The Human Respiratory System

• Respiration is a characteristic of living things.

The Human Respiratory System

• The human respiratory system takes in oxygen and gets rid of carbon dioxide.
• The air around us contains oxygen, which we breathe in.
• Oxygen from the air goes into our blood and is delivered to every cell to be used for respiration.
• Blood collects waste carbon dioxide from the cells and takes it back to the lungs.
• The respiratory system consists of organs that help take oxygen out of the air and get rid of carbon dioxide.
• The structures that air passes through: Entrance to nose/mouth → trachea → bronchi → bronchioles → air sacs.
• The trachea is also known as the windpipe, and the rings of cartilage keep it open.
• The trachea branches into two bronchi, which also have cartilage for support.
• Each bronchus divides into smaller tubes called bronchioles.
• The bronchioles lead to tiny structures called air sacs, where oxygen enters the blood, and carbon dioxide leaves.
• The larynx (voicebox) contains vocal cords that vibrate to make sound.

Gas Exchange

• Inside the air sacs, oxygen from the air goes into the blood, and carbon dioxide from the blood goes into the air, this process is gas exchange.
• The blood in the capillaries around the air sacs came from the heart and contains little oxygen and a lot of carbon dioxide.
• Air inside the air sacs contains a lot of oxygen and little carbon dioxide.
• The air inside the alveolus is very close to the blood, separated only by two very thin cells.
• Oxygen particles move from the air through the thin-walled cells and into the blood via diffusion.
• Oxygen enters red blood cells and combines with hemoglobin.
• Carbon dioxide diffuses from the blood in the capillary into the air in the air sac.
• Air sacs are also known as alveoli.
• There are lots of very tiny blood vessels in the lungs, wrapped around the air sacs, which are capillaries.
• An air sac has a wall made of one layer of cells.
• A blood capillary surrounds the outside of the alveolus and is pressed tightly against it.

Breathing

• When you breathe in, the intercostal muscles contract, enlarging the chest cavity.
• When you breathe in, the muscles in the diaphragm contract, pulling the diaphragm downwards, increasing the chest cavity volume.
• The increased volume in the chest cavity causes the pressure inside it to decrease.
• The decreased pressure causes the air to move down through the trachea into the lungs, filling the extra space.
• When you breathe out, the ribs drop down to their natural position as the intercostal muscles relax.
• When you breathe out, the muscles in the diaphragm relax, so the diaphragm becomes its normal, domed shape.
• When you breathe out, volume decreases causing the pressure to increase.
• When you breathe out, air is squeezed out of the lungs.

Respiration

• Our body needs energy for many activities like moving around, transmitting electrical impulses, and keeping our bodies warm.
• All of our energy comes from the food that we eat.
• Carbohydrates provide us with energy because the digestive system breaks them down into glucose, which goes into our blood.
• The blood delivers glucose to every cell in the body, and the cells use the glucose to get the energy that they need.
• To use energy, it has to be changed from one type to another, or be transferred.
• The energy in glucose is locked up inside it.
• To use the energy from glucose, it has to be released using tiny structures called mitochondria inside cells.
• Mitochondria releases energy from glucose through a chemical reaction called aerobic respiration, which uses oxygen from the air.
• The word equation for aerobic respiration: glucose + oxygen → carbon dioxide + water.
• In this reaction, some of the energy inside the glucose is released for the cell’s needs.