The skeletal system

Structure and function of bone

Organization of the skeleton

Joints

Functions of bone (skeleton)

Support and protection

Blood cell formation

Mineral storage (calcium especially)

Site for muscle attachmentbody movement

Bones classified by shape: long, short, flat, irregular, round

Bone enclosed in periosteum, which is continuouswith tendons and ligamentsblood vessels in periosteum

Epiphysis- endsspongy bone contains red marrowcompact bone, articular cartilage

Diaphysis- middlecompact bonemedullary cavity- contains yellow marrow (fat)lined with endosteum (squamous epithelium)

Compact boneosteocytes within lacunaearranged in concentric circles called lamellae

This surround a central canal; complex is calledHaversian system

Canaliculi connect osteocytes to central canal andto each other

Prenatal developmentskeleton is mostly cartilaginous

Cartilage cells and then osteoblasts start todeposit minerals

Cartilaginous disk (epiphyseal disk) remainsin epiphysis

Cells eventually stop dividing

Adults continually break down and build up bone

Osteoclasts remove damaged cells and releasecalcium into blood

Osteoblasts remove calcium from blood and buildnew matrix. They become trappedosteoclasts

Types of bone breaks

Simple- skin is not piercedCompound- skin is piercedComplete- bone is broken in halfPartial- broken lengthwise but not into two

partsGreenstick- incomplete break on outer arcComminuted- broken into several piecesSpiral- twisted

Fracture repair

Hematoma- blood clot in space between edgesof break

Fibrocartilage callus- begins tissue repair

Bony callus- osteoblasts produce trabeculae(structural support) of spongy bone andreplace fibrocartilage

Remodeling- osteoblasts build new compact bone,osteoclasts build new medullary cavity

Axial skeletonskull (cranium and facial bones) hyoid bone (anchors tongue and muscles

associated with swallowing) vertebral column (vertebrae and disks) thoracic cage (ribs and sternum)

Appendicular skeletonpectoral girdle (clavicles and scapulae)upper limbs (arms)pelvic girdle (coxal bones, sacrum, coccyx)lower limbs (legs)

posterior viewp. 135

Bones named and numbered in Table 7.1on page 137

Terms listed in table 7.2 (same page)

Axial skeleton supports and protects organsof head, neck and trunk

Appendicular skeleton- bones of limbs and bones that anchor them to the axialskeleton

Articulation- where joints are formed

22 bones in skull6 in middle ears1 hyoid bone26 in vertebral column25 in thoracic cage

4 in pectoral girdle60 in upper limbs60 in lower limbs2 in pelvic girdle

206 bones in all

The skull

8 sutured bones in craniumFacial bones: 13 sutured bones, 1 mandible

Craniumencases brainattachments for musclessinuses

Allows forgrowth

Vertebral column

7 cervial vertebrae12 thoracic5 lumbar1 sacrum (5 fused 1 coccyx (4 fused)

Vertebrae vary in size and morphology

Thoracic cageribsthoracic vertebraesternumcostal cartilages

True ribs are directly attached to the sternum(first seven pairs)Three false ribs are joined to the 7th ribTwo pairs of floating ribs

Clavicles and scapulae

Help brace shouldersAttachment sites for muscles

Bones of upper limb

Humerus (upper arm)Radius; ulnaCarpals, metacarpals, phalanges

Bones of lower limb

FemurPatellaTibia, fibulaTarsals, metatarslas, phalanges

Joints

Immovable (synarthoses) bones sutured togetherby connective tissue: skull

Slightly movable (amphiarthoses) connected byfibrocartilage or hyaline cartilage:vertebrae, rib/sternum joint, pubicsymphysis

Freely movable (diarthroses)- separatedligaments- hold bones togethertendons- muscle to bonelined by synovial membrane

Types of freely movable joints

Saddle: carpal and metacarpal bones of thumb

Ball and socket: shoulder and hip joints

Pivot- rotation only: proximal end of radius and ulna

Hinge- up and own movement in one plane:knee and elbow

Gliding- sliding and twisting: wrist and ankle

Condyloid- movement in different planes but notrotations: btw metacarpals and phalanges

Types of movement and examples (with muscles)flexion- move lower leg toward upperextension- straightening the leg

abduction- moving leg away from bodyadduction- movong leg toward the body

rotation- around its axissupination- rotation of arm to palm-up positionpronation- palm down

circumduction- swinging arms in circles

inversion- turning foot so sole is inwardeversion- sole is out

Elevation and depression- raising body part upor down

Aging and bonesboth bone and cartilage tend to deterioratecartilage: chondrocytes die, cartilage becomes calcified

osteoporosis; bone is broken down faster than it can be builtbones get weak and brittle; tend to fracture

easily

Risk factors for osteoporosis

Inadequate calciumLittle weight-bearing exerciseDrinking alcohol, smokingBeing female: decreased estrogen secretion

after menopauseSmall frameCaucasian or Asian ethnicity

Skeleton and other systems

Skin makes vitamin D which enhances calciumabsorption

Skeleton stores calcium for muscle contraction,nervous stimulation, blood clot formation

Red marrow- site of blood cell formation

Calcium levels regulated byparathyroid hormone and calcitoninkidneys (can help provide vitamin D)digestive system (can release calciuminto blood

Growth hormone regulates skeletal growthstimulates cell division in epiphyseal disksin long bones

Growth stops when epiphyseal disks are converted to bone

When excess growth hormone is produced inchildhoodgigantism

In adulthood- acromegaly. Bones can’t growbut soft tissue can

When muscle contracts, it shortens and causesmovement

Skeletal muscles attached to bones by tendons

Insertion- attachment to more movable boneOrigin- less movable

Flexors and extensors act on the same joint to produce opposite actions