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Skeletal System

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Skeletal System - Lesson Summary

Skeletal system gives shape to our body, while muscular system helps in movement. A newborn baby has around 300 bones, which fuse as the baby grows, resulting in 206 bones in an adult. Both bone and cartilage are specialized connective tissues.

The skeletal system has two main divisions – the axial and the appendicular skeleton. The axial skeleton consists of 80 bones, which include the skull, vertebral column, ribs and sternum. The skull consists of eight cranial bones that form the cranium and fourteen facial bones which form the face. The vertebral column consists of seven cervical vertebrae followed by twelve thoracic, five lumbar, one sacral and one coccygeal. There are twelve pairs of ribs, where each rib is a flat bone attached dorsally to the thoracic vertebrae. The vertebral column has three main functions. It protects the spinal cord, supports the head and serves as the point of attachment for the ribs.

The appendicular skeleton includes the bones of the limbs and their supporting girdles. The bones of the hand includes humerus, radius and ulna, eight carpals or wrist bones, five metacarpals or palm bones and fourteen phalanges. The bones of the leg consists of femur or thigh bone, tibia and fibula, seven tarsals or ankle bones, five metatarsals and fourteen phalanges.

Although the muscular and skeletal systems function in a coordinated manner, these systems may begin to wear and tear or exhibit some disorders.

The point at which two bones or a bone and a cartilage make contact is called a joint. These joints play an important role in the movement of the bony parts of our body as well as in locomotion.

Depending on how bones are connected to each other, joints are classified into three major types –fibrous, cartilaginous and synovial.

Fibrous joints do not allow any movement and are also referred to as immovable joints. For example, the cranial bones which fuse end-to-end with the help of fibrous connective tissues to form the cranium. In Cartilaginous joints, bones are joined with the help of cartilages. This joint is found between the adjacent vertebrae in the vertebral column, which permits limited movement.

The synovial joint is characterized by the presence of a lubricating fluid called synovial fluid filled in a synovial cavity between the articulating surfaces of the two bones. These joints allow a considerable degree of movement. Examples are Ball-and-socket joint, pivot joint, hinge joint etc.

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