Skeletal System: Bones, Joints, and Articulations Study Guide

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The thoracic cage protects vital organs and supports the upper body. It consists of the ribs, sternum, and thoracic vertebrae.

True Ribs vs. False Ribs: True ribs (pairs 1-7) attach directly to the sternum via costal cartilage. False ribs (pairs 8-12) either attach indirectly or not at all; floating ribs (pairs 11-12) are a subset of false ribs and do not attach to the sternum.
Function: Protects the heart and lungs, supports breathing movements.

The skull houses and protects the brain and sensory organs. It is composed of cranial and facial bones.

Cranial Bones: Include the frontal, parietal, occipital, temporal, sphenoid, and ethmoid bones.
Facial Bones: Include the maxilla, mandible, zygomatic, nasal, lacrimal, palatine, inferior nasal concha, and vomer.
Special Structures: Auditory ossicles (malleus, incus, stapes) are found in the middle ear and are essential for hearing. Sinuses are air-filled cavities that reduce skull weight and affect voice resonance.
Joints of the Skull: Sutures are immovable joints between skull bones. Other joints include the temporomandibular joint (TMJ), which allows movement of the jaw.
Clinical Conditions: Common conditions include cranial trauma, TMJ syndrome, mastoiditis.

The shoulder girdle connects the upper limb to the trunk and allows a wide range of motion.

Main Bones: Clavicle and scapula.
Function: Provides attachment for muscles and supports arm movement.
Clinical Relevance: "Funny bone" refers to the ulnar nerve, which can be compressed at the elbow, causing tingling or pain.

The elbow is a hinge joint formed by the humerus, radius, and ulna.

The pelvic girdle supports the weight of the upper body and protects pelvic organs.

Main Bones: Ilium, ischium, and pubis.
Function: Transfers weight from the axial skeleton to the lower limbs.
Comparison: Male pelvis is generally narrower and deeper; female pelvis is wider and shallower to accommodate childbirth.

Long bones grow via endochondral ossification at the epiphyseal plates.

Epiphyseal Plate: Region of cartilage where bone growth occurs in children and adolescents.
Clinical Relevance: Injury to the plate can affect bone growth.

Bone Anatomy: Diaphysis (shaft), epiphysis (ends), metaphysis (growth region), medullary cavity (contains marrow).
Bone Tissue: Compact bone (dense), spongy bone (porous).
Support and Protection: Bones provide structure, protect organs, and serve as levers for movement.

Joints (articulations) are classified by their structure and function.

Synarthroses: Immovable joints (e.g., sutures in the skull).
Amphiarthroses: Slightly movable joints (e.g., intervertebral discs).
Diarthroses (Synovial Joints): Freely movable joints (e.g., shoulder, knee).

Synovial joints are the most common and allow a wide range of movements.

Structure: Articular cartilage, joint cavity filled with synovial fluid, joint capsule, ligaments.
Types of Movement: Flexion, extension, abduction, adduction, rotation, circumduction.
Examples: Shoulder (ball-and-socket), elbow (hinge), wrist (condyloid).
Clinical Relevance: Damage to articular cartilage can lead to arthritis.

Common Injuries: Sprains (ligament injury), dislocations (bone displacement), strains (muscle/tendon injury).
Disorders: Osteoarthritis (degeneration of cartilage), rheumatoid arthritis (autoimmune inflammation).

Flexion vs. Extension: Flexion decreases the angle between bones; extension increases it.
Plantarflexion vs. Dorsiflexion: Plantarflexion points the foot downward; dorsiflexion raises the foot upward.
Other Movements: Abduction, adduction, rotation, circumduction.

Additional info: Academic context was added to clarify bone structure, joint classification, and clinical relevance.