Session 2: Respiratory System Flashcards
What is gas exchange?
where oxygen is acquired and carbon dioxide is removed because cell respiration creates a constant demand for oxygen and a need to remove carbon dioxide.
Describe inspiration.
Inspiration means inhaling, inspiration is achieved by increasing space and therefore decreasing pressure inside the lungs. Air flows into lungs in response to the decreased pressure. In active breathing, muscle contraction is involved in both inspiration and expiration.
Describe expiration.
Expiration means exhaling, expiration is achieved by decreasing space and therefore increasing pressure, which causes the air to flow out to equalise with air pressure.
Overall, describe air flow in the lungs.
Air flows in and out due to changes in pressure. The expansion of the lungs increases volume and decreases intrapulmonary pressure, air from outside the lungs rushes in in response to pressure gradient. Expiration decreases volume of the lungs and increases intrapulmonary pressure, air moves out of the lungs through nose and mouth.
How do ribs and muscles support air flow?
Ribs allow a little movement during respiration, there is lots of muscles helping with ventilation including the diaphragm and muscles between ribs.
List the main facts about respiratory system structure.
Mammals have paired lungs, located within the thorax. They are connected to the outside air by a system of tubular passageways (trachea - tube to mouth, bronchi, bronchioles). The lungs of the average adult weigh around 1 kg and have a volume of 4 to 7 Litres. The diapragm is a dome shaped sheet of skeletal muscle, located beneath the lungs. Overall, the larynx leads to the trachea, which leads to the bronchus and bronchioles inside the lungs.
Describe the structure of the trachea and bronchioles.
The trachea divides into 2 bronchi (one in each lung) then each bronchus divides many times, terminating in the respiratory bronchides. Each bronciole has to 2 to 11 alevolar ducts and numerous alveoli, around 150 million in each lung. Ciliated, mucus secreting epithelium lines the trachea and bronchi, it traps and removes dust and pathogens before they reach the gas exchange surfaces. The mucus traps the particles, the cilia propel the pathogens and inhaled particles that are trapped in the mucous layer out of the airways, sometimes they just go out, other times they are swallowed into the digestive system which destroys bacteria. The cilia physically moves the mucus layer.
Describe the structure of alveoli.
They are tiny air sacs at the end of bronchioles. They provide large surface area for gas exchange (around 70 metres squared). Blood capillaries surround the alveoli like nets. Phospholipid surfactant lines the inside of each alveolus and increases pulmonary compliance because alveoli tend to recoil inward after each breath, so surfactant prevents complete deflation. They are also lined with alveolar epithelial cells or pneumoctyes. Phagocytic monocytes and macrophages (immune cells) are also present to protect the lung tissue. Elastic connective tissue enables expansion/recoil of alveoli.
Describe functions and processes of the alveoli.
Gases are exchanged by diffusion between alveoli and surrounding blood capillaries. The first type of pneumocytes (90-95%) contribute to gas exchange membrane, type 2 pneumocytes secrete surfactant.
Describe the Respiratory Membrane.
It is a layered junction between alveolar epithelial cells (pneumocytes) and endothelial cells of capillary and associated basement membranes (thin, collagenous layers that underlie the epithelial tissues). Gases move freely across the membrane. There is a very small distance between them (less than half a micrometre).
Describe gas transport with reference to muscles and lung capillaries.
Respiratory gases are transported around the body by the blood and its respiratory pigment hemoglobin. In muscles, oxygen is transferred to and retained by myoglobin. Lung capillaries enable gases to diffuse back and forth quickly because they are so close to alveoli, similar to the way capillaries in tissues are very close to the body cells and enable rapid diffusion of gases.
How is CO2 carried in the blood?
85% of CO2 in the blood is carried as bicarbonate (HCO3-) formed in the blood in an enzyme driven, reversible reaction.
Overall, describe gas transport in the respiratory system (step by step)
CO2 from body cells diffuses into capillary (into blood), then this deoxygenated blood is transported to the lungs and CO2 diffuses into the lungs (is then breathed out). Then oxygen diffuses into the blood (it becomes oxygenated) and hemoglobin becomes saturated with oxygen because oxygen levels are high. Blood is then transported back to body cells, CO2 levels become high and hemoglobin releases oxygen in body tissues. Then the cycle starts again.
What are respiratory diseases?
Include diseases of bronchioles, trachea, upper respiratory tract, and lung tissue. They can range from the common cold to life threatening tuberculosis. Can be infectious or non-infectious (e.g. asthma). Non-infectious diseases can be classified as obstructive (blockage) or restrictive (stops it from working).
Describe emphysema.
Respiratory disease when the alveolar walls and surrounding capillaries are destroyed, reducing the area for gas exchange and increasing the breathing rate. It is long term, and exhalation can be difficult - air effectively becomes trapped in the lungs because the alveoli lose elasticity.
