Q4 Triceps brachii Write a complete description of the features of this muscle t

Question

Q4

Triceps brachii

Write a complete description of the features of this muscle that affect how it performs its main actions in the body, using the following template. Answer each prompt in the template.

Muscle topography or location:

Principal attachments:

Muscle shape:

Joint moved (for each joint that is located between the principal attachments):

Functional characteristics of joint (plane, pivot, gliding, etc):

Type of movements allowed by joint:

Planes of movements allowed by joint:

Relative positions of or directions between proximal and distal attachments with respect to joint; for example, inferolateral to superomedial, etc.

Muscle's “Line of Pull (orientation of main axis of muscle action relative to the segments connected by the joints); for example diagonal, orthogonal, in-line, etc.

The muscle orientation combined with the movement allowed at the joints, causes

this change in position: ________________________

of this segment of the body:______________________

in this (these) plane(s):______________________

Explanation / Answer

The triceps brachii muscle (Latin for "three-headed muscle of the arm") is a large muscle on the back of the upper limb of many vertebrates. It is the muscle principally responsible for extension of the elbow joint .

Principla attachments;

The long head arises from the infraglenoid tubercle of the scapula. It extends distally anterior to the teres minor and posterior to the teres major

The triceps brachii forms the posterior compartments of our arms. They act to extend the elbow and also extend the shoulder in part. The muscle has a close relationship with the humerus and with the radial nerve.

The long head arises from the infraglenoid tubercle of the scapula, a small bony projection from the lower part of the rim of the glenoid fossa. The three heads of triceps brachii converge into a single tendon that inserts onto the olecranon process.

The Triceps brachii has 3 origin attachment points and 1 insertion point. These Three heads merge to form a single tendon which has an insertion attachment point at the Olecranon process which is the bony prominence of the elbow, on the upper ulna.

The triceps is an extensor muscle of the elbow joint and an antagonist of the biceps and brachialis muscles. It can also fixate the elbow joint when the forearm and hand are used for fine movements,

Movements:

Pivot joints allow for rotation, which can be external (for example when rotating an arm outward), or internal (as in rotating an arm inward). When rotating the forearm, these movements are typically called pronation and supination.

Joint and movement:

As a ball and socket synovial joint, there is a wide range of movement permitted:

Extension (upper limb backwards in sagittal plane)
Produced by the posterior deltoid, latissimus dorsi and teres major.

Flexion (upper limb forwards in sagittal plane)
Produced by the biceps brachii (both heads), pectoralis major, anterior deltoid and coracobrachialis.

Abduction (upper limb away from midline in coronal plane)
The first 0-15 degrees of abduction is produced by the supraspinatus. The middle fibres of the deltoid are responsible for the next 15-90 degrees. Past 90 degrees, the scapula needs to be rotated to achieve abduction – that is carried out by the trapezius and serratus anterior.

Adduction (upper limb towards midline in coronal plane)
Produced by contraction of pectoralis major, latissimus dorsi and teres major.

Medial Rotation (rotation towards the midline, so that the thumb is pointing medially)
Produced by contraction of subscapularis, pectoralis major, latissimus dorsi, teres major and anterior deltoid.

Lateral Rotation (rotation away from the midline, so that the thumb is pointing laterally)
Produced by contraction of the infraspinatus and teres minor.

Directions:

Distal attachment: its' origin at the dorsal humerus distally from the radial sulcus. Its' fibers are connected with the medial intermuscular septum.

Proximal attachment: insertion attachment point at the Olecranon process which is the bony prominence of the elbow, on the upper ulna.

Muscle Line of Pull:

The triceps brachii muscle runs along the humerus— the upper arm bone between the shoulder and the elbow. The triceps brachii is mainly responsible for extension of the elbow joint—anatomy speak for straightening the arm—though it also helps to stabilize the relatively insecure shoulder joint.

The triceps mainly works antagonistically to the biceps brachii together finding the balance to flex and extend the elbow. The biceps do have two other flexors, brachialis and brachioradialis that work along with it to oppose the triceps, the lone extensor muscle.

The muscle orientation combined with the movement allowed at the joints, causes

this change in position: Flexion, extentension

of this segment of the body: Upper segment

in this (these) plane(s): Saggital planes

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