Human Respiratory System: Short Questions & Answers

Grade 12 Biology: Human Respiratory System - Short Questions & Answers

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Here are short, key questions and answers on the Human Respiratory System to help with your studies.

1. What is a respiratory surface? Write the properties of a respiratory surface.

A respiratory surface is an area where gas exchange occurs. It must be thin, moist, have a large surface area, a good blood supply, and good ventilation to ensure efficient diffusion of gases.

2. What organs constitute the respiratory system?

The human respiratory system consists of the upper respiratory tract (nostrils, nasal cavity, and pharynx) and the lower respiratory tract (larynx, trachea, bronchi, bronchioles, and alveoli).

3. How do the nose and nasal cavity filter incoming air?

The nose and nasal cavities are lined with cilia and a mucous membrane. The mucus traps dust and pathogens, while the cilia move these trapped particles toward the pharynx to be expelled or swallowed.

4. What is the role of the pharynx in human respiration?

The pharynx is a cone-shaped passageway that leads from the oral and nasal cavities. It serves as a common channel for both food and air, directing inhaled air toward the larynx.

5. Describe the function of the human larynx.

The larynx, or voice box, is an enlargement at the top of the trachea. It contains the vocal cords for sound production and the epiglottis, which prevents food and liquids from entering the air passages during swallowing.

6. Describe the structure and function of alveoli.

Alveoli are tiny, air-filled sacs with walls only 0.1 µm thick. Their function is to serve as the site of gas exchange, with a surrounding capillary network facilitating the diffusion of oxygen and carbon dioxide.

7. How does the contraction and relaxation of human lungs take place?

The contraction and relaxation of the lungs are passive processes. They are caused by the active contraction and relaxation of the diaphragm and intercostal muscles, which change the volume and pressure within the thoracic cavity.

8. What is the chloride shift?

The chloride shift is the movement of chloride ions (Cl−) into red blood cells. It occurs to maintain electrical balance after bicarbonate ions (HCO3−) diffuse out of the red blood cells into the plasma during carbon dioxide transport.

9. What are the advantages of having millions of alveoli rather than a pair of simple balloon-like lungs?

Having millions of tiny alveoli instead of two simple balloons vastly increases the surface area for gas exchange. This allows for a much more efficient and rapid absorption of oxygen and release of carbon dioxide.

10. Differences Between:

(a) Internal and External Respiration

• Location: External respiration occurs in the lungs (between the blood and the atmosphere). Internal respiration occurs in the tissues (between the blood and the body's cells).
• Purpose: External respiration's purpose is to get oxygen into the blood and remove carbon dioxide. Internal respiration's purpose is to supply oxygen to cells for cellular respiration and to remove the CO2 they produce.
• Gases Exchanged: In external respiration, the blood takes up O2 and releases CO2. In internal respiration, the blood releases O2 and takes up CO2.

(b) Upper and Lower Respiratory Tract

• Components: The upper respiratory tract includes the nostrils, nasal cavity, and pharynx. The lower respiratory tract includes the larynx, trachea, bronchi, and lungs.
• Primary Function: The upper tract's primary function is to filter, warm, and moisten incoming air. The lower tract's primary function is to serve as the main passageway for air to reach the alveoli for gas exchange.
• Location: The upper tract is located in the head and throat. The lower tract is located in the chest.

(c) Bronchi and Bronchioles

• Structure: Bronchi are larger tubes that are supported by C-shaped cartilage rings. Bronchioles are smaller tubes that have no cartilage in their walls.
• Size and Location: The trachea divides into the two primary bronchi. Bronchioles are the smaller subdivisions that branch off from the bronchi.
• Function: Bronchi primarily act as a main airway to and from the lungs, while bronchioles lead directly to the alveolar ducts and alveoli where gas exchange occurs.

(d) Oxyhaemoglobin and Carboxyhaemoglobin

• Bound Gas: Oxyhaemoglobin is haemoglobin bound to oxygen (O2). Carboxyhaemoglobin is haemoglobin bound to carbon monoxide (CO).
• Affinity: Haemoglobin has a high affinity for oxygen. However, its affinity for carbon monoxide is 249 times greater than its affinity for oxygen.
• Function: Oxyhaemoglobin is essential for oxygen transport throughout the body. Carboxyhaemoglobin is non-functional and is a marker of poisoning, as it prevents oxygen from being delivered to the body's tissues.

(e) Haemoglobin and Myoglobin

• Location: Haemoglobin is found in red blood cells. Myoglobin is found primarily in muscle cells.
• Polypeptide Chains: Haemoglobin consists of four polypeptide chains. Myoglobin consists of only one polypeptide chain.
• Function: Haemoglobin's main function is to transport oxygen from the lungs to the tissues. Myoglobin's main function is to store oxygen in muscles for use during physical activity.

11. List the effects of smoking.

Smoking causes several health issues, including lung cancer, other types of cancer, and chronic diseases such as emphysema and chronic bronchitis. It also damages cilia, making the lungs more vulnerable to infection.

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