There are 5 types of bones in the human body. These are long bones, short bones, flat bones, irregular bones, and sesamoid bones. Here we outline the different types of bones in the human body and explain where they are found.
Long bones are some of the longest bones in the body, such as the Femur, Humerus, and Tibia but are also some of the smallest including the Metacarpals, Metatarsals, and Phalanges.
The classification of a long bone includes having a body that is longer than it is wide, with growth plates (epiphysis) at either end, having a hard outer surface of a compact bone and a spongy inner known a cancellous bone containing bone marrow. Both ends of the bone are covered in hyaline cartilage to help protect the bone and aid shock absorption.
Short bones are defined as being approximately as wide as they are long and have a primary function of providing support and stability with little movement. Examples of short bones are the Carpals and Tarsals – the wrist and foot bones. They consist of only a thin layer of compact, hard bone with cancellous bone on the inside along with relatively large amounts of bone marrow.
Flat bones are as they sound, strong, flat plates of bone with the main function of providing protection to the body’s vital organs and being a base for muscular attachment. The classic example of a flat bone is the Scapula (shoulder blade). The Sternum (breastbone), Cranium (skull), ilium (hip bone) Pelvis and Ribs are also classified as flat bones. Anterior and posterior surfaces are formed of compact bone to provide strength for protection with the centre consisting of cancellous (spongy) bone and varying amounts of bone marrow. In adults, the highest number of red blood cells are formed in flat bones.
These are bones in the body which do not fall into any other category, due to their non-uniform shape. Good examples of these are the Vertebrae, Sacrum, and Mandible (lower jaw). They primarily consist of cancellous bone, with a thin outer layer of compact bone.
Sesamoid bones are usually short or irregular bones, embedded in a tendon. The most obvious example of this is the Patella (knee cap) which sits within the Patella or Quadriceps tendon. Other sesamoid bones are the Pisiform (smallest of the Carpals) and the two small bones at the base of the 1st Metatarsal. Sesamoid bones are usually present in a tendon where it passes over a joint which serves to protect the tendon.