bones are organs

• each bone is a complex living organ made up of many cells, protein fibers, and minerals

• they come in many sizes and shapes

• the largest bone is the femur and the smallest is the stapes

• the humerus is pictured here

the skeletal system also includes…

• joints

• cartilages

• ligaments* - bone to bone

• tendon - muscle to bone

two basic types of bones

• compact bone: dense and looks smooth and homogenous

spongy bone: composed of small pieces of bone and lots of open spacecompact bone

• in long bones, surrounds spongy bone at ends

• along shaft surrounding medullary cavity

spongy bone

• at ends or long bones

microscopic anatomy of spongy bone

• the open spaces keep bones light

• found in the ends of long bones

• also fills short bones, flat bones and some parts of irregular bones

• contains red marrow

microscopic anatomy of compact bone

• composed of a matrix of hard minera lsalts reinforced with tough collagen fibers

• mature bone cells are called osteocytes

• osteocytes are found in tiny cavities within the matrix called lacunae

gross anatomy of a long bone

• diaphysis

  • shaft

  • composed of compact bone

• epiphysis

  • end of the bone

  • composed of mostly spongy bone

other features of long bones

• articular cartilages: cover epiphyses for smooth movement

• epiphyseal line: marking left from growth at epiphyseal plate

• periosteum: fibrous, connective tissue that covers the disaphysis

bone marrow

• red marrow: in cavities of spongy bone in flat bonesa nd epiphyses of long bones, site of hematopoiesis

• yellow marrow: fat storage in medullary cavity

anatomy of the skeletal system

two divisions of the skeleton

• axial skeleton

• z

axial skeleton

• bones that form the longitudinal axis of the body make up the axial skeleton

• verterbal column

  • vertebrae

  • sacrum

  • coccyx

• bony thorax

  • ribs

  • sternum

• skull

  • cranium

  • facial bones

vertebral column

• composed of 33 bones before birth; some later fuse to form 26 separate bones (know numbers)

  • 7 cervical vertebrae

    • 7 vertebrae located in the neck

    • smallest and lightest vertebrae

  • 12 thoracic vertebrae

    • articulate with ribs

    • larger than cervial vertebrae

    • long spinous process that hooks sharply downward

  • 5 lumbar vertebrae

    • much larger than other vertebrae to support the weight of the upper body

  • sacrum: 5 fused

  • coccyx: 4 fused

atlas & axis

• atlas: the first

bony thorax or rib cage

• 12 pairs of ribs articulate with the 12 throacic certebrae posterio

• true ribs: pairs 1-7, articulate anteriorly directly to the sternum by cartilage

• false ribs: pairs 8-12, articulate indirectly or not at all

• last 2 apir do not connect at all and are floating ribs

sternum

• manubrium

• body

• xiphoid process*

the skull

• the skull is formed by two sets of bones

  • cranium

  • facial bones

• all are joined by immovable joines except for the manible (jawbone)

hyoid bone

• no direct articulation to another bone

• provides attachment for these muscles:

  • floor of mouth

  • tongue

  • larynx

  • apiglottis

auditory ossicles

• the samllest bones in the body are located in the middle ear

  • malleus

  • incus

  • stapes

appendicular skeleton

• includes the limbs and the gidles which attach the limbs to axial skeleton

  • pectoral (shoulder)

    • collar bones

    • shoulder blades

  • upper limbs

    • arms

    • hands

  • pelvic hip

    • coxal bones

  • lower limbs

    • legs

    • feet

• pectoral girdle

  • clavicle, scapula

• upper limbs

  • humerus

  • ulna

  • radias

  • carpals

  • metcarpals

  • phalanges

• pelvic girdle

  • ilium ischium

  • pubis

• lower limbs

  • femur

  • patella

  • tibia

  • fibula

  • tarsals

  • metatarsals

  • phalanges

pectoral girdle

• clavicle is commonly called the collar bone

• the scapula is commonly called the shoulder blade

arm bones

• humerus

  • upper arm

• radius

  • lower arm; elbow to thumb side of the wrist

• ulna

  • lower arm; elbow to pinkie side of the wrist

leg bones

• femur: thigh bone

• patella: knee cap

• tibia: large bone in lower leg; sometimes called the shin bone

• fibula: smaller bone in lower leg; forms the lateral ankle

shapes of bones

• long

• short

• flat

• irregular

• sesamoid

bone markings

• bumps, holes, and ridges where muscles, tendons, and ligaments are attached and where blood vessels and nerves pass through

• two categories:

  • projections or processes

    • tuberosity

    • trochanter

    • tubercle

    • process

    • condyle

  • depressions, cavities, or openings

    • meatus

    • fossa

    • foramen

joints

• also called articulatios, where two bones meet

• holds bones together, but also gives mobility

• three types

  • fibrous: no movement, (ex., skull)

  • cartilaginous: slightly moveable (ex., pubic symphysis, vertebrae)

  • synovial: bones separated by cavity filled with synovial fluid, allow the most movement

synovial joints

• articular cartilage

• fibrous articular capsule

• joint cavity contains fluid

• reinforced by ligaments

• ball and socket joints

  • most moveable type of joint

  • found in the shoulder and hip

physiology of the skeletal system

• support

  • the skeleton provides an internal framework that supports and anchors all soft organs

• protection

  • some bones protect soft body organs

• movement

  • skeletal muscles attach to bones by tendons

  • tendons use the bones as levers to move body parts

• storage

  • fat storage in yellow marrow

  • the minerals calcium and phosphorous are stored in bone tissue

• hematopoiesis: blood cell formation occurs in red marrow

developmental aspects of the skeletal system

• fontanels

  • spaces between bones of the skull in an infant

  • “soft spots”

  • fully ossified by 2 years

  • allows for growth of the brain and skull

• ossification: the formation of bone from cartilage

  • at birth, bones are part cartilage and part bone

  • the skeleton is fully ossified by age 2, except for epiphyseal (growth) plates

• longitudinal growth

  • epiphyseal plates are fully ossified by the end of adolescence

• bone formation and growth

  • ossification: bone formation

  • epiphyseal plates: provide for longitudinal growth; increase in length

  • appositional growth: increase in diameter

  • osteroblasts: bone-building cells

  • osteoclasts: bone-destroying cells

• bone remodeling

  • breaking down and reforming of bone that occurs throughout life to maintain proportion and strength as well as healthy calcium levels

• osteoporosis: weakening of the bone that occurs with aging

  • 1 in 2 women and 1 in 4 men over age 50 will have an osteoporosis-related fracture

  • osteoporosis causes tissue loss as seen in the bottom image

  • top image shows healthy bone

• hip fracture (femoral fracture)

  • occurs in the proximal end of the femur near the hip

  • the 1 year mortality rate after a hip fracture is over 30%

diseases and conditions of the skeletal system

• arthritis: inflammation of the joints

• rickets: lack of vitamin d, calcium, or phosphorus

  • bones fail to calcify; stay soft

  • usually in children ages 3-36 months

  • rare in developed countries

• herniated disc

  • portruding discs of cartilage between the vertebrae

  • can irritate nearby nerves and result in pain, numbness, or weakness in an arm or leg

• scoliosis: abnormal curvature of the spine

  • may be congenital or result from disease or trauma