Icon module 18

Innervation of the lungs

The parasympathetic and sympathetic innervations of the lungs originate in a nerve plexus in the thoracic area. In stage 13 (32 days) immigrated neural crest cells form an extrapulmonary nerve plexus originating at the vagus nerve (parasympathetic) and the cervical and upper thoracic ganglia of the symphathetic trunk. With the growth of the lung anlagen the trachea and the whole bronchial tree become increasingly supplied from proliferating and fully-grown neural crest cells. They form the intramural plexus of the lungs. At the end of the embryonic period an outer nerve plexus has formed at the tracheal and bronchial periphery, around the cartilage anlage. An inner peribronchial nerve plexus develops somewhat later in the lamina propria under the epithelium. It accompanies the formation of the bronchial smooth musculature and the glands of the bronchial mucosa. Further distal in the bronchioli, the inner and outer nerve plexus merge to form a peribronchial plexus.

Lymph vessels of the lungs

At the end of the embryonic period the lymph vessels of the lungs begin to form out of a plexus in the hilar area starting from the thoracic duct. As a peribronchial lymph vessel system they accompany the branches of the bronchi and pulmonary artery and as subpleural and intersegmental lymph vessel system the branches of the pulmonary veins.

Fig. 13 - Lymph vessel system
in the fetal period

Right jugular vein
Right jugular and
auxiliary lymph plexus
Subclavian vein
Superior caval vein
Left jugular vein
Left jugular
and auxiliary lymph plexus
Left subclavian vein
Cisterna chyli
Inguinal lymph nodes
Thoracic duct

Fig. 13

The lymph system develops out a paired system. What remains, though, is only one thoracic duct that collects the lymph of the body, including the lungs, and discharges it into the blood circulation system in the left venous angle between the left jugular vein and the left subclavian vein.