Chapter 11: Gas exchange in humans Flashcards
What are the features of gas exchange surfaces in humans?
Large surface area, thin surface, good blood supply and good ventilation with air
What is the function of cartilage in the trachea?
Helps prevent the trachea from collapsing at times when the air pressure is lower than the pressure outside it
What is the role of the ribs, the internal and external intercostal muscles and the diaphragm?
Ribs: protect the lungs and heart from physical damage
Internal and external intercostal muscles: when breathing in, external intercostal muscles contract, pulling the rib cage upwards and outwards to increase the volume of the thorax. When breathing out, the external intercostal muscles relax, causing the rib cage to drop down to its normal position, decreasing the volume in the thorax
Diaphragm: when breathing in, the muscles of the diaphragm contract, pulling the diaphragm downwards and increasing the volume in the thorax. As the volume of the thorax increases, the pressure inside it falls below atmospheric pressure, causing air to flow in along the trachea and bronchi into the lungs
How do you investigate the differences in composition between inspired and expired air?
Use the limewater test; fill 2 boiling tubes with lime water, inspire through the mouthpiece, and water will be drawn in through one boiling tube. When you expire, air will be blown into the other boiling tube. As limewater turns milky when carbon dioxide is bubbled through it, the first boiling tube will remain clear, but the second boiling tube will become cloudy
What are the differences in composition between inspired and expired air?
Inspired air has 21% oxygen compared to 16% in expired air, as our body cells use oxygen in respiration; however, expired air mixes with normal air in the bronchi and trachea, so we breathe out a mixture of air in the alveoli and atmospheric air. Inspired air has 0.04% carbon dioxide, compared to 4% in expired air. This is because body cells produce carbon dioxide in aerobic respiration, and it diffuses out of the blood and into the alveoli. Water vapour is higher in expired air than in inspired air due to it being a by-product of respiration
How do you investigate the effects of physical activity on the rate and depth of breathing?
Count the number of breaths taken at rest, and measure average chest expansion over 5 breaths using a tape measure held around the chest. Exercise for a set time, and immediately after, count the number of breaths taken and measure the average chest expansion over 5 breaths. They both will have increased
What is the link between physical activity and the rate and depth of breathing?
During physical exercise, muscles require more energy, meaning oxygen is used faster, and carbon dioxide needs to be released faster. An increased carbon dioxide concentration in the blood is detected by the brain, leading to an increased rate and greater depth of breathing
What is the role of goblet cells, mucus and ciliated cells?
Goblet cells: present on thin bones inside the nose, secrete mucus which traps pathogens before they enter the lungs
Ciliated cells: have tiny hair-like projections called cilia, which are always moving, and bacteria or dust particles get trapped in them and the mucus. Cilia sweep the mucus up to the back of the throat so that it doesn’t block the lungs
