Topic 2: Gas Exchange

Introduction• What is our atmosphere made

of?– Nitrogen (78%), oxygen (21%),

traces of carbon dioxide (<1%)• Why is breathing important?

– Allows for the exchange of O2 and CO2 between the environment and our bodies

• What is the O2 used for?– All cells require O2 for cellular respiration (for energy)

• What is the fate of the other gases?– CO2 + H2O: Expelled as waste

Topic 2-1: Anatomy of the Respiratory System

General Functions– Intake of

oxygen– Exhale carbon

dioxide– All for the

preservation of life

1. External gas exchangeBrings air into the lungs O2 diffuses into capillaries, CO2 diffuses from blood to the air

2. The circulatory system Transports blood high in O2 and low in CO2 from the lungs to the tissues

3. Internal gas exchange Diffusion of O2 from capillaries into the body

Cellular respiration occurs: C6H12O6 + 602 ―>6CO2 + 6H2O + 36 ATP

4. The circulatory system Transports blood high in CO2 and low in O2 to the lungs

The 4 steps to breathing:

Label the following diagram

Pulmonary Vein

Aorta/ArteriesInferior Vena Cava / Veins

Pulmonary artery

CO2

O2

Direction of the flow of blood

CO2O2

The Relationship between the Circulatory and Respiratory System

• Carbon dioxide diffuses from:a body cell circulatory system OUT the lungs

• Oxygen diffuses from: IN from lungs circulatory system a body cell

Breathing vs. RespirationBreathing Respiration

Intake of O2

Exhale CO2

Gases exchanged in alveoli in lungs

C6H12O6 + 6O2 = 6CO2 + 6H2O + energy

Breakdown of sugar into energy

Takes place in all cells

1. Nasal Cavity2. Pharynx (throat)

3. Epiglottis

4. Esophagus

5. Trachea

6. Bronchus (i)

7. Lung

8. Heart

9. Pleural Membranes

10. Diaphragm

11. Alveoli

12. Pleural Membranes

13. Bronchioles

14. Intercostal muscles

15. Rib

16. Cartilage Ring

17. Larynx (voice box)

Thoracic cavity (chest)

Right Lung = 3 lobes

Left Lung = 2 lobes

Abdominal cavity (below diaphragm)

http://www.youtube.com/watch?v=MrDbiKQOtlUBozeman respiratory system 8:46

Trace the flow of air as it

moves from the nose to the lungs

Nostrils

Larynx

Nasal Cavity

Bronchioles

Alveoli

Pharynx

Epiglottis

2 bronchi

Trachea

Capillaries http://www.youtube.com/watch?v=MrDbiKQOtlU

Bozeman respiratory system 8:46

Functions of the Respiratory System• Mouth and nostrils

– Air enters respiratory system• Nasal cavity

– Provides MOISTURE (allows gases to dissolve and diffuse)

– WARMS the air– Filters and traps particles

• via hair and mucous

• Pharynx (throat)– Passage for food and air

Epiglottis• Flap covering trachea during swallowing• If food enters trachea,

– Reflex: cough

•“Voicebox”•Contains 2 ligaments (vocal cords)•Air passes, vibrate ligaments and sound is produced•Cartilage protects larynx

Larynx

https://www.youtube.com/watch?v=Q-PZlj0UH0c

Trachea• Windpipe • Lined with cilia

– Mucus traps particles – Cilia act like a broom

carrying particles to the mouth

• Surrounded by rings of cartilage and smooth muscles

• Provide support – Keep trachea open

Trachea cut open (do you see the cartilage rings?)

Cilia in the trachea

Bronchi• Two branches of the trachea (left and right)• Contain cartilage

Bronchioles• Smaller branches• No cartilage• Rings of muscle –

change diameter to dilate or constrict

Trachea

Bronchi

Bronchioles

Alveoli• Tiny air sacs • Each lung - ~ 150 million

alveoli• Very thin; one cell thick• Surrounded by capillaries• Site of gas diffusion

– Diffusion occurs with the concentration gradient

• Film of lipoprotein – prevents alveoli from sticking together

Pleural Membranes• Membranes on the outer

surface of lungs and inner wall of chest cavity

• Between the two membranes is lubricant which reduces friction

Diaphragm– Dome shaped band of

muscle– Separates thoracic cavity

from abdominal cavity– Helps in inhalation and

exhalation

• Muscles attached to the ribcage

• Helps with inhalation and exhalation

Intercostal Muscles

Answer the questions on page 34 of your workbook.

Have you ever eaten ribs before? If you

have, you’re eating the intercostal muscles!

Intercostals

Exhalation PathwayAlveoli

Bronchioles

Bronchi

Trachea

Larynx

Epiglottis

Pharynx

Nasal Passage

Topic Two: BreathingGas Exchange in the Lungs

• O2 moves from atmosphere to alveoli then blood and body tissues

• Erythrocytes contain Hemoglobin (Hb) which picks up O2 in the lungs and carries it to body cells

• When hemoglobin reaches tissues with low concentration of oxygen, it releases O2

• Then O2 diffuses into the cells

Gas Exchange: Oxygen

Gas Exchange: Oxygen• Hb greatly increases the carrying capacity of

blood oxygen• Hb + O2 = oxyhemoglobin

Gas Exchange: Carbon Dioxide• Carbon dioxide (CO2) is produced in the cells by

cellular respiration• CO2 then diffuses into the blood

Gas Exchange: Carbon Dioxide

• Carbon dioxide diffuses OUT of a capillary into an alveolus

• Oxygen diffuses OUT of the alveolus into the capillary

Gas Exchange: Carbon DioxideCO2 can be transported in 3 ways:

1. ~10% of CO2 is dissolved in blood plasma

2. ~20% joins with Hb (CO2 + Hb = carbaminohemoglobin)

3. Remaining 70% of CO2 form carbonic acid• Carbonic acid = H2CO3

• This lowers blood pH• Buffered to prevent the blood from becoming too

acidic - H2CO3 changes to bicarbonate ions and H+ ions

Gas Exchange: Carbon Dioxide

Tissue Cells

CO2

diffusion

Blood Lungs

CO2+ H2O

Carbonic Acid(very

acidic)

Bicarbonate ions

(less acidic)

Exhaled CO2

Mechanism of Breathing

• Air always moves from areas of HIGH pressure to areas of LOW pressure.– This is similar to diffusion

If both of these containers have the same number of air molecules, which has higher air pressure?

