Breathing

Edited by Dr. Stefano Casali

The chest wall

The coasts

The first nine ribs articulate with the corresponding vertebral body and also with the upper vertebral body, while the last three ribs articulate only with the corresponding vertebral body. Anteriorly the ribs are articulated with the manubrium of the sternum and its junction (I and II),

or with the sternum (III-VIII), while the IX and X articulate with the upper cartilages, and the XI and XII are free. Under the thrust of the intercostal muscles, the joint of the first five ribs generates an upward and forward movement, while the VI-X rib joint generates a forward and outward / downward movement.

The Diaphragm

The muscles of the diaphragm are divided into sternal, costal, which are inserted on the last six ribs, and vertebral, inserted on the arcuate ligaments and on the vertebral processes.

The Diaphragm
seen from below

Defects of the sternal muscles (foramen and Morgagni's hernia), of the muscles of the ligaments or of the posterior ribs (Bochdalek's hernia) are frequent, and there are frequent communications between the peritoneum and the diaphragm, more frequent on the right, which are at the base of the pleural effusions in course of subdiaphragmatic pathology (Meigs syndrome, peritoneal dialysis etc.).

The diaphragm is innervated by the phrenic nerves, which run into the mediastinum. The sensory innervation of the diaphragm is scarce. Moreover, the sensory fibers of the phrenic are localized at the shoulder level, so that diaphragmatic pain can be referred to the shoulder, and neuritis of the relative metamers can cause diaphragmatic paralysis.

The intercostal muscles

The external intercostal muscles run downwards and forwards, the internal intercostals downwards and backwards. A thin muscular layer is located immediately below the parietal pleura. The intercostal vessels and nerves run below and inside the lower edge of the rib (important for pleural puncture).

The chest wall and the pleural cavity

The pleural cavity extends above the collarbone, at the level of the neck of the first rib. The dome of the pleura makes contact with the subclavian vessels anteriorly, the scalene muscles superiorly,

the brachial plexus laterally and the sympathetic ganglion superiorly and posteriorly (Horner's syndrome in Pancoast tumor). The costophrenic sinus is represented, during quiet breathing, by the reflection of the two parietal and visceral sheets and the lung occupies it only in deep breath. The lower line of the phrenic cost sinus runs horizontally and upward. The pleural cavity extends from the chest wall to the hilum, accompanying the lobar divisions.

The airways

• The upper airways include:

  the nasal cavities, the pharynx, the larynx

• The lower airways include:

  the trachea, which originates from the cricoid cartilage, has a length of 10 11 cm and bifurcates at the height of the 5th vertebra; the main bronchi and their branches

The trachea and the bronchi

The trachea consists of a cartilage wall (15-20 rings linked anteriorly by a

connective ligament and posteriorly from a muscle wall)

and is lined with ciliated columnar glandular epithelium. The structure of the main bronchi is similar to that of the trachea. The bronchial divisions are 24, and it is estimated that the normal lung contains a number of 20,000-30,000 terminal bronchioles, tributaries of as many acini in which each terminal bronchiole divides into eight respiratory bronchioles.

Lobule and pulmonary acinus:
Towards the limit of each auriferous path, the terminal bronchiole is reached. The lobule represents the structural unit of the lung and is made up of three or five terminal bronchioles. Each lobule is made up of 10-15 elementary units, the pulmonary acini. , or respiratory unit, is defined as the part of the lung fed by a terminal bronchiole. The berries vary in size and shape; in the adult the grape can reach up to 1 cm in diameter. Inside the berry you can see from three to eight generations of respiratory bronchioles which have in part

and the structure of the bronchioles, but with pulmonary alveoli opening directly into their lumens. After them are the alveolar ducts and the alveolar sacs before reaching the pulmonary alveoli. None of these units are isolated; in fact, there is a passage of collateral air between grape and grape, and between lobule and lobule, through Kohn's pores in the alveolar wall and through accessory communications between the distal bronchioles and the adjacent pulmonary alveoli.

Second part "