First learn the bony structure of the thorax, before learning first understand: thoracic vertebrae, ribs, sternum and upper limb with bone scapula and clavicle. Thoracic vertebrae: the thoracic vertebrae are irregular bones, consisting of vertebral bodies, transverse processes on both sides of the vertebral bodies, vertebral arches and spines. The thoracic spine is characterized by a heart-shaped vertebral body, elongated spinous processes that slope downward, and relatively small, rounded vertebral foramina. The upper and lower articular surfaces are basically in a frontal position. The overall arrangement of the thoracic vertebrae forms a backward curved arc, called the thoracic curve. Ribs: These include ribs and rib cartilage, which are normally symmetrical to the left and right, and there are 12 pairs of rib cartilage at the front of the ribs. The front end of the upper 7 pairs of rib cartilage are connected to the sternum (generally the front end of the 6th rib is equivalent to the height of the 10th posterior rib), 8, 9, 10 three pairs of rib front soft ribs are connected to their upper pair of rib cartilage one by one (forming a rib arch); 11, 12 pairs of rib front free, the rib cage consists of rib head, rib neck, rib nodes, rib body, rib groove; the posterior end of the rib cage is slightly inflated called rib head, and the rib concave associated with the thoracic vertebral body, rib head lateral The lateral part of the rib head is called the rib neck, and then the rib body is anteriorly, and there is a prominent rib node at the posterior lateral side of the junction of the neck body, on which the articular surface is associated with the thoracic vertebral transverse process rib recess. The internal surface of the rib body has a shallow groove near the lower edge called the rib sulcus (in which the intercostal nerve and posterior costal artery travel). The posterior part of the rib body at the sharp turn is called the rib angle. Special attention is paid to the slightly different shape of the 1st rib, which is flat and wide, with a nearly horizontal alignment. There is a node in the middle above it called the anterior oblique muscle node, which has two sulci anteriorly and posteriorly (which may be mistaken for a fracture if visualized, especially if visualized unilaterally), with the subclavian vein passing anteriorly and the subclavian artery passing posteriorly. The rest of the rib alignment is medially superior and oblique to the anterior and inferior. After 25 years of age, the first pair of rib cartilage calcifies first, and with age, the rest of the rib cartilage calcifies from the bottom up, showing irregular patches, striations, granules, or blocks of dense shadowing on x-ray, usually along the rib cage (not to be mistaken for intrapulmonary lesions). The upper and lower margins of the ribs have continuous cortical lines, but the posterior segments of the lower and middle ribs do not have clear cortical lines due to their thin lower margins and the presence of a rib sulcus, which should not be considered cortical destruction. The congenital variation of the ribs is more common, mainly in terms of morphology, number and form of connection, such as the 1st rib is underdeveloped; some of the 12th rib is very short, even unilateral or bilateral can not be seen; cervical ribs, on one or both sides of the 7th cervical vertebrae protrude outward, smaller than the 1st rib, and the alignment is straighter, more common in women. It can be distinguished from the 1st rib dysplasia based on the feature that the transverse process of the 7th cervical vertebra is inclined downward, while the transverse process of the 1st thoracic vertebra is inclined upward; forked ribs are more common, especially on the right side, and occur in the 3rd and 4th anterior ribs. The front end of the rib is bifurcated, with different patterns: some are equal in length; some are long and the other short; some are just protrusions on the rib; some are bifurcated and then united in a ring-like deformity (do not assume a cavity). Ribs adjacent to the forked ribs may be underdeveloped or absent. Jointed ribs, most often seen in the posterior part of the 5th and 6th ribs or the anterior part of the 1st and 2nd ribs, with a bridge or pseudo-joint between the two ribs. Rib fusion, most commonly seen in the right posterior rib segment, is characterized by bony fusion of the two adjacent ribs and localized loss of rib space (easily mistaken for intrapulmonary lesions). Sternum: located in the middle of the anterior thorax, all of which can be felt from the body surface, consisting of the sternal stalk (six-sided), the sternal body (two edges are wavy) and the saber process. The sternal stalk is wide at the upper part and narrow at the lower part, with three depressions at the upper edge, a central jugular vein notch, and a clavicular notch associated with the clavicle at the outer part. The sternal body is connected with the stalk at a slightly forward protrusion called the sternal angle (the same height as the anterior end of the 2nd rib, which is an important marker to determine the 2nd rib and helps to locate the heart percussion, lung auscultation and count the ribs). The sternal body is a rectangular flat bone with a rib cut on the outer edge where the 2nd-7th ribs are in contact with the cartilage. The lower part is the saber process, which is narrow and thin, with a free end and often a hole in the middle. The saber is cartilaginous when young, and the three parts of the sternum are separated until the age of 25, when they are fused into one whole bone at least at the age of 40. Scapula: located in the posterior lateral side of the thorax, usually flat against the 2nd-7th ribs between, the shape of triangular flat bone. It has two faces (anterior and posterior), three margins (medial, lateral and superior) and three angles (superior, inferior and lateral) and three fossae (subscapular, supraspinatus and infraspinatus). The front is a large and shallow fossa called the subscapularis fossa, and the back has a bone crest protruding forward and upward called the scapularis