Triceps Brachii

Examples of Triceps Brachii in the following topics:

• How Skeletal Muscles Produce Movements

  • The biceps and triceps muscle groups are an example of an agonist/antagonist pair.
  • During extension, the triceps act as the agonist while the biceps act as the antagonist.
  • Typical muscle pairings include the biceps brachii and triceps brachii, which act to flex or extend the forearm.
  • During flexing of the forearm, the triceps brachii is the antagonist muscle, resisting the movement of the forearm up towards the shoulder.
  • The triceps brachii (not shown) acts as the antagonist.

• Muscles of the Humerus that Act on the Forearm

  • Biceps Brachii - The biceps brachii is a two-headed muscle.
  • Coracobrachialis - The coracobrachialis lies within the two heads of the biceps brachii.
  • Brachialis - The brachialis muscle lies within the distal region of the biceps brachii.
  • Anconeus - The anconeus is located in the superficial region of the forearm posterior compartment and is blended with the triceps brachii.
  • Produced by the brachialis, biceps brachii, and brachioradialis of the forearm.

• Scapula

  • Immediately below the glenoid cavity is the infranglenoid tuberosity which is the origin for the long head of the triceps brachii.
  • Immediately above the glenoid cavity is the supraglenoid tubercle and associated hook like coracoid process, from which the long and short heads of the biceps brachii originate respectively.

• Humerus (The Upper Arm)

  • Between the two tubercles lies a deep grove termed the intertubercular sulcus through which the tendon of the long head of the biceps brachii runs.
  • As well as the deltoid the corocobrachialis, brachialis and brachioradialis attach to the anterior surface with the triceps brachii attaching to the posterior.

• Ulna and Radius (The Forearm)

  • The olecranon is a projection of bone which extends proximally from the ulna, the triceps brachii muscle attaches to it superioly.
  • Immediately below the head lies the radial tuberosity to which the biceps brachii attaches.

• Lever Systems

  • First-class levers are relatively uncommon in the body, but one example is the triceps brachii muscle of the upper arm which acts to extend the forearm.
  • Thinking of the relative distance between the points of attachment, the triceps brachii can be said to act at a mechanical disadvantage.
  • An example of a third-class lever in the body is the biceps brachii, which flexes the forearm towards the shoulder.

• Muscles of the Shoulder

  • Produced by the biceps brachii (both heads), pectoralis major, anterior deltoid, and corocobrachialis.
  • Muscles of the rotator cuff and presented with the triceps brachii.

• Muscles of the Wrist and Hand

  • Aconeus - The aconeus is located in the superficial region of the forearm posterior compartment and is blended with the triceps brachii.

• Muscles and Joints

  • The triceps muscle is an extensor that opens the limb.
  • The triceps are assumed to be relaxed.

• Reflexes and Diagnosis