Bones, Joints And Muscles

Bones, Joints and Muscles

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Bones: 206 in human body ■

Function: – – – – –

support (eg) pelvic bowl, legs protect (eg) skull, vertebrae mineral storage (eg) calcium, phosphate, inorganic component movement (eg) walk, grasp objects blood-cell formation (eg) red bone marrow

Osteoblasts: secrete organic part of bone matrix = osteoid ■ Osteocytes: mature bone cells, maintain bone matrix ■

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Some Reminders about Bones ■ ■ ■ ■ ■ ■

Bone = bone tissue (type of CT) A Bone = an organ Compact vs. Spongy Bone Composition: Hydroxyapatite, protoplasm, bone collagen, blood vessels, marrow Skeleton = bones, cartilage (avascular, no nerves, 80% H2O), joints, ligaments Shapes of Bones –

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Long, Flat, Irregular, Short

Before 8 weeks, embryo is all cartilage www.smso.net

Structure of Bone

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Anatomy of a Long Bone ■ ■ ■ ■ ■ ■ ■

Diaphysis Medullary Cavity Nutrient Art & Vein 2 Epiphyses Epiphyseal Plates Epiphyseal Art & Vein Periosteum – – – –

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Outer: Dense irregular CT Inner: Osteoblasts, osteoclasts Does not cover epiphyses Attaches to bone matrix via collagen fibers

Endosteum – –

Osteoblasts, osteoclasts Covers trabeculae, lines medullary cavity

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2 Types of Bone Formation ■

1) Intramembranous Ossification – – – – – –

Membrane bones: most skull bones and clavicle Osteoblasts in membrane secrete osteoid that mineralizes Osteocytes maintain new bone tissue Trabeculae forms between blood vessels Grows into thickened plates at periphery = compact bone Periosteum forms over it

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2 Types of Bone Formation : ■

2) Endochondral Ossification: All other bones – – – –

Begins with a cartilaginous model Perichondrium becomes replaced by periosteum Cartilage in diaphysis calcifies Trabeculae forms from Periosteal bud ■

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Periosteal bud = arteries & veins, cells forming bone marrow, osteoblasts, osteoclasts

Medullary cavity is formed by action of osteoclasts Epiphyses grow and eventually calcify ■

Epiphyseal plates remain cartilage for up to 20 years

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Bone Growth & Remodeling ■ ■

GROWTH Appositional Growth = widening of bone – –

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Lengthening of Bone – – –

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Bone tissue added on surface by osteoblasts of periosteum Medullary cavity maintained by osteoclasts Epiphyseal plates enlarge by chondroblasts Matrix calcifies (chondrocytes die and disintegrate) Bone tissue replaces cartilage on diaphysis side

REMODELING Due to mechanical stresses on bones, their tissue needs to be replaced –

Osteoclasts-take up (breakdown) bone ■

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Osteoblasts-lay down bone ■

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release Ca2++ , PO4 to body fluids from bone secrete osteoid to form new bone

Ideally osteoclasts and osteoblasts work at the same rate! www.smso.net

Joints (articulations) Where parts of skeleton meet ■ Allows varying amounts of mobility ■ Classified by structure or function ■ Arthrology: study of joints ■

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Classification of Joints

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Function: – Synarthroses = no/little movement – Amphiarthroses = slight movement – Diarthroses = great movement

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Joints by Functional Classification Type

Movement

Example

Synarthrosis

None (minimal)

Amphiarthrosis

Slight

Diarthrosis

Great

Sutures, Teeth, Epiphyseal plates, 1st rib and costal cart. Distal Tibia/fibula Intervertebral discs Pubic symphysis Glenohumeral joint Knee joint TMJ

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Joint Classification ■

Structure –

Cartilagenous ■ Synchondrosis:

connected by hyaline cartilage (synarthroses) ■ Symphysis: connected by fibrocartilage (amphiarthroses) –

Fibrous ■ Sutures:

connected by short strands of dense CT (synarthroses) ■ Syndesmoses: connected by ligaments (varies) ■ Gomphosis: peg in socket w/short ligament (synarthroses) –

Synovial (diarthroses) www.smso.net

Joints by Structural Classification Structure Type Cartilagenous Synchondrosis Symphysis Fibrous Sutures Syndesmoses Gomphosis Synovial

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Example Epiphyseal plates Intervertebral discs Skull Distal Tibia/fibula Teeth in sockets Glenohumeral joint Knee joint TMJ

Components of SYNOVIAL JOINTS: (Structural Joint Classification continued) ■ ■ ■

Articular cartilage: hyaline; covers ends of both bones articulating Synovial (joint) cavity: space holding synovial fluid Articular capsule: Made of 2 layers – –

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Fibrous: external, dense CT for strength Synovial membrane: internal, produces synovial fluid

Synovial fluid: viscous; in capsule and articular cartilages Reinforcing ligaments: extracapsular/intracapsular Nerves + vessels: Highly innervated, Highly vascular Meniscus (some): fibrocartilage; improves the fit of 2 bones to increase stability www.smso.net

