INDEX*Note: Various websites have different opinions about the number of bones in a baby. While some cite that there are 350 bones, some say that there are 270, and others mention that there are approximately 300 bones.
Let us begin our discussion on skeletal system, starting from the day we were born. We all are born with 350 bones, but as fully grown adults, we are left with only 206! Are you thinking where do the rest of the bones disappear? The fact is that our bones tend to fuse together as the body grows and develops. Most of our bones during birth are made of cartilage. As we grow, they form into strong bones through a process known as ossification
. This fusing of bones is important to help us carry out various functions that we need to perform as adults. Thus, the missing bones are not really "missing", they are just fused together to form a new bone structure.
If our body had no bones, we wouldn't be able to know a lot of things. For example, if it wasn't for the mobility that the bones provide us, would we know how the birds look flying up in the sky, or what does a shooting star look like? We wouldn't be able to bend and pluck beautiful flowers, or run and chase the butterflies! You must have seen the movie "Sky High" released in 2005. Remember the character named Ethan
, also known as 'Popsicle'? He had the ability to melt into a small orange puddle. In a similar way (although, not in exactly the same manner), without the skeletal system, the human body would just be like a pile of mass -- without any shape, without any structure, and without the ability to move! The human body can hold itself straight, and has a well-defined structure only because of bones. The human skeletal system not only provides the structure to stand up straight, but also protects all the important and delicate organs inside our body.
Number of Bones in the Body and Their Distribution
An adult human body has 206 bones. Each section of the skeletal system has a definite number of bones. Our skeleton is divided into two parts: (1) The Axial Skeleton
; and (2) The Appendicular Skeleton
. The axial skeleton consists of the skull and the torso, whereas the appendicular skeleton consists of the shoulders, arms, hips, and legs. This can be seen in the image above.
Bones in the Axial Skeleton
Out of the 206 bones in our body, 80 bones are found in the axial skeleton, which consists of the bones in the skull, face, and torso. There are 28 bones in the skull (including facial bones and middle-ear bones). The skull consists of 8 cranial bones, the face consists of 14 bones, and the middle-ear consists of 3 paired bones (6 in total). So, 8 cranial bones + 14 facial bones + 6 middle-ear bones = 28 skull bones.
The torso includes the hyoid bone, vertebral column, ribs, and sternum. It has 52 bones in total. These 52 bones include -- the hyoid bone located below the tongue, the 24 bones of the ribs (12 bones on each side), the sternum (breastbone), and 26 bones of the vertebral column. So, 1 hyoid bone + 24 bones in the ribcage + 1 sternum + 26 bones in the vertebral column = 52 bones in the torso.
28 bones in the skull + 52 bones in the torso = 80 bones in the axial skeleton
Bones in the Appendicular Skeleton
The appendicular skeleton consists of 126 bones and includes the arms, hands, legs, feet, shoulder girdle, and the pelvic girdle. The appendicular skeleton can also be divided into the upper and lower extremities. The upper extremity has 64 bones
comprising the bones in the shoulder girdle, the arms, and hands; whereas the lower extremity has 62 bones
comprising the bones in the pelvic girdle, legs, and feet.
Beginning with the upper extremity - the shoulder girdle has 4 bones, which include 2 shoulder blades (scapula) and 2 collarbones (clavicle), on each side. The arm and forearm has 6 bones, including 2 arm bones (humerus), 2 ulna (a long bone situated below your little finger), and 2 radius (another long bone located parallel to the ulna). Coming to the hands, each of our hand consists of 27 bones, making a total count of 54 bones in both the hands
The lower extremity consists of 62 bones. Starting with the pelvic girdle, it consists of 2 hip bones, one on each side, forming the pelvis. Then comes the legs and feet which together constitute 60 bones in total. Out of the 60, each leg consists of 4 bones -- 1 femur (thigh bone), 1 tibia (shin bone), 1 fibula (calf bone), and 1 patella (kneecap). Therefore, both the legs contain 4 x 2 = 8 bones
. Each foot consists of 7 ankle bones (tarsal bones) , 5 metatarsal bones, and 14 bones of the toes (phalanges). So, there are 52 bones in the feet (26 in each foot)
54 bones in the hands + 52 bones in the feet + 4 bones in the shoulder girdle + 6 bones in the arms and forearms + 8 bones in the legs + 2 hip bones in the pelvis = 126 bones in the appendicular skeleton
*For a detailed explanation of the various bones in the human body, click on the linked phrase.
