Lungs, Pleura and Bronchial Tree Flashcards
Describe the Trachea. Where it does it start and end, and how does it look?
- Wind pipe: a conduit for air from our upper airways down to our lower airways and into our lungs
- Begins at the lower level of the cricoid cartilage at the level of C6
- Ends by bifurcating into two main bronchi at the level of the IV disc bw T4 and T5.
- Hollow tube that is supported by cartilage- not a complete cartilage but a U-shaped ring which is deficient posteriorly and closed off by muscle. àSince supported by cartilage, airways allowed to expand and collapse with different phases of respiration.
Describe the main bronchi, differences between the left and right main bronchi.
What do the main bronchi branch into?
There is a right main bronchus and a left main bronchus- each of which goes to their respective lungs.
- The right main bronchus is shorter, more vertical and wider than the left main bronchus.
=Therefore if you aspirate something, it is more likely to end up in the right bronchus because of its arrangement.
-Usually, the left main bronchus directly enters the hilum of the left lung. But the right main bronchus often divides into he lobar bronchi before entering the hilum of the right lung.
- Next branching is at the lobar bronchi. There is one lobar bronchus for each lobe of the lung.
=Two lobar bronchi on the left and three lobar bronchi on the right.
- Beyond that there are 9-10 segmental bronchi in each lung.
=These each extend into a single bronchopulmonary segment.
Explain the lower airways.
Airways get smaller and smaller as they branch and get closer to the parts of the airways were gaseous exchange occurs - the alveoli (grape like clusters of space right around terminal parts of airway, surrounded by capillaries through which exchanges from the airways to the vascular system.
Distinguish between the lobes on Right Lung and Left Lung.
Right:
- Three lobes: superior, middle and inferior lobe.
=Separated by a horizontal fissure and oblique fissure.
Left:
- Two lobes: superior lobe and inferior one.
=Separated by an oblique fissure.
- Has a cardiac notch formed by the apex of the heart taking up some space in the left side of the thoracic cavity.
=Lingula is a projection associated with the very inferior part of the cardiac notch.
- Each lung has an apex which projects a few cms above rib 1 and therefore can be damaged by penetrating stab wounds to the neck.
- Have a base inferiorly which is concave and follows the shape of the diaphragm below.
Describe the non- respiratory ‘parenchyma’ blood supply.
Other system of blood supply to the lungs.
- Pulmonary blood supply is important for gas exchange but there is a whole lot of lung and CT/ elastic tissue that are non- respiratory parts of the lung, the parenchyma of the lung, which need blood to survive.
- Can get a little bit of movement of blood from the capillary beds supplying the alveoli into the surrounding parenchyma in the immediate vicinity.
- Non-respiratory blood supply/ bronchial supply is derived from bronchial arteries, which are direct branches from the aorta and there are a couple of those which branch off the aorta and run with the
How are the broncho-pulmonary segments supplied? And what is the clinical significance of having segments?
Bronchopulmonary segments:
- Tertiary branching of the bronchi- segmental bronchi each provide air to a single bronchopulmonary segment (9 or 10 segments per lung)
- Segmental arteries and veins follow the branching of the airways.
- Has its own air/ blood supply.
àCan surgically resect a single segment easily by clamping off a single segmental bronchus or can ligate a single artery or vein.
One of the ways of draining fluid in the lungs used in physiotherapy, where the patient lied on the side of the lung that needed to be drained at a tilt such that gravity could aid the drainage.
Describe the contents + nerve of the hilum of the lung for Right lung.
Often see two lobar bronchi- have cartilage around them and so easily identifiable from the pulmonary artery and veins. - See two because the right main bronchus usually branches before entering the hilum of the lung.
- phrenic nerve which runs anterior to the hilum and vagus nerve posterior to the hilum.
=Vagus carries parasympathetic innervation to most of the thoracic, abdominal and pelvic viscera.
In summary, at the hilum of the right lung we can see:
- Two pulmonary bronchi
- Two pulmonary arteries (unlike left lung)- posterior and superior to the pulmonary veins. - Two pulmonary veins- most anterior and most inferior vessels at the hilum .
Describe the contents + nerve of the hilum of the lung for Left lung.
- Only difference in the left lung is that there is only a single left main bronchus- hasn’t branched to the lobar bronchi before it gets to the hilum of the long.
- Also has only one pulmonary artery.
Describe the nerve supply to lungs.
Efferent nerve supply derived from the sympathetic and parasympathetic nervous system.
Sympathetic :
Takes origin from the lateral horn of thoracic spinal cord segments 1-4.
- They will follow the sympathetic efferent’s pathways back towards the spinal cord. Therefore, visceral sensory nerve supply will end up in T1-T4 and deep visceral pain will be referred to dermatomes in this area- the upper thoracic walls.
- Sympathetic chain with branches of the pulmonary nerves heading toward the lungs.
Parasympathetic:
- Does the direct opposite of the sympathetic nerve supply.
- Derived from the brain stem.
Visceral sensory nerves:
- Visceral afferents responsible for reflexes from bronchiole mucosa e.g. coughing reflex travel through the vagus nerve
Discus the lymphatics of lungs, which layer are they found, and where do they drain?
- Found superficially.
- - Drain lymph through the hilum and out towards the bronchomediastinal trunks.
Explain the hilum continuation of parietal and visceral pleura. What is its name?
Hilum is point of reflection of parietal pleura lining the thoracic wall before it continues as visceral pleura lining the lungs themselves.
At the bottom of the hilum- this reflection of the pleura is referred to as the pulmonary ligament.
àNot an actual ligament, just an inferior extension.
What is the pleura and what are they made of including sub parts.
Pleura are critical in allowing effective breathing
- Closed double-layered membrane around each lung
- Two pleural cavities are totally independent of each other.
- Two parts: visceral pleura which lines the lungs so tightly that it sticks to the external surface of the lungs. The other, more external layer is the parietal pleura which lines the body wall, the diaphragm and mediastinum.
- In b/w those two layers is the pleural cavity- this is a potential space.
=Not a large space due to the surface tension provided by the serous fluid by the two layers. This means that whenever one layer moves, the other moves with it, so in effect this isn’t actually a space.
What is the embryological origin of visceral pleura?
As embryo develops, viscera comes into space and drags with it the adjacent membrane. - Some lagging behind as is continuous with the body wall.
- Viscera then enlarges.
Describe the pleural nerve supply
Nerve supply to visceral pleura is derived from viscera itself.
- Sensory nerves innervating the visceral pleura are derived from the viscera itself.
- Follows sympathetic pathway back- therefore referred pain to same zones as lungs. T1- T4. Therefore would expect to get some referred pain back to the T1-4 dermatomes if there is a problem with the visceral pleura.
=Damage to the visceral pleura is dull and diffuse since it follows sympathetic nerve supply
- Parietal pleura lines the body wall has a sensory nerve supply derived from the body wall- mostly from the intercostal nerves. If there is anything wrong with the parietal pleura, it will be referred to the dermatome directly over the affected area.
à Body wall is somatic nerve supply- sharp and highly localized pain.
What happens in pulmonary collapse?
Number of diff types of pulmonary collapse but all due to some substance entering the pleural cavity.
- Lungs recoil due to elasticity and therefore there is no longer capacity for lungs to inflate.
- Treatment: remove air/ fluid using a syringe to aspirate the air. àGo above the rib below to avoid the intercostal neurovascular bundle.
