Chapters 7, 8, 9 Bone Tissue/Joints BSC 2085 Professor Tcherina Duncombe Palm Beach State College Skeleton • Support • Protection • Movement • Electrolyte Balance • Acid – base Balance • Blood Formation • Osseous tissue: connective: blood/marrow/cartilage/adipose/ nervous/fibrous •Calcification = mineralization Shapes of Bones • Long – levers acted upon by muscles: crowbars • Short – glide across one another in multiple directions: width/length same • Flat – enclose/protect soft organs: broad/thin/sandwich-like • Irregular 7-3 Structure of Long Bone • Compact: dense; 3/4 • Spongy/Cancellous; 1/4 • Marrow/Medullary cavity • Periosteum: osteogenic layer • Endosteum: cells dissolve bone tissue • Diaphysis: leverage • Epiphysis:tendons/ligaments • Epiphyseal plate/line • Articular cartilage • Nutrient foramina 7-4 Structure of a Flat Bone • External/internal surfaces:compact bone: sandwich-like • Middle layer:spongy bone(diploe)/bone marrow • Skull fracture may leave inner layer of compact bone unharmed 7-5 Cells of Osseous Tissue (1) • Osteogenic (stem)cells in periosteum and central canals: continual mitosis: some give rise to new osteoblasts (nonmitotic) • Osteoblasts make organic matter of matrix: stim by stress and fractures:secrete osteocalcin: stim insulin secretion/↑insulin sensitivity in adipocytes→limit growth of adipose tissue • Osteocytes = osteoblasts trapped in the matrix they formed 7-6 Cells of Osseous Tissue (2) • Osteoclasts : bone dissolving cells • 3-50 stem cells fused - resorb/deposit matrix→homeostasis →bone density/Ca2+ 3- ; PO4 7-7 Intramembranous Ossification (enlarge to osteogenic cells) (become trabeculae) • Osteogenesis=bone formation • Produces flat bones of skull/clavicle: develop w/in a fibrous sheet similar to dermis = dermal bones 7-8 Bone:osteogenic/osteoblasts/ osteoclasts osteocytes Histology of Compact Bone • Composite: polymer(collagen) and ceramic (hydroxyapatite) •Dry weight :1/3 organic; 2/3 inorganic matter •Organic matter:collagen, glycosaminoglycans, proteoglycans, glycoproteins (made by osteoblasts) •Inorganic matter:85% hydroxyapatite;10% calcium carbonate • Other minerals (fluoride, potassium, magnesium) • Combination: strength/resilience; minerals resist compression; collagen resists tension • Bone adapts by varying proportions 7-10 Bone Marrow • 2 Types • Red marrow: myeloid tissue – Hemopoietic = produces blood cells – vertebrae, ribs, sternum, pelvic girdle proximal heads of femur/humerus in adults • Yellow marrow – fatty marrow in adults: no produce blood – In long bones 7-11 Intramembranous Ossification (enlarge to osteogenic cells) (become trabeculae) • Osteogenesis=bone formation • Produces flat bones of skull/clavicle: develop w/in a fibrous sheet similar to dermis = dermal bones 7-12 Stages of Endochondral Ossification: bone from hyaline cartilage • 6th week development → 20’s 7-13 Fetal Skeleton at 12 Weeks 7-14 Bone Growth/Remodeling • 2 directions: - length: elongation= cartilage growth - width: appositional growth • Remodeling: Wolff’s Law of bones - architecture determined by stresses/bone adapts to stresses - both osteoclasts/osteoblasts Dwarfism • Achondroplastic – long bones stop growing in childhood • normal torso, short limbs – spontaneous mutation during DNA replication – failure of cartilage growth • Pituitary – lack of growth hormone – normal proportions with short stature 7-16 Mineral Deposition Mineral Resorption Mineralization = crystallization process Bone dissolved/minerals released into blood • osteoblasts produce collagen fibers • osteoclasts - minerals cover the fibers/harden the • matrix HCl/Acid phosphatase(digests colagen) - ions (calcium/phosphate/blood plasma) deposited along the fibers - ion concentration must reach solubility product •Abnormal calcification (ectopic) - may occur in lungs, brain, eyes, muscles, tendons or arteries (arteriosclerosis) Calcium Homeostasis 2+ 3- • Ca (Communication) ; PO4 • Muscle/Nervous 7-17 Hormonal Control of Calcium Balance: negative feedback • Calcitriol: form of VitD:skin/liver/kidneys: ↑blood calcium conc • PTH: ↑calcium: parathyroid glands • Calcitonin: ↓ calcium: thyroid gland: inhib osteoclasts/stim osteoblasts 7-18 Correction for Hypercalcemia 7-19 Parathyroid Glands • PTH release – blood Ca2+ levels – promotes synthesis of calcitriol • absorption of Ca2+ • urinary excretion • bone resorption Correction for Hypocalcemia 7-21 Types of Bone Fractures: 1) Stress fracture caused by trauma 2) Pathological fracture in bone weakened by disease Fractures classified by structural characteristics break in the skin multiple pieces 7-22 Healing of Fractures 2 7-23 Fractures and Their Repairs 7-24 Spinal Osteoporosis 7-25 Components of a Lever • A lever is a rigid object that rotates around a fixed point called a fulcrum • Rotation occurs when effort overcomes resistance – resistance arm and effort arm are described relative to fulcrum 9-26 Mechanical Advantage • Mechanical advantage is calculated from the length of the effort arm divided by the length of the resistance arm • Contraction of the biceps muscle causes the hand to move fast and further (MA <1.0) 9-27 First-Class Lever • Has fulcrum in the middle between effort and resistance • Atlantooccipital joint lies between the muscles on the back of the neck and the weight of the face – loss of muscle tone occurs when you nod off in class 9-28 Second-Class Lever • Resistance between fulcrum and effort • Resistance from the muscle tone of the temporalis muscle lies between the jaw joint and the pull of the diagastric muscle on the chin as it opens the mouth quickly 9-29 Third-Class Lever • Effort between the resistance and the fulcrum – most joints of the body • The effort applied by the biceps muscle is applied to the forearm between the elbow joint and the weight of the hand and the forearm 9-30 Types of Synovial Joints 9-31 Rheumatoid Arthritis 9-32 Joint Prostheses 9-33.