Skeletal and Muscular Systems

Movement and Support in Animals

Biology 137Chapter 36-1 and 36-2

THE skeletalSYSTEM

36-1

All organisms need structural support.

Exoskeletons(arthropods)

Endoskeletons(vertebrates)

MULTI-CELLULAR ORGANISMS

Cytoskeletons

UNICELLULAR ORGANISMS

Functions of the Skeleton

–The skeleton:

• supports the body.

• protects internal organs.

• provides for movement.

• stores mineral reserves (like calcium).

• provides a site for blood cell formation.

Cranium

ClavicleHumerus

Maxilla

Mandible

Radius

UlnaCarpals

Metacarpals

Phalanges

Femur

Patella

Tibia

Fibula

Sternum

Scapula

Pelvis

Tarsals

Metatarsals

Phalanges

Sacrum

Vertebrae

Ribs

Bone Structure

(Periosteum)

6 Tissues Make up BoneTissue Type Function Helpful Facts

1. Ligaments Connect one bone to

another bone

“Like to Like”

“Bone to “Bone”

2.Periosteum Supplies blood to the bone

Blood carries oxygen

3.Compact bone

Very strong – Stores Calcium

Where Haversian canals are located – which contain nerves and blood vessels

4. Spongy bone

Light but very strong Adds strength without mass

5. Marrow Makes blood cells Yellow and Red Marrow

6. Cartilage Cushions bones at joints

Soft and flexible

Bone Structure

Bone Growth

Baby Adult

Who has more bones – an adult or child?

Formation of Bone

Formation of Bone

Growth Plates

Depending on its type of movement, a joint is classified as:

1. Immovable i.e.= skull2. Slightly movable i.e.=joints between vertebrae3. Freely movable i.e.= ball and socket, hinge, pivot and saddle joints

Joints – Where Bones Meet

Examples

Gliding joint.

Slight movement.

Hinge Joint:

One direction only.

Ball & Socket Joint:

Greatest range of motion.

Fixed Joint:

No movement

Saddle Joint

Saddle joints permit one bone to slide in two directions.

Knee Joint•Synovial fluid forms a thin lubricating film over the surface of the joint.

•Synovial fluid enables the bones to slide past each other more smoothly.

•In some freely movable joints small sacs of synovial fluid called bursae form.

•A bursa reduces the friction between bones of a joint and also acts as a shock absorber.

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.

Fractures

Worn out joints may sometimes be replaced with artificial ones.

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– Red blood cells, some kinds of white blood cells, and platelets are produced by A. red marrow.

B. cartilage.

C. yellow marrow.

D. osteocytes.

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A. Mature bone cells are calledA. periosteum.

B. osteocytes.

C. bone marrow.

D. Haversian canals.

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– In freely movable joints, what covers the surfaces where the two bones come together? A. ligaments

B. cartilage

C. bursae

D. tendons

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– During ossification, cartilage is replaced byA. bone.

B. ligament.

C. marrow.

D. tendon.

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– The shoulder joint is an example of aA. ball-and-socket joint.

B. hinge joint.

C. pivot joint.

D. saddle joint.

The Muscular System

36-2The function of the muscular

system is movement.

More than 40% of the mass of the average human body is

muscle.

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 Tissue1. SMOOTH 3. SKELETAL2. CARDIAC

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

•Muscle Contraction The fibers in skeletal muscles are composed of

smaller structures called myofibrils. •Each myofibril has smaller structures called filaments.

•The thick filaments contain a protein called myosin.

•The thin filaments contain a protein called actin.

•Filaments are arranged along the muscle fiber in units called sarcomeres.

•Sarcomeres are separated by regions called Z lines.

•When a muscle is relaxed, there are no thin filaments in the center of a sarcomere.

•During muscle contraction, the actin filaments slide over the myosin filaments, decreasing the distance between the Z lines.

Muscle 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.

TRY IT!

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.

Opposing Muscles Move Us

• Skeletal muscles are joined to bones by tendons.

• Tendons pull on the bones so they work like levers.

• The joint functions as a fulcrum.

• The muscles provide the force to move the lever.

How Muscles and Bones Interact

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?

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.

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36–2

– Skeletal muscles are joined to bones by tough connective tissue called

A. ligaments.

B. tendons.

C. filaments.

D. bursae.

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36–2

– Muscle cells that are large, have many nuclei, and striations are

A. skeletal muscle cells.

B. smooth muscle cells.

C. cardiac muscle cells.

D. involuntary muscle cells.

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36–2

– Muscle that is found in the walls of blood vessels and intestines is

A. skeletal muscle.

B. smooth muscle.

C. cardiac muscle.

D. striated muscle.

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36–2

– The filaments found in skeletal muscle cells are

A. actin and myosin.

B. myosin and myofibrils.

C. actin and Z lines.

D. actin and sarcomeres.

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36–2

– The type of muscle found only in the heart is

A. skeletal muscle.

B. striated muscle.

C. cardiac muscle.

D. smooth muscle.