Bones Joints and Muscles Bones 206 in human

Bones, Joints and Muscles

Bones: 206 in human body n 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 n Osteocytes: mature bone cells, maintain bone matrix n

Some Reminders about Bones n n n Bone = bone tissue (type of CT) A Bone = an organ Compact vs. Spongy Bone Composition: Hydroxyapatite, protoplasm, collagen, blood vessels, marrow Skeleton = bones, cartilage (avascular, no nerves, 80% H 2 O), joints, ligaments Shapes of Bones – n Long, Flat, Irregular, Short Before 8 weeks, embryo is all cartilage

Structure of Bone

Anatomy of a Long Bone n Diaphysis – – n 2 Epiphyses – – n Epiphyseal Plates Epiphyseal Art & Vein Periosteum – – n Medullary Cavity Nutrient Art & Vein 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

2 Types of Bone Formation n 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

2 Types of Bone Formation : n 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 n – – Periosteal bud = arteries & veins, cells forming bone marrow, osteoblasts, osteoclasts Medullary cavity is formed by action of osteoclasts Epiphyses grow and eventually calcify n Epiphyseal plates remain cartilage for up to 20 years

Bone Growth & Remodeling n n GROWTH Appositional Growth = widening of bone – – n Lengthening of Bone – – – n n 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 bone ( = breakdown) n – Osteoblasts-lay down bone n n release Ca 2++ , PO 4 to body fluids from bone secrete osteoid to form new bone Ideally osteoclasts and osteoblasts work at the same rate!

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

Classification of Joints n Function: – Synarthroses = no/little movement – Amphiarthroses = slight movement – Diarthroses = great movement

Joints by Functional Classification Type Movement Example Synarthrosis None (minimal) Amphiarthrosis Slight Diarthrosis Great Sutures, Teeth, Epiphyseal plates, 1 st rib and costal cart. Distal Tibia/fibula Intervertebral discs Pubic symphysis Glenohumeral joint Knee joint TMJ

Joint Classification n Structure – Cartilagenous n Synchondrosis: connected by hyaline cartilage (synarthroses) n Symphysis: connected by fibrocartilage (amphiarthroses) – Fibrous n Sutures: connected by short strands of dense CT (synarthroses) n Syndesmoses: connected by ligaments (varies) n Gomphosis: peg in socket w/short ligament (synarthroses) – Synovial (diarthroses)

Joints by Structural Classification Structure Type Cartilagenous Synchondrosis Symphysis Fibrous Sutures Syndesmoses Gomphosis Synovial 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) n n n Articular cartilage: hyaline; covers ends of both bones articulating Synovial (joint) cavity: space holding synovial fluid Articular capsule: Made of 2 layers – – n n Fibrous: external, dense CT for strength Synovial membrane: internal, produces synovial fluid Synovial fluid: viscous; lubricates and nourishes; contained 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

Synovial Joint pg 215

Bursae & Tendon Sheaths n n n Bursae: flat, fibrous sac w/synovial membrane lining Tendon Sheaths: elongated bursae that wraps around tendons 3 Factors in Joint Stability: – – – pg 219 Muscle Tone Ligaments Fit of Articular Surface

pg 224 Joint Shapes n Hinge: cylindrical end of 1 bone fits into trough shape of other – n angular movement-1 plane (eg) elbow, ankle, interphalangal Plane: articular surface in flat plane – – Short gliding movement (eg) intertarsal, articular processes of vertebrae

pg 225 Joint Shapes n Condyloid: egg-shape articular surface + oval concavity – – n 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

pg 225 Joint Shapes n Saddle: articular surface both concave + convex – – side-to-side, back-forth movement (eg) carpometacarpal jt of thumb – n Ball + Socket: spherical head + round socket – – multiaxial movement (eg) shoulder, femur

!Muscles! Function: 1) movement 2) maintain posture 3) joint stability 4) generate heat !Muscles!

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

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 n Lever = rigid bar = bone n Fulcrum = fixed point = joint n Effort = force applied = muscle contraction n Load = object being moved = bone n

Movements of Muscles Extension: increasing angle between body parts n Flexion: decreasing angle between body parts n – – Dorsiflexion vs. Plantarflexion Inversion vs. Eversion Abduction: moving away from the median plane n Adduction: moving towards the median plane n Rotation: moving around the long axis n Circumduction: moving around in circles n

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

Muscle Basics to Remember 3 Types: Skeletal, Cardiac, Smooth n Origin vs. Insertion n Direct vs. Indirect Attachments n – – direct = right onto bone indirect = via tendon/aponeurosis n more common n leave bony markings = tubercle, crest, ridge, etc. n Sometimes attach to skin

Functional Muscle Groups n Agonist = primary mover of a muscle, major response produces particular movement – n (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

Functional Muscle Groups n Synergists = muscles work together, adds extra force to agonistic movement, reduce undesirable extra movement – n (eg) muscles crossing 2 joints Fixators = a synergist that holds bone in place to provide stable base for movement – (eg) joint stablilizers

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

Arrangement of Muscle Fibers n Parallel: long axis of fascicles parallel to axis of muscle; straplike (eg) biceps, sternocleidomastoid n Convergent: O = broad, I = narrow, via tendon; fan or triangle shaped (eg) pectoralis major n Circular: fascicles arranged in concentric circles; sphincter (eg) around mouth

Arrangement of Muscle Fibers n Pennate: fascicles short + attached obliquely to tendon running length of muscle; featherlike – Unipennate = fascicles insert on only 1 side n (eg) – Bipennate = fascicles insert both sides n (eg) – flexor pollicis longus rectus femoris Multipennate = many bundles inserting together n (eg) deltoid

Arrangements of Muscle Fascicles pg 269

First Class Lever n n n Effort at 1 end Load at other end Fulcrum in middle (eg) scissors (eg) moving head up and down pg 267

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

Third Class Lever n n n Load at 1 end Fulcrum at other end Force in middle (eg) using a tweezers (eg) lifting w/biceps pg 267

Mechanical Advantage n n n 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

Mechanical Disadvantage n n n pg 266 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