Human Bones

HOW MANY BONES ARE IN THE HUMAN BODY?

The average human body has 206 bones, but infants have around 270 and about 8% of adults have more or fewer than 206.

The human skeletal system is a complex and fascinating marvel of biological engineering. Not only does it provide structural support for the body, but it also aids in movement, protects vital organs, produces blood cells, and stores minerals. Given its myriad functions and intricate nature, one may wonder how many bones comprise this essential system.

The average adult human has 206 bones, but around 15% of people have more or fewer bones.

HOW MANY BONES ARE THERE IN THE HUMAN BODY?

The Average Adult

The most frequently cited number of bones in the adult human body is 206. This includes everything from the minuscule bones in the ear to the long bones like the femur that make up the limbs.

The Newborn Infant

However, newborn infants start with a higher count of around 270 bones. As they grow, some of these bones gradually fuse together to form single bones, which explains the reduced number in adults.

Range of Values

The number of bones in an individual varies due to several factors, including genetics and medical conditions. Some people have extra bones—termed “accessory bones”—or lack certain bones altogether. The bones that people are most likely to have more or fewer of are usually the sesamoid bones (small, round bones embedded in tendons), which vary in number. However, some people have more or fewer vertebrae, digits, or ribs. About 8% of people have at least one extra rib. Overall, about 15% of people have more or fewer than the standard 206 bones.

WHY THE DIFFERENCE?

Genetic Factors

Genetic variations are the primary reason for the difference in the number of bones among individuals. Some people inherit traits that lead to the development of extra bones in the feet, hands, or even the spinal column.

Medical Conditions

Certain medical conditions can also influence bone count. For instance, some individuals experience bone loss due to conditions like osteoporosis or have bones surgically removed due to trauma or diseases like cancer. Several congenital conditions impact the number of bones. For example, polydactyly results in more than the usual number of fingers or toes (more bones), syndactyly involves the fusion of digits in the hands and feet (fewer bones), and spina bifida sometimes results in an abnormal number of vertebrae.

LIST OF BONES THAT ARE IN THE HUMAN BODY

Given the standard 206 bones, they can be broadly categorized as follows:

Axial Skeleton (80 bones)

Skull (22)

Vertebral Column (33)

Ribcage (25)

Appendicular Skeleton (126 bones)

Arms and Shoulders (64)

Legs and Pelvis (62)

HERE IS THE FULL LIST OF BONES IN THE HUMAN BODY:

Axial Skeleton (80 bones)

Skull (22 bones)

1. Frontal Bone

2-3. Parietal Bones (2)

4. Occipital Bone

5-6. Temporal Bones

7. Sphenoid Bone

8. Ethmoid Bone

8-9. Nasal Bones (2)

10-11. Maxillae (2)

12. Mandible

13-14. Palatine Bones (2)

15-16. Zygomatic Bones (2)

17-18. Lacrimal Bones (2)

19-20. Inferior Nasal Conchae (2)

21-22. Vomer

Vertebral Column (33 bones, some of which fuse in adults)

23-32. Cervical Vertebrae (7)

33-43. Thoracic Vertebrae (12)

44-51. Lumbar Vertebrae (5)

52.Sacrum (5 fused vertebrae)

53. Coccyx (4 fused vertebrae)

Ribcage (25 bones)

54-77. Ribs (24, in 12 pairs)

78. Sternum

Appendicular Skeleton (126 bones)

Arms and Shoulders (64 bones)

79-80. Clavicles (2)

81-82. Scapulae (2)

83-84. Humeri (2)

85-86. Ulnae (2)

87-88. Radii (2)

89-98. Carpals (16, in 8 pairs)

99-114. Metacarpals (10, in 5 pairs)

115-144. Phalanges (28, in 14 pairs)

Legs and Pelvis (62 bones)

145-146. Pelvic Bones (2, each made of 3 fused bones: Ilium, Ischium, Pubis)

147-148. Femurs (2)

149-150. Patellae (2)

151-152. Tibiae (2)

153-154. Fibulae (2)

155-162. Tarsals (14, in 7 pairs)

163-172. Metatarsals (10, in 5 pairs)

173-206. Phalanges (28, in 14 pairs)

TYPES OF BONES AND THEIR DISTINGUISHING FEATURES

The five types of bones are long, short, flat, irregular, and sesamoid bones:

Long Bones

These bones are longer than they are wide. They mainly act as levers and are primarily found in the arms and legs. Examples include the femur and the humerus. They contain marrow and are involved in the formation of blood cells.

Short Bones

These bones are cube-shaped and almost as wide as they are long. They provide stability and support and are mainly found in the wrist and ankle. Carpals and tarsals are examples of short bones.

Flat Bones

These bones have a flat shape and primarily protect organs and anchor muscles. They are typically thin, but can be curved or flat. The sternum and the bones of the skull are examples of flat bones. They also contain marrow but are not involved in the formation of blood cells to the extent that long bones are.

Irregular Bones

These bones don’t fit into the other categories due to their complex shapes. They serve various purposes, such as protection and structural support. The vertebrae and some of the facial bones are examples of irregular bones.

Sesamoid Bones

These are small, round bones that are embedded in tendons. They protect the tendon and to increase its mechanical effect. The patella, or kneecap, is the most familiar example of a sesamoid bone. They also appear in the hands and feet.

Largest and Smallest Bones

The largest bone in the human body is the femur or thigh bone.

The smallest bones are the ossicles found in the middle ear: the malleus, incus, and stapes.

LAYERS OF BONE TISSUE

Bones consists of different layers of tissue:

Periosteum – The outer layer that contains blood vessels and nerves.

Compact Bone – The hard, dense layer that gives bones their strength.

Spongy Bone – Located beneath the compact bone; lighter and less dense.

Bone Marrow – The innermost layer; a soft tissue that produces blood cells.

REFERENCES

Chen, W.; Cheng, J.; et al. (2015). “Prevalence and variation of sesamoid bones in the hand: a multi-center radiographic study“. Int J Clin Exp Med. 8 (7): 11721–11726.

Clarke, Bart (2008). “Normal Bone Anatomy and Physiology”. Clinical Journal of the American Society of Nephrology. 3 (Suppl 3): S131–S139. doi:10.2215/CJN.04151206

Nasoori, Alireza (2020). “Formation, structure, and function of extra‐skeletal bones in mammals”. Biological Reviews. Cambridge Philosophical Society. 95 (4): 986–1019. doi:10.1111/brv.12597

Saladin, Kenneth S. (2012). Anatomy and Physiology (6th ed.). New York: McGraw Hill. ISBN 978-0-07-337825-1.

Tözeren, Aydın (2000). Human Body Dynamics: Classical Mechanics and Human Movement. Springer. ISBN 0-387-98801-7.