04-10-21 - Structure of the Lungs Flashcards
What is anatomic dead space in terms of respiration?
Why is it called this?
What is the dead space in the process?
- Everything above the respiratory bronchioles is anatomic dead space
- This is because there is no gas exchange function
- Nose, nasal cavity and sinuses
- Nasopharynx and soft palate
- Larynx
- Trachea
Where can the trachea be felt?
What does it consist of?
Where is it positioned in relation to the spine?
How is the diameter of the trachea altered?
What is it called when an emergency airway is made from the trachea/larynx?
- It is palpable (can be felt) anteriorly, above the suprasternal notch
- It consists of c-shaped rings of hyaline cartilage supporting a fibro-elastic and muscular air-transport tube
- It starts at the C6 (6TH cervical vertebrae of the spine), ends at the T4/5 (4TH/5TH thoracic vertebrae)
- Trachealis muscle (Posteriorly positioned) alters tracheal diameter.
- Tracheostomy/laryngotomy
How many lobes, lobar (secondary) bronchi, main bronchi do each lung have?
What is the division between the main bronchus of each lung called?
What are the differences between the main bronchi of each lung?
What does each lobar bronchus divide into?
How are the bronchi oxygenated?
- The right lung has 3 lobes, whereas the left lung has 2 lobes.
- Due to the right lung having 3 lobes, it has 3 (secondary) lobar bronchi, The left lung has 2 lobes, so has 2 lobar bronchi.
- Both lungs only have 1 main bronchus, each of which branch off from the trachea, with the division between these main bronchus being called the carina.
- The right lungs main bronchus is more vertical, shorter and wider than the lefts, so foreign bodies are more likely to go into the right lung.
- Each lobar bronchus then divides into segmental bronchi
- The bronchi are supplied with oxygenated blood via the bronchial arteries.
What do the segmental bronchi divide into?
Where is the only place gas exchange can occur?
- The segmental bronchi continue dividing into smaller and smaller branches
- They become conducting bronchioles, then terminal bronchioles, then respiratory bronchioles, and then final become alveoli
- The bronchioles decrease in dimeter along the way
- Gas exchange can only occur in the respiratory bronchioles with alveoli on them.
What epithelia is the trachea lined with?
What epithelia is the bronchi lined with?
What happens to the cartilage when bronchi branches into the lungs?
- The histology of the trachea is characterized by pseudostratified, ciliated, columnar epithelium, with goblet cells (simple columnar) for mucus synthesis and secretion
- This is known as respiratory epithelium
- The histology of the bronchi still has respiratory epithelium, but the height is decreased (flattened) compared to the trachea.
- As the bronchi branch into the lungs, the c-shaped cartilage rings are replaced by cartilage plates.
What happens to the bronchioles as the bronchial tree divides?
What happens to the epithelium and what surrounds it?
What happens to the cartilage and glands?
How does the bronchiole stay open?
How is this process different in people with asthma?
- As the bronchial tree divides and branches, it eventually formed bronchioles with very thin lumen (<1mm in diameter)
- The epithelium changes to become ciliated columnar (thinner/flatter), and there is a surrounding band of smooth muscle
- The cartilage and glands disappear
- The bronchiole is held open by surrounding lung tissue.
- In asthma, the smooth muscle in the wall may excessively narrow the lumen
How does epithelium change in the respiratory bronchioles?
What disappears?
What begins to occur?
- In the respiratory bronchioles, the epithelium becomes non-ciliated cuboidal (thinner and flatter)
- Goblet cells disappear.
- Gas exchange begins to occur in the respiratory alveoli that bud from the respiratory bronchioles.
What are alveoli?
What happens in the alveoli?
How are they found?
How are alveoli separated from each other?
What does this separation allow?
- Alveoli are the basic structural and functional unit of the lung, where gaseous exchange takes place.
- Alveoli are found as outpocketings of respiratory bronchioles, alveolar ducts, and alveolar sacs.
- Alveoli are separated from one another by septae (alveolar wall), which is a thin membrane containing capillaries.
- The septae is the air-blood barrier for gas exchange
What is pleura?
What is the pleural cavity?
What does it contain?
What are the 2 different types of pleura?
What are the potential different names for the pleura?
- Pleura are the membranes which cover/line the lungs within the cavity, as well as the walls.
- The pleural cavity is the space enclosed by the pleura.
- It contains serous fluid to lubricate the pleural surfaces, allowing for smooth, gliding movements between surfaces.
