Topic: The respiratory system and its functions

Author: Zyta Sendecka

Target group

Students of the 7th grade of an elementary school.

Core curriculum

III. Human body.

7. Respiratory system. The student:

1) identifies the components of the respiratory system (diagram, model, drawing, as described, etc.) and presents their functions and determines the relationship between the structure of these elements and their function;

4) analyzes the course of gas exchange in tissues and lungs; plans and conducts experiments that detect the presence of carbon dioxide and water vapor in the exhaled air.

The general aim of education

The students describe the adaptations in the structure of the lungs to efficient gas exchange and its mechanism.

Criteria of success

• You will show the location of the respiratory system organs;

• make an observation of the alveoli;

• describe the mechanism of gas exchange in the alveoli and body cells.

Key competences

• communication in the mother tongue; 

• communication in a foreign language;

• mathematical competence and basic competences in science and technology; 

• digital competence; 

• learning to learn; 

Methods / forms of work

Conversation, work with text, and replacement observation.

Individual work.

Teaching aids

• abstract;

• interactive or traditional board;

• tablets/computers;

Lesson plan overview (Process)

Introduction

1. The teacher gives the topic and lesson goals.

2. The teacher asks the students:

• Why do organisms have to supply oxygen to the body?

• Which blood component is responsible for the transport of respiratory gases?

• What is diffusion about?

• Which organs build the respiratory system and what functions do they have?

Realization

1. The teacher asks the students to use the abstract to become familiar with the structure and role of particular sections of the respiratory system.

2. The teacher asks the students to perform an interactive task by themselves.

3. The students are introduced to the film: „Structure of vertebrate lungs”.

4. The teacher stops the film on the frame showing the microscopic image of alveoli. The students make a biological drawing of alveoli in accordance with the previously learnt principles (the film entitled „How to make a microscope image drawing”). The teacher assesses the students' drawings.

5. The teacher asks the students to observe the following as the film is played:

• physical properties of the lungs,

• colour change of the liquid in which the lungs are submerged.

6. The teacher asks the students to formulate conclusions based on the observation.

7. The students become familiar with the information in the abstract about gas exchange.

Summary

• The teacher asks the students to do exercise 4 by themselves.

• The teacher asks the students to finish the sentences:

On today's lesson I have learnt that...

On today's lesson I was interested in...

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

The respiratory system and its functions

The respiratory system provides for an efficient collection and transport of respiratory gases – oxygen and carbon dioxide, as well as gas exchange. It consists of the upper and lower airways and gas‑exchange organs – lungs. The upper airways include the nasal cavity and the pharynx. The lower airways consist of the larynx, the trachea and the bronchi.

The air introduced into the body must first be heated and moisturized, as well as purified of dust. Airways have numerous adaptations to perform these functions:

• air purification – the airways are lined with an epithelium provided with cilia and mucous glands; dust particles adhere to the mucus covering the epithelium and they are stuck together; the movement of the cilia moves them to the pharynx from where the contaminants are expectorated or when swallowed they end up in the gastrointestinal tract; what is more, the inside of the nasal cavity is overgrown with hairs that are a barrier to dust; cough and sneezing are ways to get rid of excess mucus and impurities; irritants are removed by the air that comes out of the lungs under high pressure at a speed of up to 160 km/h;

• air moisturizing – water contained in the mucus evaporates and moisturizes the air, thanks to which it facilitates the penetration of oxygen into the blood in the final part of the airways;

• air heating – the inside of the nose and the airways are well supplied with blood; blood gives off heat to the air filling the airways.

From the nasal cavity the air is transported through the pharynx to the trachea. The pharynx is where the respiratory and digestive systems intersect – food from the mouth is moved through the pharynx to the esophagus.

The air from the upper airways enters the larynx, the voice organ built of cartilage connected to each other flexibly through ligaments and muscles. There is a mobile cartilage between the pharynx and the larynx – epiglottis. It works like a valve, which when breathing and speaking is raised up, and this allows for the transport of inhaled air to the larynx and the trachea. During swallowing, the epiglottis drops and closes the entrance to the larynx, protecting the airways against food particles. Sometimes, when we take a deep breath while swallowing (willing to say something more loudly), the epiglottis does not manage to close itself and food along with the stream of air goes to the larynx. This causes irritation of the mechanical receptors in the larynx and a cough reflex.

The narrowest part of the larynx is the glottis, in which sounds are made. The mucosa creates transverse folds in it – vocal cords between which there is a true glottis. While talking, the vocal cords tighten and the true glottis decreases. The air leaves the lungs and vibrates the cords, resulting in a voice. The sounds of human speech arise with the participation of the larynx, tongue, palate, cheeks, lips and teeth.

From the larynx the air passes into the trachea. It has the shape of a tube reinforced from the front with half‑ringed cartilages, which protects its walls against collapsing. In the upper part of the chest, the trachea branches into two bronchi that lead the air into the lungs.

The lungs are the organs of gas exchange in the chest. From the outside, they are protected by a thin double membrane, called the pleura, filled with a small amount of fluid. It prevents damage to the lungs due to friction on ribs and other chest bones during breathing movements.

Inside the lungs, the bronchi branch out in the form of a tree, forming a system of increasingly smaller channels called bronchioles. At their ends there are alveoli. There are about 600 million of them and they have a total area of 90 mIndeks górny 2². The bubbles that are close together form a structure similar to a grape cluster. The alveoli are surrounded by a dense network of capillaries. Between them and the air from the alveoli there takes place gas exchange through diffusion. The passage of oxygen into the blood and carbon dioxide from the blood into the alveoli is very quick and efficient due to the fact that:

• the walls of the alveoli and the capillary blood vessels are composed of a thin, single‑layered epithelium;

• the network of capillaries covering the alveoli is very dense;

• the alveoli form a very large gas exchange surface.

One of the most important signs of life is breathing. In humans, this process includes lung ventilation, gas exchange and intracellular respiration. During ventilation the collection and removal of the air from the lungs takes place. Oxygen‑rich air enters the lungs during inhalation and then, depleted of some oxygen, it is removed outside during exhalation. The following are responsible for lung ventilation:

• intercostal muscles, expanding and constricting the chest;

• diaphragm – a flat respiratory muscle separating the chest from the abdominal cavity.

During inhalation, the diaphragm contracts and lowers, whereas the external intercostal muscles also relax contract and lift the ribs up. As a result, the volume of the chest increases, the alveoli expand and aspiration of the air into the lungs takes place. When exhaling, the diaphragm relaxes and lifts passively up, the intercostal muscles also relax. At the same time, the internal muscles contract, so the ribs are lowered and the air is pushed out. The movements of the diaphragm are automatic, but to a certain extent they can be consciously modified, e.g. during diving and singing.

Lung ventilation based on rhythmic inhalations and exhalations is a process that takes place without the participation of our consciousness. Its rate depends on the content of carbon dioxide in blood – an increase in its concentration increases the frequency of breaths. At rest, a person makes about 12‑16 breaths per minute, collecting and removing about 0.5 litres of air each time. The amount of air that can fit the lungs of an adult human is usually 4,500 ml for men and 3,200 ml for women. Lung capacity is an indicator of the body's efficiency and depends on age, sex, physical fitness and smoking.

Blood transports respiratory gases between the lungs and tissues. Transmission of oxygen from the lungs to blood, and carbon dioxide from blood to the lungs is called external gas exchange. After inhalation, oxygen concentration in the alveoli is higher than in the blood flowing into the lungs. As a result, according to the concentration difference, oxygen through diffusion passes through the walls of the alveoli and capillaries to plasma, and then to erythrocytes. Carbon dioxide diffuses into the alveoli the same way. Oxygen, entering an erythrocyte, creates an unstable connection with hemoglobin and oxyhemoglobin is formed. In this form, oxygen is transported to the body's cells. That is where internal gas exchange takes place. In the capillaries, the oxygen that reaches the body’s cells is detached from oxyhemoglobin and diffuses into cells. Carbon dioxide is transmitted from the body's cells to blood plasma in which it dissolves. Part of carbon dioxide is connected to hemoglobin in an unstable manner. It is transported to the alveoli with blood.

• The respiratory system consists of the upper and lower airways and lungs.

• In the airways there is a ciliated, mucus‑producing epithelium, thanks to which the air is purified, moisturized and heated.

• The true glottis is the place where our voice is created.

• Even lungs are the organs of gas exchange.

• The process of breathing in humans and other lung organisms consists of lung ventilation, gas exchange, intracellular respiration.

• Lung ventilation involves, among others, intercostal muscles and the diaphragm.

• Gas exchange in the lungs and tissues takes place by diffusion in accordance with the concentration difference.

• External gas exchange occurs between the alveoli and blood.

• Internal gas exchange occurs between blood and the body’s cells.

• Oxygen is transported in the form of oxyhemoglobin, and carbon dioxide mainly in a dissolved form in plasma.