Synovial Joint

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pg 215

Bursae & Tendon Sheaths ■

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Bursae: flat, fibrous sac w/synovial membrane lining Tendon Sheaths: elongated bursae that wraps around tendons 3 Factors in Joint Stability: – –

pg 219

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Muscle Tone Ligaments Fit of Articular Surface

pg 224

Joint Shapes ■

Hinge: cylindrical end of 1 bone fits into trough shape of other –

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angular movement-1 plane (eg) elbow, ankle, interphalangal

Plane: articular surface in flat plane – –

Short gliding movement (eg) intertarsal, articular processes of vertebrae

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pg 225

Joint Shapes ■

Condyloid: egg-shape articular surface + oval concavity – –

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side-to-side, back+forth movement (eg) metacarpophalangeal (knuckle)

Pivot: round end fits into ring of bone + ligament – –

rotation on long axis (eg) prox. radius/ulna, atlas/dens

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pg 225

Joint Shapes ■

Saddle: articular surface both concave + convex – –

side-to-side, back-forth movement (eg) carpometacarpal jt of thumb

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Ball + Socket: spherical head + round socket – –

multiaxial movement (eg) shoulder, femur

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!Muscles! Function:

1) movement 2) maintain posture 3) joint stability 4) generate heat

!Muscles!

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Movements of Muscles Extension: increasing angle between body parts ■ Flexion: decreasing angle between body parts ■

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Dorsiflexion vs. Plantarflexion Inversion vs. Eversion

Abduction: moving away from the median plane ■ Adduction: moving towards the median plane ■ Rotation: moving around the long axis ■ Circumduction: moving around in circles ■

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Movements of Muscles Elevation: lifting body part superiorly ■ Depression: moving body part inferiorly ■ Supination: rotating forearm laterally ■ Pronation: rotating forearm medially ■ Protraction: Anterior movement ■ Retraction: Posterior movement ■

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Muscle Basics to Remember 3 Types: Skeletal, Cardiac, Smooth ■ Origin vs. Insertion ■ Direct vs. Indirect Attachments ■

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direct = right onto bone indirect = via tendon/aponeurosis ■ more

common ■ leave bony markings = tubercle, crest, ridge, etc. ■ Sometimes attach to skin www.smso.net

Functional Muscle Groups ■

Agonist = primary mover of a muscle, major response produces particular movement –

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(eg) biceps brachii is main flexor of forearm

Antagonists = oppose/reverse particular movement, prevent overshooting agonistic motion –

(eg) triceps brachii is antagonist to biceps brachii

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Functional Muscle Groups ■

Synergists = muscles work together, adds extra force to agonistic movement, reduce undesirable extra movement –

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(eg) muscles crossing 2 joints

Fixators = a synergist that holds bone in place to provide stable base for movement –

(eg) joint stablilizers

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Naming Muscles Location: (eg) brachialis = arm ■ Shape: (eg) deltoid = triangle ■ Relative Size: (eg) minimus, maximus, longus ■ Direction of Fascicles: (eg) oblique, rectus ■ Location of Attachment: (eg) brachioradialis ■ Number of Origins: (eg) biceps, quadriceps ■ Action: (eg) flexor, adductor, extensor ■

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Muscle System: uses levers to move objects How it works: A rigid bar moves on fixed point when a force is applied to it, to move object ■ Lever = rigid bar = bone ■ Fulcrum = fixed point = joint ■ Effort = force applied = muscle contraction ■ Load = object being moved = bone ■

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STOP

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Special Features of Muscle Contractibility = cells generate pulling force ■ Excitibility = nervous impulses travel through muscle plasma membrane to stimulate contraction ■ Extensibility = after contraction muscle can be stretched back to original length by opposing muscle action ■ Elasticity = after being stretched, muscle passively recoils to resume its resting length ■

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Arrangement of Muscle Fibers ■

Parallel: long axis of fascicles parallel to axis of muscle; straplike (eg) biceps, sternocleidomastoid

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Convergent: O = broad, I = narrow, via tendon; fan or triangle shaped (eg) pectoralis major

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Circular: fascicles arranged in concentric circles; sphincter (eg) around mouth www.smso.net

Arrangement of Muscle Fibers ■

Pennate: fascicles short + attached obliquely to tendon running length of muscle; featherlike –

Unipennate = fascicles insert on only 1 side ■ (eg)

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Bipennate = fascicles insert both sides ■ (eg)

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flexor pollicis longus rectus femoris

Multipennate = many bundles inserting together ■ (eg)

deltoid

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Arrangements of Muscle Fascicles

pg 269

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First Class Lever ■ ■ ■ ■ ■

Effort at 1 end Load at other end Fulcrum in middle (eg) scissors (eg) moving head up and down

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pg 267

Second Class Lever ■ ■ ■ ■ ■

Effort at 1 end Fulcrum at other end Load in middle pg 267 (eg) wheelbarrel (eg) standing on tip toes (not common in body)

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Third Class Lever ■ ■ ■ ■ ■

Load at 1 end Fulcrum at other end Force in middle (eg) using a tweezers (eg) lifting w/biceps

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pg 267

Mechanical Advantage ■

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pg 266

When the load is close to the fulcrum, effort is applied far from fulcrum Small effort over large distance = move large load over short distance (eg) Using a jack on a car

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Mechanical Disadvantage ■

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pg 266

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When the load is farther from the fulcrum than the effort, the effort applied must be greater than the load being moved Load moved quickly over large distance (eg) using a shovel