Lecture 6 Flashcards
What occurs in the respiratory zone?
Gas exchange.
What does the respiratory zone comprise of?
- Respiratory bronchioles.
- Alveolar ducts.
- Alveoli sacs.
- Alveoli.
Where does the majority of gas exchange occurs?
In the delicate balloon shaped alveoli. The alveoli are in contact with the capillaries. The combined distance air must travel is about 0.5microm.
What are the majority of cells in the respiratory bronchioles?
Cuboidal epithelial and the club cells.
What do club cells do?
Dome shaped secretory cells that can also act as stem cells to regenerate the lower airways.
What do the club cells secretions contain?
Lipoproteins that prevent luminal adhesion if the airway was to collapse. It has anti-microbial properties.
Describe Type 1 pneumocytes?
Squamous cells. Full of cytoplasm with a bump (nucleus sits). Bulk of gas exchange occurs here. Comprise of 95% of surface area of the alveoli.
Describe Type 2 pneumocytes?
Surfactant cells, that secrete surfactant (mainly a phospholipid) which is important in reducing the surface tension in the alveoli. This reduces the work of breathing.
Describe alveolar macrophages?
Wandering cells. That are occasionally in the septa as well. They are your last defence (important with heart failure).
What is the connective tissue between the capillaries?
Collagen and elastin (make up the septa). This helps support the capillary entrance and the alveoli.
What do the elastic fibres provide in the inter-alveolar septa?
Recoil associated with tidal breathing. They surround the bronchi and bronchioles and provide elasticity to the alveoli.
What do the collagen fibres provide in the inter-alveolar septa?
Plays an important structural component to the inter-alveolar septum.
What happens when there is an increase in collagen?
Fibrotic lung disease characteristic. Basically the septa will be thicker and stiffer and the diffusion distance for air will be bigger thus higher gradient of pressures.
How many circulations are in the lung?
Two - pulmonary and bronchial circulation.
Describe the pulmonary circulation?
This is a low pressure conducting circuit that carries deoxygenated blood to the alveoli for oxygenation which then returns to the left atrium.
Describe the bronchial circulation?
This is a high pressure circulation that supplies the tissues of the conducting zone.
Describe the flow of the pulmonary circulation?
Start with the pulmonary arteries which carry oxygen poor blood form the right side of the heart. Runs with airways and then you get to pulmonary capillaries, then you get pulmonary veins where they are mixed venous (oxygen has been introduced). They travel up to the hilum of the lung.
Describe pulmonary arteries?
They are large and poorly oxygenated.
Describe the systemic vessels?
In the walls of the airway, high pressure and much smaller (microscopic).
Describe the function of the pulmonary circuit?
Conducting funciton.
Where are the arteries in the pulmonary circuit?
Next to bronchi.
Where are the veins in the pulmonary circuit?
In parenchyma.
What are the pressures in the pulmonary circuit?
Arteries:
25-15mmHg.
Veins:
5-0mmHg.
Describe the function of the systemic circuit?
Supply tissue of the lung with oxygen and remove carbon dioxide.
Where are the arteries in the systemic circuit?
In ways of airways.
Where are the veins in the systemic circuit?
The veins anastomose and are azygous.
What are the pressures in the systemic circuit?
Arteries:
120-80mmHg to maybe 40mmHg.
Veins:
