Muscular and Skeletal System Powerpoint #2 Unit 8 – Chapters 35/36 Working together to create movement

Skeletal System Structures: BonesCartilageLigamentsTendons

Skeletal System Function: Supports body Protects internal organs Allows for movement Stores mineral reserves Provides 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 Parts Spongy 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 adults If 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 Bone 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

Saddle

Pivot

Structure of Joints Ligaments: Connect Bone to Bone

Anterior Cruciate Ligament

Structure of Joints Bursa:

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Types of Muscle 21  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

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 22

Skeletal Muscles work in PAIRS Bending or straightening of elbow requires the coordinated interplay of the biceps and triceps muscles 23

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 24

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 25

26 myofibril muscle fiber muscle fiber bundle Components of skeletal muscle

Muscle Fibers 27  Cylinder-shaped cells that make up skeletal muscle  Each myofibril is made up of a number of myofilaments  Diameter of fiber ( 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

High microscope magnification of sarcomeres within a myofibril 28

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 29

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 Contraction The 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