The circulatory systemis a vital organ system responsible for... Show more
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Skyler
9/9/2025
Biology
Circulatory System Notes
610
•
Sep 9, 2025
•
Circulatory System Notes PDF: Diagrams, Parts, and Heart Functions for Kids
Skyler
@skylers.notes.official
Blood Flow and Circulation
The circulatory system operates on a principle of double circulation, featuring two distinct circuits:
-
Pulmonary Circuit:
- Pulmonary arteries carry deoxygenated blood from the heart to the lungs.
- Capillaries around alveoli allow oxygen and carbon dioxide exchange.
- Pulmonary veins return oxygenated blood to the heart for distribution.
-
Systemic Circuit:
- The aorta carries oxygenated blood from the left ventricle to body tissues.
- Superior and inferior vena cavae return oxygen-poor blood to the right atrium.
Highlight: Understanding the blood flow through the heart | step by step is crucial for comprehending the circulatory system's function.
The cardiac cycle consists of alternating contractions and relaxations:
- Diastole: The relaxation stage where heart chambers fill with blood.
- Systole: A brief contraction of atria followed by a powerful contraction of ventricles.
Vocabulary: Arterioles are smaller blood vessels branched off from arteries, while venules are small vessels that converge to form veins.
Heart problems can arise from various issues:
- Arrhythmia: Abnormal heart rhythms
- Heart attack (myocardial infarction): Often due to blockage, affecting the SA node's ability to maintain normal rhythms
- Stroke: Death of brain tissue due to lack of oxygen, usually from arterial rupture or blockage
Definition: Atherosclerosis is the buildup of fatty deposits (plaque) in vessels, restricting blood flow and potentially leading to heart attacks.
Blood composition plays a crucial role in the circulatory system:
- Plasma: The fluid matrix containing various substances
- Red blood cells (erythrocytes): Transport oxygen bound to hemoglobin
- White blood cells (leukocytes): Fight infections
Example: The 3 types of blood vessels and their functions work together like a complex highway system: arteries are the main roads carrying blood away from the heart, veins are the return routes, and capillaries are the local streets delivering nutrients directly to cells.
Circulatory System Overview
The circulatory system is an essential organ system in complex organisms, responsible for transporting vital materials throughout the body. This system is necessary for any organism too complex for nutrients to diffuse directly to cells.
Definition: The circulatory system function is to transport materials like oxygen, nutrients, and hormones to body cells.
The animal circulatory system consists of a heart and a set of tubes. In vertebrates, it is a closed system where fluid is confined to vessels, with blood and interstitial fluid being distinct.
Highlight: The human circulatory system diagram shows three main types of blood vessels: arteries, veins, and capillaries.
The heart, a muscular pump, propels circulatory fluid through vessels to the body. It has four main chambers:
- Atria (right and left): Receive blood from veins
- Ventricles (right and left): Receive blood from atria and pump it out via arteries
Vocabulary: The sinoatrial (SA) node, also known as the pacemaker, is located in the wall of the right atrium and sets the rate and timing of heart contractions.
The SA node generates electrical impulses that spread through specialized junctions, with a slight delay at the atrioventricular node to allow the atria to empty completely.
Example: To understand how the circulatory system works, imagine the heart as a central pumping station, with arteries as outgoing pipes, veins as return pipes, and capillaries as tiny distribution channels reaching every part of the body.
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The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
Paul T
iOS user
Circulatory System Notes PDF: Diagrams, Parts, and Heart Functions for Kids
Skyler
@skylers.notes.official
The circulatory system is a vital organ system responsible for transporting oxygen, nutrients, and hormones throughout the body. It consists of the heart, blood vessels, and blood, working together to maintain life in complex organisms.
Key points:
- The heart acts... Show more
Blood Flow and Circulation
The circulatory system operates on a principle of double circulation, featuring two distinct circuits:
-
Pulmonary Circuit:
- Pulmonary arteries carry deoxygenated blood from the heart to the lungs.
- Capillaries around alveoli allow oxygen and carbon dioxide exchange.
- Pulmonary veins return oxygenated blood to the heart for distribution.
-
Systemic Circuit:
- The aorta carries oxygenated blood from the left ventricle to body tissues.
- Superior and inferior vena cavae return oxygen-poor blood to the right atrium.
Highlight: Understanding the blood flow through the heart | step by step is crucial for comprehending the circulatory system's function.
The cardiac cycle consists of alternating contractions and relaxations:
- Diastole: The relaxation stage where heart chambers fill with blood.
- Systole: A brief contraction of atria followed by a powerful contraction of ventricles.
Vocabulary: Arterioles are smaller blood vessels branched off from arteries, while venules are small vessels that converge to form veins.
Heart problems can arise from various issues:
- Arrhythmia: Abnormal heart rhythms
- Heart attack (myocardial infarction): Often due to blockage, affecting the SA node's ability to maintain normal rhythms
- Stroke: Death of brain tissue due to lack of oxygen, usually from arterial rupture or blockage
Definition: Atherosclerosis is the buildup of fatty deposits (plaque) in vessels, restricting blood flow and potentially leading to heart attacks.
Blood composition plays a crucial role in the circulatory system:
- Plasma: The fluid matrix containing various substances
- Red blood cells (erythrocytes): Transport oxygen bound to hemoglobin
- White blood cells (leukocytes): Fight infections
Example: The 3 types of blood vessels and their functions work together like a complex highway system: arteries are the main roads carrying blood away from the heart, veins are the return routes, and capillaries are the local streets delivering nutrients directly to cells.
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Circulatory System Overview
The circulatory system is an essential organ system in complex organisms, responsible for transporting vital materials throughout the body. This system is necessary for any organism too complex for nutrients to diffuse directly to cells.
Definition: The circulatory system function is to transport materials like oxygen, nutrients, and hormones to body cells.
The animal circulatory system consists of a heart and a set of tubes. In vertebrates, it is a closed system where fluid is confined to vessels, with blood and interstitial fluid being distinct.
Highlight: The human circulatory system diagram shows three main types of blood vessels: arteries, veins, and capillaries.
The heart, a muscular pump, propels circulatory fluid through vessels to the body. It has four main chambers:
- Atria (right and left): Receive blood from veins
- Ventricles (right and left): Receive blood from atria and pump it out via arteries
Vocabulary: The sinoatrial (SA) node, also known as the pacemaker, is located in the wall of the right atrium and sets the rate and timing of heart contractions.
The SA node generates electrical impulses that spread through specialized junctions, with a slight delay at the atrioventricular node to allow the atria to empty completely.
Example: To understand how the circulatory system works, imagine the heart as a central pumping station, with arteries as outgoing pipes, veins as return pipes, and capillaries as tiny distribution channels reaching every part of the body.
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI companion is specifically built for the needs of students. Based on the millions of content pieces we have on the platform we can provide truly meaningful and relevant answers to students. But its not only about answers, the companion is even more about guiding students through their daily learning challenges, with personalised study plans, quizzes or content pieces in the chat and 100% personalisation based on the students skills and developments.
Where can I download the Knowunity app?
You can download the app in the Google Play Store and in the Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.9/5
App Store
4.8/5
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
Paul T
iOS user