Chapter 3: Respiratory System

Select the correct answer:

1. One reason for emphysema is

A) smoking

B) exercise

C) food

D) iron deficiency

Answer: A) smoking

Explanation: Emphysema is a chronic obstructive pulmonary disease (COPD) primarily caused by long-term smoking. Cigarette smoke damages the alveolar walls, causing them to lose their elasticity and merge into larger, less efficient air sacs. This reduces the surface area for gas exchange, leading to shortness of breath. While other factors like air pollution and genetic disorders (alpha-1 antitrypsin deficiency) can contribute, smoking is the leading cause.

2. In humans during expiration:

A) diaphragm is lowered and ribs are raised

B) both diaphragm and ribs are raised

C) diaphragm is raised and ribs are lowered

D) both diaphragm and ribs are lowered

Answer: C) diaphragm is raised and ribs are lowered

Explanation: During expiration (exhalation), the diaphragm relaxes and moves upward (domes), and the external intercostal muscles relax, causing the ribs to move downward and inward. This decreases the volume of the thoracic cavity, increasing the

pressure inside the lungs relative to atmospheric pressure, which forces air out.

3. The inner most chamber of the respiratory system into which air can be drawn:

A) bronchiole

B) bronchus

C) bronchial tube

D) alveoli

Answer: D) alveoli

Explanation: The alveoli are the smallest and innermost structures of the respiratory system. They are tiny, balloon-like air sacs at the end of the bronchioles where gas exchange occurs. Oxygen diffuses from the alveoli into the blood, and carbon dioxide diffuses from the blood into the alveoli.

4. What is the percentage of oxygen in expired air when a person is resting?

A) 8%

B) 12%

C) 16%

D) 20%

Answer: C) 16%

Explanation: Inspired air contains approximately 21% oxygen. When a person exhales, the expired air contains about 16% oxygen because some oxygen has been absorbed by the body's tissues during cellular respiration. Carbon dioxide increases from about 0.04% in inspired air to about 4% in expired air.

5. Which process does not use energy released by respiration?

A) active transport to the glucose in the villi

B) diffusion of oxygen across the alveolar surface

C) maintenance of constant body temperature

D) passage of nerve impulses

Answer: B) diffusion of oxygen across the alveolar surface

Explanation: Diffusion is a passive process that does not require energy (ATP). Oxygen moves from an area of higher concentration (alveoli) to an area of lower concentration (blood) without the expenditure of energy. Active transport, maintenance of body temperature, and nerve impulse transmission all require energy released by respiration.

6. Which path does a molecule of oxygen take as it enters the body?

Answer: D) trachea [source symbol unavailable] bronchus [source symbol unavailable] bronchiole [source symbol unavailable] alveolus

Explanation: Air enters the body through the nose/mouth, passes through the pharynx and larynx, then down the trachea (windpipe). The trachea divides into two bronchi (singular: bronchus), which further divide into smaller bronchioles, and finally ends at the alveoli where gas exchange occurs.

7. When you inhale, the diaphragm:

A) relaxes and moves upward

B) relaxes and moves downward

C) contracts and moves upward

D) contracts and moves downward

Answer: D) contracts and moves downward

Explanation: During inhalation (inspiration), the diaphragm contracts and flattens (moves downward). This increases the vertical dimension of the thoracic cavity. Simultaneously, the external intercostal muscles contract, lifting the ribs upward and outward. These actions increase the volume of the thoracic cavity, decreasing pressure and allowing air to rush into the lungs.

8. Respiration in living organisms always involves:

A) carbon dioxide production

B) energy release

C) gaseous exchange

D) oxygen consumption

Answer: B) energy release

Explanation: Respiration is defined as the biochemical process by which living organisms release energy from organic molecules (like glucose) to produce ATP. While carbon dioxide production, gaseous exchange, and oxygen consumption are common in aerobic respiration, they are not universal. For example, anaerobic respiration does not require oxygen and may not produce carbon dioxide (e.g., lactic acid fermentation). Energy release is the defining characteristic of all respiration.

9. The gas exchange portion of the human respiratory system is the:

A) trachea

B) bronchi

C) larynx

D) alveoli

Answer: D) alveoli

Explanation: The alveoli are the functional units of the respiratory system where gas exchange occurs. Their thin walls (one cell thick), large total surface area (about 70-100 square meters), and rich capillary network facilitate the efficient diffusion of oxygen into the blood and carbon dioxide out of the blood.

