Biology, Eighth Edition (Raven)

Chapter 47: The Musculoskeletal System

Osteoporosis

What factors determine bone strength? Bone strength is determined by the internal structure, shape, and size of the bone. Bone is dense relative to other tissues and therefore the size and strength of a bone is generally determined by both the need for strength and the cost of increasing the weight of the organism. Strength increases with bone density, however organisms are able to reduce weight and maintain strength by having bones with support systems similar to those of a building or a bridge. Bone strength is also determined by the diameter of the bone. A thicker leg bone is stronger than a thinner leg bone. Again there is a trade off between size and weight. Heavy slow moving animals have thick limb bones while fast moving animals have slender leg bones.

View the animation below, then complete the quiz to test your knowledge of the concept.


1.	Bones in the legs, arms, spine and pelvis grow

		A)	at different rates.
		B)	at the same rate.
		C)	until age 18, then they stop.
		D)	strongest after age 30.

2.	Which of the following is not considered a weight bearing activity?

		A)	walking
		B)	running
		C)	swimming
		D)	jumping rope

3.	Trusses and arches which help form an internal scaffolding network, are found in

		A)	bone marrow.
		B)	children only.
		C)	adults only.
		D)	trabecular bone.

4.	At which of the following ages would calcium loss from bone be more than calcium deposits into bone, even when a high calcium diet is eaten?

		A)	18 months old
		B)	10 years old
		C)	18 years old
		D)	50 years old

5.	Which mineral is most important throughout life to assist in maintaining strong bone?

		A)	potassium
		B)	calcium
		C)	sodium
		D)	phosphorus