Lesson Topics

1 | Energy from Food

2 | Overview of the Respiratory System

3 | The Nose and Mouth

4 | The Pharynx, Larynx and Trachea

5 | The Lungs

6 | The Breathing Process

7 | Gas Exchange

8 | Respiratory Systems in Other Animals

9 | Summary

Lesson Summary

• Humans and other animals obtain energy when the oxygen obtained from the surrounding environment chemically reacts with digested food.

• This process is called cellular respiration and it takes place in the mitochondria of cells.

• Cellular respiration can be represented by the following chemical equation:

• glucose + oxygen → carbon dioxide + water + energy

• The respiratory system is a group of organs that work together to get oxygen into the body and carbon dioxide out of the body.

• This process is called respiration.

• Respiration consists of two main processes – breathing and gas exchange.

• Breathing moves air in and out of the lungs.

• Gas exchange moves oxygen and carbon dioxide between the lungs and the bloodstream.

• Organs that make up the respiratory system are:

• The nasal cavity (nose) and oral cavity (mouth) – the entry point to the respiratory pathway; cilia and mucus in the nasal cavity filter and removed dust particles.

• The pharynx – a short tubular section connecting the oral and nasal cavities to the larynx (as well as the oesophagus).

• The larynx (voice box) – a section at the base of the pharynx that contains the vocal cords.

• The trachea (windpipe) – a tube lined with cartilage that forms the main passageway to the lungs.

• The lungs – the main organs of the respiratory system, consisting of the bronchi, bronchioles and alveoli.

• The bronchi – two passageways branching from the base of the trachea into each lung.

• The bronchioles – branched passageways that extend from bronchi throughout the lungs.

• Alveoli – microscopic pouches that form clusters at the ends of bronchioles, surrounded by capillaries where gas exchange takes place.

• Breathing is controlled by the diaphragm and involves inhalation and exhalation.

• During inhalation, the diaphragm flattens, thereby increasing the volume of the thoracic cavity and reducing the pressure.

• This causes air to flow into the lungs.

• During exhalation, the diaphragm bends, thereby decreasing the volume of the thoracic cavity and increasing the pressure.

• This causes air to flow out of the lungs.

• Gas exchange involves the movement of oxygen and carbon dioxide between the lungs and bloodstream by the process of diffusion.

• The air in alveoli is higher in oxygen than the blood in surrounding capillaries.

• Therefore, oxygen moves from the alveoli into the capillaries.

• The blood in capillaries is higher in carbon dioxide than the air in alveoli.

• Therefore, carbon dioxide moves from the capillaries into the alveoli.

• The respiratory system in fish extracts dissolved oxygen from water.

• This is achieved through gills, which consist of gill filaments supported by a gill arch.

• Gill filaments are divided into lamellae, which are surrounded by capillaries and where gas exchange occurs.

• The respiratory systems in insects involves spiracles that are connected to trachea, which branch into tracheoles that extend throughout the body.

• Larger insects also have air sacs to help with the movement of air in and out of the body.

• Gas exchange occurs across the membranes of individual cells.

The respiratory system is a group of organs that move oxygen into the body and carbon dioxide out of the body.

(Header image: magicmine, Adobe Stock)