【PEP】Middle School Biology Grade 7 Vol. 2: From Diet to Energy: The Meaning of Respiration Through a Nutritionist's Eyes

Breathing is more than just simple "inhalation" and "exhalation"—it is thecore linkin the conversion of life energy. From a nutritionist's perspective, the foods we consume—such as corn, eggs, and chicken (as shown in the textbook tables on pp. 38–39)—are merely "fuel" stored within cells, while the oxygen taken in by the respiratory system acts as the "accelerant" that ignites this fuel.

The Vital Significance of the Respiratory System

Energy Supply Loop: Uses oxygen to release the chemical energy in food, powering all life activities such as heartbeat and muscle contraction.
Gas Exchange Gateway: Composed of the nasal cavity (containing nasal hairs, mucous membranes, and capillaries), pharynx, larynx, trachea,bronchiandlungs, ensuring that incoming air is warmed, moistened, and cleaned before it enters the body.
Structure Determines Efficiency: Patency of the respiratory tract is a prerequisite for energy conversion. For instance, bronchial inflammation increases airway resistance, disrupting the oxygen supply chain.

QUESTION 1

During long-distance running, our PE teacher always advises us to inhale through the nose and exhale through the mouth. Do you know why?

The nasal cavity preconditions the air (warms, moistens, and cleans it), preventing cold air and bacteria from directly irritating the trachea.

Inhaling through the nose increases lung capacity and helps you run faster.

Inhaling through the mouth causes excessive water loss, leading to dehydration.

QUESTION 2

How is pneumonia caused by bacteria or viruses transmitted? What is the "journey" of the pathogenic microorganisms to the site of infection?

It is mainly transmitted through respiratory droplets; the route is: nose → pharynx → larynx → trachea → bronchi → lungs.

It is transmitted through food; the route is: mouth → esophagus → stomach → lungs.

It is transmitted through contact; the route is: skin → capillaries → heart → lungs.

QUESTION 3

What is the key structure in the respiratory tract that ensures smooth airflow and prevents the trachea from collapsing?

Rich capillary network

Bone or cartilage framework

Mucus secreted by mucous membranes

QUESTION 4

The respiratory tract's ability to process air is limited. Which of the following diseases supports this view?

Pneumoconiosis

Beriberi

Scurvy

QUESTION 5

Before giving artificial respiration to a drowning victim, the first step is to clear debris from the mouth and nose. This is done to:

Prevent the spread of infectious diseases

Keep the airway clear

Keep the victim conscious