Synovial Joints - General Structure

What are synovial joints

Joints in which the articulating bones are separated by a fluid-containing joint cavity

What does the joint cavity permit in synovial joints

Lots of movement

What functional type of joints are synovial joints

Diarthroses

Where can synovial joints be found

Nearly all joints of the limbs, most joints of the body

What are the six distinguishable features of synovial joints

Articulate cartilage, joint cavity, articular capsule, synovial fluid, reinforcing ligaments, and nerves/blood vessels

Describe articular cartilage in regards to synovial joints

The smooth hyaline cartilage that covers the ends of bones; these thin cushions help to absorb compression placed on the joint, thereby keeping the bone ends from being crushed

What is the joint cavity in synovial joints

it is unique to synovial joints. It is the potential space between articulating bones. It is nearly nonexistent, but can expand if fluid accumulates or during inflammation

describe the articular capsule

AKA the joint capsule; A two layered capsule that encloses the joint cavity. There is a tough external fibrous layer and an inner synovial membrane layer. it covers all internal joint surfaces not covered by hyaline cartilage.

What is the outer, fibrous layer of the articular capsule made of

DICT, it is continuous with the periostea of articulating bones

What is the inner layer of the articular capsule made of

synovial membrane; loose CT

What is the function of the synovial membrane

Make synovial fluids

What is synovial fluid

A slippery lubricant in joint capsule that covers all free spaces

What is synovial fluid derived from

Blood

Describe synovial fluid (what is looks like/consistency)

It is a viscous, egg-white consistency due to hyaluronic acid secreted by the cells in the synovial membrane. It becomes less viscous during joint activity

What is the function of synovial fluid

Provides a slippery, weight-bearing film that reduces friction between the cartilages

What would happen without synovial fluid

Rubbing away due to friction would wear away joint surfaces and excessive friction would overheat and destroy the joint tissues

What happens when a synovial joint is under pressure

Synovial fluid is forced from the cartilages. When pressure is relieved, it seeps back into the articulate cartilages, like a sponge.

What is weeping lubrication

pressure on joints squeezes synovial fluid into and out of articular cartilage; this also nourishes cells

What cells does synovial fluid have and what do they do

They have phagocytosis cells that rid the joint cavity of microbes and foreign substances

What are the reinforcing ligaments of synovial joints

capsular, extracapsular, intracapsular

What are capsular ligaments in synovial joints

Thickened parts of the fibrous layer of the joint capsule

Where can extracapsular ligaments be found in synovial joints

Outside of the joint capsule

Where are intracapsular ligaments found in synovial joints

Deep to the capsule, covered in the synovial membrane

What does it mean when someone is double jointed

Their joint capsules and ligaments are extra stretchy and loose

Do synovial joints have nerves

Yes, they are richly supplied with sensory nerve fibers that innervate the capsule

What do the nerve fibers in synovial joints do

Some monitor pain, most monitor joint position and stretch which help the nervous system monitor posture

Do synovial joints have blood vessels

Yes, they are richly supplies with blood vessels. They supply the synovial membrane

What is special about the hip and knee joints

They have Cushioning, fatty pads between the fibrous layer and synovial membrane or bone

What divides the synovial capsule in two, either completely or partially

Meniscus or articular discs

What do articular discs do

modify articular surfaces to stabilize joint; improves the fit between articulating bone ends to make them more stable and reduce wear and tear