6.4 Gas Exchange Applications: Understanding: Ventilation maintains concentration gradients of oxygen and carbon dioxide between air in alveoli and blood flowing in adjacent capillaries Type I pneumocytes are extremely thin alveolar cells that are adapted to carry out gas exchange Type II pneumocytes secrete a solution containing surfactant that creates a moist surface inside the alveoli to prevent the sides of the alveolus adhering to each other by reducing surface tension Air is carried to the lungs in the trachea and bronchi and then to the alveoli in bronchioles Muscle contractions cause the pressure changes inside the thorax that force air in and out of the lungs to ventilate them Different muscles are required for inspiration and expiration because muscles only do work when they contract Applications: External and internal intercostal muscles, and diaphragm and abdominal muscles as examples of antagonistic muscle action Causes and consequences of lung cancer Causes and consequences of emphysema Nature of science: Obtain evidence for theories: epidemiological studies have contributed to our understanding of the causes of lung cancer. Skills: Monitoring of ventilation in humans at rest and after mild and vigorous exercises

Gas exchange Absorb one gas and release a different one. For photosynthesis: Absorb carbon dioxide and release oxygen For respiration: Absorb oxygen and release carbon dioxide

Label the key words Trachea Lung Bronchioles Bronchi Alveoli Intercostal muscles Ribs Nose Diaphragm Mouth Understanding: Air is carried to the lungs in the trachea and bronchi and then to the alveoli in bronchioles

In Humans Diffusion Between air in alveoli and blood in capillaries Concentration gradient of oxygen High concentration in lungs → Low concentration in capillaries Ventilation must occur to supply fresh air in the lungs Understanding: Ventilation maintains concentration gradients of oxygen and carbon dioxide between air in alveoli and blood flowing in adjacent capillaries

Site where gas exchange happens Alveoli Site where gas exchange happens Increase surface area Thin cell walls Two types of cells: Type I pneumocytes Type II pneumocytes Understanding: Ventilation maintains concentration gradients of oxygen and carbon dioxide between air in alveoli and blood flowing in adjacent capillaries

Type I pneumocytes Extremely thin alveolar cells Make up most of epithelial cells of alveoli Flat cells 0.15um thick Adjacent capillary also very thin Very small diffusion space Understanding: Type I pneumocytes are extremely thin alveolar cells that are adapted to carry out gas exchange

Type II pneumocytes Rounded cells Occupy 5% of alveolar surface area Secrete a fluid which coats the inner surface of the alveoli Allows oxygen to dissolve before diffusing to the blood Also prevents the alveolus walls from sticking together and collapsing Understanding: Type II pneumocytes secrete a solution containing surfactant that creates a moist surface inside the alveoli to prevent the sides of the alveolus adhering to each other by reducing surface tension

Antagonistic Muscles Muscles have two states: Contracting (shorter) Relaxing (longer) Muscles can only work in one direction If opposite directions are needed, more than one muscle is needed. When two muscles work together they are call antagonistic muscles Applications: External and internal intercostal muscles, and diaphragm and abdominal muscles as examples of antagonistic muscle action

Antagonistic Muscles When we breathe in and out… External vs Internal intercostal muscles Diaphragm vs abdominal muscles Applications: External and internal intercostal muscles, and diaphragm and abdominal muscles as examples of antagonistic muscle action

Breathing In External intercostal muscles contract, lifting rib cage Diaphragm muscles contract, pulling it downwards Volume of lungs increases Pressure inside the lungs decreases Air rushes into the lungs from the trachea to attain a pressure equilibrium Understanding: Muscle contractions cause the pressure changes inside the thorax that force air in and out of the lungs to ventilate them Different muscles are required for inspiration and expiration because muscles only do work when they contract

Breathing Out External intercostal muscles relax, rib cage falls Diaphragm muscles relax and it moves upwards Volume of lungs decreases Pressure inside the lungs increases Air rushes out of the lungs to attain a pressure equilibrium Understanding: Muscle contractions cause the pressure changes inside the thorax that force air in and out of the lungs to ventilate them Different muscles are required for inspiration and expiration because muscles only do work when they contract

Body part Inhaling Exhaling Diaphragm Intercostal muscles Chest cavity volume Pressure in lungs Air

Body part Inhaling Exhaling Diaphragm Contract Relax Intercostal muscles Chest cavity volume Increase Decrease Pressure in lungs Air Into lungs Out of lungs

Put these into the correct order to make the cycle of gas exchange Your diaphragm contracts and moves down The space inside your Chest gets bigger and you breathe in The air goes into your Lungs Oxygen is taken from the air into the blood in your lungs The blood deposits the waste carbon dioxide into the air in your lungs You Diaphragm relaxes and moves up The Space inside your chest gets smaller The Air is squeezed out of your lungs and your breathe out Put these into the correct order to make the cycle of gas exchange

The cycle of gas exchange Your diaphragm contracts and moves down The space inside your Chest gets bigger and you breath in The air goes into your Lungs Oxygen is taken from the air into the blood in your lungs The blood deposits the waste carbon dioxide into the air in your lungs You Diaphragm relaxes and moves up The Space inside your chest gets smaller The Air is squeezed out of your lungs and your breath out The cycle of gas exchange

Define the terms below. Vital capacity… Tidal volume… Volume of air moved in and out of the lungs with each breathe when you are at rest. Vital capacity… Largest volume of air that can be moved into and out of the lungs in any one breath. Ventilation rate… Skills: Monitoring of ventilation in humans at rest and after mild and vigorous exercises

6.4 Gas Exchange Applications: Understanding: Ventilation maintains concentration gradients of oxygen and carbon dioxide between air in alveoli and blood flowing in adjacent capillaries Type I pneumocytes are extremely thin alveolar cells that are adapted to carry out gas exchange Type II pneumocytes secrete a solution containing surfactant that creates a moist surface inside the alveoli to prevent the sides of the alveolus adhering to each other by reducing surface tension Air is carried to the lungs in the trachea and bronchi and then to the alveoli in bronchioles Muscle contractions cause the pressure changes inside the thorax that force air in and out of the lungs to ventilate them Different muscles are required for inspiration and expiration because muscles only do work when they contract Applications: External and internal intercostal muscles, and diaphragm and abdominal muscles as examples of antagonistic muscle action Causes and consequences of lung cancer Causes and consequences of emphysema Nature of science: Obtain evidence for theories: epidemiological studies have contributed to our understanding of the causes of lung cancer. Skills: Monitoring of ventilation in humans at rest and after mild and vigorous exercises

How will exercise affect… Tidal volume… Volume of air moved in and out of the lungs with each breathe when you are at rest. Vital capacity… Largest volume of air that can be moved into and out of the lungs in any one breath. Ventilation rate… Amount of breaths taken per minute

Prescribed Practical Record your height Record your weight Follow the sheet to complete the practical You need two hypotheses before you begin. It can be anything to do with the data you will collect. E.g. females will have a larger lung volume Collect data Analyse data Draw graphs for both hypotheses Write a conclusion (include data) Record your height Record your weight Record your gender Work out your BMI Record your vital capacity Record your tidal volume Record your ventilation rate Record your heart rate Understanding: Muscle contractions cause the pressure changes inside the thorax that force air in and out of the lungs to ventilate them Different muscles are required for inspiration and expiration because muscles only do work when they contract

Lung Diseases Lung cancer and emphysema. For each disease: What causes it? Give examples. How common is it? What are the consequences? What are the symptoms? Why is it an issue? Is there a cure? How can it be prevented? Applications: Causes and consequences of lung cancer Causes and consequences of emphysema