CBIO 2200 1nd Edition Exam 3 Study Guide Lectures 10 13 Lecture 10 September 25 What is osteology Study of bones Four components of skeletal system count as bones Living Skeleton what is happening with living skeleton metabolically active Functions of the skeleton support protection movement electrolyte balance acidbase balance blood formation Another name for bone osseous tissue Mineralization Calcification hardening of bone by minerals What does it mean that bones are dynamic They are always remodeling itself Four categories of bones flat long short irregular don t fall into other categories Bones Cartilage Ligaments Tendons teeth Characteristics of the Long Bone Compact Dense bone covers outside of bone Shaft diaphysis mid section of bone Medullary cavity inside shaft marrow cavity Epiphysis knobs on either end of shaft Spongy cancellous bone under compact bone Articular cartilage cartilage that covers epiphyses Nutrient foramina passageway for blood vessels nerves etc Periosteum surrounds outside of bone Layers of periosteum o Outer fibrous layer contain bone stem cells o Inner osteogenic layer mostly collagen Endosteum inside covering of bone connective tissue Epiphyseal plate growth plate composed of hyaline cartilage covers epiphysis and separating epiphyses and diaphysis Characteristics of Flat Bones Diploe spongy layer in the cranium and between compact bones Contains periosteum and endosteum Bone Cells Four principle cell types o Osteogenic cells bone stem cells mitotic cells o Osteoblasts cells that lay down bone not mitotic o Osteocytes mature bone cells o Osteoclasts bone dissolving cells from macrophage hemopoetic cell line have ruffled border that comes in direct contact with bone and releases enzymes that eat away at the bone important in remodeling of bone Lecture 11 October 7 Osseous Tissue 1 3 is organic matter collagen proteoglycans etc synthesized by osteoblasts o Osteogenesis imperfect or brittle bone disease caused by a collagen protein deficiency 2 3 is inorganic matter calcium phosphate etc together as hydroxyapatite o Rickets disease caused by mineral deficiency soft bones bend easily Bone Marrow where blood cells are made Red marrow myeloid tissue hemopoetic tissue in adults red marrow is mostly in axial skeleton Yellow marrow can convert to red marrow if needed found in adults not children Bone Development Ossification formation of bone Developmental methods in fetus infant o Intramembranous ossification bone forming within a membrane e g soft spots on baby s skull that produces bones How flat bones are made Mesenchyme present means it s undifferentiated Condensed mesenchyme forms spicules Blood vessels migrate to spicules Forms compact bone on outside with spongy bones in middle o Endochondral ossification bone formation in collagen This is the process that forms the long bone Start with cartilaginous model with primary ossification center in the middle first site of activity of osteoblasts As bone matures in primary ossification center blood vessels invade osteoblasts and osteoclasts activity occurring Secondary ossification center at ends of bones epiphyses Diaphysis forms as bone replaces cartilage The epiphyseal plate is the cartilage that remains in the growth plate After growth is over epiphyseal plate is replaced by bone also Fetal skeleton at 12 weeks bone has already formed but most joints are still cartilage Primary ossifications have formed but secondary ossification centers have not yet been replaced by bone Bone Elongation Metaphysis the growth zone where cartilage is being replaced by bone Layers of the metaphysis o Zone of reserve cartilage chondroblasts are always producing cartilage o Zone of cell proliferation chondrocytes multiply proliferate o Zone of cell hypertrophy cells grow in size o Zone of calcification minerals are added to the matrix o Zone of bone deposition bone matrix is laid down Directions of bone growth o Length interstitial growth stops at some point in life o Width appositional growth doesn t stop The deposition of new bone at the surface doesn t cause that bone to become thicker because osteoclasts eat away at the bone on the inside Wolff s law of bone the architecture of bone is determined by the amount of stress put on the bone Blood vessels line the cylinder and then when bone is laid down over cylinder you get layers creating osteons around blood vessels Bone remodeling occurs throughout life 10 per year Remodeling There is a balance between bone deposition and resorption breakdown Bone deformities appear as a result of disruptions in the balance o Paget s disease osteitis deformans named for Sir James Paget weakens bones Osteoblast activity outweighs osteoclast activity bone is being laid down too fast to be properly mineralized Excessive osteoclast activity bone is being eaten away faster than it is being laid down o Osteogensis imperfect brittle bone disease Autosomal dominant disorder of type 1 collagen which makes bones brittle o Osteoporosis thinning of bone too much osteoclast activity Kyphosis widow s hump regression of estrogen no bone deposition thinning of bone bones collapse this is what makes older people appear shorter Seen later in men than in women Can cause person to be confined to bed o Dwarfism Achondroplastic dwarfism normal torso but limbs are shorter than normal large head with prominent forehead long bones stop growing at normal rate result of spontaneous mutation caused by defect in fibroblast growth factor receptor 3 FGFR3 Pituitary dwarfism the pituitary gland secretes too little growth hormone everything is in proportion just overall stature is shorter Mineralization mineral deposition o Inhibitors keep other tissue from mineralization neutralized by osteoblasts o Seed crystals first few crystals formed o Abnormal calcification ectopic ossification when inhibitors don t work properly and soft tissue undergoes mineralization and forms calculus calcified mass that appears in soft tissue Mineral Resorption Osteoclasts o Ruffled border increases surface area o Hydrogen pumps on ruffled border pump hydrogen onto bone o Chloride ions are then put onto bone o Hydrochloric acid forms pH of 4 very acidic which dissolves bone minerals o Acid phosphatase dissolves protein portion of bone Calcium Homeostasis 1100 g of calcium in adult body 9 2 10 4 mg dL Slight changes can cause serious consequences e g muscle contraction blood clotting Hypocalcemia calcium deficiency can cause overly