Skeletal System

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Ligaments and Tendons

10.9   Ligaments, as strong as ropes, are the tough bands of tissue, which hold a joint together. They connect one bone to another. They hold the bones in place but still allow some movement. They are grouped together in cords, bands or sheets. A sprain occurs when ligaments covering a joint are torn or twisted. Sprains of the ankles and wrists are more common. A tendon (also called a sinew) is a strong white cord that connects a muscle to a bone. A tendon is a bundle of many tough fibres. Some tendons are round, others long or flat. One end of a tendon arises from the end of a muscle. The other end is woven into the substance of a bone. When the muscle contracts, the strong cable-like tendon is pulled. In turn, the tendon pulls the bone to which it is attached. The tendon may slide up and down inside a sheath of fibrous tissue just as an arm moves in a coat sleeve. The tendon and sheath are held in place by ligaments. A cut tendon may be sewed together.

 The Pelvis

10.10  Although the bones of males and females are essentially alike except for size, the pelvis is an exception. To accommodate pregnancy and childbirth, the female’s pelvis has a slightly different shape than that of the male. It is usually wider so there is enough room for a developing foetus. The opening at the bottom of the pelvis is larger so that a baby’s head can pass through during childbirth. The female pelvic bones are usually lighter and have less muscle attachment. This lighter structure causes females to be more susceptible to pelvic fractures than males.

 Joints

10.11 Joints are the locations where bones come together. There are three basic types of joints. Immovable joints provide little or no movement. For example, the bones that make up the skull’s cranium are joined by immovable joints called sutures. Slightly movable joints allow limited movement. This type of joint is found between the vertebrae of the spine. The names of the freely movable joints suggest the kind of motion each allows – hinge, pivot, ball-and-socket, and gliding. Hinge joints, found in the knees and elbows, allow back-and-forth movement – like a hinge in a door. Pivot joints, such as those in the neck, allow either back-and-forth movement or up-and-down movement. The shoulder and hip joints are ball-and-socket joints, which allow the greatest range of movement. Gliding joints, found in the wrist and ankles, allow for flexibility.

  The Spine

10.12 The spine supports the other parts of the body. The spine runs down the back of the body from the base of the skull till the hip bone at the lower back. It consists of separate bones called vertebrae. All these bones of the spine are held together by discs of cartilage. There are 26 cotton-reel like bones in the vertebral column. Of these 7 bones are in the neck and 12 bones at the back of the chest to which the chest ribs are attached. The lower part of the back has 5 bones. The last 2 are the fused bones of the hip and the tailbone region.