Anatomy of the Thoracic walls, airways, and lungs Flashcards
Describe the structural organisation of the entire lung
It’s made up of the lung, and the chest wall outside of it. Inbetween them are 2 connective tissue membranes. The one of the outside of the lung is called the visceral pleura, and the one on the inside of the chest wall is called the parietal pleura. The chest wall is comprised of the ribcage, sternum, intercostal muscles, and its natural recoil is outward. The lung is a spongy elastic tissue which has a natural recoil of inward. The pleura also have a couple of mL of pleural fluid (lubricant). Due to the natural recoil of the lung and chest wall, and the small volume of fluid, the intra-pleural cavity pressure is always negative (compared to atmospheric) about -5cmH2O.
Describe the process of breathing in terms of movement of the chest and lungs
Diaphragm contract, moving downward, and the intercostal muscles contract pushing the ribcage up and out, creating a larger cavity in the chest which our lungs expand to fill. Air is drawn into the lungs where it transfers into the blood, which is taken to the tissues and exchanged for CO2. The CO2 is transferred to the lungs. The diaphragm and intercostal muscles relax, decreasing the chest cavity, which results in the exhalation of CO2. Inhale 12000L of air a day.
Describe the structure of the airways
Conducting airways are the ones that conduct air, they are cartilaginous. Held open by layers of offset C rings which have openings at the dorsal side (back). Important in trachea as it makes way for the oesophagus and doesn’t impede swallowing
Describe the structure of the bronchioles
Bronchioles are not held open by C rings, they require other mechanisms for patency. Surfactant reduces surface tension and prevents airway wall collapse. Bronchioles smaller than 2mm are called small airways
Describe the structure of the bronchial tree and the function that it serves
Dichotomous branching ensures that as the number of airways increases, the length and diameter decreases proportionally, but the cross sectional area increases greatly. This means that air flow resistance is rapidly decreased, apart from at the start due to the larger airway generations (generations 3-5). The small airways greatly reduce the resistance and when the air is in the respiratory zone there is barely any resistance. Acini are the discrete anatomical regions of the alveolar regions (cluster of alveoli)
Describe COPD
COPD is a disease causes by a difference in the structure or anatomy of the small airways which results in the patient having difficulty breathing
Describe the structure of the airway wall from the outside in
C Rings are on the outside surrounding the submucosa which consists of a ring of smooth muscle, blood vessels (systemic circulation) and ECM holding it all together. Submucosal glands are present and have their distal portion embedded in the smooth muscle and project into the airway lumen and the epithelium. This is so that smooth muscle contractions result in the expulsion of mucus into the airway lumen. Epithelium of the lumen consists of mucus producing goblet cells and cilia. In healthy individuals, a thin layer of mucus covers the epithelium. The mucus has the role of trapping inhaled particles and the cilia beat to remove it - mucociliary clearance
What is a way that the alveolar region maximises the sa:v ratio
It fills all the gaps - folds back on itself, going between the airways
Describe the structure and properties of the cells that make up the alveolar region
Type 1 alveolar cells - extremely thin, ideal for gas exchange. Close relation with capillary endothelial cells, and erythrocytes. 95% of surface
Type II alveolar cells - Can replicate to replace Type 1 cells but also secrete surfactant and anti-proteases from granules. Also contribute to xenobiotic metabolism.
Macrophages - About 2-3 per alveolus in a healthy individual. Ingest inhaled particles and microbes.
Fibroblasts - Secrete ECM which holds everything together
