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

Skeletal System Structures : Bones Cartilage Ligaments

Functions 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 Axial Skeleton: spine, ribcage, skull Appendicular: arms, legs, pelvic girdle, shoulders 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 (epiphyseal plates): found in most long bones (leg and arm bones) cartilage continues to grow here until completely replaced by bone during adolescence=stop growing

Types of Joints -Ball and socket

Types of Joints- Hinge

Types of Joints- Saddle

Types of Joints Pivot

Structure of Joints Ligaments: Connects Bone to Bone Tough, fibrous tissue

Anterior Cruciate Ligament

Fractures

Structure of Joints Bursa: small fluid-filled sac provides a cushion between bones and tendons and/or muscles around a joint.

Bursitis

Arthritis

Rheumatoid arthritis Osteoarthritis

Compare Osteoarthritis and normal knee

Total Knee Replacement

Total Knee Replacements

Total Knee Replacement

Osteoporosis

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Types of Muscle 32  The human body is comprised of ~ muscles (sources varying regarding what is defined as different parts of a single muscle or as several muscles)  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  moves various parts of the skeleton  voluntary control  Repeated activation of a skeletal muscle can lead to fatigue  Can have many nuclei  Striated (striped appearance) 33

Skeletal Muscles work in PAIRS Bending or straightening of elbow requires the coordinated interplay of the biceps and triceps muscles 34

B. Smooth Muscle  Located in the blood vessels, the respiratory tract, the iris of the eye, the gastro-intestinal tract  contractions are slow and uniform  Is fatigue resistant  Activation is involuntary  Has one nucleus 35

C. Cardiac Muscle  Functions to provide the contractile activity of the heart  Activation is involuntary (like smooth muscle)  Can have 2 nuclei, usually has 1  Is very fatigue resistant 36

37 myofibril muscle fiber muscle fiber bundle Components of skeletal muscle

Muscle Fibers: Cylinder-shaped cells that make up skeletal muscle 38  Made of myofibrils which is made up of a number of myofilaments  Two types of protein myofilaments: - Actin: thin filament - Myosin: thick filament  Divided into functional units called sarcomeres, seperated by region called Z lines.  Group of fibers activated via same nerve: motor unit

High microscope magnification of sarcomeres within a myofibril 39

Muscle Contraction

Muscle Contraction Steps 1. Myosin head attaches to binding site on actin forming a cross bridge 1. After the cross bridge is formed the myosin head bends, called a power stroke, pulling on the actin filaments and causing them to slide. 1. Myosin attached to actin until another ATP binds causing it to release (explains rigor mortis) 1. Muscle contraction is a little like climbing a rope. The cross bridge cycle is: grab -> pull -> release, repeated over and over

Control of Muscle Contraction (animation)animation 1. Muscle cells are "shocked” by nerve impulses from motor neurons. 2. Neurotransmitters (acetylcholine) are released by neuron, stimulating muscle fiber to release Ca When a muscle is relaxed, tropomyosin blocks cross-bridges. 4. When Ca2+ high enough, it binds to troponin, displacing tropomyosin, exposing myosin binding sites on actin. 5. Myosin can now form crossbridge

Control of Muscle Contraction (Neuromuscular junction)

Tendons Connect Muscle to Bone

Tendon Ruptures

Terminology  Sprain: when a ligament is stretched too much  Strain: when a muscle or tendon is stretched too much