Bones

Question 1

Describe the functions of bones as a support for the mechanical function of joints and muscles, and as a reservoir for minerals.

Answer 1

Mechanical- Support and attachment for muscles, tendons, ligaments, and joints.

Protective- Protects internal organs

Metabolic- Mineral reservoir for calcium and phosphate homeostasis.

Hematopoiesis- Support blood formation.

Question 2

Describe the development of bone as a result of endochondral

Answer 2

Endochondral Ossification :

1) Bone forms as cartilage first during the 3rd month of development.
2) Blood vessels and osteogenic cells invade the cartilage framework.
3) The cartilage remains as growth plates (1st cartilaginous joint)
4) Growth plates fuse (at approx, 18 in females, 21 in males)

Question 3

Describe the development of bone as a result of intramembranous ossification

Answer 3

Intramembranous ossification:

1) Bone forms as a fibrous plate
2) Bone cells differentiate from fibroblasts and hemopoietic precursors
3) No cartilaginous phase!

Question 4

Describe the composition of bone, being principally made of type 1 collagen, along with some non-collagenous proteins that are mineralized by deposition of Hydroxyapatite.

Answer 4

Bone is composed of:
- Water 20%
- Protein 35%
> Collagen type 1 (provides toughness)
> Growth factor proteins
> Other organic matrix proteins
- Minerals  45%
> Hydroxyapatite (Provides rigidity)

Question 5

Recognize that bone is composed of cortical and trabecular elements.

Answer 5

The epiphyses of long bones are composed of trabecular (spongy) bone. This acts as a softer interface at joints.

The diaphysis of long bones is made up of cortical bone. This bone is denser and is arranged into Haversian Systems, from the way the collagen molecules form fibrils, which then form fibres and finally, sheets. This structure gives the bone its strength.

Question 6

What cells are involved in bone maintenance and renewal

Answer 6

Osteoclasts- bone-resorbing cells, derived from a hemopoietic lineage

Osteoblasts- responsible for laying down more bone, come from a mesenchymal lineage

Question 7

How does bone undergo a constant process of renewal

Answer 7

Bones are constantly monitored and remodelled to keep them at peak strength.

Osteoclasts will absorb any area of bone that has been damaged, and then osteoblasts will lay down new bone in the same area.

Osteocytes are derived from the differentiation of Osteoblasts. They act as sensors of mechanical pressure and damage.