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Structure of Bone Tissue
The adult human bones consist of two types of bone tissues.3
- Compact Or Cortical Bone: It is the hard and dense outer layer that surrounds the bone marrow. It constitutes about 80% of the bone mass.4
- Cancellous Or Spongy Bone: It is less dense and has a honeycomb-like structure. Cancellous bone constitutes about 20% of the bone mass.4

Bone Growth And Structure Changes
Ever wondered how your bones grow?
During childhood and adolescence, the bones contain growing zones called growth plates (epiphyseal plates). These growth plates contain cartilage cells that multiply and grow in length. Eventually, the cells turn into hard, mineralized bone.4
The bones also undergo two important processes – bone modeling and bone remodeling.4

Bone Modeling & Remodeling
Bone modeling refers to the process by which bones undergo a modification of an overall shape due to the activity of bone cells.4
During bone remodeling, the bone cells resorb old bone and form a new bone. Your bones undergo remodeling throughout your life.4

Bone Cells
Bones contain three main types of cells
Osteoblasts:
Osteoblasts are the bone cells that contribute to the formation of a new bone.4
Osteocytes:
Osteocytes are mature bone cells that constitute about 90%–95% of the total bone cells.5 Osteoblasts can be embedded in the bone as osteocytes.5
Osteoclasts:
These cells conduct bone resorption or breakdown of bone. Osteoclasts help remodel the old and injured bones.4
The osteoblasts and osteoclasts are responsible for the constant remodeling of the bone.5
Functions Of Bone
Your bones are more than a structure. They are highly evolved dynamic organs, capable of functions such as protection, movement, and mineral storage.6,7
Below are some of its functions in brief:

Structural Support
Bones offer support for internal structures. They bear the weight of your body and enable an upright posture.6,7

Organ Protection
Your sturdy bones along with muscles protect the delicate internal organs, which would otherwise be prone to injury.6

Physical Activity
Your bones are highly evolved structures that perform diverse mechanical functions.8 The counterforce offered by the bones to a contracting muscle is what initiates the locomotion.9 A combined effort of bone and skeletal muscle is needed to perform any form of physical activity.6

Storage Warehouse
Up to 70% of the bone weight is made of minerals; calcium is the most abundant mineral accounting for 99% of the body’s mineralized tissues.10 Bones act as a calcium warehouse, allowing nerves and muscles to function properly.6 The human body cannot produce calcium. Its only source of calcium is diet or nutritional supplements. In case your body does not absorb an adequate amount of calcium, your bones may become weak.11

Blood Cell Production
Most of your bones have a soft, spongy tissue called bone marrow, which is responsible for the production of blood cells. Bone marrow has many blood vessels and has two types of cells.
- The red marrow cells are responsible for the production of blood cells (RBC, WBC, and platelets)
- The yellow bone marrow is composed of fat cells.12

Energy Source
Did you know there are more than just minerals in your bones? Your bones have bone marrow adipose tissues, which not only act as an energy reservoir for the body but also contribute to immune function and other bodily processes.13
Bone Types
Your body consists of four types of bones and each type of bone has a distinctive shape and function.14
The different types of bones include:
Thus, bones are unique connective tissues that perform several vital functions, including support, mobilization, and protection of internal organs.1

Long Bones14
Long bones are thin, long cylindrical bones and are present in the arms and legs. They function as ‘levers’ that move when the muscles contract.

Short Bones14
Short bones have approximately equal dimensions (length, width, and thickness), and usually appear cuboid in shape. The wrist (carpals) and ankle (tarsals) contain short bones.

Flat Bones14
Flat bones have a thin, flattened, and slightly curved structure. They are present in the skull (cranium), and ribs.

Irregular Bones14
Irregular bones have a complex shape. One of the examples of irregular bones is vertebrae (spine).