What is Bone? Explain the Classification of bone.

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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.

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