What is Bone? Explain the Classification of bone.

What is BONE?

Bone is a rigid, highly vascular, dynamic, constantly changing, mineralized connective tissue. It gives characteristic form to the human body. It also gives support to human body.

Classification Of Bones:

Bones can be classified as following:

1. Developmental Classification
2. Structural Classification
3. Regional Classification
4. According to size and shape.

Developmental Classification:

This classification includes 3 types:

Intramembranous: In this type the embryonic mesenchyme directly differentiate into bony tissues. It usually occurs in embryo. The characteristic of this type of bone formation is its rapidity of formation, e.g.,

• Bones of the vault of the skull
• Bones of the face
• Clavicle.

Intracartilagenous:  In it, firstly cartilagenous model of bone is formed which later on transforms into bony tissues. For example,

• All long bones of the body except clavicle
• Short bone
• Irregular bones

Membrano-cartilagenous: At the junction of vault and base of skull the bones are formed by this method.

Structural Classification:

According to structure, there are two types of bones:

1. Compact Bone: Haversian lamellae or cylindrical lamellae are seen in it. The lamellae consist of collagen fibers, lying in calcified material ; adjacent lamellae are held together by interchange of fibers. For example: 

• Shaft of long bones.
• Outer and inner tables of the skull bones.

2.Spongy Bone:  Also known as Cancellous bone. In it lamellae are arranged flat. For example: 

• Ends of long bones 
• Diploe of skull.

Regional classification:

According to regional classification, 206 bones are present.

1. Axial Bones: ( Total 80 )

• Skull: facial bones = 22 , Hyoid bone = 1 , Ear ossicles = 06
• Vertebrae:  Cervical = 7 , Thoracic = 12, Lumbar = 5, Sacral= 5, Coccygeal= 4.
• Ribs = 24
• Sternum = 1

2. Appendicular bones: ( Total 126 )

• Bones of upper limb = 60
• Bones of shoulder girdle = 4
• Bones of lower limb = 60
• Bones of hip girdle = 2

Classification According to size and shape:

According to size and shape, there are 5 types.

1. Long Bones:  They show following characteristics:

• Two ends ( Epiphyses )
• Shaft
• Long size

Example: Humerus, Ulna, Radius, Femur, Tibia, Fibula.

2. Short Bones: They are small in size and have various shapes:

• Carpal bones( Bones of hand - 8 in number )
• Tarsal bones ( Bones of foot- 7 in number )
• 
  

3. Long-Short Bones: ( Miniature long bones )

• Two ends
• Shaft
• Short in length

Examples: Metacarpal bones, phalanges, Meta-tarsal.

4. Flat bones:  They are characterized by two thin plates of compact bone, between which lies a spongy bone. 

• Examples: Scapula, Sternum, Ribs.

https://pixabay.com/vectors/clavical-scapula-shoulder-biology-41577/

5. Irregular Bones: In it, Bones are irregular in shape.

• Example: Vertebrae.

References:

General Anatomy By Dr. Ghulam Ahmad.

https://pixabay.com/vectors/clavical-scapula-shoulder-biology-41577/

About Author:

Tayyba Saleem ( PT )

Doctor Of Physical Therapy.