The Lungs and Pleura Flashcards
What is the positioning of the lungs in the thoracic cavity?
Within the thoracic cavity the lungs are contained in the right and left pleural cavities.
The lung surface are covered by a single layer of thin smooth serous membrane called the visceral pleura. The visceral pleura reflects away from the lung at the lung root/hilum to become the parietal pleura which lines the internal aspect of the thoracic cavity.
Explain some of the features of the pleura?
There are several regions of the parietal pleura including the cervical aspect, mediastinal, costal and diaphragmatic aspects.
Between the two layers of pleura is a potential space known as the pleural cavity. It contains a few mls of serous cavity, decreasing friction during respiration.
There are some areas where the visceral pleura and the parietal pleura do not meet until full inspiration; one of which is the costodiaphragmatic recess.
The parietal pleura extents up above the ribs and a few centimeters lower than the lungs except during inspiration. Furthermore, if a kidney is being removed, because the lungs extend below the 12th rib at some points, it is important to be wary of this so as not to puncture the lung.
Explain the features of the visceral pleura and the innervation of the pleura on the lungs?
The shiny exterior of the lung is the visceral pleura which reflects at the hilum. There is a double fold of pleura that hangs down below the lung root structures which is called the pulmonary ligament.
The purpose of the extra space in the pleura reflection is for the expansion of the pulmonary veins which are capacitance vessels and must be allowed to expand. (shown in red)
All pleura/pericardium/peritoneum share the nerve supply of the organs which they are covering. So the visceral layers have an autonomic or visceral nerve supply and so the referred pain is always dull and poorly localized. The parietal layers however have a somatic nerve supply and refer pain sharply, severely and very well localized.
Explain some features of the trachea?
The trachea originates in the neck at the level of C6 and descends inferiorly through the thoracic inlet into the superior mediastinum. At level T4/T5 it bifurcates into the left and right main bronchus.
The trachea is a series of U-shaped cartilage rings closed posteriorly by the trachealis muscle.
What are some differences between the right and left main brochuses?
The RMB is shorter, wider and more vertical than the left.
The RMB and LMB enter at the hilum of the lung and divide into lobar bronchi and segmental bronchi. Each segmental bronchi supplies a bronchopulmonary segment.
Give some features of the Right Lung?
The inferior surface of the lung is concave to sit on the diaphragm as well as a rounded coastal surface which often has imprints of the ribs and a medial surface with mediastinal imprints.
The right lung is larger than the left and typically has three lobes and two fissures. The oblique fissure divides the upper and middle lobes from the lower lobe behind. The horizontal fissure separating the upper lobe from the middle lobe below.
Each lung has bronchial branches, vascular, lymphatic and neural elements that enter from the mediastinum via the hilum. In general, blue structures are the pulmonary arteries coming out of the right ventricle, the red structures are the pulmonary veins going into the left atrium.
Generally, the pulmonary artery is the anterior or superiormost structure at the hilum. The airways/bronchus is the posterior structure. The pulmonary veins are the anterior and inferior most structures at the hilum.
The imprints on the medial surface of the right lung are the veins of the mediastinum.
Give some features of the left lung.
The left lung is slightly smaller with only two lobes and an oblique fissure. It also contains a cardiac notch in the upper lobe and the ligulae hanging below that notch.
The mediastinal imprints are the heart and the aorta in the left lungs.
Bronchial veins and arteries(3-5) are also seen at the hilum with nerve and lymphatics providing vascularisation of the lungs themselves.
Explain the lymphatic system in the lungs
There are two systems of lymphatics in the lungs. The black spidery appearance of the lungs are the superficial lymphatics of the lung but there are also a deeper system that takes lymph from the airways etc. and drains into the hilar lymph nodes –> tracheobronchial lymph nodes –> thoracic duct (left) and right lymphatic duct.
Explain that autonomic nerve supply of the lungs.
Controls mucus production etc.
Parasympathetic comes from the vagus nerve and the sympathetic comes from the ganglia along the posterior thoracic wall.
