial head, and a lateral head.

image descriptionTriceps Brachii Muscle: Long Head

The long head of the triceps brachii descends between teres minor and major, dividing the wedge-shaped interval between them and the humerus into triangular and quadrangular spaces.

A posterior view of the upper arm and shoulder showing the bony elements and the associated muscles. The visible, labelled muscles are as follows: Trapezius, Deltoid, Teres Minor, Teres Major, Triceps Brachii: Long Head (highlighted in green), Triceps Brachii: Lateral Head, Latissimus Dorsi, Triceps Brachii: Medial Head.
A posterior view of the upper arm and shoulder showing the bony elements and the deeper muscles. The visible, labelled muscles are as follows: Infraspinatus, Teres Minor, Teres Major, Triceps Brachii: Long Head (highlighted in green), Triceps Brachii: Lateral Head, Latissimus Dorsi, Triceps Brachii: Medial Head.
A posterior view of the upper arm and shoulder showing the bony elements and the deeper muscles. The visible, labelled muscles are as follows: Teres Major, Triceps Brachii: Long Head (highlighted in green), Triceps Brachii: Lateral Head, Latissimus Dorsi, Triceps Brachii: Medial Head.
A posterior view of the upper arm and shoulder showing the bony elements and isolated Triceps Brachii Long Head.
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image descriptionAttachments of the Triceps Brachii Muscle Long Head : Origin and Insertion

Origin (proximal attachment)
a. Infraglenoid tubercle of the scapula.

Insertion (distal attachment)
a. Posterior olecranon process of ulna.

A posterior view of the upper arm and shoulder showing the bony elements and the associated muscles. The visible, labelled muscles are as follows: Trapezius, Deltoid, Teres Minor, Teres Major, Triceps Brachii: Long Head (highlighted in green), Triceps Brachii: Lateral Head, Latissimus Dorsi, Triceps Brachii: Medial Head.
A posterior view of the upper arm and shoulder showing the bony elements and isolated Triceps Brachii Long Head.
A posterior view of the upper arm and shoulder showing the bony elements and the attachment of the Triceps Brachii Long Head. Origin at the infraglenoid tubercle of scapula is marked by a red oval. The insertion at the posterior olecranon process of the ulna is marked by a blue oval. Transparent Triceps Brachii Long Head connects the two attachment sites.
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Actions of the Triceps Brachii Muscle Long Head:

a.  image descriptionExtends the forearm at elbow. (It also extends the arm at the shoulder).

Learning muscle anatomy is hard! Simplify your studies with this time-saving muscle anatomy reference chart for the upper limb.

Nerve to the Triceps Brachii muscle Long Head and its spinal segment:

a. Radial nerve (C7, C8).

image descriptionTriceps Brachii Muscle: Medial Head

The medial head of the triceps brachii arises from inferior two thirds of humerus to insert, along with the other two heads of the triceps, on the olecranon of the ulna.

A posterior view of the upper arm and shoulder showing the bony elements and the associated muscles. The visible, labelled muscles are as follows: Trapezius, Deltoid, Teres Minor, Teres Major, Triceps Brachii: Long Head, Triceps Brachii: Lateral Head, Latissimus Dorsi, Triceps Brachii: Medial Head (highlighted in green).
A posterior view of the upper arm and shoulder showing the bony elements and the deeper muscles. The visible, labelled muscles are as follows: Infraspinatus, Teres Minor, Teres Major, Triceps Brachii: Long Head, Triceps Brachii: Lateral Head, Latissimus Dorsi, Triceps Brachii: Medial Head (highlighted in green).
A posterior view of the upper arm and shoulder showing the bony elements and the deeper muscles. The visible, labelled muscles are as follows: Teres Major, Triceps Brachii: Long Head, Triceps Brachii: Lateral Head, Latissimus Dorsi, Triceps Brachii: Medial Head (highlighted in green).
A posterior view of the upper arm and shoulder showing the bony elements and the associated muscles. The visible, labelled muscles are as follows: Trapezius, Deltoid, Teres Minor, Teres Major, Triceps Brachii: Long Head, Triceps Brachii: Lateral Head, Latissimus Dorsi, Triceps Brachii: Medial Head (highlighted in green).
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image descriptionAttachments of the Triceps Brachii Muscle Medial Head: Origin and Insertion:

Origin (proximal attachment)
a. Inferior 2/3 of posterior humerus.

