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Functions of the skeletal system

Support, Protection, Movement, Mineral Storage, Blood Cell Production, Energy Storage

Rickets

Vitamin D, calcium, or phosphate deficiency → soft, weak bones; bowed legs; skeletal deformities; commonly affects femur & tibia

Gout

Uric acid buildup → crystal formation in joints → severe pain, redness, swelling; usually affects the big toe

Axial skeleton

Central framework; protects vital organs; includes skull, vertebrae, ribs, sternum, hyoid

Appendicular skeleton

Enables movement; includes limbs + shoulder & pelvic girdles

Types of ossification

Endochondral: from hyaline cartilage → long bones (femur, tibia, humerus); Intramembranous: from fibrous connective tissue → flat bones (skull, clavicle, mandible)

Parts of a long bone

Epiphysis (spongy bone/red marrow), Metaphysis (growth plate), Diaphysis (shaft/compact bone), Periosteum (outer membrane), Endosteum (inner lining), Osteoblasts (build bone), Osteoclasts (break down bone), Medullary Cavity (marrow)

Bone shapes

Long: femur, humerus; Short: carpals, tarsals; Flat: skull, ribs, sternum; Irregular: vertebrae, hip bones

Bony processes

Acromion (scapula) → shoulder tip/muscle attachment; Olecranon (ulna) → elbow/triceps attach; Xiphoid (sternum) → diaphragm & rectus abdominis attachment

Vertebral column regions

Cervical: neck mobility/support skull; Thoracic: rib attachment/limited movement; Lumbar: bear weight/flexible; Sacrum: connect spine to pelvis; Coccyx: vestigial/muscle attachment

Shoulder girdle bones

Clavicle + scapula → attach upper limbs, wide motion

Pelvic girdle bones

Ilium + ischium + pubis → attach lower limbs, support weight

Atlas vertebra

Supports skull, condyloid joint → nodding yes

Axis vertebra

Dens pivot → rotation no

Synovial joint types

Ball & Socket: shoulder/hip → all directions; Hinge: elbow/knee → flexion/extension; Pivot: neck (C1-C2), radius/ulna → rotation; Saddle: thumb → multiple motions; Condyloid: wrist → biaxial; Gliding: carpals/tarsals → small sliding motions

Tibia function

Primary weight-bearing bone; forms knee & ankle joints; muscle attachment for movement of foot & leg

Tendons vs. Ligaments

Tendon: muscle → bone, transmit force for movement; Ligament: bone → bone, stabilizes joints

Common movements

Flexion: decrease angle → bend elbow; Extension: increase angle → straighten elbow; Abduction: away from midline → lift arm sideways; Adduction: toward midline → lower arm; Circumduction: circular motion → arm circles

Other movements

Elevation: lift → shrug shoulders; Depression: lower → relax shoulders; Pronation: palm down → typing; Supination: palm up → holding bowl; Dorsiflexion: toes up → standing on heels; Plantarflexion: toes down → tiptoes

Key bones in skull

Frontal, parietal, temporal, occipital, sphenoid, zygomatic, nasal, maxilla, mandible

Rib cage types

True 1-7, false 8-10, floating 11-12; sternum: manubrium, body, xiphoid

Upper limb bones

Clavicle, scapula, humerus, radius, ulna, carpals, metacarpals, phalanges

Pelvis bones

Ilium, ischium, pubis, acetabulum

Lower limb bones

Femur, tibia, fibula, tarsals, metatarsals, phalanges, talus, calcaneus