types of joints + movements + levers

fibrous joints

joints that are joined by collagen fibers of CT

• no joint cavity

• mostly immovable

types

• suture

• syndesmosis

• gomphosis

suture

fibrous joint

• joint held together with very short, interconnecting fibers and bone edges interlock

• ex. found ONLY in the skull

syndesmosis

fibrous joint

• joint held together by a ligament

• fibrous tissue can vary in length but it is longer in sutures = determines movability

• ex. interosseous membrane (R+U, T+F)

• ex. distal tibiofibular joint (joint connected by ligaments)

gomphosis

fibrous joint

• “peg in socket”

• ex. peridontal ligaments (tooth in bony alveolar socket)

cartilaginous joints

joints that involve bone articulations united by cartilage

• lack a joint cavity

• not very moveable

types

• synchondroses

• symphyses

synchondroses

cartilaginous joint

• a bar or plate of hyaline cartilage that unites the bones at a synchondrosis (i.e., junction of cartilage)

• synarthrotic (immovable)

• ex. joint between the costal cartilage and manubrium of the sternum

symphyses

fibrocartilaginous joint

• shock absorber

• limited amount of movement

• hyaline cartilage may also be present

• ex. intervertebral discs

• ex. pubic symphysis

synovial joints

a type of fluid filled joint (most mobile joints in the body)

types:

• plane

• hinge

• pivot

• condylar

• saddle

• ball-and-socket

• allow for a range of movements: non-axial, uniaxial, biaxial, multiaxial

features of synovial joints

1. articular cartilage

2. joint cavity

3. articular capsule

4. synovial fluid

5. reinforcing ligaments

6. nerves and blood vessels

plane joint

synovial

• “gliding”

• nonaxial movement

• ex. intercarpal joints, intertarsal joints, joints between vertebral articular surfaces

hinge joint

synovial

• flexion and extension

• uniaxial movement

• ex. elbow joint (humerus and ulna), interphalangeal joints, knee joint

pivot joint

synovial

• rotation

• uniaxial movement

• ex. proximal radioulnar joints, atlantoaxial joint

condylar joint

synovial

• flexion and extension

• adduction and abduction

• biaxial movement

• ex. metacarpophalangeal joints (knuckles), wrist joints, metatarsophalangeal joints

saddle joint

synovial

• flexion and extension

• adduction and abduction

• biaxial movement

• articular surfaces are both concave and convex

• ex. carpometacarpal joints of the thumbs, calacaneocuboid joint

ball-and-socket joint

synovial

• flexion and extension

• adduction and abduction

• rotation

• multiaxial movement

• ex. shoulder joints, hip joints, talocancaneonavicular joint

synarthrotic

immovable joint

amphiarthrotic

slightly moveable joint

diarthrotic

moveable/freely moveable joint

gliding

sliding the flat surfaces of two bones across each other

angular movements

increase or decrease the angle between two bones, can occur in any plane of the body

• flexion

• extension

• abduction

• adduction

• circumduction

flexion

decreasing the angle between two bones

• sagittal plane

• ex. bending forward

extension

increasing the angle between two bones

• sagittal plane

• ex. bending backwards

abduction

moving a limb away from the body midline

• frontal plane

• ex. spreading toes apart, moving arm away from body

adduction

moving a limb toward the body midline

• frontal plane

• ex. bringing arm back to body

circumduction

moving a limb or finger so that it describes a cone in space

• frontal and sagittal planes

rotation

turning a bone around its longitudinal axis

• transverse plane

• two types: medial, lateral

medial (internal) rotation

rotating toward the median plane

• transverse plane

lateral (external) rotation

rotating away from the median plane

• transverse plane

supination

turning backward

• ex. rotating the forearm laterally so that the palm faces anteriorly or superiorly

pronation

turning forward

• forearm rotates medially and the palm faces posteriorly or inferiorly

dorsiflexion

lifting the foot so that its superior surface approaches the shin

• ex. corresponds to wrist extension

plantar flexion

depressing the foot (i.e., pointing toes)

• ex. corresponds to wrist flexion

inversion

sole of the foot turns medially

eversion

sole of the foot turns laterally

protraction

nonagular anterior movement

• transverse plane

• ex. mandible when it juts out

retraction

nonangular posterior movement

• transverse plane

• ex. mandible when brought back in

elevation

lifting a body part superiorly

• ex. shrugging shoulders

depression

moving the elevated body part inferiorly

• ex. chewing it is elevated and then…

opposition

the saddle joint between first metacarpal and trapezium allows for this movement

• pinching and grabbing

lever

allows a given effort to either:
1. move a heavier load

2. move a load

load

the object to move

fulcrum

the fixed point that the lever is placed on

effort

the applied force/muscle to move the load

first-class lever

lever

• seesaw

• load-fulcrum-effort

first-class lever example

example: raising your head off of your chest

load: facial skeleton

fulcrum: atlanto-occipital joint

effort: posterior neck muscles

second-class lever

lever

• wheelbarrow

• fulcrum-load-effort

*mechanical advantage

second-class lever example

example: tip-toe

load: weight of the body

fulcrum: joints in the ball of the foot

effort: calf muscles pulling upward on the heel

third-class lever

lever

• tweezers

• load-effort-fulcrum

*mechanical disadvantage

third-class lever example

example: flexing forearm

load: hand at distal end of forearm

fulcrum: elbow joint

effort: proximal radius in forearm

mechanical advantage

all second-class levers

• the muscle insertion is always farther from the fulcrum than the load

• uncommon