SKELETAL SYSTEM

The skeletal system contains bones as well as other structures that connect and protect the bones and that support other functions in the body.

Skeletal System

• Bones support your body. • They help you sit up and stand.• They make it possible for you to

lift your legs to walk up stairs.

Support

Functions

• Different parts of your body can move in different ways because of your skeletal system.

• Your knee bends when you kick a soccer ball.

• Bones can move because they are attached to muscles.

• Your skeletal system and your muscular system work together and move your body.

Movement

Functions

• The skull protects the soft tissue of your brain from damage.

• Other bones help protect your spinal cord, heart, lungs, and other organs in your body.

Protection

Functions

•Make and store materials needed by your body.

•Red blood cells are produced inside some of your bones.

•Bones also store fat and calcium. Calcium is a mineral needed for strong bones. It is also used in many other cellular processes. When the body needs calcium, it is released from the bones into the blood.

Production and Storage

Functions

A bone is an organ made of living tissue.

Structure of Bone

Structure of BoneThere are two main types of bone tissue:

compact bone & spongy bone.

Compact BoneThe hard, outer area of long bones is

made up mostly of compact bone tissue. This tissue is a thick, dense web of fibers.

Spongy BoneSpongy bone tissue is located near the

ends of long bones.

The small holes in spongy bone tissue make it look like a sponge.

Spongy Bone

Because of these holes, spongy bone tissue is not as dense as

compact bone tissue.

Spongy Bone

Spongy Bone

A short bone, such as the one in your wrist, is

mostly spongy bone tissue.

The inside of most bones is made up of a soft tissue called bone marrow.

Marrow

• There are two types of bone marrow.• Red bone marrow is the tissue where red blood

cells are made. • It is found in the spongy ends of long bones

and in some flat bones, such as the ribs.

Marrow

How long does it take to produce 2-3 million red blood cells?

Marrow

1 Second!

• Yellow bone marrow stores fat. • Yellow bone marrow is found in the longest

part of long bones.

Marrow

The strong, flexible tissue that covers the ends of bones is called cartilage.

Cartilage

•Cartilage keeps the surfaces of bones from rubbing against each other.

•It protects bones and reduces friction in joints.

Cartilage

Cartilage

•The parts of a bone that are not covered by cartilage are covered by periosteum.

•The periosteum is a membrane that surrounds bone.

Periosteum

•This thin tissue has blood vessels, nerves, and cells that make new bone tissue.

•It helps bones function and grow properly. •It also helps a bone heal after an injury.

Periosteum

Periosteum

Before you were born, your skeleton was made mostly of cartilage.

Periosteum

During infancy and childhood, the cartilage was slowly replaced by bone.

Formation of Bones

The long bones in your body, such as the bones in your legs and arms, have areas of growth that produce new bone cells.

Formation of Bones

These areas are called growth plates.

Formation of Bones

Growth plates produce cartilage that is then replaced by bone tissue.

Formation of Bones

A growth plate is the weakest part of an adolescent bone.

Formation of Bones

Growth continues until adulthood, when most cartilage has turned to bone.

Formation of Bones

Joints

•Your bones work together to move your body.

•They work together at places called joints.

•A joint is where two or more bones meet.

•Joints provide flexibility and enable the skeleton to move.

Joints

•Ligaments are tissues that connect bones to other bones.

•When the bones in joints move, ligaments stretch and keep the bones in place.

Joints

•Ligaments connect bones at joints, but they do not protect bones.

•Cartilage protects the ends of bones.

Joints

Your skeletal system has two types of joints —

Immovable Joints

&

Movable Joints

Joints

• Immovable joints are parts of your skeleton are made of bones that are connected but do not move.

• Examples: skull

Immovable Joints

Joints

• You can move in many ways because of your body’s movable joints.

• The three main types of movable joints and the ligaments that hold them together.

Movable Joints

Joints

Ball and Socket• Bones can move and rotate

in nearly all directions.• Examples: hip and

shoulder

Joints

Hinge• Bones can move back and

forth in a single direction.• Examples: fingers,

elbows, knees

Joints

Pivot• Bones can rotate.• Examples: neck, lower

arm below the elbow

Bone Injury and Diseases• Because bones are made of living tissue,

they can be injured. • Bones can break. • They can also develop disease.

Bone Injury and Diseases

• A broken bone is called a fracture. • Broken bones can repair themselves, but it

takes a long time. A broken bone must be held together while it heals.

• Sometimes a person wears a cast to hold a bone in place while it heals.

• Sometimes metal plates and screws hold a bone together while it heals.

Broken Bones

Bone Injury and Diseases

• Arthritis is a disease in which joints become irritated or inflamed, such as when cartilage in joints is damaged or wears away.

• When the joints become irritated, it can be painful to move.

• Arthritis is most common in adults. It can also affect children.

Arthritis

Bone Injury and Diseases

• Osteoporosis is a disease that causes bones to weaken and become brittle, or easily broken.

• Osteoporosis can change a person’s skeleton and cause fractures.

• Osteoporosis is most common in women over the age of 50.

Osteoporosis

Bone Injury and Diseases

Osteoporosis

Healthy Bones • One of the best ways to keep bones healthy

is to exercise.• Certain types of exercise, such as running,

walking, and lifting weights, place weight on your bones.

• These types of exercises help make bones strong and build new bone tissue.

Healthy Bones • A balanced diet also helps keep bones

healthy. • Bones need calcium and vitamin D most of all.

Healthy Bones • Calcium makes bones strong. • It is also important for cell processes. • If you do not have enough calcium in your

diet, your body will use the calcium stored in your bones. This can make your bones weak.

Healthy Bones • Vitamin D helps the body use calcium.

Homeostasis• Homeostasis is an organism’s ability to keep

its internal conditions stable. • Homeostasis requires that all body systems

work together properly.

Homeostasis• Your skeletal system helps your body maintain

homeostasis by supplying calcium to your nerves, heart, and muscles so they can function properly.

• Bones also help you respond to unpleasant stimuli, such as a buzzing mosquito. Working together with muscles, bones enable you to move away from or even swat a mosquito.