(1) Upper limbs of pectoralis major: all of them start from the lateral side of the thorax and end at the upper limb with bone or humerus, mainly including pectoralis major, pectoralis minor and serratus anterior.

The pectoralis major muscle is shallow, covering most of the chest, fan-shaped, wide and thick. From the medial half of the clavicle,

At the sternum and 1-6 costal cartilage, the muscle bundles of all parts converge outward, and the flat tendon ends at the crest of the greater tubercle of humerus. Function: the humerus can be adducted and rotated;

When the upper limb is lifted and fixed, the trunk can be lifted and the ribs can be lifted to assist inhalation.

The pectoralis minor muscle is located on the deep surface of the pectoralis major muscle and is triangular. It starts from the 3rd-5th rib and ends at the coracoid process of the scapula. work

Use: pull the scapula forward and downward; If the scapula is fixed, you can lift the 3-5 ribs to assist inhalation.

The serratus anterior muscle is located on the lateral side of the chest, starting from the lateral side of the upper 8 or 9 ribs with muscle teeth, and the muscle bundle goes backwards and passes through the shoulder.

In front of the scapula, it stops at the inner edge of the scapula. Function: can pull the scapula forward, so that the scapula is close to the chest; If the scapula is fixed, it can be lifted.

Ribs, assist inhalation. When the serratus anterior muscle is paralyzed, the medial edge of the scapula tilts upward, which is called "pterygoscapula".

(2) pectoral muscle: It participates in the formation of the chest. In the intercostal space, there are mainly external intercostal muscles and internal intercostal muscles.

The extracostal muscle is located in the shallow layer of each intercostal space, starting from the lower edge of the rib, and the muscle bundle obliquely goes forward to the next one.

The upper edge of the rib. In the intercostal cartilage space, there is no external intercostal muscle, but the external intercostal membrane connecting tissues. Function: External intercostal muscle can lift ribs,

Help breathe in.

The intercostal muscle is located in the deep surface of the extracostal muscle, and the direction of the muscle bundle is opposite to that of the extracostal muscle, and the posterior muscle bundle only reaches.

From then on, the costal angle is replaced by the costal intima connecting the tissues. Internal intercostal muscles can lower the ribs and help exhale.