Gas exchange Flashcards
What is gas exchange in humans?
Gas exchange in humans refers to the process where oxygen (O₂) from the air is taken into the body and carbon dioxide (CO₂) is removed from the body.
Name the structures involved in human gas exchange.
- Nasal cavity
- Trachea
- Bronchi
- Bronchioles
- Alveoli
Describe the structure and function of alveoli.
Alveoli are small sacs in the lungs where gas exchange occurs. They are surrounded by a network of capillaries and have thin walls (one cell thick) to facilitate diffusion of gases (O₂ and CO₂) between air and blood.
What happens during Inhalation
- the diaphragm contracts
- rib muscles lift the rib cage
- increasing chest volume.
- reduces air pressure in the lungs causing air to rush in (inspiration)
What happens during Exhalation
- the diaphragm relaxes
- rib muscles relax
- reducing chest volume
- increasing lung pressure
- pushing air out (expiration).
How is oxygen transported in the blood ?
Oxygen binds to haemoglobin in red blood cells, forming oxyhaemoglobin, which is transported to tissues.
How is carbon dioxide transported in the blood ?
- dissolved in plasma
- bound to haemoglobin
- as bicarbonate ions (HCO₃⁻) formed in RBCs
What factors affect the efficiency of gas exchange?
- Surface area of alveoli
- Thickness of respiratory membrane
- Partial pressure gradients of gases (O₂ and CO₂)
- Ventilation-perfusion matching (matching airflow to blood flow in lungs)
How does gas exchange change during exercise?
oxygen demand increases, leading to deeper and faster breathing (increased ventilation).
This enhances oxygen intake and carbon dioxide removal.
Blood flow to muscles increases, optimizing oxygen delivery and carbon dioxide removal.
Name disorders affecting gas exchange.
- Asthma
-Pneumonia - (COPD)
Asthma
Narrowing of airways, reducing airflow.
Chronic obstructive pulmonary disease (COPD)
Emphysema and chronic bronchitis, impairing airflow.
Pneumonia
Infection causing inflammation and fluid buildup in alveoli, reducing gas exchange efficiency.
How is breathing controlled?
Breathing is regulated by the respiratory center in the brainstem, monitoring blood pH, CO₂ levels (main regulator), and O₂ levels.
Chemoreceptors detect changes and adjust breathing rate and depth accordingly.
What adaptations make gas exchange efficient ?
- Large surface area of alveoli
- Thin respiratory membrane
- Rich capillary network around alveoli
- Moist lining of alveoli and respiratory tract
- Efficient ventilation-perfusion matching
Define Emphysema
Emphysema is a lung condition characterized by damage to the alveoli (air sacs) in the lungs.
This damage leads to reduced lung function, particularly affecting the exchange of oxygen and carbon dioxide.
Causes of Emphysema
Often caused by long-term exposure to irritants such as cigarette smoke, air pollution
Effects of Emphysema
- Destruction of alveoli walls, reducing surface area for gas exchange
- Loss of elasticity in lung tissue, making it difficult to exhale fully.
- Shortness of breath, coughing, and wheezing are common symptoms.
Function of elasticity in alveoli
Elasticity is crucial for alveoli to expand and contract during breathing.
Elastin in alveoli
Elastin fibers provide elasticity to the alveoli walls, allowing them to stretch during inhalation and recoil during exhalation.
Importance of elasticity in alveoli
Elasticity ensures efficient gas exchange by maintaining the proper surface area and volume of the alveoli.
Impact of loss of elasticity
- Difficulty exhaling completely, trapping air in the lungs (air trapping).
- Decreased efficiency of gas exchange.
- Increased work of breathing.
Structure cartilage in trachea
C-shaped rings of hyaline cartilage.
Function of cartilage in trachea
Provides structural support to keep the trachea open and prevent collapse during inhalation.
Structure of cartilage in bronchi
Cartilage plates in irregular shapes.
Function of cartilage in bronchi
Similar to the trachea, these cartilaginous structures provide support and maintain patency (openness) of the bronchi.
Mucus
Mucus is a viscous secretion produced by goblet cells and mucous glands lining the respiratory epithelium.
Functions of mucus
- moisturisation
- trapping particles
- protection
Moisturisation
Keeps the respiratory surfaces moist, facilitating gas exchange.
Trapping particles
Acts as a sticky trap for dust, pathogens, and other particles, preventing them from reaching deeper lung tissues.
Protection ( Mucus )
Helps protect delicate lung tissues from damage and irritation.
Location of mucus
Found along the respiratory tract, including the nasal passages, trachea, bronchi, and bronchioles.
Impact of excessive mucus
impair gas exchange by obstructing air passages and reducing the surface area available for diffusion.
Define cilia
Cilia are hair-like structures projecting from epithelial cells lining the respiratory tract.
Functions of cilia
- mucus clearance
- protection
Mucus clearance
Beat in coordinated waves to move mucus and trapped particles upwards towards the throat (mucociliary escalator), aiding in their removal from the respiratory system.
Protection ( Cilia )
Help in preventing pathogens and debris from entering deeper into the lungs.
Location of cilia
Primarily found in the upper respiratory tract (nose, trachea, bronchi), where their coordinated movement helps maintain respiratory health.
Impact of cilia on gas exchange
Effective ciliary action is crucial for maintaining a clear airway and facilitating efficient gas exchange by ensuring that mucus and particles are cleared away from the gas exchange surfaces.
Synergy of mucus & cilia
Mucus and cilia work together in the respiratory system to protect lung tissues and maintain efficient gas exchange.
Dysfunction of mucus & cilia
Conditions like smoking, pollution exposure, and certain diseases can impair the function of mucus and cilia, leading to respiratory issues.
