Gas Exchange

• Lungs work with the circulatory system to ensure that the cells in the body receive oxygen and eliminate carbon dioxide

• The process that requires oxygen and gives off carbon dioxide in the human body is cellular respiration.

Ventilation – the filling the lungs with air and breathing that air out• During this time oxygen diffuses into the blood stream and carbon

dioxide diffuses into the ling tissue

Overview of the Respiratory System

Gas Exchange – the movement/diffusion of gases• Gas exchange occurs in 2 places:1.The Lungs - oxygen from the air of the lungs moves into the blood stream and carbon dioxide moves out2.Capillary Bed – opposite gas exchange occurs, oxygen diffusion out of the blood stream and into a body cell and carbon dioxide diffuses out of the body into the capillary bed

Overview of the Respiratory System

• Single cell organisms do not have a ventilation system• As long as the oxygen concentration is high on the outside going into

the cell is not a problem

• Our bodies contain millions of cells underneath a layer of dead cell meant to protect the living cells

• Cells are too far from the outside air to directly make use of the process of diffusion (oxygen and carbon dioxide)

• The ventilation system and along with the circulatory system function together to pick up oxygen in the lungs and move the oxygen around the body

Overview of the Respiratory System

• Ventilation system ensures that the concentration of respiratory gases within the lungs encourages diffusion of gases needed for life.

• So, if you stopped breathing the oxygen in the lungs would not exceed the oxygen in the blood STOPPING THE DIFFUSION OF OXYGEN INTO THE BLOOD

Overview of the Respiratory System

Gas Exchange occurs within the alveoli

Anatomy of the Ventilation System

When you take in air through your mouth or nasal passages:

• The air first enters your trachea• Then your right and left bronchi• Then smaller and smaller branches of the bronchi• Hen very small branches called bronchioles• Finally, the air enters the small air sacs in the lungs called alveoli

Anatomy of the Ventilation System

• Alveoli are found as clusters at the ends of the smallest bronchioles

• They look like grapes• Approximately 300 million alveoli in each lung• Each cluster has surrounding capillaries• Blood enters the capillaries from the right ventricle via the pulmonary artery

• Blood is low in oxygen, high in carbon dioxide

• Oxygen diffuses through 2 cell membranes

Anatomy of the Ventilation System

Alveoli gas exchange• Two membranes:

• First is a single cell membrane making up the wall of the alveolus • Second is a single cell membrane making up the capillaries

• Carbon Dioxide diffuses in the opposite direction of oxygen in the same locations

• As long as you keep breathing and air is refreshed in the lungs the concentration of gases will allow diffusion of both gases

Anatomy of the Ventilation System

Adaptation Advantage

Spherical shape of alveoli Provides a large surface area for respiratory gases to diffuse through

Flattened, single cell thickness of each alveolus

Prevents respiratory gases from having to diffuse through more cell layers

Moist inner lining of alveolus Allows for efficient diffusion

Associated capillary bed nearby Respiratory gases do not have to diffuse far to reach single cell thick capillaries

Adaptation of Alveoli

• The lungs are not capable of creating motion on their own• The lungs work based on an inverse relationship between

pressure and volume.• This is created by the muscles and structures that surround the lungs• These include the Diaphragm, Intercostal Muscles around the ribs, and

muscles in the abdomen

Mechanism of Ventilation

An increase in volume will lead to a decrease in pressure. Whatever pressure does volume will do the opposite and vice versa

1. The diaphragm contracts and at the same time the abdominal muscles and intercostal muscles help raise the rib cage. Collectively, all of these actions act to increase the volume of the thoracic cavity

2. Because the thoracic cavity has an increased its volume, the pressure inside the cavity decreases. This leads to less pressure pushing on the passive lung tissue

3. The lung tissue increases its volume because there is less pressure exerted on it

4. This leads to a decrease in pressure inside of the lungs, also known as a partial vacuum

5. Air comes in through your open mouth or nasal passages to counter the partial vacuum within the lungs. (fills alveoli with air)

Mechanism of Inspiration

Mechanism of Inspiration• So the reverse holds true for expiration• When exercising all motions become more exaggerated