Saturday, April 14, 2012

The Human Skeleton System

Human Skeleton

       The human skeleton is made of bones, cartilage and tough fibrous tissues. It gives support and a shape to our body. It protects the organs and helps in movement. At birth, a baby has more then 300 separate bones. With the growth of body, many of these bones fuse together and thus an adult skeleton possesses only about 206 bones. The skeleton can be divided into two main parts; the axial skeleton (head and trunk) and the appendicle skeleton (arms and legs).

            Human skull is made up of 29 plates of bones, most of which fuse together after birth. The backbone or spine is made up of 33 vertebrae. The chest is enclosed by 12 pairs of ribs. Most of the ribs are connected to the back bone and to the breastbone in the middle of the chest.

            Each hand is made up of 27 small bones. The bone in the upper leg is called femur. This is the longest bone in the body. It is about 48 cm long. It is joined to the pelvic girdle in a ball and socket joint. There are 52 bones in the ankles and feet.

            Our skeleton protects the vital organs like lungs, heart and brain and provides support to muscles. It is also helpful in constituting the respiratory and hearing systems.

            The bones are surrounding by a membrane called periosteum. All bones are hollow containing blood vessels which provide the essential nutrients to the bones. Most of the bones are covered with tough fibrous tissues. The ends of the bones in moving joints are covered with cartilage. This cartilage acts as a cushion in the joints. Bones are attached to other bones by the special connective tissues called ligaments. Muscles are attached to bones by connective tissues called tendons. Some bones are long while some others are flat but they all are very strong. Most of the long bones begin with cartilage while most of the flat ones with membranes. Bones are made up of calcium and phosphorus. They also contain collagen which is a gluey kind of protein.

Section Through a Long Bone:
  • Epiphysis
  • Metaphysic
  • Periosteum
  • Hard, dense bone
  • Spongy bone
  • Marrow cavity
  • Cartilage
Some Important Human Bones:
  • Cranium or skull
  • Mandible or jawbone
  • Clavicle or collar bone
  • Scapula or shoulder blade
  • Sternum or breast bone
  • Ribs
  • Humerus
  • Vertebrae--------they constitute spinal cord
  • Radius
  • Ulna
  • Carpals or wrist bones
  • Metacarpals
  • Phalanges or finger bones and toe bones
  • Pelvis or pelvic girdle
  • Femur or thighbone
  • Patellar or knee cap
  • Tibia or shinbone
  • Fibula
  • Tarsals
  • Metatarsals
Joints
            A joint is a junction between two or more than two bones. There are many different kinds of joints in the human body. Most of the joints provide a kind of movement to the body but there are some immovable joints also i.e. those that do not move. Mainly there are three types of joints they are movable joint, gliding joint and immovable joint.

Movable Joints:
            These joints provide free movement to the body. These are found between the bones of the arms and legs and of hip and shoulder. The ends of the bones of such joints are covered with caps of though cartilage. Cartilage does not wear out easily. BAL and socket joints, hinge joints angular joints, pivot joints etc. are all movable joints.

Gliding Joints:
            At these joints, the bones do not bend but simply slide over each other. The joints of the spine are of this kind. The joints where the ribs meet the breast bone are also partially movable joints.

Immovable Joints:
            In an immovable joint, the bones are held tightly together. There is no cartilage between the joint. The joints between the bones of the skull are immovable joints. The plates of the bones fit together something like the pieces of a jigsaw puzzle. The joints where the teeth fit in the jaw bones are also immovable joints. The lower jaw is the only part of the skull that moves. These joints are also known as fibrous joints. 

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