1. BIO 238

2.  Support  Protection  Leverage- for motion  Mineral Homeostasis  Blood cell production  Hemopoiesis in red bone marrow  Triglyceride Storage

3.  Parts of a long bone:  Diaphysis  Epiphysis  Metaphysis  Articular cartilage  Periosteum  Medullary cavity  Endosteum

4. FIGURE 6.1A

5. FIGURE 6.1B

6.  Matrix=  25% water, 25% collagen fibers, 50% crystallized mineral salts  Osteogenic cells- in periosteum; Osteoblasts- secrete collagen fibers-  Build matrix and become trapped in lacunae  Become osteocytes- maintain bone  Osteoclasts – formed from monocytes  Digest bone matrix for Normal bone turnover

7.  few spaces, right below periosteum  Units = osteons (Haversian system)  Central canal- blood vessels, nerves, lymphatics  Concentric lamellae- layers of matrix  Lacunae- “lakes” contain osteocytes  Canaliculae- little canals  nutrient flow from canals and between osteocytes

8.  units containing trabeculae  spaces between trabeculae often contain marrow  Two types-  Red bone marrow- produces blood cells and platelets  Yellow bone marrow- stores fat  No osteons but include lacunae & canaliculae

9. FIGURE 6.2B

10. Ossification- formation of bone  1. initially in embryo & fetus  2. Growth  3. remodeling  4. repair of fractures

11.  Mesenchyme model - replaced with bone  Intramembranous - Bone forms directly in mesenchyme layers (membrane like)  Endochondrial - forms within hyaline cartilage developed from mesenchyme

12. FIGURE 6.3

14.  Length- chondrocytes in the epiphyseal plate divide and increase cartilage layer  On diaphyseal side they die and are replaced by bone  Stops during adolescence  Periosteum supports surface growth for thickness

15. FIGURE 6.5

16.  The adult skeleton:  maintains itself  replaces mineral reserves  Remodeling:  recycles and renews bone matrix  involves osteocytes, osteoblasts, and osteoclasts

17.  Mineral recycling allows bones to adapt to stress  Heavily stressed bones become thicker and stronger

18.  Bone degenerates quickly  Up to 1/3 of bone mass can be lost in a few weeks of inactivity  What you don’t use, you lose  Stresses applied to bones during physical activity are essential to maintain bone strength and mass

19.  A dietary source of calcium and phosphate salts:  plus small amounts of magnesium, fluoride, iron, and manganese

20.  Vitamin C is required for collagen synthesis, and stimulates osteoblast differentiation  Vitamin A stimulates osteoblast activity  Vitamins K and B 12 help synthesize bone proteins  Vitamins D helps with calcium and phosphate absorption.

21.  Growth hormone and thyroid hormones stimulate bone growth  Estrogens and androgens stimulate osteoblasts  Calcitonin and parathyroid hormone regulate calcium and phosphate levels

22.  Bones store calcium and other minerals  Calcium is the most abundant mineral in the body  Calcium ions are vital to:  membranes  neurons  muscle cells, especially heart cells

23.  Calcium ions in body fluids:  must be closely regulated  Homeostasis is maintained:  by calcitonin and parathyroid hormone  which control storage, absorption, and excretion

24.  Bones:  where calcium is stored  Digestive tract:  where calcium is absorbed  Kidneys:  where calcium is excreted

26.  Produced by parathyroid glands in neck  Increases calcium ion levels by:  stimulating osteoclasts  increasing intestinal absorption of calcium  decreases calcium excretion at kidneys

28.  Secreted by C cells (parafollicular cells) in thyroid  Decreases calcium ion levels by:  inhibiting osteoclast activity  increasing calcium excretion at kidneys

29.  Nutrition is also important for bone health  Each night we deposit minerals in our bones  These minerals are stored for use by the rest of the body  If we do not replenish the mineral supply equally or faster than it is used osteoporosis results Copyright 2010, John Wiley & Sons, Inc.

30.  Calcium and phosphate ions in blood are lost in urine  Ions must be replaced to maintain homeostasis  If not obtained from diet, ions are removed from the skeleton, weakening bones  Exercise and nutrition keep bones strong

32.  Fractures:  cracks or breaks in bones  caused by physical stress  Fractures are repaired in 4 steps

33. Copyright 2010, John Wiley & Sons, Inc.

35.  Pott’s fracture

36.  Comminuted fractures

37.  Transverse fractures

38.  Spiral fractures

39.  Displaced fractures

40.  Colles’ fracture

41.  Greenstick fracture

42.  Epiphyseal fractures

43.  Compression fractures

45.  Kyphosis – exaggerated thoracic curvature (humpback)  Lordosis – exaggerated lumbar curvature (swayback)  Scoliosis – exaggerated lateral curvature

47.  Bones become thinner and weaker with age  Osteopenia (A condition of bone in which decreased calcification, decreased density, or reduced mass occurs) begins between ages 30 and 40  Women lose 8% of bone mass per decade, men 3%

48.  The epiphyses, vertebrae, and jaws are most affected:  resulting in fragile limbs  reduction in height  tooth loss

49.  a disorder in which the bones become increasingly porous, brittle, and subject to fracture, owing to loss of calcium and other mineral components, sometimes resulting in pain, decreased height, and skeletal deformities: common in older persons, primarily postmenopausal women, but also associated with long-term steroid therapy and certain endocrine disorders.

50.  Severe bone loss  Affects normal function  Over age 45, occurs in:  29% of women  18% of men

51.  Estrogens and androgens help maintain bone mass  Bone loss in women accelerates after menopause

52.  Cancerous tissues release osteoclast-activating factor:  that stimulates osteoclasts  and produces severe osteoporosis