Joints/Articulations Part 1

Question 1

Joints

Answer 1

• also called articulations
• articulations are sites where 2+ bones meet
• articulations function to hold the skeleton together and allow movement

Question 2

2 Classifications of articulations

Answer 2

1. Structural: based on where a joint cavity is present and what material binds the joint
   - fibrous
   - cartilaginous
   - synovial
2. functional: based on what movement the joint allows
   - synarthroses: immovable joints
   - amphiarthroses: slightly moveable joints
   - diarthroses: freely moveable joints

Question 3

Fibrous Joints

Answer 3

• bones are joined by dense fibrous tissue
• no joint cavity is present
• most are immovable - dependent on the length of connective tissue fibers
  3 types:
• sutures
• syndesmoses
• gomphoses

Question 4

Sutures

Answer 4

• “seams”
• rigid interlocking joints of the skull
• allow for growth during youth
• ossify and fuse during middle age - create 1 solid unit that protects the brain
• closed, immovable sutures are referred to as synotoses “bony junctions”
• fibrous joint

Question 5

Syndesmoses

Answer 5

• bones are connected by ligaments or bands of fibrous tissue
• amount of movement varies because fiber length varies
• short fiber length: little/no movement (like inferior tibiofibular joint)
• longer fiber length = more movement (like the interosseous membrane)
• fibrous joint

Question 6

Gomphoses

Answer 6

• peg-in-socket fibrous joints
• “gompho” = nail/bolt
• ex: teeth in alveolar sockets
• fibrous connection = periodontal ligament

Question 7

Cartilaginous joints

Answer 7

bones are united by cartilage
- no joint cavity
- not highly moveable
- 2 types
* synchondroses
* symphyses

Question 8

Synchondroses

Answer 8

bones are united by a bar or plate of hyaline cartilage
- almost always synarthrotic (immoveable)
Ex:
- temporary epiphyseal plate joints - these become synotoses after plate closure
- cartilage of the 1st rib with manubrium of sternum
*cartilaginous joint

Question 9

Symphyses

Answer 9

bones are united by fibrocartilage
- hyaline cartilage is also present as articular cartilage
- symphyses are strong and amphiarthrotic (slightly moveable)
Ex:
- intervertebral joints
- pubic symphysis

Question 10

Clinical connection: herniated discs

Answer 10

• sudden or physical trauma to the spine can result in herniation of a disc
• herniated disc usually involves a rupture of the anulus fibrosus and protrusion of the spongy nucleus pulposus
• if the protrusion presses on the spinal cord or any of the spinal nerves, numbness and/or excruciating pain may occur
• in severe cases, surgical fixation is required

Question 11

Synovial Joints

Answer 11

Bones are separated by a fluid-filled joint cavity
- diarthrotic (freely moveable) and allow 1or more different types of movement
- include almost all joints in the extremities
- 6 general features and potentially bursae + tendon sheaths
- stability is influenced by 3 factors
- can be classified into 6 diff types

Question 12

6 General features of synovial joints

Answer 12

• articular cartilage
• joint cavity
• articular capsule
• synovial fluid
• reinforcing ligaments
• nerves + blood vessels

Question 13

Articular cartilage of synovial joints

Answer 13

hyaline cartilage covering the ends of the bones

Question 14

Joint cavity of synovial joints

Answer 14

small, fluid filled potential space

Question 15

Articular capsule of synovial joints

Answer 15

two layered joint covering
- External fibrous layer: made of dense, irregular connective tissue; continuous with periostea
- Synovial membrane: loose connective tissue that produces synovial fluid

Question 16

Synovial fluid of the synovial joints

Answer 16

viscous filtrate of plasma + hyaluronic acid that occupies the joint space - lubricates / nourishes articular cartilage, contains phagocytic cells to remove microbes + debris

Question 17

Reinforcing ligaments of the synovial joitns

Answer 17

• capsular: thickened part of fibrous layer
• extracapsular: outside the capsule
• intracapsular: deep to capsule, covered by synovial membrane

Question 18

Nerves + blood vessels of the synovial joints

Answer 18

nerves to detect pain, joint position, and stretch; capillary beds to supply filtrate for synovial fluid

Question 19

2 Additional features of synovial joints

Answer 19

• Fatty pads: cushioning between the fibrous and synovial layers of the joint capsule
• Articular discs: fibrocartilage wedges or discs that separates articular surfaces to improve fit, stabilize the joint, and reduce wear/tear

Question 20

Double Jointed

Answer 20

have the same amount of joints
- have joint capsules and ligaments that are more flexible/stretchy than average

Question 21

Bursae and Tendon sheath

Answer 21

bags of synovial fluid that act as lubricating “ball bearings” - not strictly part of synovial joints

Question 22

Bursae

Answer 22

reduce friction where ligaments, muscles, skin, tendons, or bones rub together

Question 23

Tendon Sheath

Answer 23

elongated bursae wrapped completely around the tendons subjected to friction

Question 24

Clinical Connection: Carpal Bones

Answer 24

• the carpal bones are arranged to be concave on the anterior side
• a ligament roofs over this concavity - forming the carpal tunnel
• several long muscle tendons and the median nerve travel through this tunnel
• overuse/inflammation of the muscles can cause irritation of the median nerve - tingling numbness, and pain in the hand

Question 25

Factors Influencing Joint Stability

Answer 25

• Shape of articular surface: shallow joint surfaces are less stable than ball-and-socket
• Number and location of ligaments: more ligaments = stronger joint
• muscle tone: low levels of contractile activity in relaxed muscles - keeps tendons taut as they cross joints

Question 26

Movements Allowed by Synovial Joints

Answer 26

All muscles attach to bone or connective tissue at no fewer than 2 points
- origin: attachment to immoveable bone
- insertion attachment to moveable bone
Muscle contraction causes the insertion to move towards the origin
* movements occur along the transverse, frontal/coronal, and sagittal planes

Question 27

Movements allowed by synovial joints

Answer 27

Range of motion
- nonaxial: slipping movements only
- uniaxial: movement in 1 plane
- biaxial: movement in 2 planes
- multiaxial: movement in/around all 3 planes

Three general types of movements
- gliding
- angular movements
- rotation

Question 28

Gliding movements

Answer 28

one flat bone surface glides or slips over another similar surface; no appreciable angulation or rotation
Examples:
- intercarpal joints
- intertarsal joints
- facet joints of the vertebrae

Question 29

Angular movements

Answer 29

increase or decrease in angle between 2 bones
- angular movements in the sagittal plane include:
- flexion
- extension
- hyperextension

Question 30

flexion

Answer 30

decreases in the angle of the joint
(angular movement in the sagittal plane)

Question 31

extension

Answer 31

increases the angle of the joint
(angular movement in the sagittal plane)

Question 32

hyperextension

Answer 32

movement beyond the anatomical position
(angular movement in the sagittal plane)

Question 33

Angular movements on the frontal/coronal plane

Answer 33

• abduction: movement away from the midline
• adduction: movement toward midline

Question 34

Circumduction

Answer 34

movement that involves flexion, abduction, extension, and adduction of a limb - moving limb creates an imaginary cone in a space