Biology Notes – Grade 10
National Curriculum Pakistan - NCP
Chapter 3: Respiratory System
Learn about the important functions, organs, and structures involved in human respiration.
1. What two main gases are exchanged during respiration?
During respiration, the body takes in oxygen from the air and releases carbon dioxide, a waste product of cellular respiration, back into the air. This exchange of gases is essential for providing energy to the body's cells.
2. What is the role of the respiratory system?
The primary role of the respiratory system is to facilitate the exchange of oxygen and carbon dioxide between the body and the external environment. It moves oxygen into the blood for delivery to cells and removes carbon dioxide from the blood for elimination.
3. What are the general problems faced by air entering the respiratory system?
Air entering the respiratory system can be cold, dry, and may contain dust particles and germs. The respiratory system has mechanisms to warm, moisten, and filter the incoming air to protect the delicate lung tissues.
4. What are the main organs of the air passage way?
The main organs of the air passage way in humans are the lungs and the air passages that lead to them, including the nasal cavity, pharynx, larynx, trachea, bronchi, and bronchioles.
5. Describe the structure of the nasal passage.
The nasal passage is a complex structure consisting of the nose, pharynx, trachea, bronchi, and bronchioles. The nose has two external openings (nostrils) leading to the nasal cavity, which is divided by a septum. The walls of the nasal cavity are lined with a mucous membrane and have cilia.
6. What are the important functions performed by the nasal cavity?
The nasal cavity performs several important functions, including warming and moistening the incoming air. The hairs lining the entrance filter out large dust particles, and the mucus traps smaller particles and germs. The nasal cavity also contains olfactory receptors for the sense of smell.
7. What is the pharynx and where is it located?
The pharynx, or throat, is a funnel-shaped passageway located behind the nasal cavity and mouth, extending down to the larynx and esophagus. It serves as a common pathway for both air and food.
8. What is the larynx and where is it situated?
The larynx, or voice box, is a cartilaginous structure located at the top of the trachea, below the pharynx. It contains the vocal cords, which vibrate to produce sound, and plays a role in protecting the airway during swallowing.
9. What is the trachea and what is its structure?
The trachea, or windpipe, is a tube that extends from the larynx down into the chest cavity, where it divides into two main bronchi. Its walls are supported by C-shaped rings of cartilage that keep the airway open.
10. How is the trachea adapted to maintain an open airway?
The trachea is held permanently open by the C-shaped rings of cartilage embedded in its walls. This structural support ensures a continuous passage for air to flow to and from the lungs during breathing.
11. What do the trachea divide into and where do they lead?
The trachea divides into two main bronchi (singular: bronchus), a right bronchus and a left bronchus. Each bronchus enters one of the lungs and further subdivides into smaller tubes called bronchioles within the lung tissue.
12. How does the structure of the bronchi change as they branch into bronchioles?
As the bronchi branch into smaller and smaller bronchioles within the lungs, the cartilaginous rings in their walls gradually disappear and are replaced by smooth muscle. The contraction and relaxation of this smooth muscle can regulate the diameter of the bronchioles, affecting airflow.
13. What do the bronchioles eventually lead to within the lungs?
The smallest bronchioles eventually lead to tiny air sacs called alveoli. These alveoli are clustered together and resemble bunches of grapes, forming the respiratory surface of the lungs where gas exchange occurs.
14. Describe the structure of the alveoli.
Alveoli are tiny, thin-walled, balloon-like sacs. Their walls are composed of a single layer of flattened epithelial cells surrounded by a dense network of capillaries. This thin structure and rich blood supply facilitate efficient diffusion of gases.
15. What is the respiratory surface of the lungs?
The alveoli collectively form the vast respiratory surface of the lungs. Their enormous number and total surface area provide a large area for the exchange of oxygen and carbon dioxide between the air and the blood.
16. Describe the location and protection of the lungs.
The lungs are located in the thoracic cavity, on either side of the heart. They are protected by the rib cage, which surrounds them, and the intercostal muscles located between the ribs. A double-layered membrane called the pleura also surrounds each lung.
17. What is the pleural membrane and pleural fluid?
The pleural membrane is a double-layered membrane surrounding each lung. The outer layer lines the chest cavity, and the inner layer covers the lung surface. Between these layers is the pleural cavity, which contains a thin layer of lubricating fluid called pleural fluid, reducing friction during breathing movements.
18. How does gas exchange occur in the alveoli?
Gas exchange in the alveoli occurs by diffusion. Oxygen from the inhaled air in the alveoli dissolves in the moist lining and diffuses across the thin alveolar and capillary walls into the blood. Simultaneously, carbon dioxide from the blood diffuses across the capillary and alveolar walls into the alveoli to be exhaled.
