In the embryo, much of the skeleton is cartilage…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
- In the embryo, much of the skeleton is cartilage. What replaces most of it in an adult?
- Name three places where cartilage remains in the adult body.
- Compare the matrix of cartilage and the matrix of bone.
- Bone has a second job, besides support. What is it, and where is it done?
Need a reminder? The key ideaShow
Connective tissue links and supports other tissues. It has cells, fibres and a matrix. Loose connective tissue includes areolar tissue, which supports the epidermis and has fibroblasts, macrophages and mast cells, and adipose tissue, which stores fat. Dense connective tissue has many fibres. In dense regular tissue the fibres lie in parallel rows, as in tendons, which join muscle to bone, and ligaments, which join bone to bone. In dense irregular tissue the fibres run in different directions, as in the skin. Cartilage has cells in cavities of a solid, pliable matrix. Bone has a hard matrix rich in calcium salts and collagen. Blood is a fluid connective tissue made of plasma, red cells, white cells and platelets.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) Bone replaces most of the cartilage.
Step 2. (b) The tip of the nose, the outer ear, the discs between the bones of the vertebral column, and the limbs and hands. Any three are right.
Step 3. (c) The matrix of cartilage is solid but pliable, and it resists compression. The matrix of bone is hard, and it is rich in calcium salts and collagen fibres.
Step 4. (d) Making blood cells. The bone marrow of some bones does it.
Answer: (a) bone; (b) nose, ear, vertebral discs, limbs; (c) pliable against hard; (d) blood cells are made in the bone marrow.
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