Working with the skeleton can be an art. I usually don't have a formal "speech" but have lots of little topics and let them mess around with the bones filling in as appropriate.
Some things to talk about:
- Fitting individual bones to where they are on skeleton. What is skeleton for?
1. Upright - Ask them to imagine what we would be like without a skeleton
2. Movement - muscles pulling on bones, joints
3. Protection - skull-brain, ribcage-heart and lungs, vertebral column-spinal cord
- Ask them to guess where certain bones go. Easy ones are skull, hand and foot. Harder ones are pelvis, spine, collar bone etc.
- Feeling bones on themselves - collarbone, kneecap, shoulder blade moving, jaw moving out
- Why we have 2 bones in forearm
- How many bones in fingers/hand/body. Often good to get them to guess how many bones there are in the hand and then explain why each finger has 3 bones etc
- Where are smallest and largest bones?
- If all else fails, get the little kids to make up the arm from the individual bones
SKULL:
-ask them obvious things like where the eyes are to get them orientated.
- Ask them why there are no ears or nose.
- Describe what the skull is for. I like to use the "helmet" protecting the squishy brain analogy.
- Explain how must have holes so all the nerves can reach the brain - like phone cables.
- show them some of the holes - optic chiasma, foramen magnum etc.
- talk about jaw and how it hinges.
FOETAL SKULL:
fetus = not fully formed - several bone plates coming
together. point to fontanelles.
- why? needs to be able to change shape - fit through birth canal
- small brain compared to adults thus need rapid growth in 1st year
- growth almost complete at about 6yrs (vs chimp = 3yr) - gives time for learning thus different capabilities of humans (intellect, sybolism, abstract thought, complex tool use, complex social behaviours etc)
- adults often ask about the 'squidgy bit' on their child's head when they were born - you could talk about the anterior fontanelle and how it can be used clinically to assess the level of hydration of the child.
- N.B. Boris is male and his pelvis won't allow you to birth this skull!
JOINTS:
- explain how even without joints we couldn't move.
- different types of joints:
- Ball and Socket - get them to put one together (hip is best). Show how it allows movement in all directions. Get them to move their arms in all directions
- Hinge - get them to put one together (elbow is best). Ask them to move their elbows and knees. Point out how birds are weird as their knees bend the other way.
HIP REPLACEMENT
-This is one of my favourite bits to talk about!
-I usually start by getting them to guess what it is. Some will get it instantly, others will come up with odd suggestions ("A gun!"). You can tell the slower ones that it is used to replace a part of the body and get them to look at the skeleton and see if they can think where it might fit. Let them hold it and move it around at different angles etc. If all else fails I usually hold up a spare femur and the hip replacement next to each other in front of me until someone realises!
-Talk about why you might need to have a hip replaced - arthritis, fractured neck of femur results in death of the head of the femur due to the poor blood supply so it must be replaced as it will not heal (many of them will know of people like grandparents who have had such replacements).
-They often ask about why the ball is so much smaller than the head of the femur, explain that we've only got half of it and there would be a replacement socket too (if you've talked about arthritis in the reasons for needing a replacement you could get them to think that you need to replace both damaged surfaces with new smooth ones).
-Then I often start pretending to be a materials scientist and briefly get them to think about what properties you'd want a replacement joint to have - e.g. ask them why it isn't made out of wood! Get them to work out that it needs to be strong, light, non-toxic and unreactive (not go rusty!). I assume ours is made out of titanium, newer and more expensive ones I believe are made from titanium (the head) and then some sort of ceramic which is much lighter. If they want more details about materials I tend to then have to send them off to ask a physicist/real materials scientist!