Trunk

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Muscles of the thoracic wall

The M. pectoralis major shapes the surface of the anterior upper thoracic wall. Beneath this muscle lies the M. pectoralis minor. These two muscles, together with the M. subclavius, belong to the group of ventral muscles of the shoulder girdle (Tab. 26).

The Mm. intercostales externi and interni fill the intercostal spaces. The Mm. subcostales and the M. transversus thoracis lie next to them on the inner side of the thoracic wall.

Mm. intercostales externi

Nn. intercostales (Nn. thoracici)

O: inferior costal margin from the Tuberculum costae to the bone-cartilage junction

I: superior costal margin of the next caudal rib

F: lift the ribs, inspiration

Mm. intercostales interni (The Mm. intercostales intimi are delineated on their inner side by the Vasa intercostalia posteriora and the N. intercostalis.)

Nn. intercostales (Nn. thoracici)

O: superior costal margin ventrally of the Angulus costae

I: inferior costal margin of the next cranial rib

F: depress the ribs, expiration

Mm. intercostales intimi (innermost part of the Mm. intercostales interni, frequently also called Mm. intercostales intimi)

Nn. intercostales (Nn. thoracici)

O: superior costal margin ventrally of the Angulus costae

I: inferior costal margin of the next cranial rib

F: depress the ribs, expiration

M. transversus thoracis

Nn. intercostales (Nn. thoracici)

O: dorsally at the Corpus sterni and Proc. xiphoideus

I: Cartilago costalis of ribs 2–6

F: tenses the thoracic wall, expiration

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Ventral muscles of the abdominal wall

The muscles of the anterior abdominal wall, the M. rectus abdominis and the M. pyramidalis, are located within the rectus sheath.

M. rectus abdominis

Nn. intercostales (Nn. thoracici)

O: outer surface of the Cartilago costalis of ribs 5–7, Ligg. costoxiphoidea

I: Symphysis pubica

F: bends the torso, abdominal press, expiration (diaphragmatic or abdominal breathing type)

M. pyramidalis (inconstant muscle)

Caudal Nn. intercostales (Nn. thoracici)

O: Symphysis pubica ventral to the M. rectus abdominis

I: Linea alba

F: ‘tenses the Linea alba’

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Lateral muscles of the abdominal wall

The M. obliquus externus abdominis, the M. obliquus internus abdominis and the M. transversus abdominis are collectively named the lateral muscles of the abdominal wall. Their tendinous plates form the rectus sheath. In both men and women, the M. cremaster separates from the M. obliquus abdominis internus and the M. transversus.

M. obliquus externus abdominis

Caudal Nn. intercostales (Nn. thoracici)

O: outer surface of ribs 5–12

I: Labium externum of the Crista iliaca, Lig. inguinale, participates in the formation of the anterior lamina of the rectus sheath

F: unilaterally active: rotates the thorax to the contralateral side bends the spinal column to the ipsilateral side bilaterally active: bends the torso abdominal press expiration (diaphragmatic breathing type)

M. obliquus internus abdominis

Caudal Nn. intercostales (Nn. thoracici); N. iliohypogastricus; N. ilioinguinalis (Plexus lumbalis)

O: Fascia thoracolumbalis (deep layer), Linea intermedia of the Crista iliaca, Lig. inguinale

I: inferior margin of the Cartilago costalis of ribs 9–12, contributes to the anterior and posterior laminae of the rectus sheath above the Linea arcuata, below which all tendinous fibres project into the anterior lamina

F: unilaterally active: rotates the thorax to the ipsilateral side bends the spinal column to the ipsilateral side bilaterally active: bends the torso abdominal press expiration (diaphragmatic breathing type)

M. transversus abdominis

Caudal Nn. intercostales (Nn. thoracici); N. iliohypogastricus; N. ilioinguinalis (Plexus lumbalis); N. genitofemoralis

O: inner surface of the Cartilago costalis of ribs 7–12, Fascia thoracolumbalis (deep layer), Labium internum of the Crista iliaca, Lig. inguinale

I: contributes to the posterior lamina of the rectus sheath above the Linea arcuata, below which it contributes to the formation of the anterior lamina

F: abdominal press, expiration (diaphragmatic breathing type)

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Dorsal muscles of the abdominal wall

The M. quadratus lumborum forms the muscular basis of the posterior abdominal wall. The M. psoas major follows medially thereof.

M. quadratus lumborum

Caudal Nn. intercostales; Rr. musculares (Plexus lumbalis)

O: Labium internum of the Crista iliaca

I: rib 12, Proc. costalis of the lumbar vertebrae L4–L1

F: bends the spinal column to the ipsilateral side

18

Spinocostal muscles

The spinocostal muscles, M. serratus posterior superior and M. serratus posterior inferior, are thin muscles of minor functional relevance and are located deeply on the autochthonous muscles of the back.

M. serratus posterior superior

Cranial Nn. intercostales (Nn. thoracici)

O: Proc. spinosus of the cervical vertebrae C6 and C7 and the thoracic vertebrae T1 and T2

I: ribs 2–5 lateral to the Angulus costae

F: elevates the ribs, inspiration

M. serratus posterior inferior

C audal Nn. intercostales (Nn. thoracici)

O: Proc. spinosus of the thoracic vertebrae T11 and T12 and the lumbar vertebrae L1 and L2

I: caudal margin of ribs 9–12

F: depresses ribs 9–12, also active during forced inspiration as an antagonist to the diaphragm

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Autochthonous muscles of the back