Chapter 6 Summary

The Skeletal System

The skeletal system performs many important functions for the body. It provides the shape and form for our bodies. It also protects, allows free bodily movement, produces blood for the body, and helps stores minerals that the body can use.

Functions

The bodies 206 bones form a fragile framework which the softer tissues and organs of the body are attached to.

Vital organs are protected by this system. The heart protects the brain, and lungs are encased by the sternum and rib cage.

Body movement is carried out by the teamwork of the muscular and skeletal systems. They are often grouped together as the muscular-skeletal system. Muscles are connected to bones by tendons. Ligaments connect the bones to each other. Where bones meet, is called a joint. Muscles, which cause movement of a joint, are connected to two different bones and contract to pull them together.

The marrow located in some bones can produce blood cells. On average of 2.6 million red blood cells are produced every second by the bone marrow to replace those blood cells worn out and destroyed by the liver.

Bones can also serve as a storage area for minerals such as calcium and phosphorus. When there is excess in the blood, buildup will occur within the bones. When the supply of these minerals within the blood is low, it will be taken from the bones to replenish the supply.

Divisions of the Skeleton

The human skeleton is divided into two distinct parts:

The axial skeleton consists of bones that form the axis of the body and support and protect the organs of the head, neck, and trunk.

The appendicle skeleton is composed of bones that anchor the appendages to the axial skeleton.

Types of Bone

The bones of the body fall into four general categories: long bones, short bones, flat bones, and irregular bones. Long bones are longer than wide and can work as levers. The bones of the upper and lower extremities are this type. Short bones are short, cube-shaped, and found in wrists and ankles. Flat bones will have broad surfaces to protect organs and attach muscles. Irregular bones are all the other bones that do not fall into any of these categories. They have varied shapes, sizes, and surfaces features and include bones in the vertebrae and a few in the skull.

Bone Composition

Bones are composed of tissues that may take one or another form. Compact, or dense bone, and spongy, or cancellous, bone are all in the skeletal system, most bones contain both types of these. Compact bone is dense, hard, and forms the protective exterior portion of all bones. Spongy bone is inside the compact bone. The bone tissue is composed of several types of bone cells encased in a web of salts.