The Skeletal System

What is your skeletal system? All of the bones in your body make up the skeletal system There are 206 bones in an adult’s human body (at birth, you had more than 300 bones!) A skeleton is a framework of living bones that supports your body

Functions of Your Skeletal System 1. The skeleton gives shape and support to your body 2. Bones protect your internal organs. For example, your rib cage protects your heart and lungs and your skull protects your brain. 3. Major muscles are attached to bone and help them move. 4. Blood cells are formed in the center of many bones in soft tissue called red marrow. 5. Major quantities of calcium and phosphorous compounds are stored in the skeleton for later use. Calcium and phosphorus makes bones hard.

Bone Structure Bones have bumps, edges, round ends, rough spots and many pits and holes. Muscles and ligaments attach to some of the bumps and pits. Blood vessels and nerves enter and leave through the holes. Periosteum is the tight-fitting, tough covering of a living bone. Small blood vessels in the periosteum carry nutrients into the bone.

Two Different Types of Bone Tissue Compact Bone This is directly under the periosteum and it is a hard, strong layer. It gives bones strength. It’s framework contains deposits of calcium and phosphate, which makes the bones hard. Bone cells and blood vessels are in this layer.

Two Different Types of Bone Tissue Continued… Spongy Bone Located toward the ends of long bones, such as your femur and Humerus bones. Has many small, open spaces that make bones lightweight. The centers of long bones have large openings called cavities. These cavities and the spaces in spongy bone are filled with marrow. Marrow can be yellow and red. Red marrow produces red blood cells at a rate of 2 million to 3 million per second!

Two Different Types of Bone Tissue Continued… Cartilage It’s a smooth, slippery, thick layer of tissue covering the ends of bones. Does not contain blood vessels or minerals. It is flexible and important in joints because it acts as a shock absorber. Makes movement easier by reducing friction Months before you were born, your skeleton was made of cartilage!

Bone Formation The cartilage eventually breaks down and is replaced by bone. Osteoblasts are bone-forming cells and they deposit the minerals calcium and phosphorus in bones, making the bone tissue hard. Osteoclast is another type of bone cell that breaks down bone tissue in other areas of the bone. This is normal. When they break a bone down, they release calcium and phosphorus into the bloodstream. This process maintains calcium and phosphorus in your blood at the levels they need to be. These elements are necessary for the working of your body.

Joints Joint is anyplace where two or more bones come together. Bones making up healthy joints are kept apart by a thin layer of cartilage (to avoid rubbing against each other as they move. Ligaments are a tough band of tissue holding the bones in place at the joints Many joints are held together by more than one ligament. (i.e. Knee) Muscles move bones by moving joints. What types of actions can you do because you have joints? Sitting, standing, picking an item up, biting off a piece of carrot, chewing, walking to class, opening a book, etc.

Types of Joints: Moveable and Immoveable Moveable Joints Pivot: One bone rotates in a ring of another bone that does not move. Example: Turning your head Ball and Socket: bone with a rounded end that fits into a cuplike cavity on another bone. It provides wider range of motion than a pivot joint. Example: Legs and arms Hinge: Has back-and-forth movement like hinges on a door. They have a smaller range of motion than a ball and socket. They are not dislocated as easily, or pulled apart, as a ball and socket joint can be. Example: Elbows, knees and fingers Gliding: One part of a bone slides over another bone. They also move in a back and forth motion. These joints are the most used in your body. You cannot write a word, use a joystick or take a step without these joints. Examples: wrists, ankles and between vertebrae.

Immoveable Joints Immovable Joints: Allows little or no movement Examples include skull and pelvis

Joints: Moving Smoothly Cartilage helps make joint movement easier. It reduces friction and allows bones to slide more easily over each other.

Common Joint Problems Arthritis is the most common joint problem. Two different types of arthritis: Osteoarthritis: cartilage breaks down because of years of use. Rheumatoid Arthritis: an ongoing condition in which the body’s immune system tries to destroy its own tissues. “Arthritis” describes more than 100 different diseases that can damage the joints. 1 out of 7 people in the U.S. suffers from arthritis. Symptoms include: pain, stiffness, and swelling of the joints.