Respiration
The human respiratory system
• Respiration happens inside all the cells in your body.
Reasoning: Every cell in your body needs energy to function, so respiration must occur
in every cell, not just the lungs.
• Respiration releases energy from food.
Reasoning: Respiration is a chemical process. While it requires some energy to start, its
primary purpose is to break down glucose (food) to release the energy our bodies need
to move, grow, and stay warm.
• Respiration happens in all living things.
Reasoning: Plants, animals, fungi, and bacteria all require energy
to stay alive; therefore, they all perform respiration.
• Respiration is a vital process that occurs in the cells of all living things, where oxygen
is used to break down nutrients from food to release the energy needed for life.
• The kind of respiration that usually happens inside our cells is called aerobic
respiration. Aerobic respiration uses oxygen. The cells produce carbon dioxide as a
waste product.
• The organs that help you to take oxygen out of the air, and get rid of carbon dioxide,
make up the respiratory system.
The structure of human respiratory system
•Nose & Mouth: The "entryway" where air enters the body.
•Trachea (Windpipe): The "main tube" that carries air down into the chest. It has strong
rings of cartilage around it.These rings of cartilage keep the trachea open and prevent it
collapsing.so that air can be kept moving in and out of your body.
•Bronchi: The "two branches" that split the air to go into each lung.
•Lungs: The "spongy bags" that hold the air while the body takes what it needs.
•Alveoli: The "tiny air sacs" where the actual trade happens—Oxygen goes into the blood,
and Carbon Dioxide comes out.
•Diaphragm: The "muscle pump" that moves up and down to force air in and out of your
lungs
•Larynx: Also known as voice box. It contains the vocal cords, which vibrate as air passes
through them to produce sound and speech.
Gas exchange
• There is blood capillary outside of the alveolus, The capillary is pressed tightly
against the alveolus, The wall of the capillary is also made of a single layer of very
thin cells.
• Gas exchange is a vital life process that occurs in the alveoli (tiny air sacs) of the
lungs, where the body swaps waste for fresh oxygen through a method called
diffusion. Because the walls of both the alveoli and the surrounding blood
capillaries are only one cell thick, gas particles can easily slip through the two thin
layers. Blood arriving from the body’s organs is high in carbon dioxide (waste from
respiration) but low in oxygen, while the fresh air inside the air sac is high in
oxygen but low in carbon dioxide. Naturally, the oxygen particles move from the air
sac into the blood—where they dissolve and bond with haemoglobin in red blood
cells—while the carbon dioxide moves out of the blood and into the air sac to be
exhaled.
Practical Record: Investigating Carbon Dioxide in Breath
Objective
To compare the carbon dioxide content of inspired (inhaled) air and expired (exhaled) air
using limewater as an indicator.
Apparatus and Materials
•Two test tubes (labeled A and B)
•Limewater (Calcium hydroxide solution)
•Two rubber bungs with holes
•Glass tubing (one long piece reaching into the liquid, one short piece above the liquid in
each tube)
•T-shaped or Y-shaped connector
•Clean rubber tubing and a mouthpiece
Experimental Setup
Method
The apparatus was assembled as shown in the diagram, ensuring that in Test Tube A,
the "inlet" pipe was submerged in limewater, while in Test Tube B, the "outlet" pipe
was submerged.
2.Both test tubes were filled with an equal volume of clear limewater.
3.The rubber tubing was checked to ensure it was perfectly clean before use.
4.Air was gently breathed in and out through the mouthpiece.
5.Inhaled air was drawn through Test Tube A, and exhaled air was blown through Test
Tube B.
6.This process was continued until a visible change was observed in the appearance of
the limewater in one of the tubes.
Observation
•Test Tube A (Inspired Air): The limewater remained relatively clear for a long period,
or only showed a very slight cloudiness.
•Test Tube B (Expired Air): The limewater turned cloudy (milky) very quickly.
Discussion
Limewater is a clear chemical indicator that turns cloudy/milky when it reacts with
Carbon Dioxide. The results show that the air we breathe out contains a significantly
higher concentration of carbon dioxide than the air we breathe in. This is because our
body cells perform respiration, a process where oxygen is used to release energy from
food, producing carbon dioxide as a waste product. This waste is carried by the blood
to the lungs and removed from the body during exhalation. Therefore, expired air has
more carbondioxide than the surrounding atmosphere (inspired air).
Breathing
How much air can you breathe out?
Measuring the volume of air you can push out of your lungs.
Materials required
Big plastic bottle with a lid
Measuring cylinder
Bendy tubing
Marker pen
Water
Big bowl
Method
1. You are going to use the plastic bottle to measure volumes. In your group of three,
discuss how you can use the measuring cylinder to mark a scale on the plastic bottle.
Then mark the scale on the bottle. The scale should go all the way from the bottom to
the top of the bottle.
2. Fill the bottle right to the top with water. Put the lid on.
3. Pour water into the big bowl until it is about half full. Turn the bottle upside down,
and hold it in the bowl. Very carefully take the lid off the bottle. You should find that
all the water stays in the bottle
4. Carefully slide the bendy tubing into the top of the bottle, under water.
5. Take a deep breath in, then put your mouth over the tubing and breathe out as
much air as you can through the tubing. Your expired air will push out some water
from the bottle. Use the scale that you drew on the bottle to record the volume of air
you breathed out.
6. If you have time, repeat steps 2 – 5 two more times. Use your three results to
calculate a mean value for the volume of air you can breathe out of your lungs.
7. Replace the tubing with another piece of clean tubing. Now another person in
your group can try the experiment.
8. Record all of your results in a table.
When you breathe in, these things happen:
• The intercostal muscles between the ribs contract (get shorter). This
pulls the ribs upwards and outwards.
• The muscles in the diaphragm contract. This pulls the diaphragm
downwards.
• These two movements make more space inside the chest cavity. They
increase the volume inside it.
• When the volume increases, the pressure inside the chest cavity and
lungs decreases.
• Air moves down through the trachea into the lungs, to fill the extra
space
When you breathe out, these things happen:
• The intercostal muscles between the ribs relax (return to normal
size). This allow the ribs to drop down into their natural position.
• The muscles in the diaphragm relax. This allows the diaphragm to
become its normal, domed shape.
• These two movements make less space inside the chest cavity. They
decrease the volume inside it.
• When the volume decreases, the pressure increases. So air is
squeezed out of the lungs