Chapter 6 Bone and Skeletal Tissue

I. Skeletal Cartilages A. Structure (3 types) 1. Consists- 2. Nerves- 3. Vasculature- 4. Surrounding-

fn: - resist outward expansion - source of blood vessels - limits cartilage thickness 5. Three types: hyaline, elastic, and fibroblastic a. Chondrocytes-

B. Hyaline Cartilage 1. most abundant 2. location: a. articular- b. costal- c. respiratory- d. nasal- 3. chondrocytes- 4. fibers-

C. Elastin Cartilage 1. more flexable 2. fibers- 3. location- a. b.

D. Fibrocartilage 1. cross between hyaline and elastin 2. fibers- 3. location- a. b. c. 4. function: resist heavy pressures and stretch

E. Growth Cartilage (two ways) 1. appositional growth- (growth from outside) a. perichondrium-

2. interstitial growth- ( growth from inside) a. chondrocytes in lucanae-

II. Classification of Bone (2 groups, 206, shape) A. Axial Skeleton 1. forms long axis of body a. skull b. vertebral column c. rib cage

B. Appindicular Skeleton 1. bones of upper/lower limbs, pelvis

C. Classification by shape 1. long bones: a. elongated shaft and two enlarged ends b. location: all bone of limbs 2. short bones- cube shaped a. location- b. seasmoid bones: 1. forms-

3. flat bones: thin, flat with small curves a. location-

4. irregular bones- complicated shape a. location-

II. Function of Bones a. support b. protection c. movement d. mineral storage- calcium, phosphorus e. blood cell formation (hematopoiecis) bone marrow

IV Bone Structure A. Gross Anatomy 1. Types of Tissue a. compact bone:

b. spongy bone:

2. Typical long bone a. Diaphysis 1. shaft- 2. made of- 3. medullary cavity- b. Epiphyses 1. ends of long bone- 2. exterior- 3. interior- 4. articular cartilage- c. Epiphyseal line 1. represents-

d. Periostium- outer membrane of bone 1. 2. outer layer- 3. innerlayer- a. osteoblasts- b. osteoclasts-

4. vesseles- 5. sharpy’s fibers-

e. Endostium 1. lines canals and internal cavities 2. contains- osteoclasts and osteocytes

3. Short, irregular and flat bones a. made of… b. diploe- c. periostium- d. endostium-

4. Location of Homatopoietic tissue in bone a. red marrow- 1. long bone- 2. flat bone- b. red marrow cavities-

c. yellow marrow 1 1. long bone- 2. anemia-

B. Microscopic Structure of Bone 1. compact bone: a. Haversian system (osteon) 1. structural unit of bone 2. pillar like- b. lamellar bone- c. haversian canal (central)- d. volkman’s canal- e. osteocytes- f. lacunae- g. caniculi- h. interstitial lamellae- i. circumferential-

2. Spongy bone a. trabeculae- b. lamallae- c. osteocytes-

C. Chemical composition of bone 1. Organic- 35% of bone a. cells- b. osteoid- 1. proteoglycans 2. glycoproteins 3. collagen fibers Fn: tensile strength and flexability 2. Inorganic- 65% of bone a. hydroxyapatites- Fn: combination of organic/inorganic  strength w/o brittleness

3. Bone markings- not smooth or featureless a. bulges, depressions, and holes b. function:

IV Bone Development (osteogenesis) A. Formation of bony skeleton 1. Intramembrane Ossification a. forms- b. 4 steps (see fig 6.7) 1) mesenchymal cell  2) osteoblasts  3) osteocytes  4) trabeculae 

2. Endochondrial Ossification a. forms- b. more complex… breakdown and model new c. hyaline cartilage  ossification long bone Steps: p. 182-3 1. formation of bone collar and primary ossification center 2. hyaline cart. Of diaphysis calcifie…then…cavitates 3. periosteal bud invades cavities  formation of spongy bone a. nutrient artery and veins b. lymphatics, nerves c. red marrow elements: osteoblasts and osteoclasts 4. formation of medullary cavity; appearance of secondary ossification center in epiphyses w/b.v. 5. ossification of epiphyses; formation of epiphyseal growth plates Summary- hyaline cartilage is being eroded and replaced by bony spicules ossification “chases Cartilage formation along the length of the shaft.

B. Postnatal growth 1. Growth in long bones a. Growth zone- 1. cartilage cells- b. Transformation zone- 1. c. Osteogenic zone- 1. 2. Summary: longitudinal bone growth- remodeling of the epiphyseal ends push away from the diaphysis

2. Growth in width a. osteoblasts- 3. Hormonal regulation of bone growth a. infancy- 1. T3 and T4- b. puberty- 1. epiphyseal plate closure- a. giantism- b. dwarfism-

VI Bone Homeostasis: Remodeling and Repair 1. Basic process- - occurs constantly - recycled 5-7% of bone mass weekly - calcium: ½ gram enters/leaves bone daily * spongy bone- * compact bone- a. Bone remodeling units- 1.osteocytes- 2.osteoblasts- b. Bone deposition: 1. Needs- 2. osteoid seam- 3. calcification front- c. Bone Resorption 1. Osteoclasts a. secrete- b. acids- c. phagocytosis, endocytosis, translocation (transcytosis) 2. Control of Remodeling a. Hormonal- 1. parathyroid hormone (PTH)- a. stimulates: 2. calcitonin- a. inhibits:

Summary: Maintain blood Ca2+ levels 9-11mg/100ml blood b. Mechanical stress- 1. Wolf’s Law- Ex: old age  bone atrophy 3. Fractures- (breaks, where, position) a. Position 1. non-displaced- 2. displaced- b. Completeness of break 1. compete- 2. incomplete- a. linear- b. transverse-

c. Skin penetration 1. Open (compound)- 2. Closed (simple)- d. Healing- (reduction- realignment of bone) 1. closed reduction- 2. open reduction- 3. immbilization- 4. time- 5. repair process…. 4 Stages fig. 6.13 1. Hematoma formation: a. mass of clotted blood forms b. bone cells begin to die c. tissue swells- inflamation 2. Fibrocartilaginous callus formation: a. granulation tissue (soft callus) begins to form after a few days b. capillaries grow  phagocytic cells clean away bacteria and debris c. fibroblast/osteoblast secreted by peri and endostium (reconstruct bone) d. chondroblasts  chondrocytes  form cartilage e. osteocytes  forming spongy bone Summary: This mass of repair tissue is called the fibrocartilaginous callus

3. Bony callus formation a. cartilaginous callus  ossification  hard bony callus 2-3 mths 4. Bone remodeling a. all excess formation material is rmoved b. all membranes and surface structures return to normal VII Homeostatic imbalance of bone (disease) Imbalance between bone formation and bone resorption underlie nearly every disease state A. Osteomalacia (soft bones) 1. mineralization- a. osteoid- b. calcium salts- results: bones soften and weaken why: insufficient calcium and Vit D B. Rickets- 1. bone growth- deformities a. bowed legs b. skull c. rib cage 2. Epiphyseal plates- if they can not be calcified… they widen and enlarge C. Osteoporosis and Pagets disease Know causes and what characterizes disease state.