7: Gas Exchange in Humans Flashcards
Why is gas exchange necessary?
It ensures a continuous supply of oxygen for the respiration in cells, and the removal of carbon dioxide produced in the process.
How does gas exchange take place?
It takes place by diffusion across a moist respiratory surface.
Explain why large multicellular organisms need a breathing system.
The surface area to volume ratio is smaller than that of unicellular organisms, and the diffusion of gases across the body surface cannot satisfy the needs of these organisms. They have a breathing system for efficient gas exchange.
State the structure through which the lungs are connected with the external environment.
Respiratory tract
Describe the airflow when we inhale.
Air flows into the nasal cavity, the pharynx, the larynx, the trachea, the bronchi, the bronchioles, and reaches the air sacs in the lungs.
Describe the airflow when we exhale.
Air flows from the air sacs in the lungs, to the bronchioles, the bronchi, the trachea, the larynx, the pharynx, and to the nasal cavity before exiting our body through the nostrils.
Describe the function of our nose.
It has features to clean, moisten, and warm the inhaled air.
State the function of hairs inside the nostrils.
They filter larger dust particles from the inhaled air.
State the function of mucus-secreting cells in the lining of the nasal cavity.
They secrete mucus, which traps dust particles and microorganisms in the inhaled air and moistens the inhaled air to prevent the moist respiratory surface inside the lungs from drying out.
State the functions of the ciliated epithelial cells in the lining of the nasal cavity.
Cilia of ciliated epithelial cells in the lining beat to sweep the mucus towards the pharynx. The mucus is then coughed up, or swallowed into the stomach where most of the trapped microorganisms will be killed by hydrochloric acid in gastric juice.
State the functions of the blood vessels in the lining of the nasal cavity.
The lining of the nasal cavity has a rich supply of blood vessels. The blood in the capillaries warms the inhaled air, which avoids irritation of the lungs.
State the material making up the larynx.
Cartilage
State the importance of cartilage in the larynx.
It prevents the larynx from collapsing due to the pressure changes during breathing.
State the importance of the shape of the cartilage of the trachea.
The trachea has a C-shaped cartilage, with the open part of the cartilage lying next to the oesophagus. This allows the oesophagus to expand when food is swallowed.
State the functions of the inner walls of the trachea and bronchi.
The inner walls are lined with mucus-secreting cells and ciliated epithelial cells, and they also have a rich supply of blood vessels. These features can clean, moisten, and warm the inhaled air.
State the importance of smooth muscles and elastic fibres in the walls of the trachea and bronchi.
The smooth muscles can contract and relax to help regulate the diameter of the airway and hence the airflow.
Compare the composition of walls of bronchi and bronchioles.
The wall of bronchioles have no cartilage unlike bronchi. Their walls are mostly made up of smooth muscles and elastic fibres. Larger bronchioles are lined with mucus-secreting cells and ciliated epithelial cells like the bronchi.
State the number of lobes in each half of the lung.
The right lung has two lobes, while the left lung has three lobes.
Compare the sizes of the left lung and right lung.
The left lung is smaller in size than the right lung, which leaves space for the heart.
Explain the colour of the lungs.
The lungs are pink in colour due to the presence of blood capillaries.
Explain the texture of the lungs.
It is spongy and elastic since is has a large amount of air-filled space and elastic fibres.
State the name of the chamber enclosed by the rib cage.
The thoracic cavity
