Learning objectives a) identify the larynx, trachea, bronchi, bronchioles, alveoli and associated capillaries and state their functions in human gaseous exchange b) describe the process of breathing and the role of cilia, diaphragm, ribs and internal and external intercostal muscles c) explain how the structure of an alveolus is suited for its function of gaseous exchange d) state the major toxic components of tobacco smoke – nicotine, tar and carbon monoxide, and describe their effects on health e) define aerobic respiration in human cells as the release of energy by the breakdown of glucose in the presence of oxygen and state the equation, in words and symbols f) define anaerobic respiration in human cells as the release of energy by the breakdown of glucose in the absence of oxygen and state the word equation g) explain why cells respire anaerobically during vigorous exercise resulting in an oxygen debt that is removed by rapid, deep breathing after exercise Learning objectives a) identify the larynx, trachea, bronchi, bronchioles, alveoli and associated capillaries and state their functions in human gaseous exchange c) explain how the structure of an alveolus is suited for its function of gaseous exchange The Respiratory System • The respiratory system comprises various organs that facilitate gaseous exchange. • Gas exchange is the exchange of gases between an organism and the environment. • In humans, the absorption of atmospheric oxygen and the removal of carbon dioxide from the body occurs in the alveoli (air sacs) in the lungs. The Respiratory System The Respiratory System nostril pharynx larynx/ voice box lungs ribs intercostal muscles trachea/ windpipe Bronchus (pl: bronchi) bronchioles alveoli diaphragm The Respiratory System Route taken by air Through nostrils pharynx larynx trachea bronchus bronchioles alveoli bronchus bronchioles alveoli Thinking question: Why is there a need for such a complex respiratory system in humans? • In unicellular organisms, gaseous exchange can take place by simple diffusion. • Large animals have a smaller surface area-to-volume ratio • Our external surfaces/ skin are often thickened for protection to prevent water loss and hence not suitable for gas exchange • We use special organs such as gills and lungs for gas exchange • Such organs have large surface area to volume ratio and thin coverings to enable efficient exchange of gases The nose Air enters through the nostrils Walls of nostrils have nasal hairs and mucous membranes that produce mucus Functions : ❑ Hairs and mucus trap dust, foreign particles e.g. bacteria ❑ Mucus warms and moistens air ❑ Sensory cells in mucous membrane detects harmful chemicals The Trachea • Airway that lies in front of the oesophagus • Supported by C-shaped rings of cartilage to ensure that the trachea is always kept open Trachea Bronchi and bronchioles The trachea branches into two tubes called the bronchi (singular: bronchus) Each bronchus branches repeatedly and ends in numerous bronchioles Each bronchiole ends in a cluster of air sacs called alveoli where gaseous exchange takes place Epithelium of Trachea and Bronchi • Membrane next to the lumen is called the epithelium • The epithelium consists of 2 types of cells 1. Gland cells 2. Ciliated cells Epithelium of Trachea and Bronchi cilia mucus Label your diagram gland cell Epithelium of Trachea and Bronchi Structure Gland cells Ciliated cells Function Secrete mucus that traps dust particles and bacteria in the air passage Have cilia which sweep the mucus containing dust particles and bacteria up the bronchi and trachea into the pharynx. The mucus can be coughed out through the pharynx or be swallowed into the oesophagus What happens if food/water accidentally enters the trachea? Alveoli (air sacs) • The alveoli are the sites of gas exchange • Numerous alveoli are found in the lungs • Each alveolus is surrounded by a network of blood capillaries Alveoli (air sacs) Label the diagram with: • • • • oxygen carbon dioxide oxygenated blood deoxygenated blood Gas exchange at the alveoli • Gas exchange at the alveoli occurs by diffusion. • Blood flowing to the lungs has a lower concentration of oxygen _______________ and a higher concentration of _______________, carbon dioxide than atmospheric air entering the lungs. • A concentration gradient for