Key Concepts in Human Respiratory System
Human Respiratory System
Functions: Supplies oxygen to body cells and removes carbon dioxide.
Breathing: Inhaling and exhaling air by the lungs.
System: The human respiratory system helps us breathe.
Structures (Figure 2.1):
Nostrils
Nasal cavity
Pharynx
Larynx
Trachea
Bronchus
Bronchiole
Alveolus
Lungs (Right and Left)
Diaphragm
Epiglottis
Intercostal muscles
Breathing Mechanism
Inhale & Exhale: Air enters and leaves through the nose.
Chest Movement: Chest rises and falls during breathing.
Direction of Air (Figure 2.2): Nose → Lungs
Correct Breathing: Essential for physical and mental health; improves performance during exercise.
Inhalation (Figure 2.3)
Intercostal Muscles: Contract and pull the rib cage upwards and outwards.
Diaphragm Muscles: Contract and pull the diaphragm to descend and become flat.
Thoracic Cavity: Increases in volume.
Air Pressure: Decreases in the thoracic cavity.
Process: Higher air pressure outside forces air to enter the lungs.
Epiglottis action during swallowing:
During swallowing, the epiglottis drops down and closes the trachea to prevent bolus (swallowed food) from entering the respiratory tract.
During breathing, the epiglottis moves up, causing the trachea to open.
Exhalation (Figure 2.4)
Intercostal Muscles: Relax and the rib cage moves downwards and inwards.
Diaphragm Muscles: Relax and curve upwards.
Thoracic Cavity: Decreases in volume.
Air Pressure: Increases in the thoracic cavity.
Process: Higher air pressure in the lungs pushes air out.
Experiment 2.1: Percentage of Oxygen in Inhaled and Exhaled Air
Aim: To study the difference in the percentage of oxygen in inhaled and exhaled air.
Problem Statement: What is the difference in the percentage of oxygen in inhaled and exhaled air?
Hypothesis: The percentage of oxygen in inhaled air is higher than the percentage of oxygen in exhaled air.
Variables:
Manipulated: Type of air in gas jar
Responding: Final water level in gas jar
Constant: Air temperature and pressure, volume of gas jar
Materials: Candle, plasticine, matches, permanent marker, water, inhaled air, exhaled air.
Apparatus: Glass basin, gas jar, gas jar cover, gas jar stand.
Procedure:
Set up apparatus (Figure 2.5).
Light candle and invert gas jar over candle (Figure 2.6).
Record final water level.
Collect exhaled air (Figure 2.7).
Repeat steps 2 and 3 with exhaled air.
Precaution: Cover gas jar with exhaled air during transfer.
Results: Compare final water levels and estimate the percentage of oxygen.
Conclusion: Determine if the hypothesis is accepted.
Experiment 2.1B: Concentration of Carbon Dioxide in Inhaled and Exhaled Air
Aim: To study the difference in concentration of carbon dioxide in inhaled and exhaled air.
Problem Statement: What is the difference in concentration of carbon dioxide in inhaled and exhaled air?
Hypothesis: Concentration of carbon dioxide in exhaled air is higher than concentration of carbon dioxide in inhaled air.
Variables:
Manipulated: Type of air passed through limewater
Responding: Condition of limewater
Constant: Concentration of limewater, volume of conical flask
Materials: Limewater, inhaled air, exhaled air
Apparatus: Conical flask, connecting tube, rubber tubing, glass tube, rubber stopper
Procedure:
Set up the apparatus as shown in Figure 2.8.
Close clip A. Inhale and hold your breath. Then, close clip B and open clip A. After that, exhale.
Observe and record if the limewater in the conical flasks where inhaled and exhaled air passes through appears clear or cloudy.
Results: Note condition of limewater after passing inhaled and exhaled air.
Conclusion: Determine if the hypothesis is accepted.
Summary of Gas Composition:
Oxygen: Higher in inhaled air, lower in exhaled air
Carbon Dioxide: Lower in inhaled air, higher in exhaled air
Formative Practice 2.1
Flow Chart Completion:
Nostrils → Nasal cavity → (a) Pharynx → (b) Larynx → (c) Trachea → Alveolus
True/False Statements:
(a) ✓ Epiglottis opens/closes the trachea.
(b) × Gas exchange occurs in the alveoli, not bronchioles.
(c) × Diaphragm moves downwards during inhalation.
(d) × CO_2 percentage is higher in exhaled air.
Importance of Good Ventilation:
Removes excess carbon dioxide, maintains air quality, and reduces the spread of airborne diseases.
