1B Joints and Cartilage

skeletal system components

bones

cartilage

ligaments

skeletal system functions

support the framework of the body

protection - shields vital organs from injury

force translation - bones work with muscles and joints to produce movement

blood cell production - bone marrow is found inside certain bones and produces blood cells

mineral storage

types of cartilage

elastic cartilage

hyaline cartilage

fibrocartilage

elastic cartilage

specialized tissue with many elastic fibers

both flexible and strong to maintain structure shape, able to bend and return back to its original shape

where is elastic cartilage found

epiglottis - small flap in your throat that returns to shape everytime you swallow

auricle (external ear) - visble part of your ear that makes it flexible

laryngeal cartilages - cartilage in your larynx (voice box) that move during speech and swallowing

hyaline cartilage

most abundant found in the body

weakest cartilage type

smooth surface for gliding, flexibility, support, friction reduction

viscoselastic connective tissue (behaves both as an solid and fluid depending on the force applied)

spreads body weight across more of the surface to stablize stress on certain joints

where is hyaline cartilage found

Articular cartilage - covers the ends of bones inside synovial joints to allow bones to slide smoothly over each other and reduces friction

Trachea/bronchi - windpipe made of c-shaped rings of cartilage to keep airways open

Epiphyseal plate - found near the ends of long bones in children/teens to allow bones to grow longer, hardens into bone once growth stops in adulthood

fibrocartilage

durable for joint support and cushioning

shock-absorber

high amount of collagen

found in symphysis joints, often need to withstand large forces

where is fibrocartilage found

intervertebral discs - soft, pad-like discs between the bones of your spine, prevents vertebrae from grinding together during movement

pubic symphysis - connects the left and right sides of the pelvis from the front, allows for a small amount of movement but mainly for stability

menisci (knee meniscus) - two crescent shape pads in each knee to protect the knee joint from wear and injury

Chondrocyte

found in all types of cartilage

mature cartilage cell that produces and maintains the cartilage matrix (collegen + elastic fibers)

Why is hyaline cartilage also called articular cartilage?

it covers the articular surfaces of bones (where they touch when forming a joint) in synovial joints

different of synovial and synchondrosis joints where hyaline cartilage is located

synovial:

• bones are not directly connected

• has a joint cavity (gap between the non-connecting bones)

• joints used for moving freely

synchondrosis:

• bones are directly connected

• no joint cavity

• little to no movement

• joints used for growth or stability

avascular

all types of cartilage has no blood vessels, lymph vessels, and nerves

cartilage doesn’t get nutrients or oxygen from blood

Femoral condyles

rounded ends of the thigh bone at the knee

coated with a smooth layer of hyaline cartilage

What happens to hyaline (articular) cartilage when a joint is loaded (force/weight is applied) and then unloaded (release of force/weight)?

When the joint is loaded, pressure pushes fluid out of the cartilage into the synovial cavity.

When the pressure is released, fresh synovial fluid containing nutrients flows back into the cartilage.

Nutrient and waste exchange happens via synovial fluid:

• superfical zone spreads the load sideways

• middle zone holds the fluid that gets unloaded and loaded

• deep zone anchors cartilage to bone so it doesn’t slide off from pressure

interstitial fluid

60-80% of water contains lipids and electrolytes

found in all types of cartilage in all tissues

types of arthritis

Osteoarthritis (OA) and Rheumatoid arthritis (RA)

what does a healthy joint look like (before arthritis)

Osteoarthritis (OA)

most common type of arthritis

gradual loss of cartilage from “wear and tear”

common causes of hip and knee replacements

Rheumatoid arthritis (RA)

autoimmune disease

inflammation of synovial cavity and cartilage decreases your mobility over time

eventually cartilage degrades and leads to exposed bone ends

nutrient change issues

classifying synovial joints by how many directions they can move

More movement = less stability
Less movement = more stability

uniaxial (moves one direction), biaxial (moves in two directions), multiaxial (moves in many directions)

uniaxial

hinge - back and forth

pivot - rotation around one axis

very stable, limited movement

Biaxial

Planar (gliding) - sliding

saddle - back-forth, side-side

condyloid (ellipsoid) - two directions + cirsumduction

moderate stability, moderate range of movement

multiaxial

ball-and-socket - rotation, bending, straightening, abduction (moving away from the midline), adduction (moving toward the midline)

most movement, least stable

Factors contributing to range of motion

shape and arrangement of articulating surfaces - tight fit = less movement, loose fit = more movement

ligaments crossing the joint - ligaments are strong bands that limit how far a joint can move, more/tighter ligaments = less movements

surronding muscles - muscles around a joint hold it in place when they contract during movement

its a balancing act to maximize function when limiting chances of injury by increasing stability, you cannot have both extremes at the same time

ligament sprains

torn ligaments are called sprains

Grade 1:

