Bones are connective tissues that differ in shapes and functions. They form a skeletal system that provides a body framework. It supports the body and allows locomotion. They are present in various shapes such as flat or wide plates with large muscle and hollow tubes with thick walls. Bones are also differentiated based on their structure and functions. This classification brings us to the compact and spongy bone structures. Both compact bone and spongy bone are parts of the bone tissue. Compact bones are the hard exterior, while spongy bones are the porous interior structures of bone tissue.
What is Compact Bone?
The external cortical layers of all bone tissues are heavy, hard, and have a smooth surface. This layer of bone tissue is called compact bone. A compact bone example would be the significant cortical bones of all long bones, such as those on arms and legs. They are hard and contain yellow bone marrow. These cylindrical bones constitute 80% of the skeletal system's weight.
What is the Spongy Bone Structure?
The interior layers of bones, which are also called cancellous or trabecular bones, make up the spongy bone structure. These bones are also found in long bone tissues, but they have a lesser amount of calcium and are made of trabeculae. The name ‘spongy bone’ comes from the several lamellar spaces in these bones, which gives it a porous structure.
What is the difference between Compact Bone and Spongy Bone?
Some interesting similarities between Compact and Spongy Bones are given below.
They are the bone tissues in animals that provide shape and support to the body.
Both types of bones contain osteoblasts and osteoclasts that are necessary for creating bones.
Both compact and spongy bones contain proteins like collagens and osteoids, which mineralize to help in bone formation.
There are inorganic mineral salts deposited in the matrix of both spongy and compact bones.
There are blood vessels, nerves, and bone marrow within the lamella of both types of bones.
They form joining sites to attach muscles and also contain cartilages and membranes such as the endosteum.
Fun Facts about Spongy Bones
Research on chimpanzees and skeletal structures of prehistoric humans show a higher percentage of spongy bones than the modern human skeletal system. It is found that trabecular bone density has decreased in the current human skeletal system. This is attributed to the sedentary lifestyle prevalent now, which has reduced the need for constant physical movement.
The following compact bone diagrams explain its structure along with the structure of spongy bones. It also shows how blood vessels are present within both types of bones.
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