oxygen and carbon dioxide is set up between the blood in the capillaries and air in the alveolus. Structure-function relationships Lungs • Numerous alveoli in lungs provide a large surface area to volume ratio for more efficient gaseous exchange Alveoli • Thin walls (one-cell thick walls) • Inner wall covered by layer of thin film of moisture • Surrounded by network of blood capillaries Alveoli (singular: alveolus) 1. Thin (one-cell thick) walls • Provides a short diffusion distance for gases, ensuring more efficient diffusion of gases in and out of alveoli 2. Thin film of moisture in inner walls of alveoli • Allows gases to dissolve in it 3. Surrounded by network of blood capillaries • Continuous flow of blood maintains concentration gradient of gases ✓ Maintains ______ concentration of oxygen in alveoli than in blood ✓ Maintains ______ concentration of carbon dioxide in alveoli than in blood allowing more efficient diffusion of gases in and out of alveoli Alveoli (singular: alveolus) Video on gas exchange at alveoli http://www.youtube.com/watch?v=XTMYSGXhJ4E How is oxygen absorbed from the lungs into blood and into cells of tissues? higher concentration of oxygen than the 1. Alveolar air contains a ________ blood plasma thin film of moisture in the inner wall of 2. Oxygen dissolves in the __________________ the alveolus and then ______________ into the blood capillaries. diffuse haemoglobin in red blood cells to 3. Oxygen combines with _________________ form ____________________. oxyhaemoglobin • This reaction is reversible. +O2 - O2 Haemoglobin Oxyhaemoglobin How is oxygen absorbed from the lungs into blood and into cells of tissues? 3. When the blood passes through oxygen-poor tissues, the oxyhaemoglobin releases oxygen, 4. which will diffuse through the walls of the blood capillaries into the cells of the tissues. +O2 - O2 Haemoglobin Oxyhaemoglobin Checkpoint 1 1. What is the function of the incomplete rings of cartilage around the trachea? A. to filter dust and bacteria out of inhaled air B. to force air out of the trachea C. to prevent the collapse of the trachea D. to protect the blood vessels supplying the lungs ( A ) Checkpoint 1 B High O2 Low O2 Checkpoint 1 Any 2 of: 1. Thin, one-cell thick walls, which provides a short diffusion distance, ensuring more efficient diffusion of gases in and out of alveoli 2. Thin film of moisture in inner walls of alveoli, which allows gases to dissolve in it 3. Each alveolus is surrounded by network of blood capillaries. The continuous flow of blood maintains concentration gradient of gases allowing more efficient diffusion of gases in and out of alveoli Checkpoint 1 Diffusion Learning objectives b) describe the process of breathing and the role of cilia, diaphragm, ribs and internal and external intercostal muscles Breathing • Breathing is part of the gas exchange process • It refers to the muscular contractions and movements of the ribs which result in air moving in and out of the lungs. • Breathing consists of two phases: • Inspiration / Inhalation = Taking in of air into lungs • Expiration / Exhalation = Giving out of air from lungs Thoracic cavity (chest cavity) • Space in the body that is protected by the rib cage and associated skin and muscles • 2 sets of intercostal muscles can be found between the ribs. • Intercostal muscles and the diaphragm at the ribcage, enable the change in volume of the thoracic cavity. Intercostal muscles • External intercostal muscles and internal intercostal muscles are found between the ribs. • They are antagonistic muscles Diaphragm • Found below thorax • Made up of a dome-shaped sheet of diaphragm muscles • When diaphragm muscle contracts – diaphragm flattens downwards • When diaphragm muscle relaxes – diaphragm arches upwards Diaphragm Class Activity : Try this How does breathing occur? Does air move in first ? Does your chest move first? Can you control your breathing ? Close your eyes and take a few deep breaths and focus on these above questions Class Activity : Try this Does air move in first? No. The muscles contract first to bring the air in Does your chest move first? The ribcage and diaphragm move at the same time, before any air rushes into your nose and mouth Can you control your breathing? Yes and no. There is a part of breathing that you cannot control (your brain does