Bone Tissue

BONE TISSUE

Bone is a hard and rigid tissue that forms the bony skeleton of the body.

Bone supports the body weight and provides attachment to muscles whereas act as lever for movements and provides protection to organs.

Inside the bone there are spaces, which are filled with the bone marrow that produce red blood cells, platelets and cells of the immune system.

Cells of the immune system produced in bone marrow include monocytes, lymphocytes, mast cells, neutrophils, eosinophils and basophils.

The only difference with other connective tissues is that its ground substance is made up of inorganic salts, mostly calcium ions.

The bone is highly vascularized, and in living conditions the bone appears pinkish in colour

• Bone consists of:
• Cells
• Fibers

Ground substances

Bone Cells; The bone contains four types of cells namely the osteoprogenator cells, osteoblasts, osteocytes, and the osteoclasts.

Bone Matrix (Intercellular substance);It is made up of the collagen fibers (osteocollagenous fibers), amorphous ground substance and inorganic salts which constitute about 74% of bone mass.

Types of Bones

• 1.Long bones e.g. femur, tibia and fibula
• 2.Short bones e.g. carpals (wrist bones)
• 3.Flat bones e.g. sternum, ribs and most skull bones (skull)
• 4.Irregular bones e.g. vertebrae and some skull bones

5.Sesamoid bones e.g. patella (kneecap)

Parts of the long bone

• A long bone is one that has greater length than width.

A typical long bone consists of the following parts:

The diaphysis is the bone’s shaft or body—the long, cylindrical, main portion of the bone.

The epiphyses (singular is epiphysis) are the proximal and distal ends of the bone.

The metaphyses (singular is metaphysis) are the regions between the diaphysis and the epiphyses.

Bone formation

• Bones formation occurs in four main stages which are;
• 1.Development of the ossification canters (special membrane)
• 2.Formation of bone matrix
• 3.Deposition of minerals or calcification

4.Formation of trabeculae and appearance of periosteum

Functions of bones

1.Support,the skeleton serves as the structural framework for the body by supporting soft tissues providing attachment points for the tendons of most skeletal muscles.

2.Protection; The skeleton protects the most important internal organs from injury for example, cranial bones protect the brain, vertebrae (backbones) protect the spinal cord, and the ribcage protects the heart and lungs.

3.Movement; when muscles contract, they pull on bones to produce movement.

4.Mineral homeostasis (storage and release);Bone tissue stores several minerals, especially calcium and phosphorus, which contribute to the strength of bone.

5.Blood cell production; bone marrow produces red blood cells, white blood cells, and platelets, a process called hemopoiesis.