10. The disease involving breakdown of air sacs of the lungs is:

A) pneumonia

B) bronchitis

C) emphysema

D) asthma

Answer: C) emphysema

Explanation: Emphysema is a chronic lung disease characterized by the destruction of the alveolar walls. This causes the alveoli to merge into larger, irregular air spaces, drastically reducing the surface area available for gas exchange. This leads to severe shortness of breath.

11. Which blood vessel surrounds the alveoli?

A) capillary

B) vein

C) venule

D) artery

Answer: A) capillary

Explanation: A dense network of pulmonary capillaries surrounds each alveolus. The walls of both the alveoli and capillaries are only one cell thick, allowing for rapid diffusion of gases. Deoxygenated blood enters these capillaries, picks up oxygen, and leaves as oxygenated blood.

12. In asthma, shortness of breath occurs due to:

A) constriction of bronchi

B) rupture of alveolar walls

C) rupturing of bronchial walls

D) accumulation of pus in alveoli

Answer: A) constriction of bronchi (Note: Inflammation and constriction both occur. Option A is the closest to the primary mechanism.)

Explanation: Asthma is a chronic inflammatory disease of the airways. During an asthma attack, the muscles around the bronchi and bronchioles contract (bronchoconstriction), and the lining of the airways becomes inflamed and swollen. This narrows the airways, making it difficult to breathe.

13. The percentage of oxygen gas in inspired air is 21% and in expired air it is 16%. This difference in the amount of oxygen gas is due to:

A) storage of oxygen gas in lung tissues

B) non-reactivity of oxygen gas with the blood

C) liberation of oxygen gas as a metabolic waste

D) utilisation of oxygen gas in energy production

Answer: D) utilisation of oxygen gas in energy production

Explanation: The difference in oxygen concentration between inspired and expired air is due to the body's consumption of oxygen during cellular respiration. Oxygen is used in the mitochondria to oxidize glucose and produce ATP (energy). This utilization reduces the amount of oxygen in the air that is exhaled.

14. Which one of the following row best describes the action of different structures associated with the process of inhalation?

Answer: C (Diaphragm: contract, Rib muscles: contract, Ribs: raised)

Explanation: During inhalation, the diaphragm contracts (flattens), and the external intercostal muscles (rib muscles) contract, pulling the ribs upward and outward. This increases the volume of the thoracic cavity.

15. Which row correctly describe the functions of the diaphragm, cilia and mucus in human gaseous exchange system?

Answer: B (Diaphragm: Contracts to cause breathing in, Cilia: Carry mucus to the throat, Mucus: Trap dust and bacteria from air)

1. How exchange of gases takes place in alveoli?

Answer: Gas exchange in the alveoli occurs by simple diffusion. Oxygen from the inhaled air diffuses across the thin alveolar and capillary walls into the blood, where it binds to hemoglobin. Carbon dioxide, which is more concentrated in the blood, diffuses from the blood into the alveoli to be exhaled. The large surface area, thin walls, and rich blood supply of the alveoli facilitate this efficient exchange.

2. What is the effect of exercise on the rate of breathing?

Answer: Exercise increases the rate and depth of breathing. During exercise, muscles consume more oxygen and produce more carbon dioxide. Chemoreceptors detect the increased CO₂ levels and decreased pH in the blood. This stimulates the respiratory center in the medulla oblongata to increase breathing rate and depth, delivering more oxygen to the muscles and removing carbon dioxide faster.

3. Compare inspired air and expired air.

Answer:

4. How viral infections like Covid-19 affect bronchi?

Answer: Viral infections like COVID-19 can affect the bronchi by causing inflammation and swelling of the bronchial lining. This leads to increased mucus production, which can obstruct airflow. In severe cases, the infection can spread to the alveoli, causing pneumonia. Symptoms include coughing, shortness of breath, and chest discomfort.

5. What is the importance of breathing in fresh air?

Answer: Breathing in fresh air is important because:

Oxygen Supply: Fresh air contains higher oxygen levels, essential for cellular respiration and energy production. Removal of CO₂: It helps in the efficient removal of carbon dioxide, preventing acidosis. Reduced Pollutants: Fresh air has fewer pollutants, reducing the risk of respiratory diseases. Mental Well-being: Fresh air improves mood, alertness, and cognitive function.

6. What is the importance of keeping nasal and oral cavity clear?

Answer: Keeping the nasal and oral cavity clear is important because:

Air Filtration: The nose filters dust, pollen, and pathogens, preventing them from reaching the lungs. Air Conditioning: The nose warms and humidifies the air before it reaches the lungs. Prevention of Infection: A clear passage reduces the risk of respiratory infections. Unobstructed Breathing: Clear airways ensure efficient airflow and oxygen intake.