Simple Model (Figure 1):
(a) Parts represented:
(i) Glass jar: Rib cage
(ii) Thin rubber sheet: Diaphragm
(iii) Y-shaped glass tube: Trachea and bronchi
(iv) Balloon: Lungs
(b) Thin rubber sheet is used to allow movement, mimicking the diaphragm's flexibility.
(c) Breathing processes:
(i) Pulling downwards: Inhalation
(ii) Pushing upwards: Exhalation
(d) Glass jar fails as rib cage because it can't expand and contract like real ribs.
Movement and Exchange of Gases in the Human Body
Process: Movement of oxygen and carbon dioxide from areas of higher concentration to lower concentration.
Figure 2.9: Shows movement and exchange in alveolus and blood capillaries.
Alveolus to Blood: Air inhaled into the alveolus has a higher concentration of oxygen compared to the blood, so oxygen diffuses into the blood.
Oxyhaemoglobin Formation:
Haemoglobin + oxygen → oxyhaemoglobin (unstable, bright red)
Oxygen Transport: Blood with oxyhaemoglobin moves from lungs to heart, then to body parts.
Body Cells: Oxyhaemoglobin decomposes to release oxygen.
Oxyhaemoglobin → haemoglobin + oxygen
Cellular Respiration:
Glucose + oxygen → carbon dioxide + water + energy
Carbon Dioxide Removal:
CO_2 released by cells diffuses into blood and is transported to the alveolus for exhalation.
Activity 2.3
Create a presentation showing gas exchange, diffusion of oxygen, oxyhaemoglobin formation, release of oxygen, cellular respiration, and diffusion of carbon dioxide.
Adaptations of the Alveolar Structure (Figure 2.10)
Thin Walls: Facilitates rapid gas diffusion.
Moist Wall: Allows gases to dissolve.
Large Surface Area: Millions of alveoli for efficient exchange.
Network of Capillaries: Maximises gaseous exchange.
Importance: Increases efficiency and maximises gas exchange in the human body.
Formative Practice 2.2
Rate of Exchange: Determined by the concentration gradient of oxygen.
Conditions:
(a) Haemoglobin to oxyhaemoglobin: High oxygen concentration
(b) Oxyhaemoglobin to haemoglobin: Low oxygen concentration
Chemical Equation for Cellular Respiration:
Glucose + Oxygen \rightarrow Carbon Dioxide + Water + Energy
High Altitude: Efficiency decreases due to lower oxygen concentration.
Adaptations of Alveolus:
Thin walls
Moist wall
Large surface area
Dense network of capillaries
Concentration Gradient: The greater the difference, the higher the diffusion rate.
Substances Harmful to the Human Respiratory System
Cigarette Tar: Sticks to and kills cells, increases mucus and phlegm production, causes lung cancer.
Carbon Monoxide: Found in cigarette smoke and vehicle exhaust. Combines with haemoglobin to form carboxyhaemoglobin, reducing oxygen transport.
Carbon monoxide + haemoglobin → carboxyhaemoglobin
Sulphur Dioxide: Released from power stations. Irritates air passage, causes cough, bronchitis, and lung cancer.
Nitrogen Dioxide: From combustion of fuels in vehicles. Irritates air passage, causes cough, breathing difficulty, and asthma.
Haze, Dust, and Pollen: Irritate respiratory system, cause respiratory diseases such as asthma.
Respiratory Diseases and Their Symptoms
Asthma: Triggered by dust, pollen, smoke. Symptoms: Shortness of breath, wheezing, coughing.
Bronchitis: Inflammation of bronchus caused by tar and irritants. Symptoms: Shortness of breath, persistent coughing, insomnia.
Emphysema: Damage to alveoli caused by harmful substances. Symptoms: Shortness of breath, pain when breathing, fatigue.
Lung Cancer: Caused by carcinogens in cigarette smoke (e.g., tar). Symptoms: Persistent coughing, blood in phlegm, pain when breathing.
Experiment 2.2: Effects of Smoking on the Lungs (Demonstration)
Aim: To study the effects of smoking on the lungs.
Problem Statement: What are the effects of smoking on the lungs?
Hypothesis: Cigarette smoke contains cigarette tar (brown-colored substance) and acidic gases that damage the lungs.
Variables:
Manipulated: Presence of cigarette smoke
Responding: Color of cotton wool and litmus solution
Constant: Rate of suction of air using the filter pump
Materials: Cigarette, cotton wool, litmus solution, matches or lighter
Apparatus: U-tube, conical flask, rubber stopper, filter pump, rubber tube, glass tube, retort stand with clamps and wooden block
Procedure:
Set up the apparatus as shown in Figure 2.13(a).
