Human body The Skeletal System Class 5

Human body The Skeletal System

Class 5

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We know that a group of organs that work together to perform a particular function for the body is called the organ system. The organ system which is made up of bones is called the skeletal system. Have you ever wondered what helps our skeletal system to make movements? How are we able to bend our elbow and knees? In this chapter, we are going to discuss about the skeletal system and how it helps us to move.

Our Skeleton

There are 206 bones in our body that are connected together to form a framework called skeleton. This framework encloses and protects all the internal organs and provides support, strength and shape to our body.

The various functions of skeleton are:

 It provides shape to our body.  It provides support and strength to our body.  It provides protection to the delicate internal organs like heart, lungs, brain etc.  It contains a jelly-like substance called the bone marrow.

 It helps in the movement of our body with the help of muscles.

 Our skeletal system consists of the skull, the backbone, rib cage, two pairs of limbs and two girdles, namely pectoral girdle and pelvic girdle.  Skull Our skull is made up of 21 fixed bones and the lower jaw. There are eight flat bones interlocked together. Inside the skull is the brain. The skull protects the brain. The facial region has fourteen bones. Among these only the lower jaw is movable. It enables us to talk and eat. The skull has openings for eyes, ears, nose and mouth. Backbone The backbone is made up of 33 small ring-shaped bones called vertebrae.  The skull is attached to the backbone, which forms the main axis of skeleton. Out of the 33 vertebrae, the first seven are present in the neck region. The vertebrae join together to form a strong column called spine or vertebral column.The joints of the vertebrae allow slight movement. Due to this, we can move our backbone forward and backward. Each vertebra has a hole through which the delicate spinal cord passes. Thus, it protects the spinal cord. Ribs and Rib cage Ribs are thin, flat and curved bones. They make a cage around our chest. This cage of bones is called rib cage. It protects our heart and lungs. Seven sets of rib pairs are connected to the sternum or the breastbone in the front and to the backbone at the back. The lowest two pairs are joined only to the backbone and are called floating ribs.  In total, there are 12 pairs of bow-shaped ribs. Limbs There are two pairs of limbs-forelimbs (arms) and hindlimbs (legs). The arms are joined to the vertebral column with the of shoulder girdles and a pair of collarbones. There is a long bone known as humerus, in the upper arm. It fits into the shoulder girdle. The forearm consists of two bones. Fingers, palms and wrists are made up of small bones. The bones of the legs are attached to the hipbone. The upper part of the leg has the longest bone of the body known as femur. It bears the weight of the whole body. It fits into the hip girdle. The lower part of the leg has shinbone and the calf bone. The long bones of the arms and the legs are hollow like structures. JOINTS AND LIGAMENTS A joint is a place where two bones join together with the help of strong tissues called ligaments. Ligaments are very strong and they allow controlled movement of joints. There are two types of joints in our body- immovable joints and movable joints. Immovable  Joints These joints allow movement of bones because of a fluid that acts as a lubricant. Movable joints are of four types : For Learning More About This chapter Watch The Videos Given Below.