Nerve supply of the autochthonous muscles. Intercostal nerves.

Diaphragm (diaphragma/диафрагма)

The diaphragm forms the partition between the thoracic and abdominal cavity. It is flat dome-shaped muscle, covered above and below with fasciae and serous membranes.

• Origin.

• The costal part (pars costalis diaphragmatis/рёберная часть диафрагмы) originates from the inner surfaces of the lower six ribs.

• The sternal part (pars sternalis diaphragmatic/грудинная часть диафрагмы) originates from the back of the xiphoid process of the sternum.

• The lumbar part (pars lumbalis diaphragmatic/поясничная часть диафрагмы) originates from the right and left crura (crus dextrum, sinistrum/правая, левая ножка) which are attached, respectively, to the upper three and the upper two lumbar vertebrae and from the medial and lateral arcuate ligaments (lig. arcuatum mediale, laterale/медиальная, латеральная дугообразная связка) which bridge over the psoas major and quadratus lumborum.

• Insertion. The fibres (striated muscle) are inserted into the central tendon (centrum tendineum/сухожильный центр).

• The diaphragm has openings:

• The aortic hiatus (hiatus aorticus/аортальное отверстие) is between right and left crura and the spine. It transmits the aorta.

• The oesophageal hiatus (hiatus oesophageus/пищеводное отверстие) is just above and to the left of the aortic hiatus. It and transmits the oesophageus.

• The caval opening (foramen venae cavae/отверстие нижней полой вены) is in the central tendon. It transmits the inferior vena cava.

• There are two paired spaces – the sternocostal and lumbocostal triangles (trigonum sternocostale, lumbocostale/грудино-рёберный, пояснично-рёберный треугольник) between the corresponding parts of the diaphragma. They are covered by the pleura and endothoracic fascia above and by the endoabdominal fascia and peritoneum below.

• Actions. The diaphragm is involved in respiration. When the muscle fibres contract, the diaphragm is lowered, thus increasing, the vertical dimension of the thorax. In the later stages of contraction, using the liver as a fulcrum it raises the lower ribs, thus increasing the width of the lower thorax. At the same time, it increases the intra-abdominal pressure and is thus used in expulsive efforts – defecation, micturition, parturition, etc.

• Nerve supply. Phrenic nerve (cervical plexus).

The fasciae of thorax

The superficial fascia (fascia superficialis/поверхностная фасция)

It is the part of the common superficial fascia of the body. The mammary gland is most important of all contents of this fascia. The fibrous septa given off by the fascia support the lobes of the gland, and the skin covering the gland.

The pectoral fascia (fascia pectoralis/грудная фасция)

It covers the muscles related with the upper limb. In the clavipectoral triangle it is called the clavipectoral fascia (fascia clavipectorale/ключично-грудная фасция).

The thoracic fascia (fascia thoracica/собственная грудная фасция)

It lines the outer surface of the thoracic cage and the external intercostal muscles.

The endothoracic fascia (fascia endothoracica/внутригрудная фасция)

It lines the inner surface of the thoracic wall.

Topography of the thorax

There are three triangles within pectoral region:

• The clavipectoral triangle (trigonum clavipectorale/ключично-грудной треугольник) is bounded by the clavicle and the superior border of the pectoralis minor.

• The pectoral triangle (trigonum pectorale/грудной треугольник) corresponds to the pectoralis minor.

• The subpectoral triangle (trigonum subpectorale/подгрудной треугольник) is bounded by the inferior borders of the pectoralis minor and pectoralis major and the anterior border of the deltoideus.

The lines of the thorax

• The anterior median line passes along the middline of the sternum.

• The sternal line passes along the border of the sternum.

• The midclavicular line passes through the middle of the clavicle.

• The parasternal line passes through the middle between the sternal and midclavicular lines.

• The anterior axillar line passes through the anterior wall of the axillary fossa.

• The posterior axillary line passes through the posterior wall of the axillary fossa.

• The midaxillary line through the middle between the anterior and posterior axillary lines.

• The scapular line passes through the inferior angle of the scapule.

• The paravertebral line passes through the tubercles of the ribs.

• The posterior median line passes through the vertebral spinous processes.

THE MUSCLES OF Abdomen (musculi abdominis/мышцы живота)

All the muscles of the anterior abdominal wall serve to protect the viscera by their contraction, to produce movement and to increase the intra-abdominal pressure, as in defecation, coughing, parturition, etc.

External oblique (m. obliquus externus abdominis/наружная косая мышца живота)

• Origin. From the outer surfaces of the lower eight ribs to the iliac crest as far forward as the anterior superior spine.

• Insertion. The free lower border forms the inguinal ligament (lig. inguinale/паховая связка) between the anterior superior iliac spine and the pubic tubercle. The muscle becomes aponeurotic and reaches the midline where it interdigitates with the opposite side to form the linea alba. The aponeurosis contributes to the anterior layer of the rectus sheath.

• Actions. Flexion of the spine, side flexion and rotation of the trunk – the right external oblique produces rotation to the left.

Internal oblique (m. obliquus internus abdominis/наружная косая мышца живота)

• Origin. From the thoracolumbar fascia, the iliac crest and the lateral half of the inguinal ligament.

• Insertion. Into an aponeurosis which is attached to the costal margin, and at the linea semilunaris (linea semilunaris/полулунная линия) the aponeurosis is divided into anterior and posterior layers, thus contributing to the rectus sheath.

• Actions. Flexion of the spine, side flexion and rotation of the trunk – the right internal oblique produces rotation to the right.

Transversus abdominis (m. transversus abdominis/поперечная мышца живота)

• Origin. From the thoracolumbar fascia, the iliac crest and the lateral one third of the inguinal ligament. Also from the inner surfaces of the lower six ribs, interdigitating with the diaphragm.

• Insertion. The aponeurosis passes to the linea semilunaris contributing to the rectus sheath. The lower fibres help to form the inquinal falx.

• Actions. Most of the fibres are transverse and thus pull in and flatten the abdominal wall.