How did the biceps and triceps change as you bent and straightened your arm?

When the arm was extended, the biceps would relax (lengthen) and the triceps would contract (shorten). The reverse happen when the arm is bent.

How do the skeletal muscles cause bones to move?

Muscles are attached to bones by tendons. The muscles work in pairs and pull against the bone to cause movement.

What did your finding about the thickness of the upper arm suggest about how muscles work?The thickness of the arm stayed the same. Muscles must work in pairs. While one contracts, the opposing muscle must relax.

The Skeletal System

The Skeletal System

• Is made up of:– bones– cartilage– tendons– ligaments– joints

The Skeletal System

–Each bone in your body is a living organ, made of different tissues.•Cells in bones take in food and use energy.

Number of Bones

• Infant or baby– 305 bones

• Adult– 206 bones

– Bones in the skull, pelvis, spine, and long bones fuse

Skeleton Formation

• As a fetus, your skeleton starts out as cartilage– Connective tissue that is stronger than

bone• As you grow, the cartilage is replaced

by bone• Your ears and nose tip remain cartilage

Functions of the Skeletal System

• Provides shape and support• Enables you to move• Protects your internal organs• Produces blood cells in the red marrow• Stores calcium and phosphorous until

your body needs them.

Bone Characteristics

• Bone is alive– Full of blood vessels– Contains nerves (pain if broken)

• Bone is made mainly of 2 minerals– Calcium– Phosphorous

• Bone grows and changes all the time

Spongy Bone

Compact Bone

Periosteum

Bone Marrow

Growth Plate

Bone Marrow

• Bone marrow is located in the hollow cavity inside of some bones– Red

• Produces blood cells

– Yellow• Fat and energy reserve

Joints of the Body

Joints

• Any place where two or more bones meet

• Ligaments: tough

bands of tissue that

hold bones together

at the joints.

Body systems that work with the skeletal system;

• circulatory system transports blood to and from the bones

• digestive system provides minerals and vitamins

• muscular system moves the bones and joints

Which cell part is like the skeletal system?

microtubules

The Muscular System

• Muscles are the motors that move body parts

• Bones and joints cannot move on their own

• There are approximately 600 muscles in your body

• 35 – 40% of body mass is muscle

Parts of the Muscular System

• skeletal muscle• smooth muscle• cardiac muscle

Voluntary Muscles

• muscles under conscious control– smiling, walking, running, typing etc…

Skeletal Muscle

• muscles attached to bones

• voluntary• striated (striped)• muscle that reacts

quickly and tires quickly

Skeletal Muscle

Muscles at Work

• Skeletal muscle movements are

results of pairs of muscles

working together.

– One muscle contracts while

the other muscle relaxes.

– Muscles always pull;

they never push.

Muscles at Work

• Results of Muscle Action

– Muscles contract

• This produces thermal energy, and it uses chemical energy.

• Thermal energy produces heat that helps keep body temperature constant.

• Chemical energy is from glucose. (When glucose is used up, muscles are tired and need to rest.)

Muscles at Work

• Results of Muscle action (cont.)

– Over time, muscles become larger or smaller, depending on how much work they do.

Involuntary Muscles

• muscles not under conscious control– You don’t have to think about them

• breathing, digesting, sneezing, heart beating

Smooth Muscle

• found inside most blood vessels and organs

• involuntary• not striated (striped)• reacts slowly and tires

slowly

Smooth Muscle

Cardiac Muscle

• found only in the heart

• involuntary• striated (striped)• does not get tired

Cardiac Muscle

Tendons and ligaments help to attach muscles to the

skeletal system so that they can work together.

Tendon

• Strong connective tissue that attaches muscle to bone

Ligament

• Bands of connective tissue connecting one bone to another bone

Functions of the Muscular System

• Allows the body to move• Aids in circulation, respiration

and digestion (circulatory and digestive system)

Body systems that work with the muscular system;

• digestive system provides energy• respiratory system provides oxygen• circulatory systems delivers oxygen

and carries away waste• excretory system also carries away

waste• skeletal system provides a frame