the skeletal system

Introduction

Despite what seems to be a solid, dry, inert material, bone is in fact a complex living organism
that is being recreated constantly; bone is metabolically active. As old bone dies new bone is
being rebuilt. There are a number of complex activities occurring as bone is destroyed and
reformed. Bones are therefore living organs that are made up of a number of different tissues,
and this includes bone tissue.
The human skeleton, in contrast to other skeletons, is built to move erect as opposed to
walking
on all fours. The skeleton provides us with shape and the power to move, but it cannot
do this in isolation. It needs many other systems of the body for it to function properly – for
example, the nervous system and the muscles and for the body to move in its various and
complex
ways (the spine, for example, allows us to twist and bend); this is attributed to the joints
and their ability to articulate.
Like a house, the human body needs a framework, but the framework for the body is not
made of wood and steel as is the case with the house. The skeletal system is made up of bones,
ligaments and tendons. The human skeleton is built to take the hard knocks of life. It is an
engineering
wonder; for its weight, bone is nearly as strong as steel.
The skeleton produces blood cells. The bones also act as storage areas for minerals, vital for
blood clotting, nerve function and contraction of muscles. The bones begin to form in utero and
continue to grow into adulthood. Bones develop from cartilage, so infants are born with large
amounts of cartilage as well as having more bones than adults. As the child ages, the bones usually
fuse together and the child ends up with the normal adult number of bones. The bones of babies
are soft, but as more minerals are deposited they become harder – this is known as ossification.

The axial and appendicular skeleton

There are 206 named bones in the adult human skeleton. For classification purposes the skeleton
is divided into two parts: the axial skeleton and the appendicular skeleton. Both have their own
purposes

BOON of the axila 

Skull

Cranium
Face
Total
8
14
22
Hyoid 1
Auditory ossicles (bones) 6
Vertebral column 26
Thorax
Sternum
Ribs
Total
1
24
25
Total number of bones in the axial skeleton 80

The axial skeleton

The axial skeleton forms the central axis of the body and consists of 80 bones. This part of the
skeleton supports the head (including the bones in the ear), neck and the torso (this is also
referred to as the trunk). It consists of the skull, the vertebral column, the ribs and the sternum.
The 80 bones in the axial skeleton are noted in Table 5.1.

The appendicular skeleton

The bones of the appendicular skeleton are those bones of the upper and lower extremities –
the arms and the legs as well as the bones that attach them to the axial skeleton. There are
126 bones in the appendicular skeleton, and these bones are shown in Table 5.2.
See Figure 5.1 depicting the human skeleton.

Bone and its functions

The skeletal system – and this includes the bones of the skeleton, the ligaments, cartilage and
connective tissues that provide stability or attach the bones – has a number of key functions:
1. provides support
2. enables movement
3. stores minerals and lipids
4. protects the body
5. produces blood cells.

Support

Apart from bone and cartilage, all body tissue is soft, and without the skeleton the body would
be jelly‐like and would not be able to stand up. The way the bones are arranged provides the
body with its shape/form. The skeletal system provides structural support for the body, providing
a bony framework for the attachment of soft tissues and organ

THE BOON OF THE APPENDICULAR

Pectoral girdle

Clavicle

Scapula

Total

2

2

4

Upper limbs

Humerus

Ulna

Radius

Carpals

Metacarpals

Phalanges

Total

2

3

4

16

10

28

60

Pelvic girdle

Pelvic bone

2

Lower limbs

Femur

Patella

Fibula

Tibia

Tarsals

Metatarsals

Phalanges

Total

2

2

3

3

14

10

28

60

Total number of bones in the appendicular skeleton 126

Total number of bones in the adult human skeleton 206

Movement

The skeleton allows and enables movement. The bones act as levers, providing the transmission

of muscular forces. A number of bones can (through leverage, contracting and pulling) change

the extent and direction of the forces generated by skeletal muscles, through the work of the

tendons and the ligaments. These movements can be very intricate, such as the ability to write,

the ability to thread a needle (the coordination of fine movement), to gross movement, such

as the ability to change body posture. The skeleton with the interaction of muscles permits

breathing

to occur. Movement becomes possible through articulation