it) and a part that you can (like holding your breath for a while). Inspiration vs. Expiration Diaphragm muscles relax Diaphragm muscles contract Diaphragm arches upwards Diaphragm flattens downwards Inspiration vs. Expiration Breathing in - Inspiration • Diaphragm muscles contract, diaphragm flattens downwards Side view • External intercostal muscles contract air enters lungs • Internal intercostal muscles relax • Ribs swing upwards and outwards ribs raised • Volume of thoracic cavity increases • This decreases air pressure in the lungs • Atmospheric pressure is now higher than the pressure within the lungs • This causes air from the atmosphere to be forced into the lungs diaphragm flattens lungs expand Breathing out - Expiration • Diaphragm muscles relax, diaphragm arches upwards and becomes dome-shaped Side view • External intercostal muscles relax air expelled from lungs lungs volume decrease • Internal intercostal muscles contract • Ribs swing downwards and inwards ribs lowered • Volume of thoracic cavity decreases • This increases air pressure in the lungs • Atmospheric pressure is now _______ than the pressure within the lungs • This causes air to be forced out of the lungs diaphragm arches upwards “Volume of thoracic cavity increases, the air pressure in the lungs decreases.” “Volume of thoracic cavity decreases, the air pressure in the lungs increases.” What is the stimulus for breathing? • Involuntary process controlled by the brain • The stimulus for breathing is a high concentration of carbon dioxide in the blood Component Inspired air Expired air Oxygen About 21% About 16.4% Carbon dioxide About 0.03% About 4% Nitrogen About 78% About 78% Water vapour Variable Saturated Temperature Variable About body temperature, 37O C Dust particles Usually present Little or none Checkpoint 2 – Question 1 Trachea Bronchus Bronchiole Checkpoint 2 – Question 1 The muscles of structure D (diaphragm) relaxes, and the diaphragm arches upwards and becomes dome-shaped. Structure E (external intercostal muscles) relax, while the internal intercostal muscles contract. These causes the ribs to swing downwards and inwards, decreasing the volume of the thoracic cavity. Checkpoint 2 – Question 2 a) Calculate, in breaths per minute, the rate of normal breathing between A and B. 3 breaths in 12 minutes 15 breaths/ minute Checkpoint 2 – Question 2 b) State the volume of air remaining in the lungs after the deep breath out. 1500 cm3 Checkpoint 2 – Question 2 c) Explain how the intercostal muscles are inhalation involved in breathing from time B to time C. During inhalation, external intercostal muscle contract, internal intercostal muscle relax, diaphragm muscles contracts and diaphragm is flattened downwards. The rib cage swings outwards and upwards and the volume of thoracic cavity increases, causing a decrease in the air pressure inside of lung. Atmospheric air forced into lungs. air enters lungs ribs raised diaphragm flattens lungs expand Components of tobacco smoke and the effects on heath Learning objectives d) state the major toxic components of tobacco smoke – nicotine, tar and carbon monoxide, and describe their effects on health Chemical Effects Nicotine • Increases chances of blood clot in blood vessels, (Addictive drug) therefore increase risk of coronary heart disease • Causes release of hormone adrenaline - increases heart rate and blood pressure Carbon monoxide • Binds irreversibly with haemoglobin in red blood cells to form carboxyhaemoglobin - reduces ability of haemoglobin to bind to oxygen, reduces efficiency of oxygen transport • Increases risk of coronary heart disease Tar • Paralyses cilia in air passages, hence trapped dust particles trapped in mucus cannot be removed. • Contains cancer-causing (carcinogenic) chemicals that cause uncontrolled cell division in the lungs - increase risk of lung cancer Other irritants Like tar, other irritants found in tobacco smoke also: • paralyse cilia lining the air passages • increase risk of chronic bronchitis and emphysema Diseases caused by tobacco smoke 1. Chronic bronchitis 2. Emphysema 3. Lung cancer chronic obstructive pulmonary disease (COPD) Chronic Bronchitis • Prolonged exposure to irritant particles in tobacco smoke leads to: • Epithelium lining of air passages become inflamed (e.g Bronchi inflammation) • Excessive