To support and protect the body's tissue and organs.

Also and important source of minerals and blood cells

Begins in utero with the differentiation of mesenchymal cells into either chondrocytes or osteoblasts

Either crystallize on a catilage framework or beceom bone-forming cells without cartilage

It induces osteocalst activeation and bone resorption

How does OPG work?

And what is it?

OPG is a protein, that binds to a protein called OPG ligand.

This attachment serves as a decoy receptor for RANKL and blocks osteroclast activity, thus decreasing bone resorption

It determines the quality of bone

Compact bone and spongy bone tissue

Highly organized into haversian systems that concists of concentric layers of crystallized matrix surrounding a central canal that contains blood vessels and nerves

Dispersed throughout the concentric layers of crystallized matrix are small spaces containing osteocytes

Canaliculi: interconnect the osteocyte containing spaces

In bars or plates

Spaces containing osetocytes are dispersed between the bars or places and interconnected by canaliculi

SHAPE: long, short, flat, or irrgular

Long bones have a broad end (epiphysis), broad neck (metaphysis), and narrow midportion (diaphysis)

Hematoma formation provides the fibrin framework for formation and organization of granulation tissue

Granulation tissue provides a cartilage model for the formation and crystallization of bone matrix

Remodeling restored the orignal shape and size to the injured bone

What is a joint?

What to they provide?

Where two or more bones attach

They provide stability and mobility to the skeleton

Synarthroses, amphiarthroses, or diathrosis: depending on the degree of movement they allow

Fibrous joints are connected by dense fibrous tissue, ligaments, or membranes

Cartilaginous joints are connected by fibrocarilage or hyaline cartilage

Synovial joints are connected by a fibrous joint capsule. Within the capsule is a small fluid-filled space. The fluid in the space nourishes the articular carilage that covers the ends of the bones meeting in the synovial joint

A highly organized system of collagen fibers and proteoglycans

The fibers firmly anchor the cartilage to the bone, and the proteoglycans control the loss of fluid from the cartilage

To help move bones and muscle

The largest muscle in the body and is mae up of millions of individual fibers

Whole muscles vary in size (2-60cm) and shape (fusiform and pennate)

In a 3 part connective tissue framework

The motor unit

defined as all muscle fibers innervated by a single motor nerver

Bundles of myofibrils arranged in parallel along the longitudinal axis and include the muscle membrane, myofibrils, sarcotubular system, aqueous sarcoplasm, and mitochondria

Type 1 and Type 2 determined by motor nerve innervation

The major muscle proteins, actin and myosin

These interact to form cross-bridge during muscle contration.

What are the nonprotien muscle constituents?

And what do they do?

They provide an energy source for contraction and regulate protein synthesis, enzyme systems, and membrane stabilization

Excitaion, coupling, contraction, and relaxation

by the 'all or nothing' phenomenon and recruitment

Muscle fiber type

Temperature

Strech

Weight of the load

Isometric and Isotonic

Muslce shortening occurs during contraction but can be seen also during pathologic and physiologic contracture

They form the cross-bridges that cause the sarcomere to shorten, a process now known as the cross-bridge theory of muscle contraction

A constant supply of ATP and phosphocreatine

These can be generated aerobically or anaerobically

Phosphocreatine concentration is an extemely sensitive indicator of muscle fiber activity

When a motor unit responds to a single nerve stimulus, it develeps a phasic contraction

The central nervous system smoothly grades the force generated by 'recruiting' additional motor units and varying the discharge frequency of each ative motor unit

Osteoblasts:build bone

Osteoclasts:breakdown bone

Osteocytes: transformed osteroblasts 

Bone forming

Derived from mesenchymal cells

Produce osteocalcin, TGF beta, MCSF, RANKL, and OPG

Transformed osteoblasts surrounded in osteoid as it hardens from depositied minerals (the actual bone cells)

Within the lacuna

Helps concentrate nutrients in matrix

Helps synthesize and replace needed elements

Aids in bone remodeling

What are Osteoclasts?

