T HE S KELETAL AND M USCULAR S YSTEM Chapter 15.1 Bones and Joints

O BJECTIVES 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

K EY T ERMS Joint Ligament Tendon Flexor Extensor Osteoporosis Arthritis

T HE S KELETON IS MADE OF B ONES 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

B ONES ARE MADE OF L IVING C ELLS 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

J OINTS C ONNECT D IFFERENT B ONES 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

L IGAMENTS Moveable joints do not hold bones tightly together Flexible but strong straps of tissue hold the bones tightly together Ligaments connect bone to bone

M USCLES 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

M USCLES AND F ORCE 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

M USCLES AND N ERVE S IGNALS 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

D ISORDERS OF THE B ONES, J OINTS, AND M USCLES 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

J OINT D ISEASE 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

S PRAINS AND S TRAINS OF L IGAMENTS 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)

S UMMARY 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

D EFINITIONS 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

D EFINITIONS 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