The pleural cavities, lungs and percardium Flashcards
What is the inferior mediastinum divided into?
The anterior, middle and posterior mediastinum
Where is the anterior mediastinum located?
Between the sternum and anterior body of the pericardial sac
What does the anterior mediastinum contain?
A few lymph nodes and the thymus gland in childhood
What is contained in the middle mediastinum
The pericardium and heart, roots of the great vessels, and the hilum of each lung
What is contained in the posterior mediastinum?
The oesophagus with the vagus nerves, descending thoracic aorta, azygos vein, and thoracic duct
What is the structure of the pleura?
Pleural cavity between visceral and parietal layers
What does the visceral layer of the pleura cover?
The lung
What does the parietal layer of the pleura cover?
The inner surface of the thoracic wall, the upper surface of the diaphragm, and the sides of the pericardium
Where do the visceral and parietal layers of the pleura become continuous with each other?
At the lung hila
What is the importance of the pleural cavities?
The mechanisms of respiration are dependent upon two sealed pleural cavities
What is found within the pleural cavity?
A small amount of serous fluid
Where is the costodiaphragmatic recess?
Between the parietal pleura lining the superior diaphragmatic surface and the parietal pleura lining the thoracic wall
When is the costodiaphragmatic recess deepest?
During full expiration
What is the difference in the appearance of the 2 plural cavities?
The left pleural cavity is smaller as the heart extends further to the left
Which pleural layer is insensitive?
Visceral
How is the parietal pleura innervated?
Receives segmental innervation from intercostal nerves and the phrenic nerves, which supply mediastinal and diaphragmatic parietal pleurae
How many lobes and fissures are in the right lung?
Three lobes (upper, middle, and lower) and two fissures: the oblique and transverse (or horizontal) fissures.
What is the difference between the size and shape of the lungs?
The left is smaller and narrower
How many lobes and fissures are in the left lung?
2 lobes (upper and lower) and 1 fissure (oblique)
What is the lingula?
a small tongue of upper lobe of the left lung between the fissure and the cardiac notch; it corresponds to the middle lobe of the right lung
Where is the apex of the lungs?
2.5cm above medial third of clavicle
What is observed at the 2nd costal cartilage concerning the surface markings of the pleurae?
Pleurae from both sides meet
What is observed at the 4th costal cartilage concerning the surface markings of the pleurae?
Left diverges to accommodate the heart
What is observed at the 6th costal cartilage concerning the surface markings of the pleurae?
Right descends to this point
What is observed at the 8th costal cartilage concerning the surface markings of the pleurae?
Crosses mid-clavicular line
What is observed at the 10th costal cartilage concerning the surface markings of the pleurae?
Crosses mid-axillary line
How far down does the lung extend?
Reaches just below the neck of the 12th rib posteriorly
How do the surface markings of the lungs compare with the surface markings of the pleurae?
The surface markings of the lungs coincide with those of the pleurae, except inferiorly, where they are approximately two rib spaces higher in full expiration.
Thus, the lungs lie opposite the 6th costal cartilage in the mid-clavicular line, the 8th costal cartilage in the mid-axillary line, and reach the 10th rib posteriorly on both sides
Where does the oblique fissure start and end?
Starts posteriorly next to the spine of T3, and curves downwards and forwards to end parallel with the 6th costal cartilage
What is the easiest way to find the position of the oblique fissure?
If the arm is abducted, the medial border of the scapula is roughly in the same line as the oblique fissure
Where is the transverse fissure located in the right lung?
It lies parallel with the 4th costal cartilage, meeting the oblique fissure at the 5th rib in the mid-axillary line
What structures are located medially to the left lung?
The left ventricle, the arch of the aorta, and the descending aorta
What structures are located inferomedially to the left lung?
The oesophagus moves to the left in front of the aorta, and may groove the left lung
What structures are located inferior to the left lung?
The lung lies on the diaphragm, with the stomach, spleen, and left kidney below
What structures are lateral to the lungs?
The costal cartilages and ribs with the intervening intercostal muscles
What structures are located medially to the right lung?
The right atrium, with a short length of inferior vena cava entering it, the superior vena cava with the azygos arch entering it, the brachiocephalic trunk, and trachea
What effect does the position of the liver have on the right lung?
