Have you ever wondered if there were no bones in our body, what would happen?
Yes, without bones the human body is like a semi-empty pack. The human skeleton is a very rigid structure made up of bones. It is primarily involved in providing support for our muscles, skin and our vital organs. If bones are not present in the human body, we won’t be able to do anything. For example, movements, digestion, reproduction etc. This is because our nerves, blood vessels, lungs, brain and visceral organs would be blocked and squeezed.
Table of contents
Skeletal system or skeleton is the hard, supportive or protective elements of the animal body. In human beings, this system is composed of 206 bones and a few cartilages.
The significance of the skeletal system is enlisted below:
The skeleton of human beings is divided into two parts based on the position of skeletal structures. These are the axial skeletal system and appendicular skeletal system.
The axial skeleton in human beings is present along the main axis of the body. The axial skeleton involves 80 bones. These 80 bones collectively formed the skull, vertebral column, sternum and ribs.
The skull is made up of four different types of bones. These include the cranium, facial, ear ossicles and hyoid bone.
The skeleton of the head is termed as a cranium or brain box. It forms the outer protective covering of the brain.
It is made up of 8 cranial bones that are as follows:
They normally form the front part of the skull. The anatomical name of facial bone is known as Viscerocranium.
It consists of 14 bones that are named below:
The facial bones perform the following functions:
Ear ossicles are also termed as auditory ossicles. There are normally three bones present in the middle part of each of the human ear. Therefore, there are a total of six ear ossicles. These bones are considered as the smallest bones of the human body.
The six ear ossicles are named as:
The hyoid bone is situated in the upper part of the throat, above the larynx. It is a U shaped bone. Hyoid bone acts as a point of attachment for certain tongue muscles and the floor of the mouth.
Skulls are classified into two types on the basis of number of articulations. These bony articulations are described as the projections on the occipital bone and hence, called the occipital condyles. These articulations connect the skull with the vertebral column. The two types of skulls are monocondylic skulls and dicondylic skulls.
The monocondylic skull has one occipital condyle at the posterior end of the cranium. This type of skull is commonly present in birds and reptiles.
In this type of skull, two rounded occipital condyles are present at the posterior end of the cranium. These articulations attach with the first vertebrae. The amphibians and mammals possess the dicondylic skull.
The vertebral column or the backbone is a curved structure that lies dorsally in the human body. It is composed of 26 serially arranged bones called vertebrae. It extends from the base of the skull and forms the framework of the trunk. The components of the vertebral column are considered as Vertebrae. The vertebral column possesses four slight bends called normal curves when viewed from the side.
Each vertebra has a typical structure. Large, disc-like flattened body called the centrum or body present at the anterior portion. The posterior portion of the vertebra is known as the neural arch. The neural arch of each vertebra forms a hole called vertebral foramen. The vertebral foramina of 24 vertebrae together form the vertebral canal or neural canal. Through this neural canal, the spinal cord passes.
Between the bodies of adjacent vertebrae, intervertebral rings are found. These rings are known as Intervertebral discs. They are involved in the following functions:
On the basis of the location, where they are present, vertebrae are classified into five major groups. These are as follows:
They are located in the neck region. They are seven in number in almost all mammals including human beings. The first cervical vertebra is the atlas which articulates with the occipital condyles. It supports the head. The second vertebra is known as the axis.
They are located in the chest region and are 12 in number. They are larger and stronger as compared to the cervical vertebrae. They articulate with ribs.
They are present in the lower back region. They are five in number and are the largest and strongest of all the vertebrae. This is because they have to bear the weight of the whole body when the body is in a standing position.
There are five sacral vertebrae that are fused and form the Sacrum. These vertebrae are separated in childhood, but start to fuse during adolescence. The sacrum is located between the innominate or hip bones.
They are four fused vertebrae that form the Coccyx. These are curved triangular bones. The vertebrae are separate during childhood but start to fuse during adolescence. It is considered as the vestigial tail in humans.
