Skeletons!

Upper part of giant ground sloth skeleton

If you have ever visited the Museum of Zoology, you will have seen that we have skeletons big and small, from our enormous fin whale greeting you as you come into the Museum, to tiny mice and the exoskeletons of insects. In this Nature Classroom we will be exploring what a skeleton is, why skeletons are important, and taking you on a guided tour of the most familiar of skeletons – yours.

Tiger skull viewed from the front

These activities support learning in the following areas:

Identify and name a variety of common animals including fish, amphibians, reptiles, birds and mammals

Describe and compare the structure of a variety of common animals (fish, amphibians, reptiles, birds and mammals, including pets)

Identify that humans and some other animals have skeletons and muscles for support, protection and movement.

What is a skeleton?

A skeleton is a framework made out of a rigid material that gives support and protection for the soft parts of an animal. When we think of skeletons we usually think of our own, an internal skeleton made out of bones. But this is not the only type of skeleton out there. There are skeletons made out of cartilage, like we see in sharks. There are skeletons that are on the outside of the body, as we see in insects. But in all skeletons we can see adaptations for the way of life of a particular animal, whether it is the way it moves, the way it feeds, the way it protects itself from predators, and this is what we will be exploring here.

Guided tour of the skeleton

We are going to look now at the main bits of a vertebrate skeleton by looking at the skeleton you are most familiar with – yours. Your skeleton is largely made of bone. This is an amazing, living material. It contains fibres of the protein collagen, and is hardened with calcium phosphate. Your skeleton is constantly changing. Even when you are fully grown, your bones will be ‘remodelled’ so they can cope with different stresses, and can knit back together if broken.

Outline sketch of a child

Task: Follow our guided tour of your skeleton. Observe your bones, how they move and what they do, and compare them with the bones of other animals.

Skull

Starting at the top we have the skull. The solid bone over the top of your skull is protecting your brain. But your skull does much more than that. We breathe through our skulls, feed through our skulls, our skulls hold our eyes, noses, ears for sensing the world around us. We can feel the muscles that work the jaws as they are positioned on the outside of the skull – put your hands on either side of your head covering your temples, and clench your jaws. Can you feel something move? What about around the jaw joint? This is your muscles contracting to push your upper and lower jaw together. Don’t do it for too long or you’ll get a headache!

Now you know a little about your skull, what about the skulls of other animals? Explore these two skulls from our handling collection:

A green turtle:

And to see adaptations in a mammal other than yourself, here is the skull of a badger:

Find out more about mammal skulls in our Jaws! Nature Classroom.

Backbone

Try nodding your head – can you move your head without moving your whole backbone? This is possible because your backbone is not just one bone, but a whole chain of bones called vertebrae. Vertebrae are made of a number of parts:

Labelled diagram showing the different parts of a vertebra
Diagram of a vertebra from the side (left) and front (right)

If you feel down the middle of your back you can feel the lumps that are the neural spines on the neural arches of your vertebrae that are there to protect your spinal cord.

There are different parts to your backbone in which the individual bones look different. The bones of your neck look different to the bones where your ribs attach, and they look different to the bones near your hips etc. The bones look different because they are doing different jobs. In some species the differences are really striking – here is a warthog skeleton labelled up so you can see the main areas of the backbone.

Warthog skeleton labelled up with the main regions of the backbone
Warthog skeleton

Question: How would you describe the differences along the backbone in these animals? Are the bones all the same or different? How many bones can you see?

Ribs

Gorilla skeleton
Gorilla

Attached to some of your vertebrae are your ribs. Put your hands on either side of your rib cage and take a deep breath in. Can you feel them move? Which direction do they move in? Your ribs are important for the way you breathe. When you breathe in, the muscles between your ribs (muscles called the intercostals) contract to pull your ribs up and out. This increases the space inside your lungs. Add to that the movement of your diaphragm – a sheet of muscles underneath your lungs that pulls down when you breathe in – and you have a quick increase in volume for the lungs, so air gets sucked in.

Turtle skeleton showing ribs and backbone fused to the shell

Question: How do you think turtles and tortoises breathe, when their ribs are fused to their shells?

Find out in our Amazing Animal Adaptations post.

Hips and Shoulders

The biggest hips in the Museum belong to our giant ground sloth

Something else that is attached to your backbone is your hips. Try wiggling your hips side to side – can you feel that your backbone has to move with them? That is because you have a really strong, bony connection between your hips and backbone. But what about your shoulders? Try moving your shoulders around. What can you feel? You can move your shoulders without having to move your backbone, and that is because you don’t have any bones connecting your shoulder to your backbone. You can feel your shoulder blade in your back – it feels quite triangular. Look at other mammal skeletons, and you will be able to spot the shoulder blade outside the ribs, like in you. But most other mammals lack another bone of the shoulder – the collar bone (also called the clavicle).

Limbs

The last part of our guided tour is looking at your arms and legs. Our limbs show lots of adaptations for the way we move and more.

Question: which are longer, your arms or your legs? And what are the joints like in them?

You will find some of the animals in our slideshow below have longer arms (or forelegs) than hindlegs, in some they are about the same, and some have no hindlegs at all. It is always a good starting place when looking at limbs. Then for understanding how limbs work, it is useful to look at how they bend, for example, your knee and elbow are like hinges, but you can rotate your arms more at the shoulder. Think about the directions they bend in – this helps us think about which bone is which in a skeleton.

Bear skeleton

This bear skeleton is labelled up to show the long bones in the limbs: the humerus, radius and ulna in the foreleg, and the femur, tibia and fibular in the hind leg. Like us, bears are flat-footed (we call this being plantigrade). When we look at some other animals, you will find they stand on their toes, so their legs look like they have an extra joint.

Question: Take a look at these other mammal skeletons from the Museum. Can you work out which bones are the humerus, femur, radius and ulna, tibia and fibula? How do you think their limbs are adapted for their way of life?

  • Cheetah skeleton
  • Yellow armadillo skeleton
  • Giraffe skeleton
  • Ringed seal skeleton
  • Skeleton of a ganges river dolphin
  • Przewalski horse skeleton
  • Gibbon skeleton suspended from a branch

Explore Further

You can find out more about how skeletons grow in our Animal Lifecycles Nature Classroom.

And discover the outer shells of molluscs in our Shell Detectives Nature Classroom.

(c) University of Cambridge & Julieta Sarmiento Photography

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