THEA 101 Lecture Notes - Lecture 3: Flat Bone, Dental Alveolus, Trochlear Notch
Joints: Chapter 9
What is a joint?
Joint = Articulation = Arthrosis
Where 2 bones come together
If our bones were not connected via
joints, we would not be able to move
since bone is too stiff to bend
Functions:
Hold the skeleton together
Give us mobility
Joints are the WEAKEST part of the skeleton
Bones never contact one another directly
They are connected through some type of
connective tissue
Classification of Joints
Joints can be classified by FUNCTION and
STRUCTURE
Functional Classifications: based on the amount of joint
movement
Synarthoses : immovable joints
Diarthroses : freely moveable joints
Structural Classifications joining material and presence
of cavity
Fibrous : dense fibrous CT; no joint cavity
Cartilaginous : cartilage tissue; no joint cavity
Synovial : hyaline cartilage; synovial cavity
Ligaments and Tendons
Ligaments – dense regular connective tissue
structures that bind one bone to another
Tendons – dense regular connective tissue
structures that bind muscle to bone
Sprain – forcible wrenching of a joint that
stretches or tears a ligament without breaking the
bone
Strain – stretched or
Fibrous Joints
Joined by Dense Fibrous Connective Tissue
No joint cavity present
Most fibrous joints are immovable = synarthrotic
The length of the fiber determines its mobility
3 types
Sutures
Syndesmoses
Gomphoses
Sutures
Articulations of the skull bones
Synarthrotic
Joints held together by extremely short
interlocking fibers of dense irregular connective
tissue
Example: Coronal suture
Syndesmoses
Joint is connected by ligaments which vary in
length depending on the joint
synarthrotic
Example: Distal tibiofibular joint: synarthrotic
Gomphoses
Peg-in-socket joint found in the tooth socket
Synarthrotic
Cartilaginous Joints
Articulating bones are united with hyaline or
fibro- cartilage
No joint cavity present
Mostly synarthotic
2 types
Synchondrosis
Symphysis
Synchondrosis
United by a plate of hyaline cartilage
Synarthrotic
Examples: Epiphyseal plate in children,
Sternocostal joints
Symphysis
Articulating bone is covered with hyaline cartilage
that attaches to a fibrocartilage pad
Amphiarthrotic – slightly moveable
Examples: Intervertebral joints, Pubic symphysis,
Sternomanubrial joint
Syovial Joints
Bones are separated by a fluid-filled cavity =
synovial cavity
All are freely-moveable diarthrotic joints
Nearly ALL joints of the limbs are synovial joints
6 distinguishing features of synovial joints
1. Articular cartilage
2. Synovial (joint) cavity
3. Articular capsule
4. Synovial fluid
5. Reinforcing ligaments
6. Nerves and blood vessels
Articular Cartilage and Joint Cavity
Articular cartilage
Hyaline cartilage
Covers end of the bones
Absorb compression
Articular Capsule
2 layered capsule around the joint
External fibrous capsule
Continuous with periosteum
Internal synovial membrane
Covers all of internal joint surfaces not
lined by articular cartilage
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Articular Capsule and Synovial Fluid
Synovial cavity
Small potential space that contains
synovial fluid
Synovial Fluid
Viscous fluid of plasma filtrate produced
by the synovial membrane
Found in all of the free spaces in the joint
cavity
Reduces friction
Ligaments Nerves and Blood Vessels
Ligaments
Capsular Ligaments
Extracapsular Ligaments
Found outside the capsule
Intracapsular Ligaments
Found within the articular
capsule but still covered by
synovial membrane
Discs and menisci
Found within the articular
capsule but are not covered by
synovial membrane; only found
in some synovial joints
Nerve and Blood Supply
Nerve fibers
Detect pain, monitor joint position
(Proprioception) and stretch
Blood vessels supply the joint and produce the
synovial fluid
Movements of Synovial Joints
Bones serve as attachments for muscles
Muscle Origin: attached to the immoveable bone
Muscle Insertion: attached to the moveable bone
Contraction of muscle results in movement of the
Insertion towards the Origin
Movement is described in terms of directionality
Determined by the axis by which movement
occurs
Along the transverse, sagittal or horizontal
planes of the body
Range of Motion
Non-axial: no axial movement; slipping
movements
Bones are flat and do NOT move around
any axis (2-D movement)
Uni-axial: movement in 1 plane
Biaxial: movement in 2 planes
Multiaxial: movement in all 3 planes
Types of Movement
Gliding
Angular
Rotation
Special movements
Gliding Movement
Simplest of the Joint Movements
One flat bone slides past another without
angulation or rotation
Back and forth
Side to side
Occur at:
Intercarpal joints
Intertarsal joints
Angular Movement
Increase OR Decrease the Angle between 2
bones
Can occur in ANY plane
Movements
Flexion
Extension
Hyperextension
Abduction
Adduction
Circumduction
Usually movement in the Sagittal plane
Flexion
Decreases the angle of a joint
Brings the articulating bones closer
together
Extension
Increases the angle of a joint
Brings the articulating bone further apart
Hyperextension
Extending BEYOND the anatomical
position
Abduction
Movement of the limb away from the
midline
Movement in the Frontal plane
Adduction
Movement of the limb towards the
midline
Movement in the Frontal plane
Circumduction
Moving in a cone Point of the cone is
stationary
Consists of flexion, extension, abduction
and adduction
Rotation
Turning of a bone AROUND it’s own long axis
Only movement between the atlas and axis
Shoulder joint
Hip joint
Medial Rotation
Rotating toward the midline
Lateral Rotation
Rotating away from the midline
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Document Summary
Joint is connected by ligaments which vary in length depending on the joint. If our bones were not connected via joints, we would not be able to move since bone is too stiff to bend. Joints are the weakest part of the skeleton. They are connected through some type of connective tissue. Functional classifications: based on the amount of joint movement. Structural classifications joining material and presence of cavity. Fibrous : dense fibrous ct; no joint cavity. Cartilaginous : cartilage tissue; no joint cavity. Ligaments dense regular connective tissue structures that bind one bone to another. Tendons dense regular connective tissue structures that bind muscle to bone. Sprain forcible wrenching of a joint that stretches or tears a ligament without breaking the bone. Most fibrous joints are immovable = synarthrotic. The length of the fiber determines its mobility. Joints held together by extremely short interlocking fibers of dense irregular connective tissue. Peg-in-socket joint found in the tooth socket.