• Stretching or slight tearing

Grade 2:

• Incomplete tear

Grade 3:

• Complete tear

• needs immediate surgery

PRICE procedure for sprains

what to do when you get a grade 1 or 2 sprain:

Protection

Rest

Ice

Compression

Elevation

components of the muscular system

muscle

tendons/aponeuroses

motor unit (motor neuron + all the muscle fibers it controls)

muscular system functions

Skeletal movement

Maintaining posture and position

Opening and closing of orifices (openings in the body)

Maintaining homeostasis

types of muscle

skeletal, cardiac, smoth muscle

skeletal muscle features

Striated muscles with myosin and actin proteins

striped looking pattern because the two proteins are arranged in a repeating pattern that slide past each other to cause muscle contraction

Under voluntary control

cardiac muscle features

Found in the heart

Striated muscle with actin and myosin, same as skeletal muscles

Involuntary control

smooth muscle features

Found in viscera (internal organs inside your chest or abdomen), blood vessels, skin

Not striated because actin and myosin are arranged randomly, no repeating pattern

Under involuntary control

myocte

muscle cell

the three muscle types contains different myocytes that are different structures so they can carry out specific functions

basic muscle properties found in all muscle types

Electrical excitability - can respond to two kinds of signals

• Electrical signals used in the heart for heartbeats

• Chemical signals used in neuromuscular cleft (gap at the connection point between nerve and muscle) for muscle contraction

Contractility

• Muscle contraction/shortening produces force

• In skeletal muscles this force pulls on bones through tendons to create movement

Extensibility

• Can stretch/lengthen (to an extent) without damage

Elasticity

• Returns to its original length after contraction (shortening) or

extension (lengthening)

• Greatest elasticity in smooth muscle

Fascia

connective tissue that surrounds muscles

contains the blood vessels and nerves needed to supply the muscle for control and activation

helps increase force by limiting how much the muscle expands outwards during contraction, allowing more force to be transferred to bone movement

sacromere

smallest unit of muscle contraction where actin (thin filament) and myosin (thick filament) interact to create force

muscle is always trying to shorten but sometimes it does not succeed due to the force not being able to overcome the load

concentric contraction

muscle shorten when actin and myosin come together

lighter load, muscle wins

eccentric contraction

muscle lengthen when actin and myosin move apart

heavy load or gravity wins, muscle loses and is forced to lengthen even though it’s active in function

single motor unit

one neuron and all its muscle fibers that it innervates (connects and controls)

several motor units are required to innervate an entire muscle

contralateral control

when the left side of your brain controls the right side of your body and vise versa

origin used for skeletal muscles

the attachment that has minimal movement or doesn’t move at all, acting as an anchor

usually closer to the body’s center, proximal

insertion used for skeletal muscles

the attachment that does move

usually father from the body’s center, distal

gets pulled toward the origin during muscle contraction, muscles cannot push

the farther a muslce attaches from a joint, it is easier for that muscle to move the joint and produce more force

phasic contractions

short, temporary muscle contractions that are on and off

used for movement and typical in skeletal muscles

can be isometric or isotonic contractions

isometric contractions

muscle contraction produces force to support the load but doesn’t shorten

no movement

actin and myosin still try to slide, but they do not manage to actually move past each other and sacromere length stays the same

isotonic contractions

includes concentric (shortening) and eccentric (lengthening) contractions

concentric: actin and myosin slide past each other, sarcomere shortens

eccentric: actin and myosin try to interact but external force is stronger and pulled away despite resistance

agonist muscle

the main muscle that produces a movement by contracting concentrically

antagonist muscle

the muscle that opposes and controls the agonist by contracting eccentrically

helps control the movement being produced by the agonist to prevent uncontrolled or rapid movement

synergist muscle

muscle that assists the agonist muscle by adding additional force or stabilizing the movement

usually contracting concentrically

muscle atrophy

progressive muscle loss that happens to everyone starting from ~age 30 and onward, less power and strength

gradual, but will acclerate if you don’t constantly use your muscle

muscle mass is replaced with fibrous connective tissue that’s non-contractile and adipose (fat)

caused by loss of motor neurons that activate muscle fibers, slower conduction speeds where nerve signals travel more slowly, and a loss of muscle fibers

benefits of excerise

increases neuron firing rate of how often it sends electrical signals, muscle mass which slows down muscle atrophy, and bone density

cardiovascular, pulmonary and neuron benefits

makes the musculoskeletal system more effective and resilent to injury

muscle strains grades

Grade 1:

• Stretching or slight tearing

Grade 2:

• Incomplete tear

Grade 3:

• Complete tear

• Doesn’t always require surgery

• aggressive physiotherapy can have equal or better outcomes than surgery

recovery process for muscle strains

Protection

Rest

Ice

Compression

Elevation