The Skeletal System: Functions Of Bones

*THE SKELETAL SYSTEM FUNCTIONS OF BONES: 1. Support and anchoring 2. Protection of vital organs 3. Movement (with the aid of muscles) 4. Storage (fats and minerals like calcium and phosphorus) 5. Hematopoiesis (blood cell formation) TYPES OF BONES: 1. Flat bone (skull, ribs) – thin, flat 2. Short bone (carpals) – generally cube-shaped 3. Irregular bone (vertebrae) – goofy shapes 4. Long bone (humerous, femur) – generally greater length than width Gross anatomy: 1. Diaphysis (bone shaft) – covered in fiberous periosteum 2. Epiphyses (head at each end of bone) – covered with articular cartilage 3. Compact bone – contains osteons or Haversian systems 4. Spongy bone 5. Yellow marrow cavity (interior of bone) – contains mostly adipose tissue Microscopic anatomy: 1. Mature bone cells called osteocytes 1. Haversian systems (the bone units found in compact bone that carry blood vessels and nerves to other parts of the bone) IMPORTANT BONE DETAILS: 1. Hardness comes from calcium salts in the bone matrix (chicken bone in vinegar) 2. Flexibility and strength from collagen fibers 3. Process of bone formation called ossification a. In fetus, hyaline cartilage “model” covered in bone matrix Bone matrix then digests away and replaces cartilage Bone matter can be built up or torn apart depending on body’s condition b. 4. CARTILAGE: Not nearly as prevalent in the body as bone a. Articular cartilage – covers bone ends to reduce friction at joints b. Epiphyseal plates – provides for longitudinal growth in childhood (a.k.a. growth plates) SUBDIVISIONS OF THE SKELETON (where the 206 bones fit): 1. Axial --- form longitudinal axis of body a. Skull i. Cranium and facial bones b. Vertebral Column i. Cervical (7 vertebrae) ii. Thoracic (12) iii. Lumbar (5) iv. Sacrum (5 fused vertebrae) v. Coccyx (4 fused) c. Bony Thorax i. Sternum and ribs 2. Appendicular --a. Pectoral (shoulder) girdle b. Arms and hands c. Pelvic girdle d. Legs and feet HOMEOSTATIC IMBALANCES IN BONE * Fractures--- 8 type 1. simple 2. compound 3. comminuted 4. compression 5. depressed 6. impacted 7. 8. spiral greenstick bone fracture repair: 1. blood forms hematoma (bruise) forms 3. bone callus replaces cartilage strengthens 2. Fibrocartilage callus 4. Bone remodels and * Rickets--- softened bones in children due to deficiency in calcium or vitamin D * Osteoporosis--- loss of bone mass leading to fragile bone structure ● common in elderly, especially women (b/c of estrogen deficiency) ● can be compounded by obesity, poor calcium intake and lack of exercise FUNCTIONS OF JOINTS AND ARTICULATIONS 1. Hold bones together 2. Provide for mobility TYPES OF JOINTS 1. Immovable joints (skull bones) – united by fibrous tissue 2. Slightly moveable joints (intervertebral joints) – cartilaginous tissue 3. Freely moveable joints (elbow, knee, hand…) – synovial cavity and synovial fluid present at point of articulation ● plane joint ● hinge joint ● pivot joint ● condyloid joint ● saddle joint ● ball-and-socket joint Joint Movement --1. flexion/extension/hyperextension 2. dorsiflexion/plantar flexion 3. abduction/adduction 4. rotation/circumduction 5. pronation/supination 6. eversion/inversion 7. retraction/protraction HOMEOSTATIC IMBALANCES OF JOINTS *Arthritis--- inflamed, swollen and painful joints 3 forms : 1. Rheumatoid arthritis ● most painful and most crippling ● occurs when joint swelling leads white blood cells to destroy the cartilage of bone ends 2. 3. Osteoarthritis (OA) ● most common ● result of aging process (“wear-and-tear” arthritis) ● caused by breakdown of cartilage around joints that causes bone to thicken, produce bone spurs which then cause restricted movement Gouty (a.k.a. gout) - build-up of material around one specific joint causing pain