Skeletal system , Axial skeleton ( vertebral column , Skull & thoracic cage )
The skeletal system in man works on supporting the body , protecting some of its organs and participating in the movement in addition to providing the man with his special shape , Skeletal system in man consists of skeleton , cartilages , joints , ligaments and tendons .
The skeleton in man consists of 206 bones , where each bone has a shape and size that are suitable for its function .
Structure of skeleton :
- Axial skeleton consists of vertebral column , skull , thoracic cage .
- Appendicular skeleton consists of ( pectoral girdle and upper limbs ) , ( pelvic girdle and lower limbs )
The axial skeleton
The vertebral column is considered as the axis of the skeleton , where its upper part is attached with the skull , At the thoracic region , it is attached with the thoracic cage and upper limbs by the pectoral girdle , Its lower part is attached with the lower limbs by pelvic girdle .
It consists of 33 vertebrae that are divided into 5 groups and differ in the shape according to the site of their presence as follows :
- 7 cervical vertebrae : articulating and has moderate size .
- 12 thoracic vertebrae : articulating and larger than the cervical vertebrae in size .
- 5 lumbar vertebrae : articulating and the largest of all vertebrae in size ( found in abdominal region ) .
- 5 sacral vertebrae : broad , flat and fused .
- 4 coccigeal vertebrae : small and fused .
The number of bones of vertebrae column in human is about 26 bones , The structure of bony vertebra consists of several parts which are :
- The centrum is the anterior thick part .
- The two transverse processes are two bony processes that attached laterally with the centrum and each one of them carries an articulating anterior bony process .
- The neutral ring is a bony ring that attached posteriorly with the centrum and surrounds the neutral canal inside which the spinal cord extends to protect it .
- The neutral spine is a posterior bony process that is directed downwards , carried by the neutral ring and carries two posterior articulating processes .
The function of vertebral column : it acts as the main support of the body , It protects the spinal cord , It helps in the movement of the head and upper body parts .
It is a bony case that consists of two parts which are :
- Posterior part ( Cerebral part ) : It consists of 8 serrated bones that are attached firmly to each other to form a cavity that encloses the brain to protect it , At the base , there is a foramen magnum through which the spinal cord is attached to the brain .
- Anterior part ( Facial part ) : It includes the face bones , two jaws and the positions of sense organs ( eyes , ears and nose ) .
A case which is slightly conical in shape , attacked posteriorly to the thoracic vertebrae ( 12 vertebra ) and anteriorly to the sternum bone .
The thoracic cage consists of twelve pair of ribs which are as follows :
First ten pairs : attached between the thoracic vertebrae and sternum bone .
The two lower pairs of ribs ( pairs no. ( 11 ) and ( 12 ) : are short and do not reach the sternum , So , they are called the floating ribs and they are attached to the vertebrae no. ( 18 ) and ( 19 ) of the vertebral column .
The rib is a curved bone that bends downwards and attached posteriorly to the centrum of the thoracic vertebra and its transverse process , The sternum is a flat bone that is pointed at its lower part which is cartilaginous and to which the first ten pairs of ribs are attached .
The function of thoracic cage : It protects the heart and two lungs , It helps the ribs movement during respiration process , where : during inspiration process , the ribs move anteriorly and laterally to increase the volume of thoracic cavity , during expiration process , the ribs move opposite to what was done in the inspiration process .