The major reabsoptive cell of the bone

Secrete HCL and cathepsin K which dissolves bone mineral, collagenace, and cytokines

Organic = bone strength

Inorganic = actual crystals

Proteoglycans

Glycoproteins

Compact bone

Cortical

85% of skeleton

Organized and stong

Made up of haverisan system: contains blood vessels and nerves, lamellae, lucunae, osteocyte and canaliculi

Spongy bone

Cancellous

Lacks haversian systems: less complex

Lamellae arranged in trabeculae; pattern determined by stress on bone

Covers bone

The outer layer contains blood vessels and nerves, some of which penetrate to the inner strucutres of the bone through channels call Volkmann canals

The inner layer is anchored to the bone by collagenous fibers that penetrate the bone

Sharpey fibers also help hold or attach tendons and ligaments

What is the structure of a long bone?

What is the function of the sturctures?

Diaphysis: long midportion (shaft)

- contained within is the elongated marrow (medullary) cavity

- contains yellow marrow or fatty tissue

Epiphysis: the broad end (bottom)

- red marrow (blood forming)

- spongy bone

Metaphysis: the broader neck 

- spongy bone

1. activation: a stimulus activated programmed osteocyte cell death (apoptosis). The distribution of these apoptotic osteocytes provides osteoclasts with information about where to begin resorbing damaged bone

2. resorption: the osteoclasts form a cutting cone with gradually resorbs bone, leaving behind an elongated cavity termed a resorption cavity. 

3. formation: laying down of new bone, termed secondary bone, by osteoblasts lining the walls of the resorption cavity. Succesive layers (lamellae) in compact bone are laid down until the resorption cavity is reduced to a narrow haverisan canal around a blood vessel

1. a central canal called the haversian canal

2. concentric layers of bone matrix called lamellae

3. tiny spaces (lacunae) between the lamellae

4. bone cells (osteocytes) within the lacunae

5. small channels or canals call canaliculi

Synarthrosis: immovable

Amphiarthrosis: slightly movable

Diarthrosis: freely movable

Hematoma formation

Procallus formation

Callus formation

Callus replacement

Remodeling

Provide stiffness and regulate movment of synovial fluid

It acts as a pump permitting fluid to be pressed out to ensure a fluid film is always present on articular cartilage

Uniaxial- elbow

Biacial- finger

Multiaxial- hip

Are elongated muscles shaped like straps and can run from one joint to another

Are broad, flat, and slightly fan shaped, with fibers running obliquily to the muscle's long axis

Epimysium: the outer most layer

- tapers at each end to form the tendon

Perimysium: subdivides the muscle fibers into bundles or fascicles

Endomysium: surround the mucsle fascicles, the smallest unit of muscle fibers

Indicates that the muscle is controlled directly by the central nervous systme

Described the striated, or striped pattern of skeletal muscle viewed under a microscope

The striations result from the organizeaiton of the muscle fibers into the contractile unites called sarcomeres

Distinguishes the skeletal muscle fibers from other contractile fibers located within the sensory oragans of the muscle

Each anterior horn cell, its axon, and the muscle fibers innervated by it are called a motor unit

Each anterior horn cell, its axon, and the muscle fibers innervated by it are called a motor unit

What is a high innervation ratio muscle? 

How is it defined?

The calf muscle

one motor axon will innervate approx 2000 muscle fibers out of 1,200,000 fibers

The higher the ration the greater the indurance

The laryngreal muscles

the lower the ration, allows for more precision of movement

They are the mechanoreceptors that lie parallel to muscle fibers and respond to stretching

They are dendrites that terminate and branch to tendons near the neuromuscular junction

They contain bundles of myofibrils, the fiber's functional subunits, in a parallel arrangement along the longituduial axis of the muscle

red muscle

slow muscle fibers

white muscle

fast motor fibers