PSK4U - Skeletal System

axial skeleton

Contains 74 bones; vertebral column, hyoid bone, skull, ribs and sternum

appendicular skeleton

64 upper extremity (like arm), 62 lower extremity (like leg) and 6 auditory

Classification of bones

Short (ex carpal bones), long (femur), flat (in skull), irregular (individual vertebrae) and sesamoid (wrapped or imbedded in tendon, ex patella)

Roles of skeleton

Protection for internal organs, framework for body shape, attachment for muscles, store essential nutrients, blood cell formation

Components of bones

Epiphysis, diaphysis, cancellous bone, epiphyseal plate, medullary cavity

hyaline cartilage

Covers ends of bones, absorbs shock, prevents surfaces from running

Epiphysis

Ends of bone

Diaphysis

Shaft of the bone

epiphyseal plate

Line across the bone from which it grows in length

Cancellous (spongy) bone

Stores red bone marrow where blood cells are manufactured

Medullary cavity

Space inside the diaphysis, contains yellow bone marrow

Periosteum

Covers surface of bone in absence of hyaline cartilage, ligaments and tendons attach here

Compact bone

Hard part surrounding yellow marrow and lends strength to hollow part of bone

Osteoblasts

Generated by stem cells, work in groups to synthesize collagen and proteins which make the bone matrix

Osteoclasts

Responsible for bone resorption (secretion of an acid and a collagen to destroy bone at the molecular level), help maintain bone integrity, control tissue levels, maintain calcium levels

Endochronal

Bone formation that begins within a cartilage, common mode, growth occurs at growth plate and continues until plate ossified, longitudinal growth impossible

Intramembranous

Cartilage not present during bone formation, essential for healing fractures and forming bones of the head

Red bone marrow

Consists of RBC, platelets and WBC, adults have 50% red 50% yellow, always red at birth, site: epiphyses of long bones and in flat bones

Yellow bone marrow

primarily fat cells (some WBC created), can be converted to red in case of trauma or blood loss

Epiphyseal plates

dark spaces on x-rays, made of cartilage

Epiphyseal lines

white lines on x-rays, endochronal longitudinal grown not possible,

Response to exercise

bones respond to exercise and repeated stress, osteoblasts have to work harder, each kg of bone can support about 5kg of muscle

exercise

positive stress on bones, thickness of bone cortex is optimized

bone cortex

dense, smooth exterior layer of bone covered by periosteum

trabeculae

bony fibers arranged throughout cancellous bone; density varies with bone type and amount of stress

osteocyte

a bone cell, becomes embedded in bone matrix

pros of exercise

adults: resistance training promotes bone development and maintenance, bone density and mass increase. children: physical activity increases bone quality and development. Use varied mechanical forces!

positive bone stress

stress creates small electrical charge at site, attracts osteoblasts to site, result increased calcium retention and bone density

specific responses

resistance training slows age-related skeletal health decline, involves ROM, places stress on bones, stress stimulates bone regeneration (slows with age)

negative bone stress

overload - too much stress in short time, repeated or overuse. inappropriate - stress at sub-optimal angles. traumatic - violent torsion, compression or tension. results in injury

aging skeleton

bone density decreases, vertebrae lose mineral content, become thinner, fluid loss in discs (shorter), changes in gait and poster affect stress angles

skeletal disease

genetics (predisposition), environment (vitD exposure, air, altitude), history (injuries), diet (calcium, mineral, vitamin)

solutions

supplement vitD and calcium

fibrous joints

bound tightly by connective tissue, no movement, ex sutures of skull

cartilaginous joints

body of one bone connects to body of another via cartilage, some movement, ex intervertebral discs

synovial joints

most movement, ex knee

joint capsule

consists of synovial membrane (allows nutrients through) and fibrous capsule (keeps synovial fluid from leaking)

fluid

synovial; lubricates joint, nourishes cartilage

joint cavity

synovial; fluid-filled space btwn body articulating surfaces

bursae

small flattened fluid sacs located at friction points

intrinsic ligaments

synovial; connective tissue that thickens and reinforces joint capsule

extrinsic ligaments

synovial; separate from joint capsule, attach bones

gliding joints

connect flat or minimally curved bone surfaces, ex btwn carpals

hinge joints

convex articulation of one bone fits into concave articulating of another, movement in one plane, ex elbow

pivot joints

allows rotation in one plane, ex atlantoaxial to rotate head

ellipsoid joints

allow movement in two planes and rotation, ex wrist

saddle joints

allow movement in two planes but no rotation, ex in thumb

ball and socket joints

allow movement in three planes and around three axes, ex hip