Chapter 8 - Joints Flashcards
Joints
A. Definition – site where two or more bones come to meet
B. Functions – give skeleton mobility and they help hold the skeleton together
Classification of Joints: Functional
A. Functional classification – based on the amount of movement that’s allowed at the joint
1. Synarthroses – immovable joint (axial skeleton) 2. Amphiarthroses – slightly movable joint (axial skeleton) 3. Diarthroses – freely movable joints – they dominate in the limbs
Classification of Joints: Structural
Structural classification – focus on the material that binds the bones together and whether or not joint cavity is present
1. Fibrous joints – immovable; sutures – coronal, squamous, etc., joint between the tibia and fibula and tooth 2. Cartilaginous joints – rigid or slightly movable; nose 3. Synovial joints – freely movable joints; knee, shoulder and elbow
Fibrous Joints: Sutures
- Definition – seams that occur ONLY between bones of the skull
- Examples – sutures – interlocking wavy bone edges that are filled with short connective fibers
Fibrous Joints: Syndesmoses
- Definition – joint bones are connected exclusively by ligaments, chords or bands
- Examples – ligaments that connect the distal ends of the tibia and fibula
Fibrous Joints: Gomphoses
- Definition – peg in socket in fibrous joint
2. Example – articulation of a tooth with its bony alveolar socket
Cartilaginous Joints: Synchondroses
- Definition – junction of cartilage; bar or plate of hyaline cartilage units bones; they are synarthoritc
- Examples – epithelial plate (found in long bones) and the joint found in between costal cartilage and the first ribs
Cartilaginous Joints: Symphyses
- Definition – amphiartic – articular surface of the bones are cover with articular (hyaline cartilage) which are fused with an intervening pad or plate of fibrocartilage; main connecting material (is compressible and a shock absorber – so it allows minimal movement)
- Examples – intravertebrial discs and pubic symphysis
Synovial Joints
A. Synovial joint structure
1. Articular cartilage – glassy-smooth hyaline cartilage cover the opposing bones surfaces (absorbs compression and keep bone ends from being crushed
2. Joint cavity – potential space that contains a small amount of synovial fluid
3. Articular capsule – joint cavity is enclosed inside of this capsule
a. Fibrous capsule – external layer and it’s tough and it’s composed of dense irregular connective tissue; it’s continuous with the periostea (outer coving of bone) of the articulating bones
b. Synovial membrane – the inner layer and it’s composed of loose connective tissue
4. Synovial fluid – slippery fluid (lubricant) that occupies all the free space within the joint capsule
5. Reinforcing ligaments – band like ligaments; they’re the thickened part of the fibrous capsule
6. Articular discs – aka menisci – discs or wedges of fibrocartledge which separate the articulating surfaces of the bones and joints
Synovial Joint Movements
Every skeletal muscle is attached to bone or other connective tissue structures at two points (origin - attached to the immovable bone and incursion – attached to a movable bone) movement occurs when the muscle contracts across the joints and the incursion moves toward the origin (shrink)
Synovial Joint Movements: Gliding
a. Definition – simplest type of joint movement; when one flat bones (or nearly flat bone surface) glides or slips over another without noticeable angulations or rotation
b. Examples – intra-carpal and intra-tarsal joints and articular processes of the vertebrae
Synovial Joint Movements: Angular Movements - Flexion, Extension and Hyperextension
A. Definitions – movements that increase or decrease the angle between two bones
B. Examples – flexion – bending movement that decreases the angle of the joint (bending head forward onto the chest) extension – increasing the angle; straighten the flexed neck; hyperextension – excessive extension that’s beyond the anatomical position
Synovial Joint Movements: Angular Movements - Dorsiflexion and Plantar Flexion
A. Definitions – dorsiflexion – up movement at the ankle joint; plantar flexion – down movement at the ankle joint
B. Examples – dorsiflexion – toes pointed up and plantar extension; plantar flexion – toes pointed down and dorsal extension
Synovial Joint Movements: Angular Movements - Abduction and Adduction
A. Definitions – abduction – moving away is movement of a limp away from the midline or median plane of the body, along the frontal plane; adduction – moving toward is the movement of a limp toward the body midline or toward the midline of the hand or foot
B. Examples – abduction – away and adduction – moving toward
Synovial Joint Movements: Angular Movements - Circumduction
A. Definition – moving a limp so that it describes a cone in space; it involves adduction,
B. Examples – using a lot of muscles at once (winding up to throw)
