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Human Musculoskeletal Anatomy: Skeletal Tissues

Rickets, osteomalacia, osteoporosis and brittle bone disease

  • 3 things to know
  • Component 3

Overview

Why a shortage of vitamin D leads to soft bones and two visible signs of rickets in a child.

What you need to know

Answer each one before you reveal it.

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Key term

Which dietary deficiencies cause rickets?

Key term

Explain why a shortage of vitamin D leads to soft bones.

Key term

Describe two visible signs of rickets in a child.

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Which dietary deficiencies cause rickets?

    Model answer

    Rickets is caused by a deficiency of vitamin D, or of calcium itself, in a growing child.

  2. 2

    Explain why a shortage of vitamin D leads to soft bones.

    Model answer

    Vitamin D is required for calcium to be absorbed from the gut, so without it too little calcium reaches the blood and the bone matrix laid down by the osteoblasts is never properly mineralised.

  3. 3

    Give two ways in which the body obtains vitamin D.

    Model answer

    Vitamin D is manufactured in the skin under the action of ultraviolet light in sunshine, and it is eaten in oily fish, egg yolk, liver and fortified foods such as margarine.

  4. 4

    Describe two visible signs of rickets in a child.

    Model answer

    The long bones of the legs bow outwards or the knees turn inwards under the child's weight, and the wrists and ankles appear swollen where the growing ends of the bones are enlarged.

  5. 5

    What is osteomalacia, and why does it not deform the skeleton in the way rickets does?

    Model answer

    Osteomalacia is the same failure of mineralisation occurring in an adult, and because the bones have finished growing and the growth plates have closed they cannot bend into new shapes, so the bones simply become soft, painful and easily broken.

  6. 6

    Which groups of people in Britain are at particular risk of vitamin D deficiency?

    Model answer

    People with darker skin, those who keep most of the skin covered, elderly or housebound people who go outdoors rarely, and anyone whose diet is very poor are all at increased risk.

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