Articulations and Joint Classifications Quiz

Articulations

• Articulations are the points where two bones connect.
• Articulations can be classified structurally as fibrous, cartilaginous or synovial.
• Articulations can be classified functionally based on their degree of motion as synarthroses, amphiarthroses or diarthroses.

Structural Classification of Joints

• Fibrous joints are united by fibrous connective tissue.
  • Subclasses are sutures, syndesmosis and gomphoses.
• Cartilaginous joints are united by means of cartilage.
  • Subclasses are synchondroses and symphysis.
• Synovial joints are joined by a fluid cavity.
  • Most joints of the appendicular skeleton.

Functional Classification of Joints

• Synarthroses are non-movable joints.
  • An example is the skull bone articulations.
• Amphiarthroses are slightly movable joints.
  • An example is between vertebrae.
• Diarthroses are freely movable joints.
  • Examples are knee elbow, and wrist articulations.

Bone Cells

• Osteoblasts are responsible for the formation of new bone and repair.
  • Osteoblasts produce collagen and proteoglycans.
  • Osteoblast secrete high concentrations of calcium and phosphate ions, forming crystals called hydroxyapatite.
  • The formation of new bone by osteoblasts is called ossification.
• Osteocytes maintain bone matrix and are formed osteoblasts after bone matrix has surrounded them.
  • Osteocytes account for 90-95% of bone cells and are long-lived.
  • Osteocyte cell bodies are housed in spaces called lacunae.
  • Osteocyte cell extensions are housed in narrow, long spaces called canaliculi.
• Osteoclasts are bone-destroying cells.
  • Osteoclasts contribute to bone repair and remodeling by removing existing bone, called bone reabsorption.
  • Bone breakdown is important for mobilizing calcium.
  • As bone is broken down, the calcium goes into the blood.

Spongy and Compact Bone

• Mature bone is called lamellar bone.
  • Lamellar bone is organized into thin concentric sheets called lamellae.
• Bone can be classified according to the amount of bone matrix relative to the amount of space within the bone.
  • Spongy bone has less bone matrix and more space than compact bone.
  • Compact bone has more bone matrix and less space.

Cranial Sutures

• The cranial bones are connected by immovable joints called sutures.
• There are four principal sutures:
  • Coronal
  • Sagittal
  • Lambdoid
  • Squamous

Cranial Bones

• Frontal bone is the anterior part of the cranium (forehead).
• Parietal bones compose the sides and roof of the cranium.
• Occipital bone compose the posterior portion and floor of the cranium.
• Temporal bones are inferior to the parietal bones on each side of the cranium.
  • Temporomandibular joint
• Sphenoid bone forms part of the cranium floor, lateral posterior portions of the eye orbits, and lateral portions of the cranium anterior to temporal bones.
  • Sella Turcica.
• Ethmoid bone is the anterior portion of the cranium, including the medial surface of the eye orbit and roof of the nasal cavity.
  • Nasal conchae

Facial Bones

• Maxillae form the upper jaw, anterior portion of the hard palate, part of lateral walls of nasal cavity, and the floors of the eye orbits.
  • Maxillary sinus.
• Palatine bones form the posterior portion of the hard palate and the lateral wall of the nasal cavity.
• Zygomatic bones are the cheek bones.
  • They form the floor and lateral wall of each eye orbit.
• Lacrimal bones are on the medial surfaces of the eye orbits.
• Nasal bones form the bridge of the nose.
• Vomer is in the midline of the nasal cavity.
  • It forms the nasal septum with the ethmoid bone.
• Inferior nasal conchae are attached to the lateral walls of the nasal cavity.
• Mandible is the lower jawbone.
  • It is the only movable skull bone.

Vertebral Column

• It is formed by 26 bones.
• The vertebral column is divided into five main regions:
  • 7 cervical vertebrae.
  • 12 thoracic vertebrae.
  • 5 lumbar vertebrae.
  • 1 sacrum.
  • 1 coccyx.
• Atlas is the first vertebra and holds the head.
• Axis is the second vertebra and rotates the head.

Function of the Vertebral Column

• Supports body weight.
• Protects the spinal cord.
• Allows spinal nerves to exit the spinal cord.
• Provides a site for muscle attachment.
• Provides movement of the head and trunk.

Sacrum

• Formed by 5 fused vertebrae.

Types of Synovial Joints

• Plane joints:
  • Intervertebral joints between articular processes of adjacent vertebrae.
  • Acromioclavicular joints between the acromion process of the scapula and clavicle.
  • Carpometacarpal joints between carpals and metacarpals 2-5.
  • Costovertebral joints between ribs and vertebrae.
  • Intercarpal joints between carpal bones.
  • Intermetatarsal joints between metatarsal bones.
  • Intertarsal joints between tarsal bones.
  • Sacroiliac joints between sacrum and hip bone (complex joint with several planes and synchondroses).
  • Tarsometatarsal joints between tarsal bones and metatarsal bones.
• Saddle joints:
  • Carpometacapal pollicis between carpal and metacarpal of thumb
  • Sternoclavicular between manubrium of sternum and clavicle
• Hinge joints:
  • Cubital (elbow) between humerus, ulna, and radius.
  • Knee between femur and tibia.
  • Interphalangeal between phalanges.
  • Talocrural (ankle) between talus, tibia, and fibula.