Human Skeleton || Axial And Appendicular Skeleton

Introductiuon:

You might have seen a very common invertebrate the earthworm,which is generally found in the soil.Have you ever thought why it always crawls on the ground?Why it moves so slowly?Why it can not stand erect like human beings and other mammmals?the answer to these question is,"It does not have any skeleton which can support it tostand erect and move faster". In previous classes you have studied the human skeleton, which not only gives proper shape to the human body but also provides support for movement. All animals, which can move fast, possess some type of skeleton. Free movement, also knwon as locomotion ia a life characteristic of all living animals. It enables them to utilize the environment in the best possible way a d save themselves from predators and a range of environmental factors. For nall types of movement the skeleton plays a basic role.

now lets go to study the man target of the article(HUMAN SKELETON)

Human skeleton:

Definition:

A skeleton is defined as the framework of hard structures that provide physical support and protection for the bodies of animals.

Expalanation: 

The shape of an organism depends upon the skeleton. At the time of birth each child has 350 bones but when the child grows. Some of these bones fused together and only 206 remained.

Function:

1_ The skeleton also provides help in the locomotion.

2_ Like other vertebrates, the human skeleton is inside the body i.e it is an endoskeleton.

3_ The skeleton is made of tissues.

4_ It contains living cells and also has nerves and blood vessels.

5_ It can also repair itself and grow.

 

For Your Information

exoskeleton:

The skeletal systemof some invertebrates e.g arthropods, is outside the body, and is called an exoskeleton.

Composition:

The human skeleton is composed of two parts i.e the axial skeleton and the appendicular skeleton.

The axial skeleton consists of 80 bones of the head, neck, and chest.

The appendicular skeleton consists of 126 bones of the limbs, and the pectoral and pelvic girdles.

Science, Technology and Society

The skeleton performs various function in th living body. These function include shape, support, movement, protection and blood cells  production. In different amimals, these function are variously performed and the shape of the skeleton in accordance with the requirement of the particulsr animal's types.

Axial Skeleton :

Meaning :

The term axias means the central point around which other structure are distributed.

Definition :

The skeleton that forms the main axis of the body is called Axial Skeleton.

The axial skeleton lies in the center of the body around which the whole body is built. The axial skeleton includes the skull, the vertebral column, the ribs and the sternum.

1. Skull :

Skull is divided into two parts i.e cranium and facial bones. The cranium consists of 8 bones, which protect brain. These are 14 facial bones, which the skeletalpart of our face.

A. Cranium: 

The cranium consists of 8 bones. Out of them 4 bones namely frontal, occipital, sphenoid and ethmoid are unpaired boneswhere 2 bones are paired namely parietal and temporal. Cranium protects the brain.

B. Facial bone:

Facial bones consist of 14 bones which make our face. Out of these 14 bones, 2 bones are unpaired. The unpaired bones are mandible and vomer.

The paired is maxilla, zygomatic, nasal, lacrimal, palatine and inferior concha.

2. Vertebral Column:

Vertebral column extended from skull to the pelvis. It consist of backbone, whichnot only allow us to stand erect but also protects the spinal cord. It consis of 33 vertebra. These vertebra are named according to their location in the body. Those 7 vertebrae present in the neck are called cervical vertebrae. 12 vertebrae which lie in the chest region are called thoraccicvertebrae. Those five vertebrae which lie in the back region are termed as the lumbar vertebrae and those nine found between the lower limbs area are called the pelvic vertebrae. The pelvic vertebrae make two sets i.e the sacrum and the coccyx. The sacrum is found by the fusion of anterior five vertebrae whereas coccyx is formed by the fusion of the four posterior vertebrae.

A. Cervical vertebra.                  7 bones

B. Thoracic vertebrae.               12bones

C. lumber vertebrae.                  5 bones

D. Sacrum vertebrae.                 5 bones

E. Coccyx vertebrae.                  4 bones

3. Chest bone and Ribes:

There are 12 pairs of ribes in the human body, which are attached on dorsal (back) side with the vertebrae. Out of the 12, 10 pairs of ribes connect anteriorly with the chest bone (sternum) either directly or through arch. The rib cage  provides support to the thoracic cavity (chest cavity) in which vital organs like the heart, lungs etc. are persent. The lower pairs of ribe are called floating ribs because they do not attach with the sternum.

4. Middle Ear Bones:

Each human ear has three bones called ossicles. These are ;

the malleus

the incus

and

the stapes.

5. Neck Bone:

There is one bone in the neck called hyoid bone.

Appendicular Skeleton:

These are the skeleton that form outside of the body. It consist of the following parts.

1. Girdle

2. Limbs

1. Girdle:

There are two types of girdle in the human skeleton. 

A. Pectoral girdle:

The pectoral girdl is attaches the forelimbs to the vertebral column. Pectoral girdle is comprised of bones called scapula, super scapula and clavicle.

B. Pelvic girdle:

The pelvic girdle is attaches the hind limbs to the vertebral column. It consists of two coxal bones. The pelvic girdle support the pelvic region.

2. Limbs:

Limbs are differentiated into,

A. Fore limbs

B. Hind limbs

A. Fore limbs (Arms and Hands):

The arms contain 6 bones (3 in each arm). The hand contain 54 bones (27 in each hand).

Each fore limbs consist of one humer, one radius, one ulna, eight carpals, five metacarpal and 14 phalanges.

B. Hind limb (Legs and feet):

The legs contains 8 bones (4 in each leg) while both feet contain 52 bones (26 in each foot).

The hind limb of human beings consists of 1 femur, 1 tibia, 1 fibula, 8 tarsal, 1 metatarsal and 14 phalanges.

Role of the Skeletal System

The skeleton performs the following function in the body.

* The skeleton forms the hard structure of the body and gives it a definite shapes.

* The skeletal muscles are attached to the bones. Hands, legs, pectoral girdle and the pelvic girdle help in movement. The muscular system has an important role in the movement. Due the attachment of the muscles in the bones, these bone can move  and thus we can move.

* The skull protects the brain and the vertebral column protects the spinal cord. Similarly, the lungs and the heart are protected in the rib cage.

* Bone marrow produces the red blood cells, platelets abd white blood cells.

* Bones store minerals salts (calcium, potassium,phosphorous). This is the reason why the bones remain hard and strong.

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