Facts Related to the Types of Bones
The bones in our body are divided into many types. Some people classify them into 4 types, some into 5 types, and some into 6. The different types of bones mentioned here, are based on their shape and size.
Long bones are those, which have greater length and lesser width. They mostly include the bones of our legs and arms. Some examples include bones like -
- Femur (thigh bone)
- Humerus (arm bone)
- Tibia (shin bone)
- Fibula (calf bone)
The image on your right shows the femur. It also happens to be the strongest and the largest bone in the body!
Short bones are those, which have approximately the same length and width (mostly cube-shaped bones). A majority of these bones are located in our wrists, hands, ankles, and feet. Some examples include bones like -
- Most of the carpal bones (eight small bones in the hand/wrist named - Trapezoid, Trapezium, Capitate, Hamate, Pisiform, Triquetrum, Scaphoid, and Lunate)
- Tarsal bones (seven small bones in the foot/ankle)
The image on your right shows the tarsal bones. The labeling is as follows: 1. Medial Cuneiform 2. Intermediate Cuneiform 3. Navicular Bone 4. Talus (ankle bone) 5. Calcaneus (heel bone) 6. Cuboid 7. Lateral Cuneiform
Flat bones are those which appear to be thin, and some may also be curved. Examples include -
- Some bones of the skull like the frontal bone, parietal bone, and the occipital bone. These bones are the part of the eight cranial bones that fuse together to form a protective shield for the brain.
- Even the rib cage and the shoulder blades (scapula) are examples of flat bones.
On your right is the diagram of the skull bones that come under this category.
As the name suggests, irregular bones have no specific shape as such. Their design is complicated, probably because of the function they perform. A good example of this type would be,
- The hyoid bone which is located in your throat at the base of the tongue.
- Other examples include skull bones like ethmoid bone and sphenoid bone.
The image on your right represents the hyoid bone. It is the only bone that doesn't connect with any other joint in the body!
The sesamoid bones are those that are embedded inside a tendon. They are located in the joints of the body, like your knees. There are approximately 230 movable and semi-movable joints in your body
that play a very important role in the movement, and endure a considerable amount of friction while we perform our everyday activities. A classic example of the sesamoid bone is the kneecap, also known as the patella
A bone called pisiform
found in the wrist is also an example of sesamoid bone.
The image on your right shows the patella or kneecap.
This category is not commonly mentioned in the classification of bones based on their shape. However, if we get into a deeper classification, then sutural bones are worth a mention.
Also known as Wormian bones or intra sutural bones
, these are the bones that are found in the sutures (or the sutural joints) formed between the cranial bones found in the skull.
The image on your right shows the sutural bones of the skull.
Facts Related to the Basic Bone Structure
Though bones may appear to be hard and solid, they are not completely made of solid material. A bone has an exterior and interior structure. The structure of the bone and its various components are explained as under:Periosteum
: It is the very first layer of the bone. The periosteum is a fibrous membrane that covers the surface of the bone. It also supplies the bone with necessary nourishment through blood vessels, and contains nerves that provide sensation to the bones.Compact bone
: Under the periosteum layer lies the compact bone (also known as the cortical bone). This is the part which we see when we look at a skeleton. The bones are made up of bone tissue (also known as osseous tissue) which is divided into two parts - compact and spongy. The compact bone is the one that safeguards the internal organs. It has small canals which absorb and release the necessary minerals needed for its growth and nourishment, thereby giving the bones the strength that they need. This bone is dense, hard, strong, and accounts for 80% of the total weight of the skeleton. Spongy bone
: Beneath the compact bone, lies the spongy bone, which as the name suggests is soft, and has a texture as that of a sponge. This texture enables this bone to accommodate the bone marrow and blood vessels. It is this bone that is responsible for the light weight and the flexibility that the skeleton has. The spongy bone accounts for the rest of the 20% weight of the skeleton, the other 80%, being the weight of the compact bone.Bone marrow
: The bone marrow is located within the medullary cavity
, also known as the marrow cavity
. There are two types of bone marrow found in the human body. These are - the red bone marrow
and the yellow bone marrow
. The red bone marrow is responsible for the formation of blood cells, while the yellow bone marrow is responsible for the storage of fatty tissues that are used by the body to gain energy in the absence of food. Long bones like the femur and humerus contain yellow marrow, whereas flat bones like the skull and ribs contain the red bone marrow. However, in children, red bone marrow is also found in the long bones. Cartilage
: When we were born, our bones were not as strong and hard as they are now. This is because when we were babies, our bones were mostly made of cartilage. A cartilage is the soft flexible substance that we can feel when we press our ears and nose. As we grow, the cartilage slowly transforms into dense and hard bones. Our bones stop growing after we reach the age of 25
. However, a point to be noted is that not all cartilage transform into bones. Apart from your ears and nose, cartilage can be found in places including the joints of the bones, ribcage, bronchial tubes, and intervertebral discs. This enables smooth movements between the bones since the cartilage protects them from rubbing against each other.
