How Many Bones Are In The Human Body?

The human body is made up of a total of 206 bones. There are different types of bones in humans, some are small like ear bones and some are very large like thigh bones. Some are long bones, some are short bones, and some have an irregular shape and are known as irregular bones, sesamoid bones are also one type of bone. Bone performs different types of functions such as providing support, protecting important internal organs, and many more. Osteoblast, osteoclast, and osteocytes are three important types of bone cells. To know more about bones, their function, and their types continue reading this article.

What are bones?

Bone is a type of special connective tissue that is made up of protein, and minerals. The special type of protein that makes bones is collagen, and calcium and phosphate are important minerals that make the bone and provide strength to it. The bone matrix is made of ground substance and collagen fibre. Osteoblast, osteocytes, and osteoclast are important types of bone cells found in matrices. Either red or yellow bone marrow is present in the centre of the bone.

Types of bones

There are five main types of bones. These types are explained below:

• Long bone: Diaphysis, epiphysis, and metaphysis are three important parts of a long bone. A diaphysis connects two ends of bones which are made of the epiphysis. The diaphysis is made up of compact bone and the epiphysis is made of spongy bone covered by a thin layer of compact bone. The metaphysis is present between diaphysis and epiphysis and site of growth during development. The marrow cavity is present between the compact bones. Examples of long bones are the fibula, tibia, humerus, phalanges, radius, and ulna.

• Short bone: The length and width of short bones are the same, and look more or less cuboid. These bones are mostly found in the tarsus and carpus of the foot and hand respectively. Spongy bones are covered by a thin layer of compact bone. Bone marrow is present inside the spongy bone. They provide stability and also allow some degree of movement. Examples of short bones are: the scaphoid bone, lunate bone, talus bone, and navicular bone, etc.

• Flat bone: flat bones are made up of spongy bone covered by two layers of compact bone. Sternum, ribs, scapula, and skull bones are examples of flat bones. Their main function is to protect internal organs such as the brain, heart, etc.

• Irregular bone: These bones are not placed under any other category due to their irregular shape. Compact bone covers a large mass of spongy bone. Ischium, pubis, and spine bones are irregular bones.

• Sesamoid bone: sesamoid bone is a small and oval-shaped bone embedded in the tendon. These bones are found at the end of long bones where tendons cross.

Functions of bones

There are 206 bones in the human, the following are the important functions of human bones:

• Bone marrow is present in the center of the bone and it is the place where all blood cells form.

• Bones support our bodies and help us to move. Proper coordination of bones is required to move our body properly and help to shift our weight.

• Protection is also one of the important functions of bones. Bones protect our internal organs from damage. For example, ribs protect our heart and lungs, and the skull protects our brain.

• Some bones store fat and release it when our body needs energy.

• Our bones store and release minerals when the level of minerals is high in the body, some amount of these minerals are stored in the bone and utilized when our body needs them.

The structure of bone

The bones are made up of the following important structures:

• Osteoblast cells

• Osteoclast cells

• Osteocytes

• Osteoid (a mixture of collagen and protein)

• Inorganic mineral salts

• Nerves and blood vessels

All bones are made up of two types of tissues: Compact bones and cancellous bones. Compact bone is hard, strong, and durable tissue that makes the outer part of the bone. It makes up about 80% of bone mass. Cancellous bones are also known as trabeculae and spongy bones. These bones make up about 20% part of the bone. These bones are lighter, less dense, and more flexible.

Osteoblast: Osteoblast is bone cells that are responsible for generating and repairing bone. These cells produce osteoid which is a protein mixture that after mineralization converts into bone.

Osteocyte: osteocytes are inactive osteoblasts that remain within the bone and perform the metabolic function in the bone.

Osteoclast: osteoclast is the cells that break down the bone and this process of breaking the bones is known as the resorption of bones.

The extracellular matrix is made up of both organic and inorganic materials. Organic material is collagen, whereas hydroxyapatite, salts such as calcium and phosphate inorganic part of the bone.

Distribution of bones in the human body

The 206 bones of an adult human can be divided into two groups: Axial and appendicular. The axial Skeleton is made of 80 bones whereas the appendicular skeleton is made up of 126 bones.

Axial Bones

There are a total of 80 axial bones present in the skull, middle ear, thoracic cage, vertebrae, and hyoid bone.

Skull is made of 28 bones divided into two types: cranial bone and facial bone. The parietal, temporal, frontal, occipital, ethmoid, and sphenoid are cranial bones.

Maxilla, zygomatic, mandible, nasal, palatine, lacrimal, vomer, and inferior nasal concha are facial bones. Malleus, incus, and stapes are ear bones. There are 26 vertebral bones divided into 7 cervical vertebrae, 12 thoracic vertebrae, 5 lumbar vertebrae, 1 coccyx, and 1 sacral vertebra. The thoracic cavity is made up of 24 ribs and 1 sternum.

Appendicular bones

The appendicular skeleton is made up of 126 bones and includes the pelvic girdle, pectoral girdle, upper limb bones, and lower limb bones.

The pectoral girdle includes 2 clavicles and 2 scapulae. Humerus, radius, ulna, carpal, metacarpal, and phalanges are upper limb bones. The pelvic girdle is made of 2 hip bones. Femur, tibia, fibula, patella, tarsal, metatarsal, and phalanges are upper limb bones.