12.10b Lungs and Ventilation Flashcards
How do the lungs provide an efficient gas exchange surface?
Short diffusion distances and large surface area.
What is the structure of the trachea?
Tube-like structure that carries air from the mouth to lungs.
What is the structure of the bronchi?
- The trachea splits into two bronchi as it enters the lungs
- Which allows air to travel to the left and right lung
What is the structure of the bronchioles?
- Bronchi further divide into smaller branches called bronchioles.
- These then supply alveoli with air.
Describe and explain how the lungs are adapted to allow rapid exchange of oxygen between air in the alveoli and blood in the capillaries around them.
Many alveoli/ alveoli walls folded provide a large surface area;
- Many capillaries provide a large surface area (So) fast diffusion;
- Alveoli or capillary walls/ epithelium/ lining are thin/ one cell thick / short distance between alveoli and blood;
- Flattened/ squamous epithelium (So) short diffusion distance/ pathway / (So) fast diffusion;
- Ventilation / circulation; So Maintains a diffusion / concentration gradient (So) fast diffusion;
Describe the gross structure of human gas exchange system and how we breathe in and out
Named structures – trachea, bronchi, bronchioles, alveoli
- Above structures named in correct order OR Above structures labelled in correct positions on a diagram
- Breathing in – Diaphragm contract and external intercostal muscles contract
- Volume increases and pressure decreases in thoracic cavity.
- Breathing out – Diaphragm relaxes and internal intercostal muscles contract
- Volume decrease and pressure increase in thoracic cavity
Outline the process of inspiration/inhalation.
- External intercostal muscles contract pulling ribcage up and out.
- (Internal intercostal muscles relaxes)
- Diaphragm contracts and pulls down.
- Thoracic cavity volume increases.
- Pressure in the lungs LOWER than atmospheric pressure.
- Air moves into the lungs down a pressure gradient.
Outline the process of expiration/exhalation.
- External intercostal muscles relax.
- (Internal intercostal muscles contract)
- Ribs are pulled downwards and inwards.
- Diaphragm relaxes and moves upward.
- Thoracic cavity volume decreases.
- Pressure in the lungs is greater than atmospheric pressure.
- Air moves out of the lungs down a pressure gradient.
What is a squamous epithelial cell?
One cell thick layer with very thin diffusion distance to optimise diffusion
What are alveoli?
Small sacs at the end of the bronchioles that act as a barrier between air in the lungs and the blood
What are some adaptations of the alveoli?
- Very large surface area- maintain higher diffusion rates.
- Rich blood supply- circulates to maintain a large concentration gradient between gases in the blood and alveoli.
- Squamous epithelial- very thin, short diffusion pathway.
- Dense capillary network- short diffusion pathway
Explain the diffusion of gases when deoxygenated blood arrives to the lungs.
- Deoxygenated blood from pulmonary artery has a low concentration of oxygen and high concentration of carbon dioxide (compared to air inside alveoli)
- As this blood reaches capillaries surrounding alveoli, oxygen diffuses into blood across squamous epithelial membrane and into endothelial wall of capillary. Moves from high to low O2 concentration.
- Simultaneously, CO2 moves from blood into alveoli. Concentration of CO2 in blood from pulmonary artery is greater than inhaled air in alveoli.
- Both gases simply diffuse in opposite directions from high to low concentrations.
- Blood is circulated away from alveoli by heart contractions, moving newly oxygenated blood away from lungs and back to heart to be pumped around body.
How is a concentration gradient of CO2 and O2 maintained at the alveolar squamous epithelium?
- Through the circulation of blood by the heart and ventilation of air through breathing.
- This ensures gases diffuse efficiently in opposite directions and don’t reach equilibrium.
