gas exchange 6.4 Flashcards
Define gas exchange and ventilation.
gas exchnage is the diffusion of oxygen and CO2 through the walls of the alveoli.
Ventilation is the exchange of air between the atmosphere and the lungs – achieved by the physical act of breathing
State the location of gas exchange in humans. + Outline the mechanism of gas exchange in humans.
Between alveoli and the blood stream in adjacent capillaries.
Gases diffuse because the concentration gradient in the alveolous has a higher oxygen concentration and lower concentration of CO2 than the blood in the capillary.
Draw a diagram showing the structure of an alveolus and an adjacent capillary.
see notion
Describe how the structure of the alveoli increases surface area for gas exchange.
many alveolus- increases sufrace area for more efficient gas exchange
capillaries surround the alveoli which means gases only need to travel small distance to diffuse
alveoli are moist which increases the rate of diffusion by dissolving the gases
alveoli are flexible single cell layer can strech and become even more thin to faciliate more gas exchnage.
Outline the structure of type 1 pneumocytes.
Function: Involved in gas exchange between alveoli and capillaries.
Structure:
Flattened shape and extremely thin.
Connected by occluding junctions, which prevent the leakage of tissue fluid into the alveolar air space.
Amitotic and unable to replicate.
Outline the structure and function of type II pneumocytes.
Function: Responsible for the secretion of pulmonary surfactant, which reduces surface tension in the alveoli.
can divide to replace type 1.
Structure:
Cuboidal in shape and posses many granules to store surfactant components.
Describe two functions of the fluid secreted by type II pneumocytes.
pulmonary surfactant is a Film of moisture that allows oxygen in the alveolous to dissolve and then diffuse to the blood in the alveolar capillaries.
It also provides an area from which carbon dioxide can evaporate into the air and be exhaled.
Outline the flow of air into the lungs.
Air enters through the nose/mouth and is passed to the trachea
Air travels down the trachea until it divides into two bronchi
Inside each lung, the bronchi divide into smaller airways called the bronchioles.
Each bronchiole ends with alveoli, where gas exchange with the blood stream occurs.
state the role of cartilage in the trachea and bronchi.
Cartilage allows the air passage to remain open, even when pressure inside is low or high in the surrounding tissues.
State the role of smooth muscle fibres in the bronchioles.
To vary the width of the airways. This allows the contraction of the lumen to minimise the harmful substances breathed in.
State the relationship between gas pressure and volume.
Outline the pressure and volume changes that occur during inspiration and expiration.
If the particles of gas spread out, the pressure becomes lower and vice versa. Gas will move from high pressure regions to low pressure regions.
Explain the contraction and relaxation of muscles through the use of antagonistic muscle pairs.
Antagonisitc muscle pairs are two muscles that do opposite movements.
E.g. External intercostal muscle contracts during inspiration and relax during expiration, the internal intercostal does this inverse.
This allows the ribcage to do opposite movements.
Outline the mechanisms for ventillation
Inhalation
external intercostal muscle contracts moving ribcage up and out.
The diaphragm contracts and becomes flatter and moves down.
The volume of the thorax is increased by these muscle movements and the pressure drops below atmospheric pressure.
The air flows into the lungs until the pressure inside the lungs rises to atmospheric pressure.
Expiration
internal intercostal muscles contract soo the ribcage moves down and in.
The abdominal muscle contracts pushing the diaphragm up into a dome shape.
The volume of the thorax decreases and the pressure rises above atmospheric pressure.
Air flows out of the lung until the pressure returns to atmospheric pressure.
Outline the causes of lung cancer.
List symptoms of lung cancer.
Many causes inc;
Smoking
Asbestos
Air pollution
Certain infections
Genetic predisposition
symptoms:
Coughing up blood
Wheezing
Respiratory distress
Weight loss
Outline the causes of emphysema.
State the symptoms of emphysema.
Emphysema is mostly caused by smoking.
Damage to lung tissue leads to the recruitment of phagocytes to the region, which produce an enzyme called elastase.
The elastase, which is released as part of an inflammotary response, breaks down the elastic fibres in the alveolar wall.
Elastase activity can be blocked by an enzyme inhibitor, but not when elastase concentrations are increased.
symptoms:
Shortness of breath
Phlegm production
Expansion of the ribcage
Increased risk of chest infections