- The visceral pleura refers to the pleura covering the lungs
- The parietal pleura are the membranes which cover/line the cavity walls
- The pleura are continuous with each other.
- Depending on where the pleura is located, a different name is used.
What is the pressure in the pleural cavities?
Why is it like this?
What can happen if damage is done to the pleural membranes?
- In the pleural cavities at the bottom of each lung, there is a gap
- This gap is at a slight negative pressure.
- This means the lung is always partially inflated at all times
- Keeping the lung partially inflated reduces the energy required to re-expand the lung.
- If damage is done to the pleural membranes, the negative pressure can be lost, resulting in a collapsed lung
How are lungs separated from one another?
• The lungs are separated from one another by the mediastinum.
How is the structure of the left lung different from the right?
Why is this?
What are the different structures of the left lung?
What are they for?
- The left lung contains 2 lobes instead of 3
- The left lung is slightly longer and narrower than the right lung
- This is predominantly to make room for the heart and pericardium.
- The oblique fissure separates the 2 lobes of the lung.
- The cardiac notch houses the structures of the heart
- The base has the diaphragmatic/inferior surface, which is above the diaphragm.
What is the hilum of the lung?
What structures does it contain?
What type of blood enters the lungs?
What type of blood/ leaves the lungs?
What vessels are used?
Where does the blood come from/go?
Why is this strange?
- The hilum is the root of the lung whereby structures pass into and out of the lung
- The hilum of the left lung contains the main bronchus, pulmonary artery, pulmonary veins (superior and inferior), hilar lymph nodes
- Deoxygenated blood enters the left lung from the right ventricle of the heart via the pulmonary artery
- Oxygenated leaves the left lung towards the left atrium via the pulmonary veins
- Arteries normally carry oxygenated blood, and veins normally carry deoxygenated blood, but in this case, it is reversed.
How is the structure of the right lung different from the left?
Why is this?
What are the different structures of the right lung?
What are they for?
• The right lung contains 3 lobes instead of 2
• The right lung is slightly wider, but shorter than the left lung.
• This is mainly due to the right dome of the diaphragm being higher on this side.
• Since there is an extra lobe, there is an extra fissure to separate the lobes
• This is called the horizontal/transverse fissure.
The base has the diaphragmatic/inferior surface, which is above the diaphragm.
What is the hilum of the right lung?
What structures does it contain?
What type of blood enters the lungs?
What type of blood/ leaves the lungs?
What vessels are used?
Where does the blood come from/go?
Why is this strange?
- The hilum is the root of the lung, whereby structures pass into and out of the lung.
- The hilum of the right lung contains main bronchus, pulmonary artery (superior and inferior), pulmonary veins (superior and inferior), hilar lymph nodes.
- Deoxygenated blood enters the right lung from the right ventricle of the heart via the pulmonary arteries
- Oxygenated leaves the right lungs towards the left atrium via the pulmonary veins
- Arteries normally carry oxygenated blood, and veins normally carry deoxygenated blood, but in this case, it is reversed.
How does the lung sit superiorly and inferiorly?
How is this affected by breathing?
- Superiorly, the apex of the lung and pleura are above the clavicle
- Inferiorly, the pleura extends down the costal margin, but the lungs end 2 ribs higher
- During normal/quiet respiration, the lungs do not extend to the lower parts of the pleural cavity.
What are the two types of intercostal muscle?
What are they each used for?
How are each positioned?
- The internal intercostal muscles – These depress the ribs, pulling them inferiorly during deep exhalation.
- The external intercostal muscles – These elevate and lift the ribs during deep inhalation.
- The internal intercostal muscles run from bottom right towards top left.
- The external intercostal muscles run from bottom left to top right
What is the structure of the diaphragm like?
What nerve supplies it?
- The diaphragm is muscular at its periphery, but is tendinous centrally
- It has left and right domes
- Motor and sensory supply is by the phrenic nerve (c3, 4, 5 keeps the diagram alive)
Label the structures on this normal chest radiograph.
1
What is a pneumothorax?
What does it lead to?
How is it treated?
What are the signs of a pneumothorax on a chest radiograph?
- A pneumothorax occurs when air enters into the pleural cavity
- This leads to a collapsed lung
- The air must be removed to allow the lung to expand again
- A needle is inserted just above the rib to avoid damage to the neurovascular bundle, that runs just inferior to each rib.
- On a chest radiograph, the right lung only fills about half of the right thoracic cage, with the vascular markings at the border of the lung
