BONE

1. BONE 206 bones in adult 270 bones at birth organization axial skeleton- 80 bones skull- 29 bones vertebral column- 26 bones thorax (ribs and sternum)- 25 bones appendicular skeleton- 126 bones pectoral girdle- 4 bones upper limbs- 60 bones pelvic girdle- 2 bones lower limbs- 60 bones

2. BONE FUNCTIONS support - attaches to most skeletal muscles movement - needs articulations protection - brain, heart, lungs, blood forming tissue, bladder mineral reserve - Ca, P, Na, K blood cell production red marrow storage of energy yellow marrow

3. BONE FUNCTIONS • acid-base balance absorb or release alkaline salts detoxification removes heavy metals and other foreign elements from the blood

4. Bone Problem Ann is a 55 year old white woman who is postmenopausal and who has done little exercise in her life Ann has experienced a fracture of the hip and is concerned about possible osteoporosis Ann does not understand the cause or treatment of osteoporosis she decided to have a bone density test

5. BONE TYPES 1. Compact or dense bone 2. Spongy or cancellous bone

6. EXTERNAL ANATOMY OF LONG BONE diaphysis -- shaft epiphysis with proximal and distal ends medullary or marrow cavity center of ________________ fat storage- yellow marrow gelatinous bone marrow -- reddish jelly that replaces yellow marrow in old age endosteum thin layer lines ___________ cavity dense irregular connective tissue contains _______________ cells

7. EXTERNAL ANATOMY OF LONG BONE periosteum double layer of dense irregular connective tissue outer fibrous layer inner osteogenic layer elastic fibers, blood vessels, bone cells lines outside of bone sharpey’s fibers ______________ fibers that penetrate into bone matrix no periosteum at ends- ___________ cartilage

8. EXTERNAL ANATOMY OF LONG BONE Compact bone outer surface of bone Spongy bone or _________________ central regions of flat bone within epiphyses of long bones reduces weight of bone forms along lines of stress contains _________ marrow

9. RED BONE MARROW Major areas: Ribs Sternum Vertebrae Innominate bones Head of femur Head of humerus

10. HISTOLOGY OF COMPACT BONE Haversian systems or osteons Haverisan canals - contains blood vessels & nerves Volkmann's canals - perpendicular to HC connect HC to outside blood vessels 1/2 liter of blood per minute lamellae - ring of hard calcified intercellular substance concentric interstitial circumferential lacunae - spaces that contain _______________ canaliculi - connect osteocytes connected by __________ junctions

11. CELLS IN BONE a. osteogenic cells - found in cellular layer of periosteum, endosteum and Haversian canals - ________ cells --> osteoblasts

12. CELLS IN BONE b. osteoblasts - produce bone matrix - before calcium salts are deposited -- __________ - promotes deposition of calcium in the matrix - osteoblasts become surrounded by bone and are now called ___________ - not mitotic

13. OSTEOBLAST FORMING BONE

14. CELLS IN BONE c. Osteocytes - cannot divide - two functions 1. maintain and monitor protein and mineral content of matrix 2. participate in repair of damaged bone - if released from lacunae can form ___________ or ______________cells

15. CELLS IN BONE d. osteoclasts in Howship's lacunae - multinuclear- up to 50 nuclei - derived from _____________ - sends out projections toward bone and secrete two substances: 1. ___________ enzymes - acid phosphatase - from lysosomes and digest collagen 2. acids- _______ and ___________ acids - dissolve bone salts

16. HISTOLOGY OF SPONGY BONE no haversian systems thin plates called ____________ osteocytes in lacunae canaliculi but link to surrounding red bone marrow

17. MATRIX OF BONE 1. inorganic salts- 67% hydroxyapatite- Ca10 (PO4)6(OH)2 other salts Mg, Na, K, CO3- not in crystal form strontium, uranium, plutonium, lead, gold 9 of 14 of the major radioactive products from hydrogen bomb function allows bone to withstand __________ calcination remove organic material by __________

18. MATRIX OF BONE 2. organic framework or osteoid -- 33% collagenous fibers and chondrin function provide bone with great _________ strength ability to resist stretching and twisting acid treatment remove inorganic salts with acid leaves the protein

19. OSSIFICATION begins 6th week of embryo continues until about age of 25 types Intramembranous ossification flat bones of skull, mandible and clavicle called dermal bones Endochondral ossification most of the bones in the body formed from hyaline cartilage

20. INTRAMEMBRANOUS OSSIFICATION 1. Mesenchyme cells --> osteoblasts --> osteocytes osteoblasts secrete ___________ matrix osteoid becomes mineralized thru crystallization of Ca salts -- using enzyme __________________ called ossification center 2. Blood vessels begin to grow spicules meet and fuse together

21. INTRAMEMBRANOUS OSSIFICATION 3. Spongy bone gives rise to compact bone on the outside 4. Ossification is incomplete at birth dense irregular CT left are called fontanels _______________ at birth most close by 12 months, all close by 24 months

22. ENDOCHONDRAL OSSIFICATION 1. Hyaline cartilage (step 1) perichondrium 2. Bony collar (step 2) osteoblasts gather on inner surface of perichondrium -- begin laying down bone called the bony collar in the center, cartilage cells enlarging and dying

23. ENDOCHONDRAL OSSIFICATION 3. Primary ossification center (steps 3 and 4) cartilage cells dying and calcified matrix begins to degenerate blood vessels enter matrix carrying: ______________ to form bone ______________ to dissolve bone forming marrow cavity 3rd month of fetal life