mucus secreted by epithelium • Cilia on the epithelium paralysed • Mucus and dust particles cannot be removed • Air passage becomes blocked, breathing becomes difficult • Persistent and violent coughing to clear air passages Emphysema Persistent and violent coughing may lead to emphysema • Partition walls between the alveoli break down because of the force from the coughing. • This results in ___________ surface area for gaseous exchange • The lungs lose their elasticity and become inflated with air. • Breathing becomes difficult, wheezing and severe breathlessness result. Emphysema Emphysema Lung Cancer • Carcinogens in tobacco smoke can cause mutations in the DNA in lung cells • Causes lung cancer, which is a result of uncontrolled division of cells in the lungs, producing lumps of tissues (tumours) in lungs Summary video: COPD http://www.youtube.com/watch?v=2nBPqSiLg5E Checkpoint 3 B Nicotine Tar, irritant particles Carbon monoxide A Checkpoint 3 D Test yourself! https://www.bbc.co.uk/bitesize/guides/zsry39q/test Learning objectives e) define aerobic respiration in human cells as the release of energy by the breakdown of glucose in the presence of oxygen and state the equation, in words and symbols f) define anaerobic respiration in human cells as the release of energy by the breakdown of glucose in the absence of oxygen and state the word equation g) explain why cells respire anaerobically during vigorous exercise resulting in an oxygen debt that is removed by rapid, deep breathing after exercise Respiration Respiration is the oxidation of food substances with the release of energy in living cells Aerobic respiration Anaerobic respiration (requires oxygen) (does not require oxygen) Energy currency – ATP • During respiration, ATP is produced • ATP = Adenosine triphosphate • A high-energy molecule that stores energy for cellular processes Respiration vs Breathing 2 different but related processes: 1. Respiration Oxidation of food molecules within living cells to release energy (Aerobic & Anaerobic respiration) 2. Gaseous exchange (breathing) Exchange of gases between the body and the surroundings Respiration Respiration is the oxidation of food substances with the release of energy in living cells Aerobic respiration Anaerobic respiration (Requires oxygen) (Does not require oxygen) Aerobic respiration Recall: What is this? What does it do? Mitochondria: The site of aerobic respiration Aerobic respiration The breakdown of food substances (glucose) in the presence of oxygen with the release of large amount of energy. • • • • Occurs in the mitochondria Glucose is oxidised, producing carbon dioxide and water, releasing a large amount of energy o some of the energy is released as heat Aerobic respiration The breakdown of food substances (glucose) in the presence of oxygen with the release of large amount of energy. Word equation • glucose + oxygen → water + carbon dioxide (A large amount of energy is released) Chemical equation • C6H12O6 + 6O2 → 6CO2 + 6H2O Anaerobic respiration The breakdown of food substances (glucose) in the absence of oxygen • Less efficient than aerobic respiration → less energy released • In humans, anaerobic respiration can happen in muscle cells during vigorous exercise • Anaerobic respiration takes place in the cytoplasm of the cell, not mitochondria • In muscle cells, this process produces lactic acid and releases a small amount of energy. Anaerobic respiration The breakdown of food substances (glucose) in the absence of oxygen Word equation: glucose → lactic acid (A small amount of energy is released) Note: absence of carbon dioxide and water as products Anaerobic respiration in yeast • Anaerobic respiration could take place in many other living organisms (e.g. yeast cells, bacteria). • Lactic acid is not necessarily a product in some of these cases. E.g. Anaerobic respiration in yeast glucose ethanol + carbon dioxide A small amount of energy is released Aerobic and anaerobic respiration in human muscles during exercise Imagine doing a 2.4km run.. • There are more vigorous muscular contractions during exercise. • More _________ energy is required for more vigorous muscular contractions. aerobic respiration • So, a higher rate of _________________ takes place in muscle cells. • Glucose is oxidised at a higher rate to release energy at a higher