Lecture 7 Osseous Tissue Bio-11 JPHubbard Dynamic and ever-changing throughout life

1. Lecture 7 Osseous Tissue Bio-11 JPHubbard • Dynamic and ever-changing throughout life • Skeleton composed of different tissues • cartilage, bone tissue, epithelium, nerve, blood forming tissue, adipose, and dense connective tissue

2. Functions: • Support • Movement and leverage • Protection • Storage of minerals (Ca especially) and fat • Blood cell production

3. Types of Bones – Shape Know some examples: • Long Bone • Flat Bone • Irregular Bone • Short Bone • Two additional types – vary with individuals: • Sutural Bones • Sesamoid Bone

4. Gross Anatomy of Long Bone • _______________ tough connective tissue layer covering bone attachment of tendons and ligaments blood vessels in periosteum • ______________- ends spongy bone compact bone, articular cartilage • ______________- middle compact bone medullary cavity- contains yellow marrow (fat) lined with endosteum (squamous epithelium)

6. Bone = Osseous tissue • a type of connective tissue – What characterizes connective tissue? • Cells? • Vascular • matrix What differentiates bone from other connective tissues?

7. Bone Cells • _____________ – build bone, lay down matrix • _____________ – mature bone cells • Osteoprogenetor – mesenchyme cells which differentiate into osteoblasts, largely inner layer of periosteum • _________________ – large cells, destroy bone • Activity of osteoblasts, osteoclasts impacted by hormones from thyroid/parathyroid

8. Matrix • Collagen fibers – • Protein • like reinforcing rods • What would be the effect of lack of collagen? • Minerals: provide rigidity • Calcium salts

9. Bone Micro-Anatomy – Osseous Tissue • Two types: • 1. Compact bone • Osteon – Basic organizational unit • Diaphysis long bone, outer layers at epiphysis and of flat bone • 2. Spongy Bone – no osteons • Trabeculae provide bracing effect • Red Marrow produces blood cells • Ends of long bones + inside flat bones

11. Compact Bone – Osteon basic unit • Central canal: blood vessels at center of osteon • Lamella: Concentric layers of matrix • Lacunae: contain osteocytes between layers of lamella • Canaliculi: canals which connect lacunae

12. Trabeculae of Spongy Bone • oriented along lines of stress - Latticework • Harbor and protect red marrow ( blood cells develop) No true Osteons.

13. Bone Development Prenatal : (embryonic and fetal) skeleton is mostly cartilaginous Ossification – the process of mineralization of tissue (hyaline cartilage, fibrocartilage) resulting in formation of bone Cartilage cells and then osteoblasts start to deposit minerals

14. Bone Formation – 2 ways: 1) Intramembrannous ossification – Flat Bones - bone formed between sheets of connective tissue 2) Endochondral ossification –Long Bones - formed from hayaline cartilage model • increase in length until puberty at epiphyseal plate • increase in diameter due to activity of cells under periosteum • Control from growth hormone (GH) + other endocrine hormones

16. Rickets and Osteomalacia • Disorders resulting in abnormal/poor ossification • Rickets: • Vitamin D deficiency • Bowed limbs • Pain • Limbs easily broken • Osteomalacia • Failure of adult bone to ossify • hip fractures are common

17. Growth hormone regulates skeletal growth stimulates cell division in epiphyseal disks in long bones Growth stops when epiphyseal disks are converted to bone When excess growth hormone is produced in childhoodgigantism In adulthood- acromegaly. Bones can’t grow but soft tissue can

18. Healing is faster in bone than in cartilage due to lack of blood vessels in cartilage Healing of bone is still slow process due to vessel damage Clinical treatment closed reduction = restore pieces to normal position by manipulation open reduction = surgery Fracture & Repair of Bone

19. Bone Repair – Similar to Development

20. Bone Remodeling • Continuous Process • distal femur is fully remodeled every 4 months • Osteoblast build - stimulated by • Weight bearing activity • Blood Ca levels via endocrine hormones (calcitonin stimulates) • Numbers increased by estrogen/testosterone • Osteoclasts • Stimulated by dropping blood Ca level via parathyroid hormone • Calcitonin inhibits

21. Small changes in blood levels of Ca+2 can be deadly: • (plasma level maintained 9-11mg/100mL) • cardiac arrest if too high • respiratory arrest if too low • This is an example of a _____________ feedback loop.

22. Aging & Bone Tissue • Bone is being built through adolescence, holds its own in young adults, but is gradually lost in aged. • Demineralization = loss of minerals • very rapid in women 40-45 as estrogens levels decrease • in males, begins after age 60 • Decrease in protein synthesis • decrease in growth hormone • decrease in collagen production which gives bone its tensile strength • bone becomes brittle & susceptible to fracture

23. Osteoporosis • Loss in bone density • Affected by age, sex, race, nutrition, exercise • Particular problem for women after menopause due to decreased estrogen • Diet factors with negative impact: alcohol, caffeine, certain antibiotics and other drugs • Positive: Exercise increases bone mass, Fosamax, vitamin D, hormone replacement therapy, calcium fluoride