Your circulatory system is like a dual-lane motorway that keeps... Show more
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9 Dec 2025
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Transport in Animals for WJEC EDUQAS A-Level Biology
Sanjana
@sanjana_101
1 / 3
Mammalian Double Circulatory System
Think of your heart as having two separate jobs running simultaneously. The pulmonary circuit sends deoxygenated blood to your lungs via the pulmonary artery, whilst the systemic circuit pumps oxygenated blood around your entire body through the aorta. This double system is brilliant because it maintains high pressure for rapid oxygen delivery - exactly what active mammals like us need.
Your heart's plumbing system includes some key players you need to know. The pulmonary veins bring oxygenated blood back from the lungs (confusingly, these veins carry oxygenated blood!), whilst the vena cava returns deoxygenated blood from your body tissues.
The heart's valves work like one-way gates. The tricuspid valve (3 flaps) sits between the right atrium and ventricle, the bicuspid valve (2 flaps) separates the left chambers, and semilunar valves prevent blood flowing backwards from arteries into ventricles.
💡 Remember: The cardiac cycle has three stages - diastole (everything relaxed), atrial systole (atria contract), and ventricular systole (ventricles contract). The sino-atrial node (SAN) acts as your heart's natural pacemaker, starting each heartbeat.
Heart Conduction and Blood Pressure
Your heart's electrical system is remarkably clever. The sino-atrial node (SAN) fires electrical impulses that spread across both atria simultaneously, making them contract together. However, connective tissue prevents this signal reaching the ventricles directly - instead, it travels through the atrioventricular node (AVN) and down the Bundle of His to Purkinje fibres.
This delay system ensures your atria finish emptying before your ventricles start pumping. It's like a perfectly timed relay race that happens roughly 70 times per minute throughout your entire life.
Blood pressure tells a story of physics in action. Pressure is highest leaving your heart through the aorta, then drops progressively due to friction. Arterioles create a massive pressure drop because of their large total surface area, whilst capillaries slow blood flow right down for efficient exchange.
Your blood contains about 55% plasma and 45% cells. Plasma is your body's delivery service, transporting glucose, amino acids, hormones like adrenaline, proteins, and even distributing heat around your body.
💡 Key insight: Blood pressure decreases as distance from the heart increases, but venous return is helped by muscle contractions that massage blood back towards your heart.
Blood Cells and Transport
Your white blood cells (leucocytes) come in two main varieties that you should recognise. Granulocytes have granular, bumpy-looking cytoplasm and lobed nuclei - these are your body's pac-man cells that engulf bacteria. Agranulocytes have clear cytoplasm and round nuclei, and they're your antibody factories.
Red blood cells (erythrocytes) are engineering marvels. Their biconcave disc shape maximises surface area for gas exchange whilst staying flexible enough to squeeze through tiny capillaries. They've ditched their nucleus entirely to pack in more haemoglobin, which can carry 12 times more oxygen than plasma alone.
This nuclear sacrifice is a fascinating trade-off. Without a nucleus, red blood cells can carry maximum oxygen, change shape easily, and provide shorter diffusion distances. However, they can't repair themselves, make new proteins, or reproduce, giving them a lifespan of only about 120 days.
💡 Remember: The biconcave shape isn't just for looks - it's a perfect compromise between maximum surface area and flexibility for navigating your body's narrowest blood vessels.
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This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
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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.
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very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
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I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
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 apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
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
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
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
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
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 apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
Transport in Animals for WJEC EDUQAS A-Level Biology
Sanjana
@sanjana_101
Your circulatory system is like a dual-lane motorway that keeps you alive every second of the day. Understanding how blood moves around your body, what controls your heartbeat, and why your blood is perfectly designed for transport will help you... Show more
Mammalian Double Circulatory System
Think of your heart as having two separate jobs running simultaneously. The pulmonary circuit sends deoxygenated blood to your lungs via the pulmonary artery, whilst the systemic circuit pumps oxygenated blood around your entire body through the aorta. This double system is brilliant because it maintains high pressure for rapid oxygen delivery - exactly what active mammals like us need.
Your heart's plumbing system includes some key players you need to know. The pulmonary veins bring oxygenated blood back from the lungs (confusingly, these veins carry oxygenated blood!), whilst the vena cava returns deoxygenated blood from your body tissues.
The heart's valves work like one-way gates. The tricuspid valve (3 flaps) sits between the right atrium and ventricle, the bicuspid valve (2 flaps) separates the left chambers, and semilunar valves prevent blood flowing backwards from arteries into ventricles.
💡 Remember: The cardiac cycle has three stages - diastole (everything relaxed), atrial systole (atria contract), and ventricular systole (ventricles contract). The sino-atrial node (SAN) acts as your heart's natural pacemaker, starting each heartbeat.
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Heart Conduction and Blood Pressure
Your heart's electrical system is remarkably clever. The sino-atrial node (SAN) fires electrical impulses that spread across both atria simultaneously, making them contract together. However, connective tissue prevents this signal reaching the ventricles directly - instead, it travels through the atrioventricular node (AVN) and down the Bundle of His to Purkinje fibres.
This delay system ensures your atria finish emptying before your ventricles start pumping. It's like a perfectly timed relay race that happens roughly 70 times per minute throughout your entire life.
Blood pressure tells a story of physics in action. Pressure is highest leaving your heart through the aorta, then drops progressively due to friction. Arterioles create a massive pressure drop because of their large total surface area, whilst capillaries slow blood flow right down for efficient exchange.
Your blood contains about 55% plasma and 45% cells. Plasma is your body's delivery service, transporting glucose, amino acids, hormones like adrenaline, proteins, and even distributing heat around your body.
💡 Key insight: Blood pressure decreases as distance from the heart increases, but venous return is helped by muscle contractions that massage blood back towards your heart.
Sign up to see the contentIt's free!
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Improve your grades
Join milions of students
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Blood Cells and Transport
Your white blood cells (leucocytes) come in two main varieties that you should recognise. Granulocytes have granular, bumpy-looking cytoplasm and lobed nuclei - these are your body's pac-man cells that engulf bacteria. Agranulocytes have clear cytoplasm and round nuclei, and they're your antibody factories.
Red blood cells (erythrocytes) are engineering marvels. Their biconcave disc shape maximises surface area for gas exchange whilst staying flexible enough to squeeze through tiny capillaries. They've ditched their nucleus entirely to pack in more haemoglobin, which can carry 12 times more oxygen than plasma alone.
This nuclear sacrifice is a fascinating trade-off. Without a nucleus, red blood cells can carry maximum oxygen, change shape easily, and provide shorter diffusion distances. However, they can't repair themselves, make new proteins, or reproduce, giving them a lifespan of only about 120 days.
💡 Remember: The biconcave shape isn't just for looks - it's a perfect compromise between maximum surface area and flexibility for navigating your body's narrowest blood vessels.
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
Where can I download the Knowunity app?
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Is Knowunity really free of charge?
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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
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
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
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
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 apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
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
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
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
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
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 apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user