6.4 Gas Exchange 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 Skills: -Monitoring of ventilation in humans at rest and after mild and vigorous exercises Nature of science: -Obtain evidence for theories: epidemiological studies have contributed to our understanding of the causes of lung cancer.

Gas exchange Absorb one gas and release a different one. Plants: Absorb carbon dioxide and release oxygen Humans: Absorb oxygen and release carbon dioxide

Label the key words onto your diagram of the lungs Trachea Lung Alveoli Bronchioles Bronchi Ribs Intercostal muscles Diaphragm Mouth Nose

Match up the key words Trachea Alveoli Bronchi Ribs Intercostal muscles Diaphragm Pipe that transports air from mouth to bronchi Protects the lungs Increase the surface area in the lungs Contract when inhaling Transports air from trachea to bronchioles Pushes down when inhaling

In Humans Diffusion Between air in alveoli and capillaries Concentration gradient of oxygen High concentration in lungs  Low concentration in capillaries Ventilation must occur to supply fresh air in the lungs

Alveoli Site where gas exchange happens Increase surface area Thin cell walls Two types of cells: -Type I pneumocytes -Type II pneumocytes

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

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 capillary walls from sticking together and collapsing

Antagonistic muscles Muscles have two states: 1.Contracting (shorter) 2.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

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

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

How do we breathe? Body partInhalingExhaling Diaphragm Intercostal muscles Chest cavity volume Pressure in lungs Air

How do we breathe? Body partInhalingExhaling DiaphragmContractRelax Intercostal musclesContractRelax Chest cavity volumeIncreaseDecrease Pressure in lungsDecreaseIncrease AirInto lungsOut of lungs

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

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. 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.

Measure your lungs What is your hypothesis?

Your investigation 1.Record your height 2.Record your weight 3.Record your gender 4.Work out your BMI 5.Record your vital capacity 6.Record your tidal volume 7.Record your ventilation rate 8.Record your heart rate Mild: running on spot Vigorous: HIIT video