Types of Bones in Human Body
A set of bones in different shape and size along with cartilage (a firm connective tissue) builds body structure, which gives a particular shape to the body and protects it. There are five different types of bones in the human body. Human bones are mainly differentiated based on various grounds but mainly determined by the shape, size of the bones and also on their width to height ratio. Furthermore classification can be done on the on the basis of development, location, region and function etc.
Types of bones on the basis of shape and size
Bone is the basic unit of the human skeletal system and provides the framework for and bears the weight of the body, protects the vital organs, supports mechanical movement, hosts and manages hematopoietic cells.
There are 5 types of bones in the human body classified on the basis of shape and size. These are long bones, short bones, flat bones, irregular bones and sesamoid bones.
Different types of bones have various shapes related to their particular purpose and task in the body. For example, the pisiform bone of the wrist is the size and shape of a pea, whereas the femur (thigh bone) is nearly two feet long in some people and has a large, ball-shaped head. The unique shape of each bone serves a specific requirement.
1. Long Bones
Long bones are the longest bones in the body. These long bones are longer and less wide. They usually have a shaft with heads at both ends. They are mostly made up of compact bone. Long bones function to support the weight of the body and facilitate movement.
These bones are mostly located in the appendicular skeleton. These bones are found in the lower limbs namely the tibia, fibula, femur, metatarsals, and phalanges and in the upper limbs that are the humerus, radius, ulna, metacarpals, and phalanges.
Long Bones are categorised by their tubular shaft (diaphysis) with a rounded end (epiphysis) on each end. Long bones anatomy can be explained as major 2 main parts namely diaphysis and epiphysis.
i. Long bones have a shaft which is called ‘diaphysis’ that makes up most of the bone’s length.
ii. There is an ‘epiphysis’ (growth plate) at each end of the long bones. They have a hard outer surface made of compact bone and a spongy inner known as cancellous bone containing bone marrow. This helps to guard the bone and give support to shock absorption.
In addition long bones are segregated into 3 categories as below:
Miniature Long Bones: These are long in shape but much smaller in size, example metacarpals, metatarsals and phalanges of both upper and lower limb.
Typical Long Bones: They have an elongated shaft with two ends, example humerus, femur, radius, ulna, tibia and fibula bones.
Modified Long Bones: These bones does not have medullary cavity as other long bones but have modified shaft such as clavicle and vertebrae.
2. Short Bones
On the basis of shape and size short bones are defined. These bones are more or less as broad as per their length and thickness. They have no medullary cavity which is present in the typical long bones.
Their primary function is to hold the body frame together with firmness while having little movement.
Short bones also have a tubular shaft and articular surfaces at both ends. They consist of only a thin layer of compact hard bones with cancellous bone on the inside along with relatively large amounts of bone marrow.
These bones can be of any shape and named accordingly. Short bones are often cube-shaped. Cuboid, cuneiform, scaphoid, trapezoid and carpals and tarsals (wrist and foot bones) are the examples of short bones in a human body.