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Structure of Long Bone

Structure of Long Bone

Although there are many different types of bones in the skeleton, we will discuss the different parts of a specific type of bone: the long bone. The femur, tibia and fibula in the leg, and the humerus, radius and ulna in the arm are all examples of long bones.

Structure of Long Bone

Parts of a long bone.

Epiphysis: The head of each end of a long bone consists largely of spongy bone and is covered with hyaline cartilage.

Spongy bone: Found in the epiphysis of long bones and contains red marrow.

Red bone marrow: Found in the spaces between the trabeculae in spongy bone. This is where the red blood cells are made at the rate of 2 -3 million per second. White blood cell types are also produced here.

Trabeculae: The struts in the network of irregular bony plates in the epiphysis of bones which transfer stresses from the epiphysis to the diaphysis which has a much thicker layer of compact bone and resists stress better.

Diaphysis: Cylindrical shaft of a long bone composed of hard compact bone on the outside.

Periosteum: The membrane of dense fibrous connective tissue which surrounds the outside surface of the shaft of a long bone. It has blood vessels which enables it to nourish the bone and repair injuries. It also provides a surface for the attachment of muscles by means of tendons and ligaments.

Endosteum: The delicate connective tissue layer lining the inside surface of compact bone.

Marrow cavity: This is filled with yellow marrow which consists largely of fat.

Optional Activity: Draw and label a longitudinal section of a long bone

In this activity you need to draw and label the parts of a long bone.


Make sure that you follow all the guidelines for biological drawings:

  1. Give your diagram a caption or heading
  2. Your diagram must take up at least half a page
  3. Your drawing should be in pencil
  4. Label lines should be drawn with a ruler
  5. Label lines should not cross


Optional Investigation: Investigating organic and inorganic components of bones


Experiment A: Remove the inorganic component of bone in order to investigate the organic component

Experiment B: Remove the organic component of bone in order to observe the properties of the inorganic component


Bunsen burner and methylated spirits: Wear safety goggles and no loose fitting clothes. Do not wear synthetic clothes that easily catch fire (cotton and wool clothes are preferable).

Hydrochloric acid: Wear closed shoes, safety goggles, a lab coat and gloves.


Experiment A

  • two small chicken bones
  • two test tubes
  • dilute hydrochloric acid/white vinegar

Experiment B

  • towel
  • one small chicken bone
  • pipe clay triangle or wire gauze on a tripod stand
  • bunsen burner or Methylated spirits burner


Experiment A

  1. Label two test tubes with your initials and A and B. Put a bone in each test tube.
  2. Cover Bone A with water and Bone B with dilute hydrochloric acid. Leave for a few days. The acid will dissolve out the mineral component of the bone leaving behind the organic part.
  3. Take out Bone A and dry it.
  4. Use tweezers to take Bone B out of the acid. Rinse it under the tap and dry it.
  5. Compare the two bones and write down how they appear and whether they are soft or hard, flexible or brittle.

Experiment A: observations

The bone that was in the hydrochloric was much softer and more flexible than the bone in water. This is because the acid reacts with the calcium phosphate in the bone and removes the calcium from the bone tissue. It is the calcium salts in the bone tissue make the bones strong and hard. Calcium salts precipitate out of the bone and this precipitate can be seen in the bottom of the test tube.

NOTE: If you leave the chicken bone in the hydrochloric acid too long you will also remove the collagen.

Experiment B

  1. Place the chicken bone (Bone C) on a pipe triangle or wire gauze on a tripod stand.
  2. Roast the bone strongly for 10 minutes. Roasting will burn off the organic component of bone (mainly the protein collagen) leaving behind the mineral part.
  3. Allow the bone to cool down completely before you touch it.
  4. Describe the appearance of Bone C stating whether it is soft or hard, flexible or brittle.


Note down your observations in your lab notebook.


What can you conclude about the different organic and inorganic components of bones?

Sample Answer

The inorganic component of bone (calcium) helps make bone hard and rigid. The organic component of bone (collagen) helps give bone its flexibility and strength, so that it is not too brittle and does not snap, crumble or break.


  1. What are the main inorganic components of bone?
  2. What changes have occurred in Bone A?
  3. What properties have been removed from Bone B with the loss of its inorganic components?
  4. Which deficiency disease can have similar effects on bones in children?
  5. What is the role of Bone B in this experiment?
  6. What protein makes up the main organic component of bone?
  7. What changes took place in Bone C during the roasting process?
  8. What properties have been removed from Bone C with the loss of its organic component?

Sample Answers

  1. Calcium and phosphate (calcium phosphate).
  2. None. Bone A was kept in water.
  3. Calcium has been removed from the bone tissue, and the bone has become flexible and soft.
  4. Rickets.
  5. Bone B was the experiment as it was covered with the hydrochloric acid and an observation needed to be made.
  6. Collagen, which is an elastic protein which improves fracture resistance.
  7. The organic components were burnt away and the bone turned to ash.
  8. The bone ash contains calcium oxide and the collagen has been destroyed, therefore the bone is no longer flexible and becomes brittle.


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