Skeletal and Muscular Systems

Movement and Support in Animals

Biology 137

There Are Two Types of Skeletal Systems

ExoskeletonsEndoskeletons

Functions of the Skeleton

1. Supports the body

2. Protects the soft body organs

3. Makes blood cells and platelets

4. Stores calcium and other minerals

5. Helps with movement

How can bones help your immune system?

• Bone marrow has many useful cells!– Red marrow produces red blood cells

which carry oxygen throughout the body.– Red marrow also produces white blood

cells to fight disease!– Yellow marrow helps store fats and

produces red blood cells during major injury.

Do you know the bones of the skeleton?

Cranium

ClavicleHumerus

Maxilla

Mandible

Radius

UlnaCarpals

Metacarpals

Phalanges

Femur

Patella

Tibia

Fibula

Sternum

Scapula

Pelvis

Tarsals

Metatarsals

Phalanges

Sacrum

Vertebrae

Ribs

Bone Growth

Baby Adult

Who has more bones – an adult or child?

Formation of Bone• When you are developing as a baby, your

bone starts as cartilage.• Blood vessels stimulate cartilage and turn it

into potential bone cell (Ossification)• Cells secrete hormones that make the bone

harden.• Osteoblasts build bone & store calcium.• Osteoclasts break down bone & release

calcium.

Bone Structure

Growth Plate

(Contains Red Marrow)

(Also called compact bone)

(Periosteum)

(Contains yellow marrow)

6 Tissues Make up BoneTissue Type Function

1. Ligaments Connect one bone to

another

2. Periosteum Supplies blood to the bone

3. Compact bone Very strong – Stores Calcium

4. Spongy bone Light but very strong

5. Marrow Makes blood cells

6. Cartilage Cushions bones at joints

Joints – Where Bones Meet

Gliding joint.

Slight movement.

There are 4 Main Types of Joints

Hinge Joint:

One direction only.

Ball & Socket Joint:

Greatest range of motion.

Fixed Joint:

No movement

The Muscular System

It will “pump you up!”

Lou Ferrigno – The Hulk

Where do we find muscle?• EVERYWHERE!

– Muscles are located everywhere on the body!• Ex: Arms, legs, back, stomach, face,

hands, feet, etc.

There Are Three Types of Muscle Tissue

Muscle Type: Skeletal• SKELETAL (striated or striped)

– cells are long, cylindrical, and rarely branched– Many nuclei along edges of cells– Attached to bones by tendons

• Only operate when you want them to-- VOLUNTARY• Controlled by the nervous system.• Necessary for movement of the skeletal system.

Muscle Type: Smooth• SMOOTH (involuntary)

– No striated (striped) pattern– Cells contract slower, but longer– Found in walls of blood vessels, digestive tract

(intestine, stomach), urinary bladder and in the iris• Work automatically without thinking about it. Works

even while you sleep.• Controlled by the nervous system.• Small, spindle shaped cells.

Muscle Type: Cardiac• CARDIAC

– Found only in the heart– Striated (striped) like skeletal muscle– One nucleus with branched ends– Will continue to contract if nerves to heart are cut

• Only found in the heart.• Never gets tired.• Cells connected like a tightly

woven bag.

Muscles and Contraction

Every movement is done in pairs! One muscle contracts, while the

other relaxes.– Ex: As you move your hand up to your

shoulder, you tighten your bicep and it contracts. The muscle on the other side of your arm, the tricep, relaxes.

– The opposite happens when you return your hand to your waist, the tricep contracts and the bicep relaxes.

Muscles Work In Pairs

One muscle bends (flexes) a joint, and an opposing muscle is needed to straighten (extend) it.

How Do Muscles Work?

A muscle can only pull. It does this by becoming shorter. When it contracts, the joint bends.

Endoskeleton vs. Exoskeleton

Muscle Filament Structure

Sliding-Filament Model

Acetylcholine (ACh) depolarizes the plasma membrane of the muscle fiber

Neuromuscular junction

Opposing Muscles Move Us

TRY THIS AT HOMEHow does fatigue or rest affect

muscle performance?• Volunteer #1 – Do twenty pushups• Volunteer #2 – Rest in your chair• Lift two books over your heads.• Which one has the most trouble?

Do you think muscles ever change their performance based on rest or tiredness?

What are some examples of this?

Skeletal System Problems

Fractured bones (cracks and breaks).

Sprains: stretched or torn ligaments (bone-to-bone).

Strains: stretched or torn tendons (muscle-to-bone).

Diseases: Arthritis, osteoporosis, cancer, leukemia.

Why do your muscles get tired?

• Why can’t your nerves just tell the muscles to contract more?– When muscles are working they are using

energy and producing lactic acid (remember lactic acid fermentation???)

– Eventually, the muscles get fatigued and this affects performance.

– You get cramps when there is a lack of oxygen and the lactic acid builds up.

Fractures

Worn out joints may sometimes be replaced with artificial ones.

Sometimes Knees Wear Out Too

Daily Herald, Monday, March 29, 2004

Implants Replace Worn or Damaged Joint Surfaces In The Knee

The End