Skeletal System Skeletal Anatomy

[Pages:13]Skeletal System

bones, cartilage and ligaments are tightly joined to form a strong, flexible framework

bone is active tissue:

?5-7% bone mass/week

daily Calcium requirement: 1200mg/day

Functions of Skeletal System:

1. Support

strong and relatively light; 20% body weight

2. Movement

framework on which muscles act act as levers and pivots

3. Protection

brain, lungs, heart, reproductive system

4. Mineral storage (electrolyte balance

99% of body's calcium is in bone tissue (1200-1400g vs friction

C. Lower Leg

consists of two bones: tibia and fibula connected by an interosseous membrane along their length

tibia (=shinbone)

main bone, articulates with both femur and foot ?more strength, less mobility

medial & lateral condyles ? articulate with condyles of femur

tibial tuberosity ? attachment of patellar ligament medial malleolus ? forms medial bulge of ankle

fibula

small, offers extra support for lower leg and foot but does not actually bear weight

head lateral malleolus

D. Foot

like hand, made of many bones

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Tarsals

the weight of the body is carried mainly by the two largest, most posterior ankle bones

calcaneus ? forms heel of foot, Achilles tendon articulates here

talus ? articulates with tibia and fibula

distal proximal

cuboid

lateral intermediate medial

cuneiform cuneiform cuneiform

navicular

talus calcaneous

lateral

medial

Metatarsals

Phalanges

thick angular bones; must support all the weight of the body

arches: strung with ligaments to provide double arches = shock absorbers

the foot has 3 arches

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Articulations (joints)

Articulations = joints between bones

hold bones together while usually allowing some movement

can be categorized into three general kinds by the degree of movement & the structure of the joint

A. Immoveable Joints = Synarthroses (="joined together", joint) bones are joined by fibrous connective tissue

B. Slightly Moveable Joints =Amphiarthroses (=on both sides, joint)

bones are joined by some kind of cartilage

eg. fibrous or hyaline

C. Freely Moveable Joints = Diarthroses (through a joining)

most complex joint structure

articulation is enclosed by synovial membrane

ends of each bone are padded with articular cartilage

joint cavity is filled with synovial fluid

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produced by the interlocking shapes of the foot bones attached by strong ligaments and pulled by strong muscle tendons while walking or running

arches also furnish more supporting strength than any other type of construction ?more stability

if ligaments and muscles weaken, arches are lost = flatfootedness = fallen arches

? more difficult walking, foot pain, back pain

high heals redistribute the weight of foot?throw it foreward; ends of metatarsals bear most weight

?sore feet

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entire joint is connected by a joint capsule that is continuous with the periosteum of each bone

often supported by ligaments

ligaments ? bind bones together across joints

more elastic than tendons

hold joints in place

limit their range of motion

sometimes includes fluid filled bursae bursae = synovial sacs spaced around joints between tendons or ligaments

to cusion, reduce tension & friction Examples of the 3 kinds of articulations

diarthroses predominate in the limbs; synarthroses and amphiarthroses are largely restricted to the axial skeleton

Immoveable (Fibrous) Joints

eg. sutures ? only in skull

eg. gomphoses

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-teeth in socket eg. syndesmoses

- fibrous bands (ligaments) between two bones * some syndesmoses may allow slight movement - distal tibiofibular joint

Slightly Moveable (Cartilaginous)

eg. symphyses -fibrocartilage pad or disc -midline of body -symphysis pubis -intervertebral discs

eg. synchondroses -hyaline cartilage joins two bones -provides strength with some flexibility -a few may be immoveable; eg epiphyseal discs; temporary -costal cartilage between ribs and sternum

Freely Moveable (Synovial)

- most body articulations - bones separated by a joint cavity, covered with articular

cartilage and enclosed within an articular capsule lined with synovial membrane.

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Selected Synovial Joints

Temporomandibular Joint

jaw joint is a modified hinge joint

in addition to hinge-like motion can also allow side to side motion of the jaw

because of its shallow socket the TMJ is one of the most easily dislocated joints in the body

even a deep yawn can dislocate it

poor occlusion of teeth or teeth grinding can cause pain in ear and face and stiffness of joint

Shoulder Joint

stability has been sacrificed for dexterity; shallow glenoid cavity

the head of the humerus is held in place by tendons of 4 muscles which form the "rotator cuff" that encircles the shoulder joint.

[subscapularis, supraspinatus, infraspinatus, teres minor]

a vigorous movement of the arm can stretch or tear the rotator cuff

eg baseball pitchers

Knee Joint

the knee is the largest and most complex joint of the body

mainly a hinge joint

but it also permits slight medial and lateral rotation during leg extension

collateral ligaments join the bones of the upper and lower legs

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- provide for many different kinds of motion

- the shape of the articular surfaces determine the movements allowed at a synovial joint:

nonaxial = adjoining bones do not move around a specific axis

uniaxial = movement occurs around a single axis

biaxial = movement can occur around two axes; both front and sagittal planes

multiaxial = movement can occur around all three axes; frontal, sagittal and transverse planes

eg. plane joint (nonaxial)

- femur and patella at knee

eg. pivot joint (uniaxial)

- atlas & axis

- radius at hand

eg. hinge joint (uniaxial)

-fingers, toes, elbow

eg. condylar joint (biaxial)

- metacarpals to phalanges

eg. saddle joint (biaxial)

- carpometacarpal joint of thumb

eg. ball and socket joints (multiaxial)

-shoulder, hip

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cruciate ligaments act as restraining straps to prevent over extension or over flexion at the knee

two menisci of fibrocartilage help absorb shock the tendons of many muscles reinforce the joint capsule the patella, embedded in the patellar ligament

Exercise and Synovial Joints

synovial fluid is warmed by exercise and becomes thinner ?this is more easily absorbed by articular cartilage ?provides more effective cushion against compression

this warmup and compression also helps to distribute nutrients to cartilage cells (nonvascular tissue) and squeeze out metabolic wastes

? warm up is good for you

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