Observe and record the color of the cotton wool and litmus solution.
Switch on the filter pump for 10 minutes.
Switch off the filter pump.
Observe and record the change in color of the cotton wool (if any) and litmus solution in a table.
Repeat steps 1 to 5 with a lighted cigarette as shown in Figure 2.13(b).
Observation: Note changes in the color of the cotton wool and litmus solution.
Conclusion: Determine if the hypothesis is accepted.
Formative Practice 2.3
(a) Harmful Solids: Dust, pollen, haze, cigarette tar.
(b) Harmful Gases: Carbon monoxide, sulphur dioxide, nitrogen dioxide.**Substance released by plants that is harmful: Pollen.
Symptoms of Diseases:
(a) Emphysema: Shortness of breath
(b) Lung Cancer: Persistent cough
(c) Bronchitis: Persistent coughing
(d) Asthma: Shortness of breath
Diseases from Cigarette Smoke: Bronchitis, Lung cancer and Emphysema.
Passive Smoker: A person who inhales cigarette smoke but does not smoke themselves.
Adaptations in Respiratory Systems
Three Features for Gaseous Exchange:
Thin respiratory structures (e.g., alveoli)
Large surface area (e.g., millions of alveoli)
Moist surface (e.g., moist alveoli)
Moist Outer Skin (Frogs):
Skin is thin and permeable.
Covered by mucus to dissolve gases.
Dense network of blood capillaries for diffusion.
*Other respiratory structures of frogs: Lungs and oral cavity.
Gills (Fish):
Filaments and lamellae provide a large surface area.
Gills are surrounded by water to easily dissolve gases.
Trachea (Insects):
Air enters/leaves through spiracles controlled by valves.
Tracheoles have thin, moist walls for gaseous exchange.
Grasshoppers have air sacs for increased gas exchange during activity.
Formative Practice 2.4
Respiratory Structures:
(a) Fish: Gills
(b) Insects: Trachea
(c) Amphibians: Moist outer skin, lungs.
Adaptations in Frog Skin: Thin skin, moist surface due to mucus.
Insect Circulatory System: Not involved because trachea directly diffuses gases into cells.
Importance of Exercise: Strengthens respiratory muscles, improves lung capacity and efficiency.
Healthy Lifestyles: Avoid smoking, maintain good air quality.
Gaseous Exchange in Plants
Process: Plants take in oxygen and remove carbon dioxide during respiration.
Photosynthesis: During the day, plants take in carbon dioxide and give out oxygen.
Parts Involved: Leaves, stems, and roots provide a large surface area for gaseous exchange.
Aerial roots provide access to air.
Diffusion of Carbon Dioxide (Figure 2.18)
When CO2 is used in photosynthesis, the concentration of CO2 in the cells becomes lower compared to the concentration of CO_2 in the air space between the cells.
This difference in concentrations allows the diffusion of carbon dioxide from the atmosphere through the stoma, into the air space between the cells.
Stomatal Pore and Guard Cells
Stoma: Stomatal pore bounded by guard cells.
Guard Cells: Contain chloroplasts.
Stomata Opening/Closing: Open during photosynthesis, close in darkness or during water loss.
Osmosis in Guard Cells
Osmosis: Movement of water molecules from high to low concentration through a semipermeable membrane.
Process in Guard Cells:
In light, guard cells produce glucose.
Water diffuses into guard cells, becoming turgid and curved, opening the stoma.
At night or on hot days, water diffuses out, guard cells become flaccid and straight, closing the stoma.
Importance of Unpolluted Environment for Plants
Haze and Dust: Reduce sunlight, prevent gaseous exchange.
Acidic Gases (Sulphur Dioxide, Nitrogen Dioxide): Dissolve in rainwater to produce acid rain, which kills plant cells and acidifies soil.
Preventive Measures: Ban open burning, limit vehicles, encourage alternative energy.
Formative Practice 2.5
Mangrove Plant Parts: Roots, stem, leaves.
Leaf Structure:
P: Guard Cell
Q: Stomatal Pore
(a) Stomata Open: During the day because of photosynthesis, which increases glucose and turgidity in guard cells.
(b) Stomata Closed: At night due to lack of light for photosynthesis, reducing water intake.
(c) Stomata Closed on Hot Days: To prevent water loss.Effects of Polluted Air: Reduces photosynthesis, prevents gaseous exchange, and damages/kills plant cells.