THE SKELETAL AND MUSCULAR SYSTEM

Chapter 15.1

Bones and Joints

OBJECTIVES

Describe the structure and function of bones Explain the roles of joints and muscles in

movement Contrast skeletal, cardiac and smooth

muscles Describe some disorders of bones, joints, and

muscles

KEY TERMS

Joint Ligament Tendon Flexor Extensor Osteoporosis Arthritis

THE SKELETON IS MADE OF BONES

There are 206 bones in the adult body Calcium Phosphate is the mineral that makes bones hard The toughness of bone gives the body

strength Bones are not rigidly connected to each other

Exception: the bones of your skull

BONES ARE MADE OF LIVING CELLS

Bones contain blood vessels and nerves The blood carries nutrients to and wastes away

from the bone cells Many bones have a spongy interior called marrow

which produces blood cells The main function of bones are to:

Allow movement, support the body, and protect internal organs

The picture shows an osteocyte

JOINTS CONNECT DIFFERENT BONES

• A place where two or more bones are connected is a joint

• There are several types of joint:– Fixed joints connecting the skull plates– Pivot joints like your elbow– Hinge joints like your knee– Ball and socket joints like you shoulder– Gliding joints like your fingers or toes– Saddle joint like your thumb

LIGAMENTS

Moveable joints do not hold bones tightly together

Flexible but strong straps of tissue hold the bones tightly togetherLigaments

connect bone to bone

MUSCLES

• There are three types of muscle:– Cardiac

• Found only in the heart

– Skeletal, (move in pairs)• Attach to two or more

bones– Flexor– Extensor

– Smooth• Found in the bladder

and digestive system

MUSCLES AND FORCE

Bones need muscles to allow them to move

Tendons are the attachment point for muscles to bones

Muscles must be anchored to more than one bone to allow for movement

Muscles work in pairs to flex and extend the bone through the range of motion of the joint

MUSCLES AND NERVE SIGNALS

Muscles contract due to nerve signals

Muscles relax after the signal has passed

Sometimes muscles contract without YOU having to think about it Breathing Blinking

DISORDERS OF THE BONES, JOINTS, AND MUSCLES

Osteoporosis is a bone disorder

Bones can “break” when under stress Osteocytes or “bone

cells” can heal a broken bone given time

A fracture or break causes bone cells to fill in the gap

JOINT DISEASE

Arthritis causes pain by the ends of bone rubbing together at the joint

The smooth covering is worn away and the bones begin to show signs of damage

SPRAINS AND STRAINS OF LIGAMENTS

The picture is of a sprained elbow, notice the joint is displaced

Ligaments, tendons, and muscles may all become damaged by the displacement

Muscles repair first, then tendons, then ligaments, (if at all)

SUMMARY

Bones are living tissue. They produce blood cells, allow movement,

support the body, and protect internal organs Bones move when skeletal muscles contract

in response to chemical signals from the brain and spinal cord

Dietary calcium and certain types of exercise can strengthen bones

DEFINITIONS

A joint is a place where two or more bones meet

A ligament is a strong strap of body tissue that holds the bones of a joint in place

A tendon is a strong cord of body tissue that connects skeletal muscle to bone

DEFINITIONS

A flexor muscle is a muscle that decreases the angle between two bones

An extensor is a muscle that increases the angle between two bones

Osteoporosis is a bone disorder in which the bone becomes less dense and more fragile

Arthritis is a condition in which the joints become swollen and painful