Some Interesting and Fun Facts
Did you know?
Though the structure of us humans and giraffes are completely different, there is but one similarity! Any guesses? Well, what is the one feature of the giraffe that is astonishing? That's right - the neck. Did you know that the number of bones in the neck of a human being and a giraffe are the same? Both of them have 7 bones (vertebrae) in the neck. The bones in the giraffe's neck, are of course longer, but the number is the same as humans.
Have you ever thought ...
Are teeth counted among bones? I mean, when you look at a skeleton, you also look at the teeth ... then why have we not mentioned about them? Well, teeth surely are a part of the skeletal system - but they are not counted among the bones of the body. The structure of the teeth is different from the bones. Unlike bones, teeth are made up of substances including enamel
, and pulp
. Enamel is considered to be the hardest substance in our body!
Are bones living or nonliving?
Most people think that bones are just a non-living structure which give shape to our body, but that is not true! Think for yourself, if they were just a non-living frame for the body, how would they grow? How would they heal after a fracture? We have already discussed the structure of the bone, and the fact that they are made up of living cells. So, the next time someone tells you bones are dead - tell them that they are very much alive!
OMG! Our bones are so strong!
Do you have any idea how strong your bones are? If you take proper care of your bones by eating and exercising the right way, your bones can become as strong as steel. Yes, it's true! Imagine if our skeleton was made up of steel, how heavy would it be! Compared to steel, our bones are extremely light. If you compare the strength of a human bone, and the strength of steel per ounce, bones can bear more stress. Research also states that our bones are four times stronger than concrete
. Exercising and eating calcium-rich foods makes our bones stronger day by day.
A new bone every 10 years!
Would you believe me if I tell you that our bones completely renew in every 10 years? Yes, our bones do not share their age with us. In fact, they undergo constant renewal through a process known as remodeling
. Every year, our bones replace 10% of their old bone tissue with a new one. The credit to this renewal goes to the two types of bone cells called osteoclasts
. The osteoclasts identify that the bone has reached the end of its life cycle and break down its tissues. The osteoblasts then, make sure that new bone tissues take place of the old ones, making sure that the bones are always as good as "new"!
You are taller in the mornings!
Did you know that we are taller in the morning and shorter in the evening? This is because the activities performed during the day makes the discs between the vertebrae compress. This compression occurs due to gravity, thereby reducing your height during the day. However, when you sleep in the night, the discs go back to normal, due to which we gain about half an inch or so when we measure our height in the morning.
Where are the maximum bones found?
Did you know that our hands have the maximum number of bones in the entire body? Yes, there is a very close competition between the hands and feet. The placement of the bones in both these parts are very much similar. The feet have 52 bones in total (each foot has 26), whereas the hands have 54 bones in total (each hand has 27 bones). Another interesting point to be noted here, is that the hands and feet constitute of more than half of the bones in the human body, 106!
Bones help us hear!
The human skeletal system helps in hearing. Surprised? Yes, bones play an important role in the mechanism of hearing. The three ear bones (collectively called ossicles); the malleus, incus, and stirrup (stapes) in the middle ear, play an important role in helping us hear sounds. The stirrup is the shortest and lightest bone in the human body, with a size like that of a rice grain. Also, only the middle ear consists of bones; the outer ear and the nose is made up of cartilage.
Isn't our body a magnificent machine that takes care of its own! I mean, who would have thought that the bones in the skeletal system go through continuous renewal, without making us face any difficulty. Who would believe that our bones are as good as new in every 10 years. Before I conclude, I would leave you with another interesting fact - after the age of 25, our spine may start shrinking, thereby reducing our height. Any guesses why? The discs between the vertebrae column may shrink, causing the bones to move closer
. So, if you wish to keep your bones healthy, make sure you eat right, exercise daily, and lead an active life. Take care of your bones so that they can take care of you in return. For now, start by correcting your sitting posture!