Muscular and Skeletal SystemPowerpoint #2

Unit 8 – Chapters 35/36

Working together to create movement

Skeletal System

Structures: Bones CartilageLigaments Tendons

Skeletal SystemFunction:

Supports bodyProtects internal organsAllows for movementStores mineral reservesProvides a site for blood cell formation

How many bones in a human Skeleton?– 206

How many in babies?~ 300

What are bones?– A solid network of living cells

and protein fibers that are surrounded by deposits of calcium salts

Bones: 3 PartsSpongy bone–Not soft or spongy–Very strong–Structure

resembles the supporting structure of bridges.

–Strong but lightweight

Compact bone:–Very dense (no

spaces like spongy bone)

– Outer portion of bone

–Contains Haversian canal for veins and arteries to run through

Haversian Canals

Bone Marrow:–Soft tissue–Found in bone cavities–Yellow Marrow: fat cells–Red marrow:

makes red blood cells, platelets and most white blood cells~1/2 red marrow turns into yellow in adultsIf severe blood loss, some yellow can turn back to red

Development of bone:

Cartilage: Tough, elastic, connective tissue– Found in: ears, between bones, larynx,

and other various places.

Development of Bonehttp://www.youtube.com/watch?v=78RBpWSOl08

Ossification: cartilage replaced by bone

– Osteoblasts:cells that build bone

– Osteoclasts:cells that break down bone– growth Plates: found in most long bones

(leg and arm bones) cartilage continues to grow here until completely replaced by bone during adolescence

Types of Joints

Ball and socket

Types of Joints

Hinge

Types of Joints

Saddle

Types of Joints

Pivot

Structure of Joints

Ligaments: Connect Bone to Bone

Anterior Cruciate Ligament

Structure of Joints

Bursa:

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Types of Muscle

The human body is comprised of 324 muscles Muscle makes up 30-35% (in women) and 42-47%

(in men) of body mass.

Three types of muscle:

Skeletal muscle

Smooth muscle

Cardiac muscle

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A. Skeletal (Striated) Muscle Connects the various parts of the skeleton through one or more

connective tissue tendons During muscle contraction, skeletal muscle shortens and moves

various parts of the skeleton Activated through signals carried to the muscles via nerves

voluntary control Repeated activation of a skeletal muscle can lead to fatigue Can have many nuclei

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Skeletal Muscles work in PAIRSBending or straightening of elbow

requires the coordinated interplay of the biceps and triceps muscles

B. Smooth Muscle

Located in the blood vessels, the

respiratory tract, the iris of the eye, the

gastro-intestinal tract

The contractions are slow and uniform

Is fatigue resistant

Activation is involuntary

Has one nucleus

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C. Cardiac Muscle

Has characteristics of both skeletal and smooth

muscle

Functions to provide the contractile activity of

the heart

Is very fatigue resistant

Activation of cardiac muscle is involuntary

(like smooth muscle)

Can have 2 nuclei, usually has 1

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myofibril muscle fiber muscle fiber bundle

Components of skeletal muscle

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Muscle Fibers Cylinder-shaped cells that make up skeletal muscle

Each myofibril is made up of a number of myofilaments

Diameter of fiber (0.05-0.10 mm) Length of fiber (appr. 15 cm)

Each fiber contains contractile machinery and cell organelles

Group of fiber activated via same nerve: motor unit

Each fiber has capillaries that supply nutrients and eliminate

waste

Divided into functional units called sarcomeres

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High microscope magnification of sarcomeres

within a myofibril

Muscle Contraction

Organized in series (attached end to end)

Two types of protein myofilaments:

- Actin: thin filament - Myosin: thick filament

Projecting from each myosin are tiny contractile myosin bridges

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Muscle Contraction During muscle contraction the

myofilaments myosin and actin slide toward each other and overlap. This shortens the sacromere and the entire muscle. Muscle cells are "shocked" by nerve impulses from motor neurons.

Muscle ContractionThe filaments slide together because myosin attaches to actin

and pulls on it. Myosin head (H) attaches to actin filament (A), forming a cross bridge.

After the cross bridge is formed the myosin head bends, pulling on the actin filaments and causing them to slide:

Muscle contraction is a little like climbing a rope. The cross bridge cycle is: grab -> pull -> release, repeated over and over

(a) At rest b) Contraction

Tendons

Connect Muscle to Bone

Tendon Ruptures