【Shanghai Edition】Junior High School English Grade 9, Semester 1: The Beginning of Breathing: Lung Capacity and the Need for Transport

As the opening section of 'Transport of Substances within the Human Body,' we reveal the first gateway for oxygen entering the circulatory system:the lungs. Oxygen does not passively enter; instead, it is driven by pressure differences created through changes in thoracic volume—this is the fundamental force behind substance transport into the system.

Core Physiological Mechanisms

Respiratory Power: The core formula indicates that, generally, every 1 cm descent of the diaphragm increases thoracic volume by about 270 mL. This expansion creates negative pressure, which is key to drawing in oxygen.
Definition of Lung Capacity: Refers to the amount of air exhaled after a maximal inhalation. It is a key indicator of cardiorespiratory function and determines the total volume of 'oxygen supply' available to the circulatory system.
Microscopic Potential: An average person has 300–400 million alveoli, while long-term athletes can mobilize up to 700 million. This allows them to maintain efficient oxygen delivery even under high-demand conditions.

Environmental and Health-Related Transport Barriers

Cigarettes contain over 4,700 chemical compounds, including 43 carcinogens. Long-term smoking leads to 85% of lung cancer cases. Environmental pollution and smoking cause cumulative damage to the respiratory system, withaccumulativeimpact, significantly impairing oxygen transport efficiency.

QUESTION 1

Lung capacity refers to the volume of air exhaled during _____. It is one of the key indicators reflecting _____. A healthy respiratory system should have _____ lung capacity.

maximal inhalation followed by maximal exhalation; cardiovascular and pulmonary function; greater

after normal inhalation followed by maximal exhalation; lung size; moderate

QUESTION 2

The human respiratory system has self-cleaning and self-protective functions. Which of the following is NOT an example of this?

Nasal hairs filter dust

Tracheal cilia move to expel mucus

Number of alveoli increases with exercise

QUESTION 3

Which of the following statements about the relationship between physical exercise and lung capacity is incorrect?

Exercise strengthens respiratory muscles

Exercise directly increases the rate at which carcinogens from cigarettes are expelled

Exercise improves alveolar recruitment rate

QUESTION 4

The textbook compares capillaries to country lanes connecting countless homes. What do these 'countless homes' represent?

Various organs in the human body

Tissue cells throughout the body

QUESTION 5

When inflammation occurs in the body, which type of blood cell increases significantly? What is the main component of pus flowing from wounds?

White blood cells; dead white blood cells and pathogens

Red blood cells; necrotic tissue and plasma

Integrated Analysis of Circulatory System and Health Indicators

Reflections Based on Cardiorespiratory Function and Disease Prevention

An elderly individual who has smoked long-term and lacks physical activity recently had a check-up revealing low lung capacity and abnormal blood pressure. During a brisk walk, he experienced shortness of breath and his heart rate rapidly rose to 140 beats per minute.

1. Why does physical exercise increase lung capacity? If you're dissatisfied with your current lung capacity, what exercises would you consider? 2. What is the significance of increased heart rate during exercise? Is faster always better?

Answer:
1. Physical exercise strengthens respiratory muscle contraction, increases thoracic expansion range, and enhances alveolar recruitment. Recommended activities include long-distance running, swimming, or deep breathing exercises. 2. Increased heart rate helps pump more blood per unit time to meet muscle oxygen demands. However, faster is not always better—excessive rates shorten the cardiac relaxation phase, reduce ventricular filling, lower stroke volume, and increase cardiac workload.

3. Which is thicker—the walls of the atria or ventricles? Is there a difference in thickness between the left and right ventricular walls? How does this structure relate to function? 4. Please provide at least three practical recommendations (minimum 150 words) for an elderly person with hypertension.

Answer:
3. Ventricular walls are thicker than atrial walls; the left ventricular wall is thicker than the right. Ventricles must pump blood to the entire body or lungs against high resistance, requiring stronger contraction force provided by thick walls. The left ventricle handles systemic circulation, involving longer distance and highest resistance, thus having the thickest wall. 4. Recommendations: First, strictly limit salt intake (no more than 6 grams daily) to reduce sodium-induced water retention. Second, quit smoking and limit alcohol, as smoking damages vascular endothelium and causes vasoconstriction. Third, engage in regular aerobic exercise such as jogging or tai chi to improve vascular elasticity. Finally, follow medical advice and take medication regularly without interruption, and maintain emotional stability. Sustained healthy lifestyle habits are essential for effective blood pressure control.