gonad, and the flattened lateral end of the steel is called the shoulder peak, which is the highest point of the shoulder. There is a fossa above and below the gon, called suprascapular fossa and infrascapular fossa respectively. The medial edge is opposite to the spine (when the upper limb is raised, this edge is the projection of the oblique fissure), and the lateral edge is thicker and opposite to the axillary fossa. The upper margin is the shortest, with a small incision near the lateral side called the scapular incision (through which the suprascapular nerve passes), and a finger-like projection from the lateral side of the incision called the rostral process (with muscular attachment), with the upper angle corresponding to the 2nd rib. The inferior angle corresponds to the 7th rib, which is easily palpable and is also a somatic marker to determine the number of ribs (in developing scapulae, the secondary ossification center of the inferior angle may occasionally project into the lung field not to be mistaken for a fracture or intrapulmonary lesion). The lateral horn is enlarged and has a pear-shaped articular surface called the articular glenoid, which forms the shoulder joint with the humeral head. There are superior and inferior glenoid nodes above and below the articular glenoid, respectively. (The gender difference of the scapula is large, generally the male diameter is larger than the female) Clavicle: located between the neck and the chest (the whole length can be felt on the body surface, is an important bony mark), the clavicle is “~” shaped, smooth above and rough below, divided into two ends as one. The inner side is rough and called the sternal end, which is connected to the sternal stalk to form the sternoclavicular joint. The lower edge of the inner end of the clavicle is sometimes seen as a semicircular defect with irregular edges, called the rhomboid fossa, which is where the rhomboid ligament is attached (not to be mistaken for bone destruction), and the epiphysis of the inner end of the clavicle appears at the age of 18-20 and is irregularly crescent-shaped (not to be mistaken for a fracture). The lateral flattening is called the acromion end, which is associated with the acromion. The clavicular body has two curves, with the medial 2/3 convex forward and the lateral 1/3 convex backward. The outer and middle 1/3 junction of the clavicle is thin (fractures tend to occur here). The bony thorax consists of the thoracic vertebrae, ribs and sternum and the scapula and clavicle. First of all each thoracic vertebra is separated from each other with the help of intervertebral discs, anterior anterior longitudinal ligament of the vertebral body and posterior longitudinal ligament of the posterior edge of the vertebral body, yellow ligament between adjacent arch plates, interspinous ligament between adjacent spinous processes and supraspinous ligament behind the spinous processes. The posterior end of the rib forms two synovial joints with the thoracic vertebrae, the rib head and the rib recess form the rib head joint, and the rib node and the transverse rib recess form the transverse rib joint, both of which are collectively called the rib vertebral joint (the rib vertebral joint is the hub of the thoracic respiratory movement). The posterior segment of the rib is traveling horizontally outward, and the anterior segment is traveling from the upper to the lower inclination (because the anterior segment of the rib is flat and thin, it is not as clear as the image of the posterior segment of the rib on X-ray plain film, and the uncalcified part of the cartilage is not visible). The two adjacent rib gaps are called the anterior and posterior rib gaps, and generally the ribs are symmetrical on both sides, with the corresponding rib gaps being equal in width. The adjacent intercostal spaces are connected by the external intercostal muscle that starts from the lower edge of the superior rib and ends obliquely downward at the upper edge of the inferior rib and the internal intercostal muscle that starts from the upper edge of the inferior rib and ends upward at the lower edge of the superior rib (the internal and external intercostal muscles are intrinsic thoracic muscles). The ribs and intercostal space are often used as localization markers for thoracic lesions, e.g., the 4th posterior rib is at the same height as the sternoclavicular joint on a standard posteroanterior radiograph, while the 10th posterior rib corresponds to the anterior level of the 6th anterior rib at the same height as the roof of the diaphragm. The anterior ribs are connected to the sternum, the cartilaginous connection between the anterior end of the first rib and the sternal stalk, the anterior ends of the 2nd-7th ribs form the sternoclavicular joint with each rib notch of the sternal body, the anterior ends of the 8th-10th ribs are connected to the superior rib cartilage in turn (their lower edges together form the rib arch), and the anterior ends of the 11th and 12th ribs are free. The thorax is conical with a slightly flattened front and back. The upper thoracic opening is small, sloping from posterior upward to downward, enclosed by the 1st thoracic vertebrae, the 1st rib and the upper edge of the sternal stalk, which is the passage between the neck and the thoracic cavity. The lower thoracic opening is larger and is enclosed by the 12th thoracic vertebral body, the 12th rib, the anterior end of the 11th rib, the rib arch and the saber process. The angle between the two lateral rib arches is called the lower sternal angle. The shape and size of the thorax are related to age, gender, health status and other factors. The thorax of newborns is similar to the anterior and posterior diameter and is barrel-shaped; the thorax of the elderly is flat and long. In adult women, the thorax is short and garden, and the diameter is smaller than that of men. In children with rickets, the anterior and posterior diameter of the thorax is large, and the sternum protrudes forward, forming a “chicken chest”. Patients with emphysema have an enlarged thorax with a “barrel-shaped chest”.