Air Pressure

http://www.youtube.com/watch?v=mA_fNMe9hoQ&safety_mode=true&persist_safety_mode=1&safe=active

Bill Nye 2:05 – 3:30 Lung balloon demo6:25 – 7:23 Lung SA7:24 – 7:58 R side bigger than L

Inspiration (Inhalation)1. Intercostal muscles

contract, pulling ribs up and out

2. Diaphragm contracts, straightening (flattens)

3. Abdominal muscles relax, allowing compression by diaphragm

4. Volume increases, air pressure in lungs decreases, air rushes in

Expiration (Exhalation)1. Intercostal muscles relax,

ribs spring back (down and in)

2. Diaphragm relaxes, rising to ORIGINAL position

3. Abdominal muscles contract, pushing abdominal organs up against the diaphragm

4. Elastic fibers in lungs shrink, helping force air out

5. Volume decreases, air pressure in lungs increases, air rushes out

Inspiration and ExhalationNotice what’s happening

to the diaphragm and lung volume when you

inhale and exhale

Inspiration Expiration

Intercostals contract = ribs up and out

Intercostals relax = ribs down and in

diaphragm contracts = moves down = pulls air in

diaphragm relaxes = moves up = pushes air out

• The amount of air that moves in and out of the lungs with each breath can be measured with a spirograph

Respiratory Volume

Normal breath

Forceful inhalation

Forceful exhalationAmount of air that remains in lungs

Total amount of air that can be inhaled and exhaled

• Tidal volume: volume of air that can be inhaled and exhaled in a normal breath

• Inspiratory reserve volume: Additional volume of air that can be taken into the lung

• Expiratory reserve volume: Additional volume of air that can be forced out of lungs

• Vital capacity (aka total lung volume): total volume of air that can be moved in and out of the lungs

• Residual volume: amount of air that remains in the lungs

Respiratory Volume

Regulation of Breathing• Breathing controlled by nerves

– The medulla oblongata = in the brain– The medulla contains chemoreceptors – test amount of CO2 in the blood

• If chemoreceptors stimulated by an increase in CO2, the medulla causes the

– Diaphragm to move– Increased breathing

rates, lowers CO2 levels

• Can be controlled – Medulla will take

over if CO2 builds up

Control of Breathing

1. Carbon dioxide rises in the cells during cell activity.

Carbon dioxide rises in the blood

2. Increased blood carbon dioxide stimulates chemoreceptors in the medulla.

3. Stimulation of the rib and diaphragm muscles increases the breathing rate. Carbon dioxide is removed from the blood.

Breathing rate is MOSTLY influenced by Carbon Dioxide!

Factors Affecting Breathing RateCondition Effect on Breathing Rate

High blood carbon dioxideLow blood oxygenCarbon monoxide

High blood adrenaline levels

Increases (to remove CO2)Increases

Increases

Increases

Exercise increases breathing rate!

Carbon monoxide competes with

Oxygen for hemoglobin

Adrenaline rushes cause an increase in breathing rate!

• Inflammation of bronchioles

• Air passages get smaller• Excess mucus• Harder to exhale than

inhale• Can lead to asthma and

emphysema

Disorders: Bronchitis

Disorders: Bronchial Asthma• Reversible

narrowing of the bronchial passage.

• Tissues that line the walls of the bronchioles swell and may cause bronchiole spasms.

Emphysema• Increased resistance to

airflow• Over-inflation of the

lungs• Alveoli cannot handle

pressure– Rupture– Less SA for gas exchange– Lowers O2 levels

Lung Cancer• Uncontrolled growth of cells =

tumour• Less surface area for diffusion• Blockages may occur• People have smoked tobacco for

centuries• How is related to this class?• Canadian Council for Tobacco

Control

• Lung cancer– Most common type of death from cancer– 50% OF SMOKERS WILL DIE FROM SMOKING RELATED CAUSES

Healthy vs. Unhealthy

The effects of chewing tobacco

1. hair loss 2. cataracts 3. wrinkling 4. hearing loss6. tooth decay7. lung ailments9. heart disease16. cancer:

a) of the lungs b)of the tongue c) of the mouth, salivary

glands and pharynx

Other Effects of Smoking

Lung Cancer

http://www.youtube.com/watch?v=gGcsBltFkds&safety_mode=true&safe=active

Bill Nye Respiration Start – 3:00 and 6:40 – 7:57

Stop smoking video: http://www.youtube.com/watch?v=wUSWXzHi0GE&safety_mode=true&safe=active

Other Disorders...• Pneumothorax

– a collapsed lung

• Laryngitis– swelling of the larynx

• Respiratory Distress Syndrome– when the lipoprotein on the alveoli is

missing in some newborns (especially premature babies) so extreme force is required to overcome the surface tension of the alveoli – different breathing patterns, often results in death