3 The nasal passages and lungs Air is drawn into the body via the nose or mouth. There are advantages to breathing through your nose:the air is warmed so that it is closer to body temperaturetiny hairs and mucus in the nose filter the air, preventing larger dust and pollen particles reaching the alveolimucus moistens the air, making it easier for the alveoli to absorb.Air then travels through the larynx, trachea (windpipe), bronchi (one bronchus to each lung) and bronchioles to the alveoli, where oxygen passes into the bloodstream.
4 Mechanisms of breathing – inspiration When you breathe in:Intercostal muscles pull ribs up and outintercostal muscles between the ribs contract, pulling the chest walls up and outthe diaphragm muscle below the lungs contracts and flattens, increasing the size of the chestthe lungs increase in size, so the pressure inside them falls. This causes air to rush in through the nose or mouth.Diaphragm contracts and moves down
6 Mechanisms of breathing – expiration When you breathe out:Ribs move in and downIntercostal muscles between the ribs relax so that the chest walls move in and down.The diaphragm muscle below the lungs relaxes and bulges up, reducing the size of the chest.The lungs decrease in size, so the pressure inside increases and air is pushed up the trachea and out through the nose or mouth.Diaphragm relaxes and bulges up
8 Gas exchange at the alveoli The alveoli are bunches of tiny air sacks inside the lungs.Each individual sack is called an alveolus.When you breathe in, they fill with air.The alveoli are covered in tiny capillaries (blood vessels).Gases can pass through the thin walls of each alveolus and capillary, and into the blood stream.Gases can also pass from the blood stream, into the alveolus.
10 Composition of inhaled and exhaled air GasAmount in inhaled airAmount in exhaled airOxygenCarbon dioxideNitrogenWater vapour21%Very small amount79%Small amount17%3%79%Large amountWhat are the main differences between inhaled and exhaled air?Ask the students to compare the relative amounts. Point out that:The amount of oxygen inhaled is greater than the amount of oxygen exhaled. Consider the efficiency of respiration at the cells.The amount of carbon dioxide is greater in exhaled air.The amount of nitrogen is the same.Mouth to mouth resuscitation works because there is still a lot oxygen left in exhaled air.Why does mouth-to-mouth resuscitation work?
11 Respiratory rate is how many breaths you take per minute. Measuring breathingTidal volume is the amount you breathe in and out in one normal breath.Respiratory rate is how many breaths you take per minute.Minute volume is the volume of air you breathe in one minute.Vital capacity is the maximum volume of air you can breathe out after breathing in as much as you can.Clarify and expand on the definitions with the studentsResidual volume is the amount of air left in your lungs after you have breathed out as hard as you can.
13 Calculating minute volume Remember:Minute volume is the volume of air you breathe in one minute.You can calculate a person’s minute volume by multiplying the volume of air they breathe in one breath, by their respiratory (breathing) rate.QuestionIf you breathe 14 times in one minute (respiratory rate) and you breathe 0.5 litres in each breath, what is your minute volume?Get students to calculate the answer before revealing it.Point out that at rest, the volume of air breathed in each breath will be the person’s tidal volume. During extreme exercise, it may be closer to their vital capacity.Answer:Minute volume = 14 × 0.5 litres= 7.0 litres
14 Breathing during exercise Muscle cell respiration increases – more oxygen is used up and levels of CO2 rise.The brain detects increasing levels of CO2 – a signal is sent to the lungs to increase breathing.Breathing rate and the volume of air in each breath increase. This means that more gaseous exchange takes place.The brain also tells the heart to beat faster so that more blood is pumped to the lungs for gaseous exchange.More oxygenated blood gets to the muscles and more CO2 is removed.
15 The effects of exercise on lung structures In the long-term, regular exercise strengthens the respiratory system.The respiratory muscles (the diaphragm and intercostals) get stronger, so they can make the chest cavity larger.This larger chest cavity means more air can be inspired, therefore increasing your vital capacity.More capillaries form around the alveoli, so more gaseous exchange can take place.Relate these facts to improvements in performance. Emphasise that lungs are NOT muscles and therefore do not increase in size – they function more efficiently.Gas exchange can now take place more quickly meaning exercise can be maintained at a higher intensity for longer.
16 Key Terms The role of the blood As well as controlling body temperature, one of the basic roles of the blood is as a transporter and it is through this function that the oxygen, glucose and waste products are all transported around the body.Key TermsGlycogen: the main form of carbohydrate storage, which is converted into glucose as needed by the body to satisfy its energy needsLactic Acid: a mild poison and waste product of anaerobic respirationGaseous Exchange: the process where oxygen is taken in from the air and exchanged for carbon dioxide.
17 Make sure you understand the process of gaseous exchange and that aerobic respiration is with oxygen. Knowing activities that require aerobic respiration is also vitalIt is crucial that you are able to identify the difference between aerobic and anaerobic exercise and respiration. You should be able to give good examples of activities for both