@Rbt_bodybuilding Triceps muscles anotomy
Introduction
The triceps brachii is a large, thick muscle on the dorsal part of the upper arm. It often appears in the shape of a horseshoe on the posterior aspect of the arm. The primary function of the triceps is the extension of the elbow joint. It is composed of three heads (tri = three, cep = head): a long head, a lateral head, and a medial head. The tendons all have different origins, but the three heads combine to form a single tendon distally.
The long head originates from the infraglenoid tubercle of the scapula, while both the lateral head and the medial head both originate from the humerus. The three heads converge into a single tendon, which attaches to the proximal portion of the olecranon process (the bony prominence of the elbow) located on the upper portion of the ulna.[1]
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The triceps brachii is located in the dorsal compartment of the arm. The lateral intermuscular septum separates the dorsal part of the arm from the ventral aspect, which is where the flexors of the arm are (biceps, brachialis, and brachioradialis).
Long head—The origin of the long head is the infra-glenoid tubercle of the scapula. Because it attaches to the scapula, the long head not only extends the elbow but will also have a small action on the glenohumeral or shoulder joint. With the arm adducted, the triceps muscle acts to hold the head of the humerus in the glenoid cavity. This action helps prevent any displacement of the humerus. The long head also assists with the extension and adduction of the arm at the shoulder joint. The lateral head is also active during the forearm extension at the elbow joint when the forearm is supinated or pronated.
Medial head—The origin of the medial head is at the dorsal humerus, inferior to the radial groove and connecting to the intermuscular septum. The medial head does not attach to the scapula and therefore has no action on the glenohumeral joint, whether with stabilization or movement. However, the medial head is active during the forearm extension at the elbow joint when the forearm is supinated or pronated.
Lateral head—The lateral head originates at the dorsal humerus as well, but unlike the medial head, it is superior to the radial groove, where it fuses to the lateral intermuscular septum. This head is considered to be the strongest head of the three. It is active during the extension of the forearm at the elbow joint when the forearm is supinated or pronated.[3]
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Embryology
The mesoderm develops during the third week following the gastrulation process. In the third week, the paraxial mesodermal layer begins to organize into segments called somitomeres. These consist of concentric layers of mesodermal cells formed with cranial to caudal progression. Subsequently, they organize in somites. The somites appear with a frequency of about three pairs a day so that at the fifth week are recognizable 42 to 44 pairs of somites, of which there are four occipital pairs, seven cervical, twelve thoracic, five lumbar, five sacral, and between eight and ten coccyx pairs.
The triceps brachii begins to develop during the fifth week of embryogenesis. The muscle originates from the dorsal muscle mass of the upper limb bud and is derived from the paraxial mesodermal leaflet.[4]
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Blood Supply and Lymphatics
The arterial supply to the triceps is provided by the deep brachial artery, which is a branch of the brachial artery and is supplied by ulnar collateral arteries.[5] The venous drainage is the brachial vein that runs with the deep brachial artery.
Lymphatic vessels, like lymph nodes, are divided into superficial and deep. The superficial lymphatic collectors are the cutaneous lymphatic capillaries, especially of the hand, from which they course proximally in the forearm to form three groups: medial, lateral, and anterior collectors. In the arm, then they continue to get to the armpit to the axilla.[6]
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