Types of Synovial Joints

Joint Structure and Types

• A joint is covered by an articular capsule and lined by a synovial membrane, except on the articular surfaces.
• The joint cavity may be divided by an articular disc of cartilage (e.g., knee and TMJ joints).
• Joints are connected by ligaments and have a wide range of movement.

Synovial Joints

• Classified into three types based on the axis of movement:
  • Uniaxial joints (one axis, two movements):
• Hinge joints (transverse axis, e.g., elbow and inter-phalangeal joints)
• Pivot joints (vertical axis, e.g., radio-ulnar joints)
  • Biaxial joints (two axes, three movements):
• Condylar joints (e.g., knee and temporomandibular joints)
• Ellipsoid joints (e.g., wrist joint)
• Saddle joints (e.g., carpo-metacarpal joint of the thumb)
  • Multiaxial joints (more than two axes, more free mobility):
• Ball and socket joints (e.g., shoulder and hip joints)
• Plane joints (e.g., intercarpal and intertarsal joints)

Synovial Joint Characteristics

• Articular surfaces are covered by hyaline cartilage.
• There is a joint cavity.

Movements at Synovial Joints

• Gliding movement: one surface glides over the other (e.g., plane joints).
• Angular movement:
• Flexion and extension (around transverse axis)
• Abduction and adduction (around antero-posterior axis)
• Rotation movement: rotation around a longitudinal axis.
• Circumduction: a combination of all movements in sequence.

Arterial Supply of Long Bones

• Periosteal arteries: branches from periosteum to compact bone.
• Nutrient artery: enters the shaft through the nutrient foramen and divides into upper and lower branches.
• Epiphyseal artery: supplies the end of the bone.
• Metaphyseal artery: supplies the junction between the shaft and the end of the bone.

Fibrous Joints

• Characters:
• Fibrous tissue between articulating bones.
• No joint cavity.
• No movement.
• Types:
• Suture (e.g., skull bones).
• Gomphosis (e.g., tooth in mandible).
• Syndesmosis (e.g., inferior tibiofibular joint).

Cartilaginous Joints

• Characters:
• Cartilaginous tissue between articulating bones.
• No joint cavity.
• Very limited or no movement.
• Types:
• Primary (temporary, no movement, e.g., epiphyseal plate of cartilage).
• Secondary (permanent, minimal movement, e.g., intervertebral disc, symphysis pubis).

Skeletal Muscles

• Classified based on the direction of muscle fibers to the line of pull:
  • Muscles with fibers parallel to the line of pull:
• Strap-like.
• Fusiform.
• Quadrilateral.
  • Muscles with fibers oblique to the line of pull:
• Pinnate: - Unipinnate. - Bipinnate. - Multipinnate. - Circumpinnate.
• Non-pinnate: - Triangular. - Circular.

Muscle Tissue

• Consists of elongated cells specialized to respond to stimulation by contracting.
• Three histological types: skeletal, cardiac, and smooth muscle, differing in appearance, physiology, and function.