Insertion (distal attachment)
a. Posterior olecranon process of ulna.

A posterior view of the upper arm and shoulder showing the bony elements and the associated muscles. The visible, labelled muscles are as follows: Trapezius, Deltoid, Teres Minor, Teres Major, Triceps Brachii: Long Head, Triceps Brachii: Lateral Head, Latissimus Dorsi, Triceps Brachii: Medial Head (highlighted in green).
A posterior view of the upper arm and shoulder showing the bony elements and the associated muscles. The visible, labelled muscles are as follows: Trapezius, Deltoid, Teres Minor, Teres Major, Triceps Brachii: Long Head, Triceps Brachii: Lateral Head, Latissimus Dorsi, Triceps Brachii: Medial Head (highlighted in green).
A posterior view of the upper arm and shoulder showing the bony elements and the attachment of the Triceps Brachii Medial Head. The area of origin at the inferior 2/3 of posterior humerus is highlighted in red. The insertion at the posterior olecranon process of the ulna is marked by a blue oval. Transparent Triceps Brachii Medial Head connects the two attachment sites.
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Actions of the Triceps Brachii Muscle Medial Head:

a.  image descriptionExtends the forearm at elbow.

Learn the anatomy of the arm and shoulder muscles more efficiently with this step-by-step guide. 

Nerve to the Triceps Brachii muscle Medial Head and its spinal segment:

a. Radial nerve (C7, C8).

image descriptionTriceps Brachii Muscle: Lateral Head

The lateral head of the triceps brachii, one of three heads of the muscle, originates from the humerus, superior to the radial groove to insert on the olecranon process.

A posterior view of the upper arm and shoulder showing the bony elements and the associated muscles. The visible, labelled muscles are as follows: Trapezius, Deltoid, Teres Minor, Teres Major, Triceps Brachii: Long Head, Triceps Brachii: Lateral Head (highlighted in green), Latissimus Dorsi, Triceps Brachii: Medial Head.
A posterior view of the upper arm and shoulder showing the bony elements and the deeper muscles. The visible, labelled muscles are as follows: Infraspinatus, Teres Minor, Teres Major, Triceps Brachii: Long Head, Triceps Brachii: Lateral Head (highlighted in green), Latissimus Dorsi, Triceps Brachii: Medial Head.
A posterior view of the upper arm and shoulder showing the bony elements and the deeper muscles. The visible, labelled muscles are as follows: Teres Major, Triceps Brachii: Long Head, Triceps Brachii: Lateral Head (highlighted in green), Latissimus Dorsi, Triceps Brachii: Medial Head.
A posterior view of the upper arm and shoulder showing the lateral head of the triceps brachii muscie.
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image descriptionTriceps Brachii Muscle Lateral Head Attachments: Origin and Insertion

Origin (proximal attachment)
a. Proximal portion of posterior humerus, superior to radial groove.

Insertion (distal attachment)
a. Posterior olecranon process of ulna.

A posterior view of the upper arm and shoulder showing the bony elements and the associated muscles. The visible, labelled muscles are as follows: Trapezius, Deltoid, Teres Minor, Teres Major, Triceps Brachii: Long Head, Triceps Brachii: Lateral Head (highlighted in green), Latissimus Dorsi, Triceps Brachii: Medial Head.
A posterior view of the upper arm and shoulder showing the lateral head of the triceps brachii muscie.
A posterior view of the upper arm and shoulder showing the bony elements and the attachment of the Triceps Brachii Lateral Head. Origin at the proximal portion of posterior humerus, superior to radial groove is marked by a red oval. The insertion at the posterior olecranon process of ulna is marked by a blue oval. Transparent Triceps Brachii Lateral Head connects the two attachment sites.
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Actions of the Triceps Brachii Muscle Lateral Head:

a.  image descriptionExtends the forearm the at elbow.

Learn the muscles of the arm faster with this step-by-step muscles of the arm and shoulder study guide. 

Nerve to the Triceps Brachii muscle Lateral Head and its spinal segment:

a. Radial nerve (C7, C8).