19. Why is it important to breathe through the nose rather than the mouth?
Breathing through the nose is preferable because the nasal cavity filters out dust and germs, warms, and moistens the air before it reaches the lungs. This protective function helps prevent infections and irritation of the respiratory tract.
20. What can happen if food particles enter the trachea?
If food particles enter the trachea (windpipe), they can obstruct the airway, leading to choking and difficulty breathing. The epiglottis normally prevents this by covering the trachea during swallowing.
21. Why is it important to maintain good oral hygiene?
Maintaining good oral hygiene helps prevent the growth of bacteria in the mouth. These bacteria can be inhaled into the lungs, potentially causing respiratory infections and other health problems.
22. What are the two phases of breathing?
Breathing, or ventilation, consists of two main phases: inhalation (inspiration), the process of taking air into the lungs, and exhalation (expiration), the process of expelling air from the lungs.
23. What muscles are primarily involved in breathing?
The primary muscles involved in breathing are the diaphragm, a large dome-shaped muscle at the base of the chest cavity, and the intercostal muscles, which are located between the ribs.
24. Briefly describe what happens during inhalation.
During inhalation, the diaphragm contracts and flattens, and the external intercostal muscles contract, lifting the rib cage up and outward. This increases the volume of the thoracic cavity, decreasing the pressure inside the lungs, causing air to rush in.
25. Briefly describe what happens during exhalation.
During exhalation, the diaphragm relaxes and returns to its dome shape, and the external intercostal muscles relax, allowing the rib cage to move down and inward. This decreases the volume of the thoracic cavity, increasing the pressure inside the lungs, forcing air out.
26. Name four common respiratory diseases.
Four common respiratory diseases are Bronchitis, Emphysema, Pneumonia, and Asthma. These conditions affect different parts of the respiratory system and can impair breathing.
27. What is bronchitis characterized by?
Bronchitis is characterized by the inflammation of the lining of the trachea, bronchi, and bronchioles. This inflammation leads to symptoms like coughing and increased mucus production in the airways.
28. What is the main cause of chronic bronchitis?
The main cause of chronic bronchitis, a long-term form of the disease, is prolonged irritation of the airways, most commonly due to smoking. Air pollution or industrial dusts can also contribute.
29. What is the primary characteristic of emphysema?
Emphysema is a chronic respiratory disease where there is gradual damage to the alveoli, the tiny air sacs in the lungs. This damage leads to a decrease in the surface area available for gas exchange, making breathing difficult.
30. What is the main cause of emphysema?
The primary cause of emphysema is long-term irritation of the lungs, most often due to cigarette smoke. Air pollution and industrial dusts can also contribute to the development of this condition.
31. What part of the respiratory system is primarily affected by pneumonia?
Pneumonia is an infection of the alveoli, the air sacs in the lungs. This infection causes the alveoli to fill with fluid or pus, leading to difficulty in breathing and reduced oxygen intake.
32. What are common causes of pneumonia?
Pneumonia is commonly caused by infections from various microorganisms, including bacteria (like Streptococcus pneumoniae), viruses, and fungi. The specific cause often influences the symptoms and treatment.
33. What are the main characteristics of asthma?
Asthma is a chronic inflammatory disease of the airways, characterized by episodes of wheezing, coughing, chest tightness, and shortness of breath. These symptoms occur due to the narrowing of the airways, often triggered by irritants or allergens.
34. How is asthma typically treated?
Asthma is often treated with inhalers. Some inhalers contain bronchodilators that help to relax the muscles around the airways and widen them, making breathing easier. Other medications help to reduce inflammation in the airways.
35. What is the primary characteristic of lung cancer?
Lung cancer is characterized by the uncontrolled growth of abnormal cells that form tumors in the lungs. These cancerous cells can invade and destroy healthy lung tissue and may spread to other parts of the body.
36. What is a major cause of lung cancer?
A major cause of lung cancer is the inhalation of carcinogens, with tobacco smoking being the leading risk factor. Exposure to other substances like radon, asbestos, and air pollution can also increase the risk.
37. What are the treatments for lung cancer?
Common treatments include surgery to remove the tumor, chemotherapy to kill cancer cells with drugs, and radiation therapy to target and destroy cancerous cells with high-energy rays.
38. Briefly describe the diaphragm and rib cage movements during inhalation.
During inhalation, the diaphragm contracts and moves down, while the rib cage moves up and out. These actions expand the chest cavity, allowing air to enter the lungs.
39. What are the main differences in oxygen and carbon dioxide levels between inspired and expired air?
Inspired air has higher oxygen (21%) and lower carbon dioxide (0.04%), whereas expired air has lower oxygen (16%) and higher carbon dioxide (4%). This reflects the exchange of gases during respiration.