Figure 1.1
Anatomical lines of the anterior chest wall (Tilmann BN (2010), Ventrale Rumpfwand. In: Anatomie, Springer-Verlag Berlin Heidelberg, S. 816, Abb. 21.1)
Certain ribs and intercostal spaces can be located by palpating these structures.
The margin between the corpus and manubrium sterni is called the angulus sterni (Ludovici or sternal angle) which is visible and located next to the second rib. The first ribs cannot be palpated as they are covered by the clavicles. The second ribs and below can be identified.
1.3 Bony Components and Joints
The sternum consists of the manubrium sterni, the corpus sterni, and the processus xiphoideus. The manubrium is linked with the clavicles on each side and also with the first ribs with the help of cartilagenous joints, called synchondroses. Ribs 2–7 articulate laterally at the corpus sterni. The xiphoid is not attached to any ribs.
In general, the ribs in humans are numbered the same as their corresponding vertebral bodies. There are 12 pairs of ribs with some of them rudimentary and fused with the vertebral bodies in so called rib stumps.
The ribs are divided into real ribs (costae verae, 1–7) that have sternal joints, false ribs (costae spuriae, 8–10) with cartilagenous joints to the costal arch (arcus costalis), and free ribs (costae fluctuantes, 11–12) that end in the soft tissue of the lateral chest wall. The 12th rib is not always present.
The head of the rib (caput costae) articulates laterally with the vertebral body and there is a second articulation between the transverse process and the vertebral body. The rib neck is located between these articulations and acts as the longitudinal axis for rib movement. The neck of the rib is followed by the body of the rib (collum costae), turning anteriorly at an angle (angulus costae). Anteriorly all bony tissue is followed by cartilage which represents the elastic link with the sternum (Fig. 1.2).
Figure 1.2
Bony chest (a) view from anterior, (b) view from posterior (Tilmann BN (2005), Rumpfskelett In: Atlas der Anatomie, Springer-Verlag Berlin Heidelberg, S. 187/188, Abb. 4.1, 4.2. (jeweils oberer Abschnitt ohne Becken))
The ribs move upwards during inspiration around their rib neck and downwards during expiration. This volume increase and decrease is due to changes in both the sagital and transverse directions. The mobility of the chest is guaranteed by the joints between the vertebral bodies and ribs as well as by the interactions between the cartilage, sternum, and costal arch.
The costosternal complex moves cranially and ventrally (sagittal extension). The lower ribs move towards cranially and laterally to increase the diameter of the chest in the transverse direction (Fig. 1.3).
Figure 1.3
Movement of the ribs during inspiration and expiration (van Gestel A et al. (2010), Atembewegungsapparat. In: Physiotherapie bei chronischen Atemwegs- und Lungenerkrankungen, Springer-Verlag Berlin Heidelberg, S. 17, Abb. 2.2)
At the lower edge of the rib, the sulcus costaeis is located where the intercostal vessels and the intercostal nerve run. The intercostal muscles are attached to the edges of the ribs (Fig. 1.9).
1.4 Muscles of the Chest Wall
The lung itself does not have any muscles and therefore the muscles of the chest wall and diaphragm are responsible for the movements that let us breathe. Some of the chest wall muscles can be used as helpful anatomical landmarks.
At the neck, the chest is attached by the three scalene muscles, the intercostal muscles, and the muscles eminating from ribs 1 and 2 to the vertebral bodies (1–7). They are responsible for the flexion of the upper spine anteriorly and for lifting the ribs during inspiration (Fig. 1.4).
Figure 1.4
Chestwall muscles, view from anterolateral (Tilmann BN (2005), Muskeln der Brustwand. In: Atlas der Anatomie, Springer-Verlag Berlin Heidelberg, S. 204, Abb. 4.30 (jeweils oberer Abschnitt ohne Becken))
The Pectoralis major muscle covers the upper and lateral part of the chestwall like a shelf and creates the outline of the chestwall. It originates from the medial clavicle, the sternum, the cartilages of ribs 5–7, as well as from the rectus sheath, and inserts at the tuberculum majus humeri. The lower edge of the muscle creates the anterior axillary plication. This muscle causes a strong adduction and rotation of the arm and its lower portion acts as an auxillary breathing muscle.
The Pectoralis minor muscle is completely covered by the Pectoralis major muscle. It derives from the ribs 3–5 and connects to the processus coracoideus of the shoulder. This muscle pulls the shoulder anteriorly and downwards and also lifts the chest as an auxillary breathing muscle (Fig. 1.5).
Figure 1.5
Muscles of the anterior chestwall (Tilmann BN (2005), Muskeln der Brustwand. In: Atlas der Anatomie, Springer-Verlag Berlin Heidelberg, S. 207, Abb. 4.33 (oberer Abschnitt))
The intercostal muscles consist of two layers of short muscles between the ribs oriented in different directions. The more external layer is made of the intercostales externi muscle which is oriented craniolaterally to mediocaudally from the lower edge of the upper rib to the upper edge of the rib below. The intercostales interni muscle is located underneath oriented opposite of the externi and therefore from craniomedial to laterocaudal. Both muscles help to maintain the appropriate tension of the rib cage. The outer muscles lift the chest up (inspiration) and the inner ones lower it and strengthen expiration.
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