6.1 2.2.2 human skeleton  (Page 3/4)

Unlike the pelvic girdle the pectoral girdle is not fused to the spine but is connected by muscles to the back of the thorax so its role as a supportingstructure is much less than the pelvic girdle.. Instead it gives the shoulders greater freedom of movement which in turn allows greater mobility of the arms.. Any limit to movement is provided by the clavicle.-

Functions of pectoral girdle

• Forms a strong support for the attachments of the arms.
• Provides large area of bone for the attachment of muscles.
• Forms ball and socket joints with the arms which allows freedom of movement

Pelvic girdle and the legs

The pelvic girdle consists of hip bones joined in the front by the pubic symphesis and attached to the sacrum at the back.

Each hip bone consists of three fused bones namely the:

1. ilium, which forms the upper flared portion
2. ischium, which is the lowest and strongest part and
3. pubis, which forms the anterior part.

Portions of all three bones contribute to the formation of the acetabulum, the deep socket that holds the head of the femur (thigh bone) to form the hip joint.

The female pelvic girdle is wider and lighter than the male as an adaptation to pregnancy and childbirth.

The femur is the largest and strongest bone in the body. The upper end forms a ball and socket joint with the hip bone while the lower end articulates with the tibia to form the hinge joint of the knee.

The patella or kneecap is a flat triangular bone which is embedded in the tendon of the thigh muscle and attached by ligament to the tibia.

There are two bones in the lower leg: the tibia or shin bone which is the larger of the two and supports most of the mass. The upper end articulates with the femur while the lower end articulates with one of thetarsal bones to form the ankle joint. The fibula (calf bone) is smaller than than the tibia and serves mainly for the attachment of muscles

The structure of the foot is similar to that of the hand. However the foot supports the weight of the body, so it is stronger and less mobile than thehand.. There are seven tarsals or ankle bones only one of which articulates with the tibia. The largest of these is the heel bone(calcaneum) to which the calf muscle is attached and which presses firmly on the ground when one stands, walks or runs.

There are 5 metatarsal bones the which form the ball and arch of the foot.

The 14 phalanges of the toes are the counterparts of those in the fingers, with the big toe having two phalanges and the other 4 having 3 phalanges each. .

Functions of skeleton:

1. Movement – allows body to move because muscles attach to the bones to give them leverage
2. Protection – protects vital organs ( skull=brain, ribcage=heart and lungs and pelvic bones=digestive tract and reproductive organs)
3. Support – provides shape and support to body
4. Storage of minerals - bones store minerals such as calcium and phosphate ions
5. Hearing - bones in the middle ear, called the hammer, anvil and stirrup, amplify sound waves and assist in the hearing process
6. Red blood cells production - long bones and flat bones contain red bone marrow to produce red blood cells