Topic 9 Gaseous Exchange. Flashcards
What is a gaseous exchange surface?
A gaseous exchange surface is a specialized structure in organisms that facilitates the exchange of gases, primarily oxygen and carbon dioxide, between the internal environment (such as blood or cells) and the external environment (such as air or water).
Describe the pathway of air from the nasal cavity/mouth to the alveoli and back.
When air is inhaled, it enters through the nasal cavity or mouth, passes through the pharynx (throat) and larynx (voicebox), and moves into the trachea. The trachea divides into two primary bronchi, each entering a lung. These further divide into smaller bronchioles, which continue to branch until they become terminal bronchioles. Terminal bronchioles subdivide into respiratory bronchioles, leading to alveolar ducts, which supply air to the alveoli where gas exchange occurs.
During exhalation, this pathway reverses, expelling carbon dioxide-rich air from the alveoli through the alveolar ducts, respiratory bronchioles, terminal bronchioles, bronchioles, tertiary and secondary bronchi, primary bronchi, trachea, larynx, pharynx, and finally out through the nasal cavity or mouth.When air is inhaled, it enters through the nasal cavity or mouth, passes through the pharynx (throat) and larynx (voicebox), and moves into the trachea. The trachea divides into two primary bronchi, each entering a lung. These further divide into smaller bronchioles, which continue to branch until they become terminal bronchioles. Terminal bronchioles subdivide into respiratory bronchioles, leading to alveolar ducts, which supply air to the alveoli where gas exchange occurs.
During exhalation, this pathway reverses, expelling carbon dioxide-rich air from the alveoli through the alveolar ducts, respiratory bronchioles, terminal bronchioles, bronchioles, tertiary and secondary bronchi, primary bronchi, trachea, larynx, pharynx, and finally out through the nasal cavity or mouth.
Describe the structure of the respiratory system.
- Upper respiratory tract.
- Lower respiratory tract.
- Alveoli.
Describe the structure of the respiratory system:
- The upper respiratory tract.
The upper respiratory tract serves as the gateway to our respiratory system. It begins with the nose and includes the nasal cavity and pharynx.
The nasal cavity, lined with cilia and mucus, warms, filters, and humidifies incoming air, protecting the lungs from irritants.
The pharynx, a shared passage for air and food, connects the nasal cavity to the lower respiratory tract.
Describe the structure of the human gas exchange system, limited to:
- Lungs.
The lungs are two large, spongy organs located in the thoracic (chest) cavity, protected by the rib cage. They are responsible for gas exchange and are divided into lobes; the right lung has three lobes (upper, middle, and lower), while the left lung has two lobes (upper and lower) to accommodate the heart’s position. The surface area of the lungs is significantly increased by tiny air sacs called alveoli, which are clustered at the ends of bronchioles. The lungs are surrounded by a pleural membrane that creates a pressure gradient necessary for inhalation and exhalation.
What happens directly after air flows through the nose and the trachea?
As air flows through the nose and the trachea, it is warmed to body temperature and moistened by evaporation from the lining, so protecting the delicate surfaces inside the lungs from desiccation (drying out).
Describe the structure of the respiratory system:
- The lower respiratory tract.
The lower respiratory tract consists of
the trachea, bronchi, bronchioles, and alveoli.
The trachea, or windpipe, transports air from the upper respiratory tract to the lungs. It is supported by C-shaped rings of cartilage that prevent the trachea from collapsing during breathing.
The trachea branches into two bronchi, each leading to a lung. The bronchi further subdivide into smaller bronchioles, eventually ending in tiny air sacs called alveoli.
Describe the structure of the human gas exchange system, limited to:
- Bronchioles.
As bronchi branch out within each lung, they become smaller tubes known as bronchioles. These structures lack supportive cartilage and can collapse. Bronchioles further divide into terminal bronchioles and respiratory bronchioles that lead directly to alveolar ducts that open into clusters of alveoli where gas exchange occurs.
Describe the structure of the respiratory system:
- The alveoli.
The alveoli are the primary sites of gas exchange, their thin walls, surrounded by a network of capillaries, facilitate the diffusion of oxygen into the bloodstream and carbon dioxide out of the blood.
Each alveolus is lined with a thin layer of squamous epithelium, maximizing the efficiency of gas exchange.
Distribution and functions of respiratory system components:
- Cartilage.
Cartilage, found in the trachea and bronchi and provide structural support, preventing collapse or bursting of the airways as air pressure changes during breathing.
The C-shaped rings of cartilage in the trachea allow for flexibility while maintaining an open passage for air.
There is a regular arrangement of cartilage in the trachea and an irregular arrangement in the bronchi.
Distribution and functions of respiratory system components:
- Goblet cells.
Goblet cells which scattered among the ciliated epithelial cells, produce mucus, a sticky substance that traps dust, bacteria, and other foreign particles, preventing them from reaching the lungs.
The mucus is then moved upwards by the cilia, protecting the respiratory system.
Distribution and functions of respiratory system components:
- Ciliated epithelium.
Ciliated epithelium lines the trachea, bronchi, and bronchioles, equipped with tiny hair-like structures called cilia.
These cilia rhythmically beat, moving mucus and trapped particles upwards, expelling them from the respiratory tract.
Distribution and functions of respiratory system components:
- Squamous epithelium.
The alveoli are lined with thin squamous epithelium, facilitating rapid diffusion of oxygen and carbon dioxide.
The thin layer of cells (one cell thick) minimizes the distance between the air in the alveoli and the blood in the capillaries, maximizing the efficiency of gas exchange.
Distribution and functions of respiratory system components:
- Smooth muscle.
Smooth muscle in the bronchi and bronchioles controls the diameter of the airways, regulating airflow.
This allows for bronchodilation, widening of the airways, during exercise or when encountering irritants. It also facilitates bronchoconstriction, narrowing of the airways, to protect the lungs from harmful substances.
Distribution and functions of respiratory system components:
- Elastic fibres.
Elastic fibres, found in the walls of the alveoli and bronchioles, enable the lungs to stretch and recoil during breathing. They help maintain the shape of the airways and promote efficient ventilation.