7. Differentiate between:

a. Respiration and Breathing

Answer: Breathing is the mechanical process of inhaling and exhaling air. Respiration is the biochemical process of releasing energy from glucose.

b. Respiration and Photosynthesis

Answer: Respiration releases energy by breaking down glucose. Photosynthesis stores energy by synthesizing glucose using light energy.

c. Inhalation and Exhalation

Answer: Inhalation is the intake of air into the lungs. Exhalation is the expulsion of air from the lungs.

d. Smoker and Passive smoker

Answer: A smoker actively inhales tobacco smoke. A passive smoker inhales secondhand smoke from others. e. Bronchitis and Pneumonia

Answer: Bronchitis is inflammation of the bronchi. Pneumonia is an infection of the alveoli. f. Aerobic and Anaerobic respiration

Answer: Aerobic respiration requires oxygen to produce ATP. Anaerobic respiration occurs without oxygen. g. Pharynx and Larynx

Answer: The pharynx is the throat (passage for food and air). The larynx is the voice box. h. Glottis and Epiglottis

Answer: The glottis is the opening to the larynx. The epiglottis is the flap that covers the glottis during swallowing.

1. Describe the structure of human respiratory system.

Answer: The human respiratory system consists of the upper and lower respiratory tracts.

Upper Respiratory Tract:

1. Nose and Nasal Cavity: Filters, warms, and moistens air. Contains hairs, mucus, and cilia.

2. Pharynx: Throat; passage for air and food.

3. Larynx: Voice box; contains vocal cords. The epiglottis prevents food from entering.

Lower Respiratory Tract:

4. Trachea: Windpipe; lined with ciliated epithelium and C-shaped cartilage rings.

5. Bronchi: Two main branches entering the lungs.

6. Bronchioles: Smaller branches within the lungs.

7. Lungs: Paired organs containing alveoli. The right lung has three lobes, the left has two.

8. Alveoli: Tiny air sacs where gas exchange occurs. Surrounded by capillaries.

Mechanics: The diaphragm and intercostal muscles facilitate breathing by changing thoracic volume.

In summary, the respiratory system is designed to bring oxygen into the body and remove carbon dioxide.

2. Define breathing. Write the mechanism of breathing.

Answer: Breathing: Breathing (ventilation) is the mechanical process of moving air into and out of the lungs.

Mechanism:

Inhalation (Inspiration):

Diaphragm contracts and flattens. External intercostal muscles contract, lifting ribs. Thoracic volume increases. Pressure decreases (Boyle's Law). Air rushes into the lungs.

Exhalation (Expiration):

Diaphragm relaxes and domes upward. External intercostal muscles relax, ribs lower. Thoracic volume decreases. Pressure increases. Air is pushed out.

In summary, breathing is a mechanical process driven by pressure changes in the thoracic cavity.

3. Differentiate between composition of inspired and expired air.

Answer:

In summary, expired air has less oxygen, more carbon dioxide, and more water vapor than inspired air.

4. State the symptoms, causes and treatments of:

a. bronchitis

Answer:

Symptoms: Persistent cough, mucus production, wheezing, shortness of breath. Causes: Viral/bacterial infection, smoking, air pollution. Treatment: Rest, fluids, bronchodilators, antibiotics (if bacterial), avoiding irritants.

b. emphysema

Answer: Symptoms: Shortness of breath, wheezing, chronic cough, barrel chest. Causes: Smoking, long-term exposure to air pollutants. Treatment: Smoking cessation, bronchodilators, corticosteroids, oxygen therapy, lung volume reduction surgery.

c. pneumonia

Answer:

Symptoms: Cough with phlegm, fever, chills, shortness of breath, chest pain. Causes: Bacterial, viral, or fungal infection. Treatment: Antibiotics, antivirals, antifungals, rest, fluids, oxygen therapy.

d. asthma

Answer: Symptoms: Wheezing, shortness of breath, chest tightness, coughing. Causes: Allergens, genetic factors, respiratory infections, exercise. Treatment: Bronchodilators, inhaled corticosteroids, avoiding triggers. e. lung cancer

Answer: Symptoms: Persistent cough, coughing blood, chest pain, weight loss, shortness of breath. Causes: Smoking, exposure to radon, asbestos, air pollution. Treatment: Surgery, chemotherapy, radiation therapy, targeted therapy, immunotherapy.