Question

1. In a tabular form, list the muscles of respiration and their nerve supply

2. Describe about the venous drainage of the thoracic cavity

3. Write about the surface anatomy of the lungs and pleurae

Answer 1

Ans ;

1. Muscles of inspiration -

Diaphram - phrenic nerves from C3 to C5

External intercostal - thoracic spinal nerve

Expiration muscles

Internal intercostal - thoracic spinal nerves

Forced expiration -

Rectus abdominus - lower thoracic nerves T5 - T 12

External and internal oblique - lower intercostal nerves , iliohypogastric nerve and ilioinguinal nerve

2. Venous drainage of thoracic cavity:

The inferior vena cava is the inferior of the two venae cavae, the large veins that carry deoxygenated blood from the body into the right atrium of the heart. The inferior vena cava carries blood from the lower half of the body whilst the superior vena cava carries blood from the upper half of the body. It is formed by the joining of the right and the left common iliac veins, usually at the level of the fifth lumbar vertebra.

The azygos vein is a vein running up the side of the thoracic vertebral column draining itself towards the superior vena cava. It connects the systems of superior vena cava and inferior vena cava and can provide an alternative path for blood to the right atrium when either of the venae cavae is blocked.

The internal jugular vein is a paired vein collecting the blood from the brain, the superficial parts of the face, and the neck. An internal jugular vein is a type of jugular vein.

The hemiazygos vein (vena azygos minor inferior) is a vein running superiorly in the lower thoracic region, just to the left side of the vertebral column.

The left and right brachiocephalic veins (or innominate veins) in the upper chest are formed by the union of each corresponding internal jugular vein and subclavian vein. This is at the level of the sternoclavicular joint. The left brachiocephalic vein is usually longer than the right.

In human anatomy, the internal thoracic vein (previously known as the internal mammary vein) is a vessel that drains the chest wall and breasts

3. Surface anatomy of lungs

Anatomically, the lung is described by an apex, three borders, and three surfaces. The apex lies above the first rib.

The three borders include the anterior, posterior, and inferior borders. The anterior border of the lung corresponds to the pleural reflection, and it creates a cardiac notch in the left lung. The cardiac notch is a concavity in the lung that is formed due to the heart. The inferior border is thin and separates the base of the lung from the costal surface. The posterior border is thick and extends from the C7 to T10 vertebra, which is also from the apex of the lung to the inferior border.

The three surfaces of the lung include the costal, medial, and diaphragmatic surfaces. The costal surface is covered by the costal pleura and is along the sternum and ribs. It also joins the medial surface at the anterior and posterior borders and diaphragmatic surfaces at the inferior border. The medial surface is divided anteriorly and posteriorly. Anteriorly it is related to the sternum, and posteriorly it is related to the vertebra. The diaphragmatic surface (base) is concave and rests on the dome of the diaphragm; the right dome is also higher than the left dome because of the liver.

The right and left lung anatomy are similar but asymmetrical. The right lung consists of three lobes: right upper lobe (RUL), right middle lobe (RML), and right lower lobe (RLL). The left lung consists of two lobes: right upper lobe (RUL) and right lower lobe (RLL). The right lobe is divided by an oblique and horizontal fissure, where the horizontal fissure divides the upper and middle lobe, and the oblique fissure divides the middle and lower lobes. In the left lobe there is only an oblique fissure that separates the upper and lower lobe.

Pleura -

Commencing at the sternum, the pleura passes lateralward, lines the inner surfaces of the costal cartilages, ribs, and Intercostales, and at the back part of the thorax passes over the sympathetic trunk and its branches, and is reflected upon the sides of the bodies of the vertebræ, where it is separated by a narrow interval, the posterior mediastinum, from the opposite pleura. From the vertebral column the pleura passes to the side of the pericardium, which it covers to a slight extent; it then covers the back part of the root of the lung, from the lower border of which a triangular sheet descends vertically toward the diaphragm. This sheet is the posterior layer of a wide fold, known as the pulmonary ligament.

From the back of the lung root, the pleura may be traced over the costal surface of the lung, the apex and base, and also over the sides of the fissures between the lobes, on to its mediastinal surface and the front part of its root. It is continued from the lower margin of the root as the anterior layer of the pulmonary ligament, and from this it is reflected on to the pericardium (pericardial pleura), and from it to the back of the sternum.

Above the level of the root of the lung, however, the mediastinal pleura passes uninterruptedly from the vertebral column to the sternum over the structures in the superior mediastinum. Below, it covers the upper surface of the diaphragm and extends, in front, as low as the costal cartilage of the seventh rib; at the side of the chest, to the lower border of the tenth rib on the left side and to the upper border of the same rib on the right side; and behind, it reaches as low as the twelfth rib, and sometimes even to the transverse process of the first lumbar vertebra. Above, its cupula projects through the superior opening of the thorax into the neck, extending from 2.5 to 5 cm. above the sternal end of the first rib; this portion of the sac is strengthened by a dome-like expansion of fascia (Sibson’s fascia), attached in front to the inner border of the first rib, and behind to the anterior border of the transverse process of the seventh cervical vertebra