Human Skeleton | Bone and Cartilage | Types of Joints

 Human Skeleton

Human Skeleton

Skeletal system or skeleton is defined as the framework of hard articulated structures that provide physical support attachment for skeletal muscle and protection for the bodies of animal. Like other vertebrates the human skeleton is on the in side of the body and is called endoskeleton. In the living body the skeleton is very much alive. Bones and cartilages are made of living cells and also have nerves and blood vessels in them. They grow and have the ability to repair themselves.

Role of Skeletal System

The big function of skeletal system are protection supported and movement. In our body skeleton works very closely with the muscular system to help us move. similarly skeleton provides protection to many internal organs skull protect brain vertebral column protect spinal cord and ribs protect most of our other internal organs. Vertebral column also provides the main support to our body mass.

Bone and Cartilage 

Overall the human skeleton is made of bony framework but certain parts this framework is supplemented by cartilage.

Bone

Bone is the hardest connective tissue in body. Bones not only move support and protect the various parts of body but also produce red and white blood cells and store minerals.

The hard outer layer of a bone is called compact bone while the interior of bone is soft and porous. It is called spongy bone. Spongy bone contain blood vessels and bone marrow.

like cartilage the matrix of bone also contains collagen. But it is also contains minerals calcium and phosphate. We know that cartilage contains a single type of cell. On the other hand bones contains different types of cell. The mature bone cells are called osteocytes.

Cartilage 

Cartilage is a dense clear blue white firm connective tissue. The cell of cartilage are called chondrocytes. Each chondrocyte lies in a fluid space called lacuna present in the matrix of cartilage. The matrix of cartilage also contain collagen fibres. Blood vessels do not enter cartilage. there are three types of cartilage.

* Hyaline Cartilage is strong yetflexible. It is found covering the ends of the long bones in the nose larynx trachea and bronchial tubes.

* Elastic cartilage is similar in structure to hyaline cartilage . It is also quite strong but has elasticity due to a network of elastic fibres in addition to collagen fibres. It is found in epiglottis pinna etc.

* Fibrous cartilage is very tough and less flexible due to large number of thick collagen fibres present in knitted form. It is found in intervertebral discs.

Components of Human Skeleton

The 206 bones in the adult human skeleton are organized into a longitudinalaxis axial skeleton to which appendicular skeleton is attached.

* Axial skeleton

Axial skeleton consists of the 80 bones in the head and trunk of body. It is composed of five part. Skull contains 22 bones out of which  8 are cranial bones and 14 are facial bones. These are 6 middle ear ossicles ( three in each ear ). There is also a hyoid bone in neck. Vertebral column contains 26 bones. The chest is made of a chest bone called sternum and 24 ribs.

* Appendicular Skeleton

Appendicular skeleton is composed of 126 bones. Pectoral girdle is made of 4 bones. Arms have 6 bones. Both hands have 54 bones. Pelvic girdle has 2 bones. Legs have 6 bones. Both feet have 54 bones.

Types of Joints

Moveable joints

Immoveable joints

A joint the location at wich two or more bones make contact. They allow movement and provide mechanical support. Joints can be classified on the
basis of the degree of movement they allow.

Immoveable joints : Such joints allow no movement the joint between the skull bones.

Slightly moveable joints : Such joints allow slight movements joints between the vertebrae.

Moveable joints : They allow a variety of movements shoulder joint, elbow joint, knee joint etc. there are many types of moveable joints in body. The main types are hinge joints and ball - and - socket joints. Hinge joints move back and forth like the hinge on a door and allow movements in one place only. The knee and albow are hing joints.

Ball-and-socket joints allow movement in all directions. The hip and shoulder joints are ball-and-socket joints.