It is characterised as a flat bone which is located in the center of the anterior thoracic wall. It measures about 15 cm in length. The sternum is also known as a breast bone. It provides the point of attachment for ribs. It protects the organs of the thoracic region like lungs and heart.
The sternum is divided into three segments. These segments of the sternum normally fuse around the age of 25. The parts are as follows:
It is the superior part of the sternum.
It is the middle and largest part of the sternum.
It is considered as the inferior and smallest part of the sternum.
In human beings, ribs are present in 12 pairs. They are flat bones and are arranged in the form of a cage and therefore, called the rib cage. The ribs, thoracic vertebrae and sternum together form a ribcage. They protect the internal organs present in the thoracic cavity and the kidneys. Rib cage is essential for the process of breathing and respiration.
Ribs are bicephalic because they have two articular surfaces. Each rib is articulated dorsally with the vertebral column (thoracic vertebrae) and ventrally with the sternum.
Ribs are classified into three types on the basis of their attachment at the ventral side.
The first seven pairs of ribs are called true ribs. They are attached to the thoracic vertebrae, dorsally. They are connected to the sternum ventrally with the help of hyaline cartilage, called costal cartilage.
The 8th, 9th and 10th ribs are called False or Vertebrochondral ribs. They do not articulate directly with the sternum but anteriorly they join the seventh rib with the help of hyaline cartilage.
The last two pairs of ribs (11th and 12th) are not connected ventrally to the sternum or the cartilage and are therefore called floating ribs.
Q1. Determine the structure which is excluded from the axial skeleton.
Solution: On the basis of the position of the skeletal structures in the body, the skeleton is divided into two types: axial and appendicular skeletal systems.
Q2. Determine the function which is incorrect for hyoid bone.
Solution: The hyoid bone is situated in the upper part of the throat, above the larynx. It is a U shaped bone. Hyoid bone acts as a point of attachment for certain tongue muscles and the floor of the mouth. It aids in swallowing and speech. The movement of the head is possible with the help of neck muscles. Hence, the correct option is c.
Q3. Match the Column A with Column B
Q. 11th & 12th
R. First- 7th
Solution: The first seven pairs of ribs are true ribs that are directly connected with the sternum. 8th, 9th and 10th pairs of ribs are known as false ribs because they are connected with the 7th pair of ribs with the help of hyaline cartilage. 11th and 12th pairs are floating ribs because they are not connected with the sternum and they hang in the air. Hence, the correct option is a.
R. First- 7th
Q. 11th & 12th
Q4. Identify the given image and label the structures.
Answer: The given image represents the structure of a typical vertebra. Label ‘a’ represents the ‘centrum’ which is a large, disc-like flattened body at the anterior portion. Label ‘c’ represents the ‘neural arch’ which is located at the posterior portion of the vertebra. Label ‘b’ represents the ‘vertebral foramen’. The neural arch of each vertebra forms a hole called vertebral foramen.
Question1. Are axial and appendicular skeletons the same?
Answer: The bones in the axial and appendicular skeletons are different. However, they combined to form the structural framework of a human being. The axial skeleton consists of the bones along the main axis. On the other hand, the appendicular skeleton consists of the bones of the appendages.
Question2. Is it correct to say that humans possess a tail?
Answer: Humans possess a tail, but it is present only for a short period during the embryonic development. It is present around the 5th to 6th week of intrauterine life. The human embryo has a tail which consists of 10 – 12 vertebrae. Normally by 8 weeks, the human tail disappears. But the coccyx or tailbone remains in human beings which is formed by the fusion of four coccygeal vertebrae.
Question3. Which bone is considered as the smallest bone in human beings?
Answer: Stapes are the smallest bone in the human body. They are two in number, one in each ear. Malleus is considered as the second smallest bone in the human body.
Question4. Which is the only bone in the human skull which is movable?
Answer: Mandible is the only bone in the human skull which is movable. It is also known as the lower jaw. It allows the closing and opening of the mouth. It is the strongest and largest bone in the human skull. It aids in mastication and forms the jaw line.
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