Gas Exchange Flashcards
What is gas exchange?
The exchange (diffusion) of oxygen and carbon dioxide to and from the blood at the alveoli and the respiring tissues
What four properties do all gas exchange surfaces share?
o They are permeable (permeable to CO2 and O 2 –
which are small, non-polar and hydrophobic gases)
o They are large (have large surface area)
o They are moist
o They are thin
Adaptations of Mammalian Lungs for Gas Exchange
Oxygen cannot diffuse into all our cells directly from the air, nor can waste products be directly ejected from the body.
- We have specialized organ systems, which are efficient, but need delivery of nutrients and removal of
waste. The ventilation system ensures the blood can be the medium for this. - Our lungs are moist
membranes, allowing oxygen to diffuse into the blood and carbon dioxide to diffuse out. - The ventilation system maintains a large concentration gradient between the alveoli and the blood.
- Breathing out keeps the CO2 concentration in the alveoli low, so it diffuses out of the blood. Breathing
in keeps O2 concentration in the alveoli high, so it diffuses into the blood.
What is the nasal cavity?
o Inside the nose
o Lined with mucous membrane
o Air is warmed and moistened
o Mucus and cilia (tiny hairs) trap foreign particles such as dust, dirt or debris
What is the Pharynx?
o Common to both diges.ve and
o respiratory systems
o At the bottom is the epiglottis (open for breathing/closed for eating)
Functions of the low respiratory tract?
- Larynx: maintains an open airway, routes food and air appropriately, assists in sound production
- Trachea: transports air to and from lungs
- Bronchi: branch into lungs
- Lungs: transport air to alveoli for gas exchange
What is the larynx?
o Made of cartilage
o Used for sound produc.on
o Vocal cords are pulled together when air is being expelled to cause
vibrations/sound
What is the trachea?
o Flexible tube made of semicircular loops of car.lage
o Approx. 10 -12 cm in length
o Splits into two branches- bronchi
What is the bronchi?
o Branch off the trachea and enters each lung
o Conducts the air into lungs
What are the lungs?
o Notice that the Right lung has 3 lobes, left lung has 2 lobes
o Space between the pleural membrane and the lung is filled with fluid
o Pleural membrane surrounds each lung.
o Interpleural space is the space between pleural
membranes-cover the surfaces and prevent fric.on when inhaling and exhaling
o Outer layer is attached to the chest wall and inner layer to the surface of the lung
What is the bronchioles?
o Each bronchi branches off into smaller tubes called
bronchioles where they lead into the alveoli
Features of the lungs
o Notice that the Right lung has 3 lobes, left lung has 2 lobes
o Space between the pleural membrane and the lung is filled with fluid
o Pleural membrane surrounds each lung.
o Interpleural space is the space between pleural
membranes-cover the surfaces and prevent fric.on when inhaling and exhaling
o Outer layer is attached to the chest wall and inner layer to the surface of the lung
What are alveoli?
o Alveoli in the lungs are found as clusters at the ends of the smallest bronchioles.
o Each cluster of alveoli has a surrounding capillary bed.
o The blood in these capillary beds is coming from the heart (pulmonary arteries) and therefore, is low in O 2 levels and high in CO2 levels.
o Surfaces are wet- so gases are dissolved, making diffusion easier
o O 2 from the alveoli diffuse across two cell membranes into the capillaries and CO2 diffuses from the blood in the capillaries to the alveoli.
How do concentration gradients affect ventilation and gas exchange?
o For gas exchange to be efficient, high concentra8on
gradients must be maintained in the alveoli.
o Breathing in increases the concentration gradient of oxygen between the alveoli and blood – so it diffuses into the blood.
o Breathing out removes CO 2 (and unused O 2 ), between blood and alveolus – so CO 2 will diffuse out.
o The continuous movement of blood throughout the dense network of blood vessels (the capillary bed) ensures a low concentration of O 2 as blood which has become enriched with O 2 is immediately moved away.
Boyle’s law and breathing in the lungs
The mechanism of breathing occurs according to the principle of Boyle’s Law (pressure is inversely proportional to volume)
o When the volume of the thoracic cavity increases,
pressure in the thorax decreases
o When the volume of the thoracic cavity decreases,
pressure in the thorax increases
* Gases will move from a region of high pressure to a region of lower pressure (similar to movement via concentration gradient)