24. ENDOCHONDRAL OSSIFICATION 4. Secondary ossification center (step 5) shortly after birth in the proximal epiphysis, a secondary ossification center forms no marrow cavity forms at two years old secondary ossification center forms at the distal epiphysis two areas of cartilage left after 2 years old a. ___________ cartilage - on ends b. ___________ plate - between primary and secondary ossification centers

25. ENDOCHONDRAL OSSIFICATION 5. End of endochondral ossification (step 6) for most bone, stops by ages of ________ epiphyseal plate ossifies to form the epiphyseal line articular cartilage only remaining cartilage found at the ends of the bone

26. PRIMARY OSSIFICATION CENTERMETAPHYSIS Zone of reserve cartilage Zone of cell proliferation chondrocytes multiply and become arranged into longitudinal columns of flattened lacunae Zone of hypertrophy chondrocytres cease to divide and hypertrophy

27. PRIMARY OSSIFICATION CENTERMETAPHYSIS 4. Zone of calcification minerals (Ca++) are deposited in matrix 5. Zone of bone deposition chondrocytes die osteoblasts invade and lay down trabeculae osteoclasts erode bone away and leave marrow cavity osteoblasts continue to lay down compact bone on the bony collar

28. BONE GROWTH - LENGTH on epiphyseal side chondrocytes continually reproduce by _________ on diaphyseal side chondrocytes swell and become surrounded by calcified matrix chondrocytes die, bone replaces chondrocytes bone is eroded away by osteoclasts, marrow cavity forms epiphyseal plate remains constant ______________ epiphyseal plate becomes ossified- _____________ 18 years in females 20 years in males

29. BONE GROWTH - DIAMETER compact bone remains constant _____________ marrow cavity increases in diameter balance between osteoblasts and osteoclasts not always same

30. PIEZOELECTRIC EFFECT bone is deposited in proportion to compressional load compression causes a ________ potential at the site remainder of bone has a _________ potential

31. REQUIREMENTS FOR BONE GROWTH 1. Salts Ca & P calcium is the most abundant mineral in body stores 99% of calcium in bone plasma - Ca++ stores 85-90% of P in bone plasma - HPO4-2 and H2PO4-1 Mg, F, Fe, and Mn

32. REQUIREMENTS FOR BONE GROWTH 2. Vitamins Vit. A -- stimulates chondroitin sulfate synthesis Vit. K and B12 -- synthesis of proteins Vit. C -- collagen synthesis and stimulates osteoblast differentiation Vit. D3 -- forms calcitriol which causes increased absorption of Ca and P from intestine

33. REQUIREMENTS FOR BONE GROWTH 3. Hormones calcitriol -- Ca & P absorption from small intestine other hormones: Growth hormone Thyroid hormones Glucocorticoids Insulin sex hormones (estrogen and testosterone) stimulates osteoblast activity and closure of epiphyseal plate Estrogen has a stronger effect so growth starts and stops earlier than with testosterone anabolic steroids (testosterone) and prematurely close epiphyseal plate

34. REQUIREMENTS FOR BONE GROWTH 3. Hormones (continued) Parathyroid hormone from parathyroid gland increases blood calcium - 10% fluctuation is normal increase blood Ca by 30% --> neurons and muscles are unresponsive decrease blood Ca by 35% --> neurons excite and may cause convulsions works on three levels a. Bone increases number & activity of osteoclasts decreases activity of osteoblasts

35. REQUIREMENTS FOR BONE GROWTH 3. Hormones (continued) Parathyroid hormone b. Kidney increases reabsorption of Ca increases excretion of P c. Intestine activate vitamin D3 to calcitriol cholesterol --> (UV light) --> Vit. D3 --> calcidiol (liver) --> calcitriol (kidney, PTH) increases absorption of Ca and P from intestine

36. REQUIREMENTS FOR BONE GROWTH 3. Hormones (continued) Parathyroid Hyperparathyroidism _________ PTH depresses nervous system brittle bones, kidney stones Hypoparathyroidism _________ PTH increased excitability of nervous system respiratory paralysis

37. REQUIREMENTS FOR BONE GROWTH 3. Hormones (continued) Calcitonin from parafollicular cells or C cells of the _________ decreases blood Ca acts mainly on bone decrease activity of osteoclasts increases activity & number of osteoblasts infants - _____________ adults - ______________ accounts for movement of 0.8 grams of Ca per day

38. Problem - OsteoporosisTreatments Hormone Replacement Therapy (HRT) types estrogen (ERT) estrogen + progestin (HRT) side effects nausea, bloating, breast tenderness, high blood pressure and blood clots issue of a relationship between breast cancer and estrogen use is still to be determined.

39. Problem - OsteoporosisTreatments Alendronate Sodium and Risedronate Sodium biphosphonates (bind to hydroxyapetites) reduces bone loss, increased bone density, and reduces risk of spine fractures and hip fractures side effects rare - abdominal pain, nausea, heartburn, irritation of esophagus Raloxifene selective estrogen receptor modulators (SERMs) produces increase in bone mass side effects rare - hot flashes and deep vein thrombosis Calcitonin side effect - may cause allergic reaction- flushing of face and hands, urinary frequency, nausea and a skin rash

40. Problem - OsteoporosisPrevention calcium 1000 - 1300 mg per day vitamin D fortified dairy products, egg yolks, saltwater fish and liver exercise weight-bearing bone mineral tests