Your skeletal and muscular systems work together as the body's... Show more
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235
•
Updated Mar 23, 2026
•
Jesse
@jesse_lily
Your skeletal and muscular systems work together as the body's... Show more





Your skeletal system contains 206 bones split into two main parts: the appendicular skeleton (126 bones for movement) and the axial skeleton (80 bones for protection). Think of it as your body's scaffolding that also doubles as a calcium storage warehouse.
Joints come in three flavours depending on how much you need to move. Fibrous joints don't budge (like your skull), cartilaginous joints allow slight movement with shock-absorbing pads, and synovial joints are your body's ball bearings - complete with lubricating fluid for smooth action.
Your bones aren't just static structures. Osteoclasts constantly break down old bone while osteoblasts build new bone tissue. This remodelling process keeps your skeleton strong and helps regulate calcium levels in your blood.
Quick Tip: Remember the bone types by function - long bones (like your femur) work as levers, flat bones (like your sternum) protect organs, and short bones (like those in your wrist) provide strength and stability.

Long bones like your femur have a brilliant design that maximises strength whilst staying relatively lightweight. The diaphysis (shaft) contains dense compact bone, whilst the epiphysis (ends) contain cancellous bone with a honeycomb structure perfect for housing bone marrow.
The periosteum acts like a protective jacket around your bones, and articular cartilage covers the ends to reduce friction at joints. Your medullary cavity stores marrow that produces blood cells - quite clever really.
Ligaments are tough fibrous bands that hold bones together at joints and prevent excessive movement. Think of them as your body's safety straps that stop dislocations during sport or daily activities.
Bone features have specific names: fossae are shallow depressions that fit with condyles (bumps) to form joints, whilst processes and tuberosities provide attachment points for muscles and tendons.
Remember: Growth plates close when you stop growing, which is why childhood fractures need extra care - damage here can affect future bone development.

Understanding movement terminology makes describing human motion much clearer. Flexion decreases joint angles (like bending your elbow), whilst extension increases them. Abduction moves limbs away from your body's midline, and adduction brings them back.
Your body moves through three distinct planes of movement. The sagittal plane handles forward-backward movements like running, the frontal plane manages side-to-side actions like cartwheels, and the transverse plane deals with rotational movements like spinning.
Anatomical terms help pinpoint exact locations. Anterior means front, posterior means back, medial refers to towards the body's centre, and lateral means away from the centre. These terms are essential for any sports science or medical context.
Different sports emphasise different planes - footballers primarily use sagittal plane movements, whilst dancers and gymnasts utilise all three planes extensively.
Study Hack: Practice identifying planes by watching sports clips - you'll quickly spot which movements happen in which plane, making exam questions much easier.

Your body contains three muscle types with distinct jobs. Cardiac muscle powers your heart automatically, smooth muscle controls digestion and blood vessel diameter, and skeletal muscle creates voluntary movement and makes up 40% of your body mass.
Muscle fibre types determine your athletic strengths. Slow-twitch fibres excel at endurance activities like marathons, Type 2a fast-twitch fibres suit team sports and boxing, whilst Type 2b fast-twitch fibres power explosive movements like sprinting and jumping.
Muscle contractions work in three ways. Concentric contractions shorten muscles (lifting phase of bicep curls), eccentric contractions lengthen muscles under tension (lowering phase), and isometric contractions maintain position without changing length (holding a plank).
Muscles work in teams: the agonist creates movement, the antagonist relaxes to allow it, fixators provide stability, and synergists assist the main movement. This coordination ensures smooth, controlled motion.
Key Concept: Eccentric contractions cause most muscle soreness but also promote the greatest strength gains - that's why the lowering phase of exercises is so important.
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.
You can download the app from Google Play Store and Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
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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 Knowunity AI. 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 Knowunity AI. 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
Jesse
@jesse_lily
Your skeletal and muscular systems work together as the body's framework and movement machinery. Understanding how your 206 bones connect, protect vital organs, and team up with muscles to create movement is essential for A-level biology and sports science.