An overview of the posterior arm muscles

A test yourself image of the posterior view of the upper arm and shoulder showing the bony elements and the associated soft structures. The visible structures are labelled 1-8 and the answers in the box below are concealed.
A test yourself image of the posterior view of the upper arm and shoulder showing the bony elements and the deeper muscles. The visible structures are labelled 1-8 The answers in the box below are as follows 1.Trapezius 2. Deltoid 3. Teres Minor 4. Teres Major 5. Triceps Brachii: Long Head 6. Triceps Brachii: Lateral Head 7. Latissimus Dorsi 8. Triceps Brachii: Medial Head.
A test yourself image of the posterior view of the upper arm and shoulder showing the bony elements and the deeper muscles. The visible structures are labelled 1-9. The answers in the box below are as follows 1.Supraspinatus 2. Deltoid 3. Infraspinatus 4. Teres Minor 5.. Teres Major 6. Triceps Brachii: Long Head 7. Triceps Brachii: Lateral Head 8. Latissimus Dorsi 9. Triceps Brachii: Medial Head.
A test yourself image of the posterior view of the upper arm and shoulder showing the bony elements and the deeper muscles. The visible structures are numbered 1-8. The answers in the box below are as follows 1. Supraspinatus 2. Infraspinatus 3. Teres Minor 4. Teres Major 5. Triceps Brachii: Long Head 6. Triceps Brachii: Lateral Head 7. Latissimus Dorsi 8. Triceps Brachii: Medial Head.
A test yourself image of the posterior view of the upper arm and shoulder showing the bony elements and the deeper muscles. The visible structures are numbered 1-7. The answers in the box below are as follows: 1. Infraspinatus 2. Teres Minor 3. Teres Major 4. Triceps Brachii: Long Head 5. Triceps Brachii: Lateral Head 6. Latissimus Dorsi 7. Triceps Brachii: Medial Head.
A test yourself image of the posterior view of the upper arm and shoulder showing the bony elements and the deeper muscles. The visible structures are numbered 1-7. The answers in the box below are as follows 1. Infraspinatus 2. Teres Minor 3. Teres Major 4. Triceps Brachii: Long Head 5. Triceps Brachii: Lateral Head 6. Latissimus Dorsi 7. Triceps Brachii: Medial Head.
A test yourself image of the posterior view of the upper arm and shoulder showing the bony elements and the deeper muscles. The visible structures are numbered 1-6. The answers in the box below are as follows 1. Teres Minor 2. Teres Major 3. Triceps Brachii: Long Head 4. Triceps Brachii: Lateral Head 5. Latissimus Dorsi 6. Triceps Brachii: Medial Head.
A test yourself image of the posterior view of the upper arm and shoulder showing the bony elements and the deeper muscles. The visible structures of the forearm are numbered 1-5. The answers in the box below are as follows 1. Teres Major 2. Triceps Brachii: Long Head 3. Triceps Brachii: Lateral Head 4. Latissimus Dorsi 5. Triceps Brachii: Medial Head.
A test yourself image of the posterior view of the upper arm and shoulder showing the bony elements and the deeper muscles. The visible structures are numbered 1-4. The answers in the box below are as follows 1. Triceps Brachii: Long Head 2. Triceps Brachii: Lateral Head 3. Latissimus Dorsi 4. Triceps Brachii: Medial Head.
A test yourself image of the posterior view of the upper arm and shoulder showing the bony elements and the deeper muscles. The visible structures are numbered 1-2. The answers in the box below are as follows 1. Triceps Brachii: Long Head 2. Triceps Brachii: Lateral Head.
A test yourself image of the posterior view of the upper arm and shoulder showing the bony elements and the isolated Triceps Brachii Long Head labelled 1.
A test yourself image of the posterior view of the upper arm and shoulder showing the bony elements and the attachment of the Triceps Brachii Long Head. Origin at the infraglenoid tubercle of scapula is marked by a red oval. The insertion at the posterior olecranon process of the ulna is marked by a blue oval. Transparent Triceps Brachii Long Head connects the two attachment sites.
Test yourself while observing the Triceps Brachii muscle Long Head
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Interactive quiz about the muscles that act on the posterior forearm

Muscles That Act On The Posterior Forearm

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