Gas Exchange in Humans 17/04. Flashcards
What are the 4 features of gas exchange surfaces in humans?
- Large surface area to allow faster diffusion of gases across the surface.
- Thin walls to ensure diffusion distances remain short.
- Good ventilation with air so that diffusion gradients can be maintained.
- Good blood supply to maintain a high concentration gradient so diffusion occurs faster.
What percentage composition of nitrogen, oxygen, carbon dioxide, and water vapor in inspired and expired air?
- Nitrogen
78 - 78. - Oxygen
21 - 17 - Carbon dioxide
0.04 - 4. - Water vapor
Variable - Saturated
What is the function of the rings of cartilage that surround the trachea (and bronchi)?
The function of the cartilage is to support the airways and keep them open during breathing.
If they were not present then the sides could collapse inwards.
What happens during breathing in (inspiration)?
- External intercostal muscles contract and internal intercostal muscles relax, causing the ribs to move upwards and outwards.
- Diaphragm contracts and flattens.
- Volume of the thorax increases, and pressure inside the thorax decreases.
- Air is drawn in.
What happens during breathing out (expiration)?
- External intercostal muscles relax, internal intercostal muscles contract causing the ribs to move downwards and inwards.
- Diaphragm relaxes and becomes dome-shaped.
- Volume of the thorax decreases, and the pressure inside the thorax increases.
- Air is forced out.
Describe the difference in composition between inspired and expired air.
It contains less oxygen.
It contains more carbon dioxide.
It contains more water vapor.
It is warmer.
Why is there less oxygen and more carbon dioxide in expired air than in inspired air?
Oxygen is used in cells for respiration and carbon dioxide is produced as a waste product of respiration. The carbon dioxide is released from the blood at the alveoli and diffuses into the lungs before being exhaled. Thus there is more carbon dioxide in exhaled air.
Why is there more water vapor in expired air than in inspired air?
Water evaporates from the moist lining of the alveoli into the expired air as a result of the warmth of the body.
Describe the effects of physical activity on the rate and depth of breathing.
When exercise is carried out, muscles increase the rate of respiration to produce energy for muscle contraction. Aerobic respiration requires oxygen; thus a greater amount of oxygen is demanded and a greater amount of carbon dioxide is produced as a waste substance that diffuses into the blood.
Why would an increased rate and greater depth of breathing occur?
An increased carbon dioxide concentration in the blood is detected by the brain, leading to an increased rate and greater depth of breathing allowing gas exchange to happen more rapidly, expelling the carbon dioxide whilst taking in more oxygen.
The function of cilia and mucus is often a 3-mark question on the extended paper. The examiners are looking for you to state the following:
- The mucus is produced by goblet cells and traps bacteria, dust, and particles and prevents them from getting into the lungs and damaging the fells there.
- The cilia beat.
- And push the mucus away from the lungs towards the nose and throat where it can be removed.
What is breathing?
The action of drawing air into the body (inspiration) and pushing air and waste gases out of the body (expiration).
How do we show that we breathe out carbon dioxide?
Air is blown through a straw into limewater, the limewater turns from colorless to milky.
Define gaseous exchange.
Gaseous exchange is the movement of oxygen in inhaled air into the blood and the movement of carbon dioxide from the blood into the airways of the lungs.
