Chapter 9: Articulations (Joints)

Joint (articulation)

•any point where two bones meet, whether or not the bones are movable at that interface

Arthrology

science of joint structure, function, and dysfunction

Kinesiology

study of musculoskeletal movement

-A branch of biomechanics, which deals with a broad variety of movements and mechanical processes

There are many different types of joints; we will discuss the following 3:

-Fibrous joints

-Cartilaginous joints

-Synovial joints

Fibrous Joint

adjacent bones are bound by collagen fibers that emerge from one bone and penetrate into the other

Other terms for fibrous joint

synarthrosis or synarthrodial joint)

3 types of fibrous joints

-Sutures (i.e., in skull)

-Gomphoses (i.e., tooth socket)

-Syndesmosis (eg., radio-ulnar, tibio-fibular)

sutures (fibrous joints)

immobile or slightly mobile fibrous joints in which short collagen fibers bind the bones of the skull to each other

Gomphosis (fibrous joint)

attachment of a tooth to its socket

- attached via short connective tissue fibers

Syndesmosis (fibrous joint)

a fibrous joint at which two bones are bound by long collagen fibers

Other terms for Cartilaginous joint

amphiarthrosis or amphiarthrodial joint

cartilaginous joint

two bones are linked by cartilage

-Examples include pubic symphysis and intervertebral discs

pubic symphysis

joins right and left pubic bones with interpubic disc

Bodies of vertebrae joined by ________

intervertebral discs

Synovial joint

joint in which two bones are separated by a joint cavity

Other terms for synovial joint

diarthrosis, or diarthrodial joint

what feature of synovial joints makes them important to quality of life?

their mobility

articular cartilage

layer of hyaline cartilage that covers the facing surfaces of two bones

Joint cavity

separates articular surfaces

outer fibrous capsule

continuous with periosteum of adjoining bones

inner, cellular, synovial membrane

composed mainly of fibroblast-like cells that secrete synovial fluid and macrophages that remove debris from the joint cavity

synovial fluid

slippery lubricant in joint cavity

Purpose of synovial fluid

- Rich in albumin and hyaluronic acid

- Nourishes articular cartilage and removes waste

- Makes movement of synovial joints almost friction free

Joint (articular) Capsule

connective tissue that encloses the cavity and retains the fluid

In a few synovial joints, _________ grows inward from the joint capsule, forming a ___________.

*fibrocartilage

*meniscus

Meniscus (specialized synovial joint)

-Moon-shaped fibrocartilage in knee

-These cartilages absorb shock and pressure

-Guide bones across each other and improve their fit together

-Stabilize the joints, reducing the chance of dislocation

Tendon

strip of collagenous tissue attaching muscle to bone

Ligament

strip of collagenous tissue attaching one bone to another

Bursa

fibrous sac filled with synovial fluid, located between muscles, where tendons pass over bone, or between bone and skin

How does exercise affect synovial fluid?

It warms the synovial fluid, making it less viscous and more easily absorbed by cartilage.

What happens after exercise causes synovial fluid to warm up?

Cartilage then swells and provides a more effective cushion.

What is the result of repetitive compression of nonvascular cartilage during exercise?

Fluid and metabolic waste is squeezed out of the cartilage.

what happens to cartilage when weight is removed after exercise?

cartilage absorbs synovial fluid like a sponge taking in oxygen and nutrients to the chondrocytes

What happens to cartilage without exercise?

it deteriorates more rapidly from inadequate nutrition and waste removal

Muscles attach to bones via _________.

tendons

To allow movement, muscles MUST.....

Cross one or more joints

Muscles actively ________ and passively ________.

shorten, lengthen

- They cannot exert force by lengthening

Long bones act as levers to enhance what?

the speed or power of limb movements

Lever

any elongated, rigid object that rotates around a fixed point called a fulcrum

•Two kinds of advantage conferred by a lever

- exerting more force

- moving the resisting object farther or faster. Ex: movement of a rowing boat

Mechanical advantage (MA) of a lever

the ratio of its output force to its input force

arthritis

a broad term for pain and inflammation of a joint

Osteoarthritis (OA)

most common form of arthritis

-"Wear-and-tear arthritis"

Rheumatoid Arthritis (RA)

-This is an autoimmune disease, in which the immune system attacks the joints.