KIRIWINA HIGH SCHOOL
DEPARTMENT OF SCIENCE
Subject: SCIENCE Grade level: 9 Class: 9D
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Unit: 9.4 Our Body
Topic: Human Respiratory System
Lesson Notes
Key concepts:
Respiratory system- is the system in humans that takes up oxygen and expels carbon dioxide
Respiration- process of releasing energy and carbon dioxide by combination of oxygen and
food in the body
Surface area- the diffusion of gases
Breathing- inhaling and exhaling of the air from the lungs
Oxygen- air that moves into the body
Carbon dioxide- air that moves out of the body
Lungs- main organ of respiratory system and puts oxygen into the bloodstream
Alveoli- Structures of the lungs where gas exchange occurs
Respiratory system in Human
Almost all living things (except some bacteria) need oxygen to live. The lungs are the organs
involved with breathing. They are the main organs that make up the respiratory system. The
respiratory system is responsible of taking oxygen into the lungs and eliminating water and
carbon dioxide from body.
Human respiratory system is the system in humans that takes up oxygen and expels carbon
dioxide. The respiratory system consists of organs and breathing structures that allow gas
exchange occur.
Respiration begins at the nose or mouth, where oxygenated air is brought in before moving
down the pharynx, larynx, and the trachea. The trachea branches into two bronchi, each
leading into a lung, each bronchus divides into smaller bronchi, and again into even smaller
tubes called bronchioles. At the end of the bronchioles are air sacs called alveoli, and this is
where gas exchange occurs.
The respiratory tract conveys air from the mouth and nose to the lungs, where the gases
oxygen and carbon dioxide are exchanged between the alveoli and the capillaries. This is the
path that air takes when you inhale and exhale:
Diagram: The respiratory system
1. Air enters the body through the nose or mouth.
2. The air moves goes into the throat and passes through the windpipe or trachea.
3. The trachea divides into two tubes called bronchi. Each bronchus extends into one of the
lungs.
4. Inside of the lungs, the bronchi branch into smaller and smaller tubes. At end of the
smallest tubes are air sacs called alveoli. Each alveolus is surrounded by capillaries.
When the air is in the air sacs or alveoli, two important things happen:
1. The blood picks up oxygen from the alveoli.
2. The alveoli pick up carbon dioxide from the blood.
When you exhale, you breathe out the carbon dioxide. Some waste water and heat are also
exhaled. The respiratory tract is made up of the structures that air passes through when we
breathe.
The respiratory tract and walls of the air sac can be damaged by certain chemicals from
smoking cigarettes and tobacco. The cigarette smoke contains harmful chemicals such as
nicotine and tar. The other behavioural risk factor like eating too much fatty foods that can
cause related respiratory diseases such as bronchitis, emphysema, and lung cancer.
Compiled by: Mr Samson TK. Kunuyobu………………………..uog/2019
SUMMARY ON WHAT THE STUDENTS HAVE LEARNT
 Almost all living things (except some bacteria) need oxygen to live.
 Respiratory system is responsible for obtaining oxygen and expelling carbon dioxide
from the lungs inside the body.
 Respiration is the process in which involves gaseous exchange (breathing) and
cellular respiration.
 The cellular respiration can be expressed by the following equation:
Food (digested) + Oxygen
Carbon dioxide + water + energy
 The two phases of breathing in humans: inhaling and exhaling of air in and out of the
lungs.
 Small animals exchange gas directly with the environment while the vertebrates the
exchange of gases in the special organs such as the lungs in humans and gills for fish.
 The lungs are the main organ of the respiratory system and function as a gas exchange
in the body. The other organs of the respiratory are nose, mouth, pharynx, larynx,
trachea and bronchi where they provide passageway for gases.
 Behavioral risk factors are referred to as smoking, chewing betelnuts, and taking
unbalanced diet. The air passage can be affected respiratory diseases like bronchitis,
emphysema, high blood pressure and lung cancer.