Skeleton forms the main supporting framework of the body formed by joining of individual bones, and is primarily designed for a more effective production of movements by the attached muscles.
Bone is a connective tissue , impregnated with calcium salts. Connective tissue forms one third of the bone and calcium salt about two thirds.
The inorganic calcium salts are mainly calcium phosphate, partly calcium carbonate, and traces of other salts. These make it hard and rigid, which can afford resistance to compressive forces of weight-bearing and impact forces of jumping.
The organic connective tissue makes it tough and resilient , which can afford resistance to tensile forces.
Despite its hardness and high calcium content the bone is very much living tissue. It is highly vascular, with a constant turn-over of its calcium content.
It can mould itself according to changes in stress and strain it bears, it shows disuse atrophy and overuse hypertrophy.
Functions of bones
1 Bones give shape and support to the body, and resist all forms of stress.
2 They provide surface for the attachment of muscles, tendons, ligaments, etc.
3 They serve as levers for muscular actions.
4 The skull, vertebral column and thoracic cage protect brain, spinal cord and thoracic viscera, respectively.
5. Bone marrow manufactures blood cells.
6 Bones store 97% of the body calcium and phosphorus.
7 Bone marrow contains reticulo-endothelial cells which are phagocytic in nature and take part in immune response of the body.
Our body contains 206 bones. If number of accessory bones are also counted, the count becomes variable and can go up to 350 bones depending on age.
It is important to understand normal structures and functions in order to locate abnormality.. Only then we can recognize abnormal functions. Our skeleton is our basic structure on which everything else is laid.
Let us familiarize ourselves with bones in our body. We start from top and move down. The number after the name of bone would correspond to number in the adjoining diagram.
Skull is formed by cranium and mandible. Cranium is further composed of multiple bones that are united to each other. The lines of the union are called sutures. these sutures are lax in children to allow brain growth. Mandible constitutes our lower jaw that we used whole day for speaking, eating or gesturing
- Cranium (1-9)
- Mandible (7)
There are six bones in middle ears, three in either side. These bones are not shown in diagram. these bones are called Malleus, Incus and Stapes.
Hyoid bone (Not shown in diagram) is present in throat and serves as support to cartilages of trachea or wind pipe. It also serves as attachments to various muscles that help in movement of trachea.
Shoulder Girdle is an area of shoulder that is formed by the following bones
- Clavicle (25) : It is a bone that connects thoracic cage to upper limbs and also functions for transmittal of forces.
- Scapula(29): It is a complexely structured bone that articulates with clavicle, thorax and takes part in formation of shoulder joint.
Thorax is a cage like structures that functions to protect vital structures that it contains like lungs, heart etc. it is formed by ribs on either side which are connected to sternum in front and to vertebrae on back.
- Sternum (10)
- Ribs (28)
Spine or Vertebral column
This is formed by multiple vertebra which are named according to area
- Cervical vertebrae (8)
- Thoracic vertebrae ( Not shown but are present between cervical and lumbar vertebrae
- Lumbar vertebrae (14)
- Sacrum (16)
- Coccyx- Not shown but follows Sacrum
- Humerus (11) – The bone that connects shoulder to elbow. This bone is normally cylllindrical but flares when it comes near elbow and becomes flat. Its flares on either sides form ridges called condyles (26)
- Ulna (12): The bone that forms elbow joint by artculating with humerus. This is the bone that protrudes on back of elbow on flexion. It can be felt on aspect of forearm on side of little finger.
- Radius (13): This is the bone on other side of forearm i.e. on side of thumb. It forms a joint with ulna on upper side. The part that takes part in this joint formation is called head of radius(27). This joint allows twisting movements of elbow called pronation and supination.
Hand & Wrist
Hand is quite a complex structure and requires a separate discussion. Its constiuent bones are not marked in diagrams. For purpose of completion I list here names of bones. We would discuss them in detail in later posts.
- Carpals or Wrist Bones- These bones connect forearm to hand
- Phalanges: These include proximal phalanges, intermediate phalanges and distal phalanges
Pelvis or pelvic girdle is formed by many bones on either side which on one hand are connected to spine and on other side to lower limbs. Pelvis functions to transmit the weight to lower limbs and also protect the vital structures like rectum and bladder. Ilium (15), pubis and ischium ( both visible but not marked) are bones that unite to form pelvis.
Structure of lower limb is quite similar to upper limbs with modifications done for weight bearing purpose.
Femur(18), tibia (20) and fibula (21) are long bones that form lower limb. Femur is bone of thigh whereas other two bones are present in leg. Another important bone called patella (19) is present on anterior side of knee joint and is commonly known as knee cap.
Foot is as complex as hand, so I am just going to list the names. The bones are not marked in diagram
- phalanges: proximal phalanges, intermediate phalanges and distal phalanges
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