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Improve your grades
Join milions of students
Your skeletal system contains 206 bones split into two main parts: the appendicular skeleton (126 bones for movement) and the axial skeleton (80 bones for protection). Think of it as your body's scaffolding that also doubles as a calcium storage warehouse.
Joints come in three flavours depending on how much you need to move. Fibrous joints don't budge (like your skull), cartilaginous joints allow slight movement with shock-absorbing pads, and synovial joints are your body's ball bearings - complete with lubricating fluid for smooth action.
Your bones aren't just static structures. Osteoclasts constantly break down old bone while osteoblasts build new bone tissue. This remodelling process keeps your skeleton strong and helps regulate calcium levels in your blood.
Quick Tip: Remember the bone types by function - long bones (like your femur) work as levers, flat bones (like your sternum) protect organs, and short bones (like those in your wrist) provide strength and stability.

Access to all documents
Improve your grades
Join milions of students
Long bones like your femur have a brilliant design that maximises strength whilst staying relatively lightweight. The diaphysis (shaft) contains dense compact bone, whilst the epiphysis (ends) contain cancellous bone with a honeycomb structure perfect for housing bone marrow.
The periosteum acts like a protective jacket around your bones, and articular cartilage covers the ends to reduce friction at joints. Your medullary cavity stores marrow that produces blood cells - quite clever really.
Ligaments are tough fibrous bands that hold bones together at joints and prevent excessive movement. Think of them as your body's safety straps that stop dislocations during sport or daily activities.
Bone features have specific names: fossae are shallow depressions that fit with condyles (bumps) to form joints, whilst processes and tuberosities provide attachment points for muscles and tendons.
Remember: Growth plates close when you stop growing, which is why childhood fractures need extra care - damage here can affect future bone development.

Access to all documents
Improve your grades
Join milions of students
Understanding movement terminology makes describing human motion much clearer. Flexion decreases joint angles (like bending your elbow), whilst extension increases them. Abduction moves limbs away from your body's midline, and adduction brings them back.
Your body moves through three distinct planes of movement. The sagittal plane handles forward-backward movements like running, the frontal plane manages side-to-side actions like cartwheels, and the transverse plane deals with rotational movements like spinning.
Anatomical terms help pinpoint exact locations. Anterior means front, posterior means back, medial refers to towards the body's centre, and lateral means away from the centre. These terms are essential for any sports science or medical context.
Different sports emphasise different planes - footballers primarily use sagittal plane movements, whilst dancers and gymnasts utilise all three planes extensively.
Study Hack: Practice identifying planes by watching sports clips - you'll quickly spot which movements happen in which plane, making exam questions much easier.

Access to all documents
Improve your grades
Join milions of students
Your body contains three muscle types with distinct jobs. Cardiac muscle powers your heart automatically, smooth muscle controls digestion and blood vessel diameter, and skeletal muscle creates voluntary movement and makes up 40% of your body mass.
Muscle fibre types determine your athletic strengths. Slow-twitch fibres excel at endurance activities like marathons, Type 2a fast-twitch fibres suit team sports and boxing, whilst Type 2b fast-twitch fibres power explosive movements like sprinting and jumping.
Muscle contractions work in three ways. Concentric contractions shorten muscles (lifting phase of bicep curls), eccentric contractions lengthen muscles under tension (lowering phase), and isometric contractions maintain position without changing length (holding a plank).
Muscles work in teams: the agonist creates movement, the antagonist relaxes to allow it, fixators provide stability, and synergists assist the main movement. This coordination ensures smooth, controlled motion.
Key Concept: Eccentric contractions cause most muscle soreness but also promote the greatest strength gains - that's why the lowering phase of exercises is so important.
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.
You can download the app from Google Play Store and Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
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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 Knowunity AI. 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 Knowunity AI. 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