A&P Chapter 9 - Joints

how is movement possible?

joints

what are joints/articulations

where two bones meet

what does the joint structure determine

how join moves and its strength

how does joint mobility affect strength?

the more mobile, the weaker the joint

two ways of join classification

degree of motion, anatomy of the joint

three degrees of motion

synarthrosis, amphiarthrosis, diarthrosis

synarthrosis

immovable

amphiarthrosis

slightly movable

diarthrosis

freely movable

types of joint anatomy

fibrous, cartilaginous, synovial

what are bone joints

when bones fuse

types of fibrous joints

syndesmosis, suture, gomphosis

what type of joint is a suture based on movement

synarthrosis

what type of joint is gomphosis based on movement

synarthrosis

what type of joint is syndesmosis based on movement

amphiarthrosis

suture

located only between bones of the skull. edges of bones are interlocked and bound together at the suture by dense fibrous connective tissue

gomphosis

binds teeth to sockets in the maxillae and mandible. the fibrous connection between the socket and tooth is called a periodontal ligament

syndesmosis

bones are connected by a ligament.

example: distal joint between tibia and fibula

types of cartilaginous joints

synchondrosis, symphysis

what type of join is synchondrosis based on movement?

synarthrosis

what type of joint is symphysis based on movement?

amphiarthrosis

synchondrosis

rigid connection between the ends of the first pair of vertebrosternal ribs and manubrium of the sternum. another example is the epiphyseal plate

symphysis

articulating bones are connected by wedge or pad of fibrocartilage

example: pubic symphysis

what’s a type of bony joint

synotosis

what type of joint is synotosis based on movement

synarthrosis

synotosis

totally rigid, immovable joint created when two bones fuse and the boundary between them disappears. example: the fusel of an infant’s left and right mandibular bones, epiphyseal lines, frontal suture

type of diarthrosis joint

synovial

synovial joints are surrounded by

joint capsule

joint capsule structure

2 layers: fibrous capsule layer, synovial membrane

fibrous capsule layer of the synovial joint capsule purpose

encases the joint

synovial membrane layer of the synovial joint capsule purpose

doesn’t cover articulating fibers, produces synovial fluid

articular cartilage structure

hyaline cartilage, left over from endochondral ossification, lacks a perichondrium, matrix containing more water than other hyaline cartilage

articular cartilage function

reduce friction within joint, separated by thin film of synovial fluid (preventing the articular cartilage on bone bones touching each other)

do synovial joints have articular cartilages?

yes

what are synovial joints filled with?

synovial fluid

synovial fluid structure

clear, vicious, sticky solution similar to interstitial fluid

synovial fluid function

lubrication, nutrient distribution, shock absorption

synovial fluid - lubrication

cartilage soaks up synovial fluid like a sponge. when the cavity is squeezed, it releases the fluid to reduce friction

synovial fluid - nutrient distribution

since cartilage is avascular synovial fluid circulates to provide nutrients and remove waste

synovial fluid - shock absorption

distributes fluid

synovial joint accessory structures

ligaments, tendons, menisci and fat pads, bursae, nerves and vessels

why are synovial joints weaker?

freely movable

why must synovial joints be stabilized?

movement outside of normal range can cause damage

joint stabilizer factors

articular surfaces, ligaments, muscle tone

how can menisci help stabilize a joint?

lock/unlock knee joint

ligaments

dense regular connective tissue that connects bone to bone. resists excessive extension and lateral rotation

damage to ligaments

if they’re stretched, they stay stretched. if too much force is applied they snap

muscle tone

muscles are always slightly contracted in living tissue. this doesn’t move the joint, but stabilizes it, keeping tension on the ligaments that are attached to the joint. why working out can stabilize joints

synovial joint classification factors

type of motion, range of motion

classes of synovial joints

gliding, hinge, condylar, saddle, pivot, ball and socket

gliding joint

flattened/slightly curved surfaces that slide across one another, but amount of movement is minimal

gliding joint example

between clavicle and manubrium

hinge joint

permit angular motion in a single plane, like the opening and closing of a door

hinge joint examples

elbow, knee, ankle, interphalangeal joints

condylar joint/ellipsoidal joint

oval articular face nestled within a depression on the opposing surface

condylar join examples

radiocarpal joint, metacarpophalangeal 2-5, metatarsophalangeal

pivot joint

only permit rotational movement

pivot joint examples

atlantoaxial joint, proximal radioulnar joint

ball and socket joint

round head within a cup-shaped depression. moves angularly, circumduction, rotation

ball and socket joint examples

shoulder, hip

types of movement

flexion, extension, hyperextension, dorsiflexion, plantarflexion, abduction, adduction, circumduction, rotational (internal and external), supination, pronation, inversion, eversion, protraction, retraction

flexion

bends joint and decreases angle of the joint

extension

bends joint and increases angle of the joint

hyperextension

extreme extension of the join beyond its normal straight position

flexion stance vs. extension stance

fetal postion vs anatomical position

dorsiflexion

moving toes/foot upward

plantarflexion

moving toes/foot downward (towards the plantar of the foot)

abduction

moves away from midline (think kidnapping/abduction)

adduction

moves toward midline (think ADDing to body)

circumduction

movement of ball and socket ointment in a circle without rotation (doesn’t change the angle of distal joints)

rotational

ball and socket joint. spinning around a single point. limited movement

internal rotation

rotation initiates at shoulder/hip and bone spins towards midline

external rotation

bone spins away from midline

supination

turns palms upwards (think super, superior)

pronation

turn palms downward

pronation/supination

rotation of the hand at the elbow due to the rotation of the radius

inversion

turning soles of feet medially

eversion

turning soles of feet laterally

protraction

move body part like the jaw forward

retraction

move body part like the jaw backward

elevate

push body part upwards (shrug shoulders)

depress

push body part downwards (open jaw)

3 articulations of the knee joint

2 between tibia and femur, one between patella and femur

where are the menisci located in the knee joint

between the tibia and femur

menisci function

cushion, stabilize

how is the knee joint stabilized?

quadriceps tendon, patellar ligament, popliteal ligament, lateral/medial collateral ligaments, anterior/posterior cruciate ligaments

quadriceps tendon

connects quad to patella

patellar ligament

connects patella to tibial tuberosity

popliteal ligament

back of knee, prevents overextension

lateral/medial collateral ligament

prevents from bowing out/in. attach to the condyles of tibia

anterior cruciate ligament

connects the posterior of the femur to the anterior tibia

posterior cruciate ligament

connects anterior femur to posterior tibia

what type of joint is the knee

hinge

how does the tibia rotate when knee joint fully extended?

it turns laterally, jamming the lateral meniscus between the tibia and fibula to lock the knee ointment in place and allow us to stand for long periods of time

how does the tibia rotate when the knee joint is flexed?

rotates medially, requires muscle contraction