Unit D Lesson D13 Animal Joints
Completion requirements
Lesson D13: Amazing Joints in Animals
Video Lesson
To move, animals and humans depend on joints in their skeleton structures. Watch this video to learn more about some amazing joints in animals and humans!
Lesson D13: Structural Joints and Friction
Flexible Spines
Some people such as dancers, divers, and gymnasts are very flexible. They can move their joints with a wider range of motion than most people can. People who are flexible have tendons and ligaments that stretch well.
Cats are very flexible animals. They can arch their backs easily and curl their tails. Cats have a stretchy cushioning material between the bones in their spines. These flexible joints let cats twist their bodies in strange ways.
Cats also have a few more bones in their spine than humans have, which also helps their flexibility.
Some people such as dancers, divers, and gymnasts are very flexible. They can move their joints with a wider range of motion than most people can. People who are flexible have tendons and ligaments that stretch well.
Cats are very flexible animals. They can arch their backs easily and curl their tails. Cats have a stretchy cushioning material between the bones in their spines. These flexible joints let cats twist their bodies in strange ways.
Cats also have a few more bones in their spine than humans have, which also helps their flexibility.
Reading and Materials for This Lesson
Science in Action 7
Materials:
Science in Action 7
Reading: Pages 313-318
Materials:
pipe cleaner, drinking straw, scissors
Connections
Connections: Health and Wellness
>> Human Joints
Many joints in the human skeleton are movable, but some are fixed, such as the bones making up the skull.
When babies are born, they have a couple of soft spots on their heads where the bones of the skull are not completely joined together. The skull bones join together completely by the time the babies are about a year and a half old.
Babies should be held and watched very carefully so they do not accidentally bump their heads.
Figure D.3.13.1 – In baby skulls, the fixed joints are not yet completely joined together.
Figure D.3.13.2 – Babies must be held carefully – they have soft spots on their heads.
Figure D.3.13.3 – Adult skulls have fixed joints. The skull plates have all joined together.
Try It!
Spine Models
The spine is a very interesting structure that allows for a wide variety of movement. Many animals rely on their flexible spine to survive.
Materials:
Instructions:
The spine is a very interesting structure that allows for a wide variety of movement. Many animals rely on their flexible spine to survive.
Materials:
- pipe cleaner
- straw
- scissors
Instructions:
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Slide the full straw onto the pipe cleaner.
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Try bending the structure. What do you notice about the shape of the structure?
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Take the straw off the pipe cleaner, and cut the straw into 4 equal pieces. Thread these straw pieces onto the pipe cleaner.
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Try bending the structure. What do you notice about the shape of the structure?
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Take the 4 straw pieces off the pipe cleaner. Cut each piece of straw into 4 equal pieces to make a total of 16 straw pieces. Thread these straw pieces onto the pipe cleaner.
- Try bending the structure. What do you notice about the shape of the structure?
Questions:
Think about the following questions very carefully. Then, type or write your answers. When you have your answers, click the questions for feedback.
Think about the following questions very carefully. Then, type or write your answers. When you have your answers, click the questions for feedback.
The structure was less flexible when it had less straw pieces. The structure with one piece of straw could not bend. The structure with 4 pieces of straw bent, but it could only bend into a square shape. The structure was more flexible when it had more
pieces. The structure with 16 pieces of straw could bend into a curved shape.
Snakes are much more flexible than humans are because they have more bones in their spines. Humans have 33 bones in their spines, and snakes have between 200 and 400. Thus, snakes have more joints in their spines, which allows them to coil and twist in
ways that humans cannot.
Cracking Joints
Knuckles are another name for the joints in fingers. People sometimes bend their finger joints on purpose to crack their knuckles, which makes popping sounds.
Knuckles are another name for the joints in fingers. People sometimes bend their finger joints on purpose to crack their knuckles, which makes popping sounds.
Figure D.3.13.7 – The sound of cracking knuckles is caused by fluid movement in the joints. Photo by
Jaysin Trevino.
Figure D.3.13.8 – You will be told to not crack your knuckles if you don't want to get arthritis.
Watch More
Watch this video to learn why knuckles crack and pop.
Fixing Body Joints
Arthritis is a disease that causes pain, swelling, and stiffness in joints. Arthritis can be caused by injury to a specific joint. Joint cartilage wearing down over time causes arthritis, too, especially in elderly people. Rheumatoid arthritis is an autoimmune disease, which means the immune system in the body attacks itself. Even young people can get that disease.
There is no Self-Check for this lesson. Please continue to the next lesson.