Pushes the lung upwards, making it shorter but broader than the left
What are the structures at each lung hilum?
- A bronchus
- Pulmonary arteries
- Pulmonary veins
- Bronchial arteries
- Lymph nodes
- Nerves of the pulmonary plexus
Where do the bronchial arteries arise and what do they supply?
Arise from the aorta and supply the bronchial tree
What do lymph nodes at the hila drain?
The tracheobronchial nodes
Where do the bronchi lie in the hilum?
Posteriorly
Where do the arteries lie in the hilum?
Superiorly
Where do the veins lie in the hilum?
Anteroinferiorly
How many bronchi are at each hilum?
One on the left as it is larger
(the right main bronchus and the upper lobe bronchus)
Two on the right
How are the bronchi held open?
Plates of cartilage and composed of fibromuscular membrane
What lines the bronchi?
Pseudostratified ciliated columnar epithelium
What is the primary bronchi?
The main bronchus
What is the secondary bronchi?
The lobar bronchi
What is the tertiary bronchi?
Branches that go to bronchopulmonary segments
How many bronchopulmonary segments are there in each lung?
10
How many segments there in the upper lobe?
3 (apical, anterior and posterior)
How many segments are there in the middle lobe?
2 (medial and lateral)
How many segments are there in the lower lobe?
5 (apical, anterior, posterior, medial and lateral)
How many segments are there in the lingula?
2 (upper and lower)
How does lymphatic drainage occur from the lung?
Both plexuses converge on lymph nodes at the lung hila
Efferents from hilar nodes drain to nodes around the carina, the tracheobronchial nodes
These drain upwards to mediastinal nodes and then to the thoracic duct or right lymphatic duct
How may hilar (bronchopulmonary) nodes appear in a smoker?
Blackened
What is the nerve supply to the lungs?
The vagus nerve (parasympathetic) for bronchoconstriction to decrease dead space, thus making quiet respiration more efficient
The thoracic sympathetic chain for bronchodilatation to increase air flow when necessary
Where does the left phrenic nerve descend?
Over the left ventricle, passes anterior to the hilum
Where does the right phrenic nerve descend?
Alongside the superior vena cava, right atrium, and inferior vena cava. Passes anterior to the hilum
Where does the left vagus nerve lie?
Where does it descend?
The aortic arch
Passes posterior to the hilum and converges with the right vagus to form the oesophageal plexus
Where does the right vagus nerve lie?
Where does it descend?
Passes medial to the azygos venous arch to lie on the right of the trachea
Passes posterior to the hilum and converges with the right vagus to form the oesophageal plexus
What shape is the fibrous pericardium?
Concial
What is the upper end of the pericardium fused with?
The ascending aorta, pulmonary trunk, and superior vena cava
What is the lower end of the pericardium fused with?
The central tendon of the diaphragm
What is enclosed within the fibrous pericardium?
The heart and roots of great vessels
What is the pericardial cavity?
The potential space between the two layers of serous pericardium, and normally contains a thin film of fluid, enabling the heart to move and beat in a frictionless environment
What are the 2 layers of serous pericardium?
Parietal layer lines the fibrous pericardium
This is reflected to cover the heart and great roots as the visceral pericardium
Where is the transverse sinus located?
Within the pericardial sac between the arterial and venous ends of the heart
What is anterior to the transverse sinus?
The ascending aorta and pulmonary trunk
What is posterior to the transverse sinus?
The superior vena cava and pulmonary veins
What is the clinical relevance of the transverse sinus?
It can be used for passing slings through when clamping off the major vessels during cardiac surgery
What is the oblique sinus?
A recess in the pericardial cavity between the pulmonary veins and behind the left atrium.
It allows distension of the left atrium. It is similar to the hilum of the lung, where the visceral layer reflects to become parietal
How are the fibrous and serous parietal layers of the pericardium innervated?
They receive a somatic sensory supply from the phrenic nerves
How is blood supplied to the fibrous and serous parietal layers of the pericardium?
By small pericardiacophrenic branches of the internal thoracic artery
How is sensory information transported from the pericardium?
The visceral layer has sensory afferents which travel with the sympathetics
