Bones | axial and appendicular skeleton of human skeletal system





What is bones ? 

Bone is one-third connective tissue. it is impregnated with calcium salts which constitute the remaining two-third part.
The inorganic calcium salts makeit rigid and hard ,which can efford resistance to compressive force of weight- bearing  and impact forces of jumping. The organic connective tissue is tough and flexible,which can afford resistance to tensile force. In strength, bone is comparable to iron and steel.
The inorganic calcium salt is hydroxy apatite [Ca10(PO4)6(OH)2] .

Division of the Skeletal system- bones are 206 in human there are divided into following- 

Axial Skeleton

Skull

Cranium .                                8 
Face.                                        14
Hyoid .                                     1
Auditory ossicles                   6
(Mellus,incus,stapes)

Thorax

Sternum.                                     1
Ribs .                                            24

Appendicular Skeleton
Pectoral(shoulder) girdles

Clavicle.                                          2
Scapula .                                          2

Upper extermities

Humerus.                                       2
Ulna.                                                2
Radius.                                             2
Carpals .                                           16
Metacarpals .                                   10
Phalanges .                                       28

Pelvic(hip) girdle

Pelvic or hip bone .                       2


Lower extermities

Femur .                                             2
Fibula .                                              2
Tibia .                                                 2
Patella.                                                2
Tarsals.                                               14
Metatarsals.                                       10
Phalanges.                                          28
.                                                             206



Classification of bones 

According to shape
1. Long bones : they have three processes of long bones.

a) Typical long bones : these are Humerus, radius, ulna,femur, tibia and fibula.

b) short long bone : metatarsals ,Metacarpals and phalangas. 

c) flat bone : sternum, scapula and ribs .
d) irregular bones: hip bone 

e) pneumatic bones:  Mexilla and sphenoid.

2) Developmental classification

a) Membrane bones : skull- frontal, occipital, temporal and parietal 

b) Cartilaginous bones:  Humerus ,femur ,vertebral column and thoracic cage.

c) Membrano-cartilaginous bones : Mendible ,occipital ,temporal and sphenoid .

3) Regional classification

a) Axial skeleton : skull ,vertebral column and thoracic cage.

b) Appendicular skeleton : Pectoral region ,Upper limb,lower limb,pelvic girdle ...


4) Structural classification

a) Microscopically : they have include two bones - 
Compact bones
Cancellous bones 

Compact bone : it located at the shaft of long bone ,arrange to form haversian system ,include yellow bone marrow and it is hard .


Cancellous bones:  it is located at the epiphysis of long bones, arrange in meshwork ,produce red bone marrow and it is spongy.


b) Microscopically

Lamellar bone : it is found in the mature human bones, compact or cancellous are composed of thin plates of bone tissue  is 
called to Lamellae.

Woven bones : seen in fetal bone .

Fibrous bones:  It is found in young foetal bones .


Dentine 

Cement : occur in teeth .