rate. Imagine doing a 2.4km run.. Breathing rate increases: • Oxygen is taken in at a higher rate • So that aerobic respiration can take place at a higher rate, for more efficient release of energy • Carbon dioxide is also removed from body at a higher rate. pant.. pant.. pant.. Imagine doing a 2.4km run.. Heart rate increases: • So oxygen and glucose can be pumped to the muscles at a higher rate • This allows higher rate of aerobic respiration to release energy faster After long period of exercising… Need more energy… Not enough oxygen… Anaerobic respiration in muscles • During intense or long periods of vigorous exercise e.g. 100m sprint, marathon • Oxygen supplied to muscles is not enough to meet the oxygen demand • Amount of oxygen taken in is less than amount of oxygen required, leading to an oxygen debt ▪ Oxygen debt is the amount of oxygen required to convert all the lactic acid accumulated back to glucose. • There is insufficient oxygen taken in for aerobic respiration to take place fast enough to release the large amount of energy required. (This is because there is a limit to our breathing rate and heart rate!) Anaerobic respiration in muscles • Anaerobic respiration takes place in the muscles, in energy to release the extra the absence of __________ energy required. Lactic acid is produced and ____________________ small amount of energy • ___________ is released in the process. • Note: Maximum rate of aerobic respiration is still taking place! Anaerobic respiration in muscles After a race… 1. Body needs to rest 2. Lactic acid is gradually removed from muscles and transported to the liver to be oxidised to glucose. 3. Breathing rate continues to be high for some time • • Provides sufficient oxygen to muscle cells to repay oxygen debt Provides oxygen to oxidise lactic acid into glucose in the liver 4. When all lactic acid has been converted, the oxygen debt is repaid. Checkpoint 4 Number of breaths per second (rate of breathing) Volume of air taken in in each breath during exercise Checkpoint 4 • Volume of air taken in and given out in each breath is larger during exercise than before exercise. • More vigorous muscular contractions is needed during exercise. • More air is taken in during exercise to provide larger amount of oxygen to muscle cells for aerobic respiration, for the release of larger amount of energy for vigorous muscular contractions. • More carbon dioxide is released in the process, so a larger volume of carbon dioxide is brough to lungs to be released. Checkpoint 4 • Rate of breathing is higher during exercise than before exercise. • This allow oxygen to be transported to muscle cells faster / more efficiently. • So aerobic respiration can take place more efficiently, and release of large amount of energy for vigorous muscular contractions faster. • As carbon dioxide is released faster during exercise, the higher rate of breathing allows carbon dioxide to be given out more efficiently. Checkpoint 4 Checkpoint 4 Lactic acid concentration is 0 arbitrary units in the muscles from 0 to 2 mins. Aerobic respiration takes place in the first 2 minutes of the race, when there is sufficient oxygen provided to the muscles. Lactic acid is not produced. Lactic concentration in the muscles increases from 0 arbitrary units to 7.5 arbitrary units from 2 minutes after the start of rate to 6 minutes after the start of race. After 2 minutes, insufficient oxygen is taken in (oxygen taken in is lower than oxygen demand) for aerobic respiration to take place to release energy. As a result, anaerobic respiration also takes place, producing lactic acid. From 6 minutes to 10 minutes, lactic concentration in the muscles decreases from 7.5 arbitrary units to 4 units. When the race ended after the first 6 minutes. Breathing rate remains high. Lactic acid is brought to the liver, where it is oxidised to glucose. Investigating respiration Recall… glucose + oxygen → energy carbon dioxide + water is released How can we show that respiration has taken place? 