Topic 6.4

Gas Exchange

Why do we need Oxygen???

• Aerobic cellular respiration– Biochemical pathway– Chemical bonds within a glucose molecule

are broken..releasing Energy – This E is stored as ATP

– Requires O2 and gives off CO2

– Each of the 6 C in glucose are given off as CO2

6.4.1 Distinguish between ventilation, gas exchange and

cellular respiration• Ventilation = breathing (filling lungs with air

and exhaling)• Gas exchange = the movement of gases

– O2 in the lung tissues diffuses into the bloodstream

– CO2 from blood diffuses into lung tissues

– Occurs in two locations:• In the lungs

• In capillary beds where CO2 diffuses into blood and O2 diffuses into body cells

Relationship between ventilation, gas exchange and cell respiration

Lung air air

ventilation CO2 diffuses out of alveolus O2 diffuses into alveolus

Capillary

gas exchange

Body Cell cell respiration O2 is a reactant for aerobic cellular respiration

CO2 is a product of aerobic cellular respiration

Co2 diffuses out oflung capillaries

Co2 diffuses intobody capillaries

O2 diffuses intolung capillaries

O2 diffuses out ofbody capillaries

6.4.2 Explain the need for a ventilation system

• Amoeba has no ventilation system????• They need gas exchange????

• Our bodies are so thick-only our outside cells are exposed to air– All our cells need O2 and are too far away to

make use of diffusion of O2 and CO2

• Maintain [ ] levels of gases within the lungs

Anatomy of the Ventilation System

Pathway of the Ventilation System• Air enters your trachea

• Passes into your right and left 1◦ bronchi

• Branches smaller and smaller

• Smallest branches = bronchioles

• Finally, air enters the small air sacs called alveoli– Clustered at the ends of the smallest bronchioles– Appearance similar to “bunch of grapes”– Approx. 300 million in lungs– Surrounded by capillary bed

6.4.3 Features of Alveoli that adapt them to gas exchange

Adaptation Advantage

spherical shape provides a large surface area for respiratory gases to diffuse through

flattened, single cell thickness

prevents respiratory gases from having to diffuse through more cell layers

moist inner lining allows for efficient diffusion

associated capillary bed nearby

respiratory gases do not have to diffuse far to reach single cell thick capillaries

6.4.5 Mechanisms of Ventilation• Tissues that make up our lungs are passive…not

muscular• Muscles surround the lungs

– Diaphragm– Abdominal muscles– Intercostal (rib) muscles

• Breathing is based on the inverse relationship between pressure and volume– in volume leads to a in pressure– Lungs are in thoracic cavity (thorax) which is a closed

environment– Lungs have opening through the trachea (via nose and

mouth)– These 2 environments (lungs and thorax) affect each other

6.4.5 Mechanisms of Ventilation (cont.)• Mechanisms of Inspiration: (steps reversed for

expiration)

1. Diaphragm contracts while abdominal and intercostal muscles raise the rib cage…this the volume of thoracic cavity

2. Since volume in thoracic cavity, the pressure which leads to less pressure pushing on the passive lung tissue

3. Lung tissue in volume since there is less pressure

4. in pressure inside lungs is known as partial vacuum

5. Air comes in through mouth and nose to counter the partial vacuum (fills alveoli with air)

2 Questions

1. Create a list of steps which represent what your body would do to accomplish a single expiration (breathing out).

2. Pneumonia (excess mucus) and smoking (tar) create an extra lining inside of each of the alveoli. Describe how and why this could become life threatening.