Secondary TwoTopic: Bones and

JointsSub Topic: Bone

Growth

Content Purpose• Students will understand the how bone grow.

• Students will learn the concepts behind growing tall.

Language Purpose• Growth plates

• Osteoblasts• Osteoclasts

Social Purpose• One conversation• No sleeping• Putting of palm on whiteboard• Class too noisy and need to

quieten down

In the previous lesson, you’d learnt…

BONE GROWTH FROM BIRTH

The Growing BoneWhen you first get

started in your mum’s womb, your bone looks like this at about 4 weeks.

The “bone” is mainly a “lump of cartilage”.

Periosteum grows around the cartilage and controls the shape and thickness of the bone.

Periosteum

The Growing BoneAt about 8 weeks,

bone cells will start to form in the middle.

The cartilage will slowly be changed into bone cells and grows in length and thickness.

Bone Cells

The Growing BoneAfter birth, the

marrow cavity will start to form.

Growth plates (epiphyseal plates), which are bands of cartilage, remains to aid in the growth of the bone.

Form

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The Growing BoneThe bone continues to grow after

birth, which gives rise to the growing height till adulthood.

The Growing BoneIn summary…

Feeling Lost?Not biology classOnly required to have a rough

idea that:◦Bone started as one whole piece of

cartilage◦After birth, the bone continues to

grow at the Growth Plate (medical name known as Epiphyseal Plate)

◦One stops growing when the Growth Plate is “fused”

GROWING TALLER…What do you know about growing tall?

QuestionWhich bone in your body

determines a large portion of your height?◦Femur (thigh bone) and tibia (shin

bone)

Growth PlatesRecall:

◦The presence of the growth plates in the bone aids the growing of the length of the bones (eg. Femur and tibia)

Growth plates will not be present in your bones forever

Fusion of Growth PlatesFemur (thigh bone)

◦Upper end fuses around 18 yrs old◦Lower end fuses around 20 yrs old

Tibia (shin bone)◦Upper end fuses around 16-18 yrs

old◦Lower end fuses around 15-17 yrs

oldWhat does

this mean

for you?

http://www.medhelp.org/posts/Orthopedics/What-bone-age-do-the-growth-plates-completely-close/show/996787

You still can grow taller

How?

Factors Affecting HeightGenes

◦Determined by parentsDietExercisingLifestyle

Determined by you

Factors: GenesHeight is a polygenic trait

◦Influenced by several different genesEstimated height

◦Boys: (Sum of height of both parents + 13cm) / 2

◦Girls: (Sum of height of both parents - 13cm) / 2

◦+/- about 10cmGenes determines your

maximum possible heightYou can’t grow taller than what your body genes had decided

for you

Factors: DietCalcium is required for bone

growthSources:

◦Dairy products: eg. milk, yoghurt, cheese.

◦Non dairy products: eg. Bok choy, almond, orange, seaweed

Source: http://greatist.com/health/18-surprising-dairy-free-sources-calcium

Factors: Diet

Have you ever wonder:◦Why I drank so much milk and I never grow

tall?Reasons are:

◦Genetic reasons; or◦Lack of vitamin D

Vitamin D◦Vital to promote the body absorption of the

calcium that we take in◦Best source: Sun◦Lead an active lifestyle, go under the sun!

Factors: ExercisingIncreases the rate of the process of

osteoclast and osteoblast (elaborated later)◦ In turn increases the speed of bone growth

Weight bearing exercises◦Exercises that makes one goes against gravity◦Eg. Running, jumping, climbing of stairs

Helps not only in length growth of bone◦Also helps in maintaining strong bones in

adults◦Often prescribed for elderlies to maintain

healthy bones

Factors: LifestyleOne important factor that helps

in bone growth, but often neglected by us.

What is it?

Sleep

Factors: LifestyleWhy sleeping helps in growing taller?Body undergoes repair and building /

rebuilding when at restSimilar in bone growthRecommended at least 8 continuous

hours of sleepNot to disturb bio-clock to “confuse”

body◦ i.e. you do not sleep the 8 hours during

daytime

BONE GROWTH IN ADULTHOOD

Osteoblasts vs. OsteoclastsIn adulthood, bones continue to

undergo process of building and re-modelling

Why?◦Strengthening of bones◦Damaging of bones via stress /

impact◦Need to re-build bones◦Similar to maintenance of buildings:

Need to replace older parts with newer parts

Osteoblasts vs. OsteoclastsOsteoblasts

◦Cells that are responsible to make new bone cells

Osteoclasts◦Cells that are responsible to

breakdown bone cellsLet’s watch a video for better

illustration

Repair of BoneWhat happens if we break our

bone?

As we age…Our bones get

◦Lighter (less dense)◦More brittle◦Grow shorter

Common bone issues when old◦Osteoporosis

Important to exercise and eat healthily in order to keep bones healthy

Lets Recap!What is growth plate (epiphyseal

plates)?

Refers to the 2 bands of cartilage at the end of the bone. It is responsible for the length growth of long bones before 16-20 years old.

Lets Recap!What is osteoblasts?

Cells that are responsible to make new bone cells.

Lets Recap!What is osteoclasts?

Cells that are responsible to make breakdown bone cells.

Lets RecapWhat is important in the diet for

bone growth?

Calcium + Vitamin D