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General Education
Lesson 9: Respiratory System
(Human Systems)
What is the Respiratory System?
The respiratory system is a network of organs and structures that work together to bring oxygen into your body and release carbon dioxide as waste. Respiration is the process of breathing in air that contains oxygen and breathing out air that contains carbon dioxide. Your respiratory system is like a gateway that exchanges gases with the environment, taking in what your body needs and getting rid of what it does not need.
- The respiratory system takes oxygen from the air you breathe in and releases carbon dioxide that your body does not need.
Main Function of the Respiratory System
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| Image from Professor Dave |
Supplies body with oxygen and releases CO2 as waste.
The respiratory system has one primary job: to get oxygen into your blood so all your cells can use it, and to remove carbon dioxide (a waste product) from your blood so it can be exhaled.
Two Main Processes of Respiration
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| Image from GeeksofGeeks |
Respiration has two main parts that happen during breathing:
1. Inspiration - the process of inhaling. When you breathe in, you take oxygen-rich air into your lungs.
How it happens:
- Your diaphragm (a muscle below your lungs) contracts and moves downward
- This increases the space in your chest cavity
- Air rushes into your nose or mouth
- Air travels through your airway to your lungs
- What enters your body: Oxygen-rich air (about 21% oxygen)
Inspiration is when you breathe in and oxygen enters your body.
2. Expiration - the process of exhaling. When you breathe out, you release carbon dioxide and other gases from your lungs.
How it happens:
- Your diaphragm relaxes and moves upward
- This decreases the space in your chest cavity
- Air is pushed out of your lungs
- Air leaves through your nose or mouth
- What leaves your body: Carbon dioxide waste (along with some oxygen that was not used)
Expiration is when you exhale and carbon dioxide waste leaves your body.
The Respiratory Pathway
Air travels through several structures as it moves into and out of your lungs. Let's follow the journey of air:
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Image from FreePNGimg |
1. Nose - the external opening where air enters your body.
- Warms air as it enters
- Moistens air with mucus
- Traps dirt and particles with nose hairs (cilia)
Your nose warms, moistens, and filters the air before it goes deeper into your respiratory system.
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Image from Flaticon |
2. Pharynx (Throat) - the passageway for both air and food. It is the tube behind your mouth and nose.
- Air from nose passes through pharynx
- Food from mouth also passes through pharynx
- The epiglottis (a flap) directs food to the esophagus and air to the larynx
- About 5 inches long
- Lined with mucus that moistens air
- Connects nose and mouth to the larynx
The pharynx is the passageway where air continues its journey to the lungs.
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Image from Wikimedia Commons |
3. Epiglottis - a small flap of tissue that acts like a trap door.
- Prevents the entrance of food into the trachea
- When you swallow, the epiglottis covers the opening to the trachea (windpipe)
- When you breathe, the epiglottis moves out of the way so air can enter the trachea
- Works automatically without you thinking about it
- Without the epiglottis, food could go into your lungs instead of your stomach, which would be very dangerous.
The epiglottis is a flap that makes sure food goes to your stomach and air goes to your lungs.
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Image from Mind the Graph |
4. Larynx - the voice box. It is the part of your respiratory system where sound is produced.
- In your neck, below the pharynx and above the trachea
- Air passes through on its way to the lungs
- Vocal cords vibrate to produce sound
Vocal Cords:
- Two small folds of tissue inside the larynx
- When air passes between them, they vibrate
- This vibration creates sound that becomes your voice
- Different pitches come from how tightly the vocal cords are stretched
- Different volumes come from how much air is pushed through
- When you are silent, vocal cords are relaxed and air passes through without vibrating
- When you speak or sing, vocal cords tense up and vibrate as air passes through
- Tighter vocal cords make higher pitches
- Looser vocal cords make lower pitches
The larynx is your voice box. The vocal cords inside vibrate to create the sound of your voice.
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Image from Wikimedia Commons |
5. Trachea - the windpipe. A tube that carries air from the larynx to the lungs.
- About 4 to 5 inches long
- Lined with rings of cartilage that keep it open
- Covered with cilia (tiny hairs) and mucus that trap particles
- Leads to the lungs
- Air passes through on its way to the lungs
- Mucus traps particles and bacteria
- Cilia sweep trapped particles upward toward the mouth to be expelled
The trachea is the windpipe that carries air from your larynx straight down to your lungs.
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Image from Freepik |
6. Lungs - the main organs of the respiratory system where gas exchange happens.
- In your chest, on either side of your heart
- Two lungs, but the right lung is slightly larger
- Spongy texture filled with tiny air sacs
- Covered with a double membrane called pleura
- The lungs contain millions of tiny air sacs called alveoli. These alveoli are where the magic happens: oxygen enters the blood and carbon dioxide leaves the blood.
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| Image from Vecteezy |
Alveoli:
- Tiny, grape-like air sacs in the lungs
- Surrounded by tiny blood vessels called capillaries
- Walls are extremely thin (one cell thick) allowing gases to move easily
- Very large total surface area because there are millions of them
Gas Exchange:
When blood flows through the capillaries around the alveoli:
- Oxygen from inhaled air moves through the alveolar wall into the blood
- Carbon dioxide from the blood moves through the alveolar wall into the air sacs
- This oxygen-rich blood then travels to the heart to be pumped to the body
- Carbon dioxide stays in the lungs until you exhale and breathe it out
The lungs are the main organ where oxygen enters your blood and carbon dioxide leaves your blood. Tiny air sacs called alveoli do this gas exchange.
How the Respiratory System Works
(Summary)
Step 1: You take a breath (Inspiration)
- You breathe in through your nose or mouth
- Air passes through the nose (warmed, moistened, filtered)
- Air travels through the pharynx
- The epiglottis is out of the way, allowing air to enter the larynx
- Air passes the vocal cords (which are relaxed if you are just breathing)
- Air travels down the trachea
- Air enters the bronchi (tubes that branch into each lung)
- Air reaches millions of alveoli in the lungs
Step 2: Gas exchange happens
- Oxygen from the inhaled air passes through alveolar walls into the blood
- Blood carrying oxygen goes to the heart
- The heart pumps oxygen-rich blood to the body
- Meanwhile, carbon dioxide from used blood enters the alveoli
Step 3: You exhale (Expiration)
- Carbon dioxide in the alveoli needs to leave your body
- Your diaphragm relaxes
- Pressure in your chest increases
- Air containing carbon dioxide is pushed out
- Air travels back up the trachea
- Air exits through your larynx
- Air passes through the pharynx
- Air exits through your nose or mouth
Step 4: The cycle repeats
- You take another breath in
- The process continues throughout your life
You breathe in oxygen, it enters your blood in the lungs, you breathe out carbon dioxide waste, and then you breathe in again.
Respiratory System Quiz: click here
