Pleura and the lungs Flashcards
Mediastinum
The region between the right and left pleura which contains many structures:
- Oesophagus
- Trachea
- Heart
- Nerves
- Blood vessels
Thoracic cavity
Essentially the ‘chest’ region that contains:
- The right and left pleural cavity.
- The mediastinum and its structures.
Embryonic development of the pleura and the lungs.
Starts to occur during weeks 4-6, originating from the endodermal layer.
The primitive trachea branches out to form lung buds.
Lung buds push out into the pericardioperitoneal canal and rapidly divide.
As the lung buds push out, it takes its lining with it, eventually forming the visceral pleura.
The parietal is separated from the visceral pleura through the pleural cavity which develops from the pericardioperitoneal cavity.
Visceral pleura
The deeper pleura that adheres to the lungs, difficult to separate from the lung.
Connects with the parietal pleura at the hilum (lung root).
Parietal pleura
The more superficial pleura that lines the internal thoracic wall. It is separated from the visceral pleura through the pleura cavity.
This pleura is divided into 4 parts, according to its location:
- Cervical pleura (near the root of the neck).
- Diaphragmatic pleura (on top of the diaphragm).
- Costal pleura ( facing the ribs).
- Mediastinal (facing the mediastinum).
Pleural cavity
The space that separates the visceral pleura from the parietal pleural.
Contains serous fluid that allows surface tension between both pleura. The fluid is mainly composed of water which allow H-bond formation.
This allows the lung to always expand as the visceral pleura is always attached to the parietal pleura.
When the distance between the two pleura increases due to invasion of excess material (pleural effusion/ pneumothorax), this disrupts the cohesion and can cause lung to collapse
Pleural effusions:
- Haemothorax (blood)
- Chylothorax (chyle)
- Pyothorax (pus)
Recess (pleural cavity)
Excess pleural cavity present around the lung in certain regions.
Costomediastinal (anteriorly, near the cardiac notch)
Costodiaphragmatic (posteriorly)
Fluid can be sampled from these areas for diagnostic tests.
Innervation of the parietal pleura
Cervical pleura: 1st intercostal nerve.
Costal pleura: Intercostal nerves.
Mediastinal pleura: Phrenic nerve.
Diaphragmatic pleura: Phrenic nerve and lower intercostal nerves.
Innervation of the visceral pleura.
Autonomic pulmonary plexus: branches of the vagus nerve and sympathetic trunk.
There are no sensory neurones at the visceral pleura. Therefore it is not possible to feel pain from the visceral pleura. All pain is from the parietal pleura.
Surfaces of the lung
Costal- facing the ribs
Mediastinal- facing the mediastinum.
Diaphragmatic (base)- facing the diaphragm.
Borders of the lung
Anterior, inferior and posterior border.
The right lung
Larger, heavier, shorter and wider lung containing:
3 lobes, separated by 2 fissures:
Superior
Middle
Inferior
Fissures- oblique and horizontal.
Contains 10 bronchopulmonary segments.
The left lung
Smaller lung.
Contains 2 lobes separated by one fissure- the oblique fissure.
Superior and inferior lobes.
Cardiac notch- space for where the heart sits.
Contains lingula, ‘tongue’-like structure.
Hilum
Root of the lung that contains the structures that enters and exits the lungs.
Contains:
- Main bronchus, posteriorly.
- Pulmonary arteries, superiorly.
- Pulmonary veins, inferiorly.
- Pulmonary nerve plexus entry.
- Lymphatic vessels and nodes.
- Bronchial veins and arteries.
Trachea
Main airway that starts from the larynx (at C6) and bifurcates at T4/5 (sternal angle).
Contains:
- C-shape hyaline cartilage that allows its flexibility and resistance to tension.
- Trachealis muscle, posteriorly which allows constriction of the airway.
- Carina- the point at which it bifurcates into the bronchi.
- Ciliated epithelium and mucous membranes.