Starter M Complete the wordsearch Ossification and Bone

Starter… M Complete the wordsearch

Ossification and Bone Growth Lesson 5

Learning Objectives. . . By the end of this lesson you will understand. . *Ossification and the process of how bones grow *The sections of a typical long bone *The effects of exercise on bones and joints

Growth and Development A typical long bone is made up of a number of sections: Cartilage Epiphysis (end) White, smooth and slipperyprotects the end of bones Compact bone Hard and strong Marrow Cavity Diaphysis Filled with soft yellow pulp - marrow Periosteum Tough, fibrous outer skin that covers the shafts of the bone Spongy bone Epiphysis Hard, light and strong, sometimes contains red marrow

The Journey… l Bones start life as cartilage inside the womb l Over the years, this turns into bone by a process called OSSIFICATION

4 Weeks after Conception l l l A periosteum grows around the cartilage. It will control the shape and thickness of the bone. Calcium salts build up.

8 Weeks after Conception l l l Bone cells appear in the middle. They start changing the cartilage onto bone. The periosteum also lays down bone.

Birth l l By the time you are born, the bones are mostly cartilage. They are quite soft and easily bent.

9 years Old l l l Bone cells appear at the ends and change them to bone. Two bands of cartilage remain - called growth plates. Cartilage dies off leaving ‘honeycombs’ – gaps filled with blood vessels, osteoblasts and osteoclasts.

15 years Old l l The plates grow at the edge - so the bone gets longer. At the same time, thinner edge is being turned into bone.

23 years Old l l Growth stops when the plates are all bone. The only cartilage left in the bone is the thin layer at each end.

Ossification l The whole process is controlled by hormones. l If there is too much growth hormone, the cartilage in the plates grows too fast and the person ends up a giant. l If there is too little the person fails to grow.

l Cartilage Prevents bones rubbing together. Becomes thicker with exercise. l Compact bone Hard and strong, it protects the bone from breaking. Becomes thicker with exercise. l Marrow cavity Contains bone marrow. Production of red and white blood cells is speeded up by exercise. l Spongy bone Helps with shock absorption. This increases through exercise. Using the key words, write a paragraph on how these effects of exercise relate to a sporting example

Bones and Ageing l Men’s bones are bigger and heavier than women’s. l All bones get lighter as people get older, because the osteoblasts don’t work so hard. l Many older people suffer from osteoporosis, where bones get so weak they break easily. l But exercise keeps those osteoblasts working. So its important to exercise even when you get old.

Plenary… Quiz time… 2 teams… 1 winner…

Homework l It’s that time already… Revise all the work covered during the last 5 lessons for a test next week.