1. Carbon dioxide is produced 2. Energy is released • In the form of heat Investigating respiration • Carbon dioxide production • How to test for carbon dioxide? Potassium hydroxide: Removes carbon dioxide Limewater: White precipitate formed in limewater in presence of carbon dioxide Try it yourself! • Potassium hydroxide in flask A removes carbon dioxide that enters. • Air entering flask B should / should not contain carbon dioxide. • White precipitate should / should not form in the limewater in flask B. • Air entering flask C will/will not contain carbon dioxide. • Hence, any carbon dioxide detected in flask D would be due to respiration by the snails. Investigating respiration Production of carbon dioxide Using hydrogencarbonate indicator • Carbon dioxide dissolves in water to form a slightly acidic solution. • What colour will the indicator in each test tube turn? orange / yellow With insect: ____________ red Control: ___________ • What is the use of the control? • To show that any change in colour of the indicator is due to the insect Investigating respiration Release of heat Why use a vacuum flask? What is the antiseptic for? What is the purpose of the cotton wool? What is set-up B for? What is the expected result? Investigating respiration • Why use a vacuum flask? Prevent loss of heat to the surroundings • What is the antiseptic for? To kill microorganisms. When the microorganisms respire, they release heat. In addition, heat is also released during decomposition of seed by microorganisms. • What is the purpose of the cotton wool? Cotton wool is porous, allowing carbon dioxide, oxygen and other gases to diffuse in and out of the setup Investigating respiration • What is set-up B for? Serve as a control to show that change in temperature is due to respiration of the live seeds. • What is the expected result? Temperature in A will increase but temperature B will remain constant. Seeds in A are alive and some energy released during respiration is lost as heat. Dead seeds in B do not respire; no heat is released. Checkpoint 4: Study the experiment testing respiration and photosynthesis. Answer the questions that follow. Hydrogencarbonate solution Results Test tube A B C D Content Snail + indicator hydrilla plant + indicator hydrilla plant + snail + indicator indicator Initial colour of hydrogencarbonate solution red red red red Final colour of hydrogencarbonate solution yellow purplish red light yellow red Purpose of rubber bung To prevent carbon dioxide from the atmosphere entering the test tube. Atmopheric carbon dioxide will change the colour of the indicator from red to yellow. To prevent loss of carbon dioxide from the set-up into the atmosphere. Conclusion Test tube A: Carbon dioxide given off during respiration dissolved in the indicator and formed a weak acidic solution which turned the indicator yellow. Test tube B: Rate of photosynthesis is higher than the rate of respiration. Carbon dioxide was taken in by the plant resulting in a slightly acidic to neutral solution turning the indicator yellowish red/ alkaline solution turning solution purplish red. Conclusion Test tube C: Rate of respiration is higher than the rate of photosynthesis in the hydrilla plant. Carbon dioxide was given out by both hydrilla plant and snail resulting in a more acidic solution turning indicator light yellow. or Test tube C: Rate of photosynthesis is higher than respiration. CO2 given out by both plant and snail is taken in by plant for photosynthesis, less CO2→ less acidic, yellow. Sources of experimental errors ▪ Rate of respiration / photosynthesis in the different snails and hydrilla plants could be different, thus affecting colour change of indicator. ▪ Light intensity reaching each container may not be the same affecting the rate of photosynthesis for container B and C thus affecting colour change. Improving Accuracy ▪ Use different lamps with the same light intensity for each container. ▪ Use parts of the same hydrilla plant in test tube B and C; hydrilla plants should have same number of leaves / of the same length. ▪ Use snails of the same size / age. Extension ▪ Extension : Smoking and vaping ▪ Activity 3 in this SLS lesson: https://vle.learning.moe.edu.sg/mrv/moelibrary/lesson/view/0c398f4b-712a-4f02-bb6b1dbde59dcfff/page/47227723 ▪ Extension : Anaerobic respiration in yeast ▪ Extension : Let’s build a lung model Extension: Let’s build your own lung model! • Which part of the respiratory system does each part of the model represent? • Using the model, explain how you breathe. • State two limitations of your model and how it does not accurately represent the breathing mechanism.
