Anatomy Joint unit

structural and functional

What are the two classifications of joints?

structural

Classification of joint that relies on anatomy of the joint

functional

Classification of joint that is based on the amount of movement possible (range of motion)

fibrous, cartilaginous, bony, synovial

types of structural joints

synarthrosis, amphiarthrosis, diarthrosis

types of functional joints

synarthrosis

an immovable joint which can be fibrous or cartilaginous depending on the connection of the bones formed by the joint

amphiarthrosis

a slightly moveable joint which can be fibrous or cartilaginous depending on the connection formed by the bone

diarthrosis

a freely movable joint which is subdivided functionally according to their planes of movement

suture

(fibrous synarthrosis) joint located between the bones of the skull. The edges of bones are interlocked at the suture

gomphosis

(fibrous synarthrosis) binds teeth to bony sockets in the maxilla and mandible

synchondrosis

(cartilaginous synarthrosis) a bridge between two articulating bones

synostosis

(bony synarthrosis) an immovable joint created when two bones fuse and the boundary between them disappears

syndesmosis

(fibrous amphiarthrosis) bones connected by a ligament

symphysis

(cartilaginous amphiarthrosis) bones connected by a wedge of fibrocartilage

synovial

(diarthrosis) permits a wider range of motion than other joints do

articular capsule

a two layered joint capsule that surrounds a synovial joint

synovial membrane and fibrous capsule

what two things are in an articular capsule

articular cartilage

- cartilage that covers articulating surfaces
- has no periochondrium and watery matrix
- surface is slick & smooth

synovial fluid

clear, viscous solution with an egg yolk like consistency

lubrication, nutrient distribution, shock absorption

3 functions of synovial fluid

lubrication

when cartilage is compressed synovial fluid goes into the space between surfaces to reduce friction between moving surfaces. when compression stops the fluid is pulled back

nutrient distribution

the synovial fluid circulates continuously to provide nutrients and act as a waste removal route for the chondrocytes of cartilage.

shock absorption

synovial fluid cushions joints that are subjected to compression from shocks and sudden impacts (fluid amount increases as pressure increases)

meniscus

fibrocartilage pad located between opposing bones w/ synovial joints
function: subdivide a synovial cavity, channel flow of fluid, and allow variation of shapes.

fat pads

localized masses of adipose tissue covered by a layer of synovial membrane
function: protect articular cartilage and act as packing material for the joint

ligaments

localized thickenings that support, strengthen, and reinforce synovial joints

intracapsular and extracapsular

2 types of ligaments

intracapsular ligament

ligament located inside the joint capsule

extracapsular ligament

ligament located outside the joint capsule

tendons

not part of the joint but connect the fleshy part of muscle to the bones that make up a joint

bursae

small, thin, fluid-filled pockets in connective tissue that reduce friction and act as shock absorbers, they contain synovial fluid and lined by synovial membrane

synovial tendons sheaths

tubular bursae that surround tendons where they cross bony surfaces

adventitious bursae

bursae that develop in abnormal locations because of abnormal stresses

factors that stabilize synovial joints

- collagen fibers of the joint capsule and any accessory
- shapes of the articulating surfaces and menisci which prevent movement
- the presence of other bones, skeletal muscles or fat pads around the joint
- tensions in tendons attached to the articulating bones