Gas Exchange in Mammals Flashcards
What are the parts of the human gas exchange system?
The trachea, the bronchi, the bronchiolitis, the alveoli, the diaphragm, the ribs and the intercostal muscles.
How do gases move in and out of the alveoli?
Oxygen diffuses from the air space into the blood across the alveoli epithelium and then the capillary epithelium. Carbon dioxide moves in the opposite direction.
How is the human gas exchange system adapted for gas exchange?
- The branching of the trachea into the bronchi and bronchioles increases the surface area for gas exchange.
- The large number of alveoli and the folding of their wall increases the surface area for gas exchange.
- The aveolar epithelium is thin meaning there is a short diffusion distance for oxygen and carbon dioxide.
- The alveoli are surrounded by many capillaries that provide a large surface area for gas exchange.
- Ventilation of the lungs helps maintain a concentration gradient.
How does inspiration occur?
- The external intercostal muscles contract and the internal intercostal muscles relax, which pulls the ribcage upwards and outwards.
- The diaphragm contracts and flattens.
- The volume of the thoracic cavity increases.
- The pressure in the thoracic cavity decreases and so the air moves into the lungs by moving down a pressure gradient.
How does expiration occur?
- The external intercostal muscles relax and the internal intercostal muscles contract, which pulls the ribcage inwards and downwards.
- The diaphragm relaxes and becomes dome shaped.
- The volume of the thoracic cavity decreases.
- The pressure in the thoracic cavity increases and so the air moves into the lungs by moving down a pressure gradient.
What is a spirometer used for?
To take measurements involving the volume of air in the lungs.
What is the tidal volume?
The volume of air in a normal breath at rest.
What is the forced expiration volume?
The greatest volume of air that a person can breathe out in one second.
What is the forced ventilation rate?
The number of breaths per minute.
What is the forced vital capacity?
The total volume of air that the person can breathe out in a single breath.
What is pulmonary ventilation rate?
Ventilation rate x tidal volume
What are the symptoms of fibrosis?
Fatigue, shortness of breath, dry cough and chest pain.
How does fibrosis affect the lung structure and function?
- Scar tissue forms due to exposure to certain particles, infection or pulmonary TB.
- Scar tissue is less elasticated and thicker compared to normal lung tissue meaning the lungs cannot expand properly. The rate of diffusion is also slower across the thickened alveolar epithelium.
- This decreases the tidal volume and the FVC of the lungs. This reduces the rate of gas exchange of oxygen to cells for respiration and the release of energy, which causes fatigue.
- To make up for the lack of air the ventilation rate increases.
What are the symptoms of emphysema?
Shortness of breath and weakness.
What causes emphysema?
- Long-term smoking and exposure to air pollution means particles get trapped in the alveoli.
- This causes inflammation and triggers phagocytes to release plaster which is an enzyme that breaks down the elastin of the alveoli.
What effect does emphysema have on lung function and structure?
- The destruction of the elastin of the alveoli makes them less elastic.
- This decreases the FEV and the rate of gas exchange. This then means that less oxygen goes to cells for respiration and the release of energy and carbon dioxide builds up in the blood.
- The ventilation rate increases to make up for the lack of air.
What causes asthma? What effect does asthma have on the structure and function of the lungs?
- The muscle wall of the bronchi contract which causes the goblet cells in the bronchi to secrete mucus.
- People with asthma secrete an excess amount of mucus which reduces the diameter of the Airways and reduces the flow of air.
- This reduces the FEV of the lungs and increases the ventilation rate.
