CBIO 2200 1nd EditionExam # 3 Study Guide Lectures: 10 - 13Lecture 10 (September 25)- What is osteology? Study of bones- Four components of skeletal system: Bones, Cartilage, Ligaments, Tendons (teeth count as bones)- Living Skeleton: what is happening with living skeleton/metabolically active- Functions of the skeleton: support, protection, movement, electrolyte balance, acid-base 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)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 cellso 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 diaphysisCharacteristics of Flat Bones- Diploe: spongy layer in the cranium and between compact bones- Contains periosteum and endosteumBone Cells- Four principle cell typeso Osteogenic cells: bone stem cells; mitotic cellso Osteoblasts: cells that lay down bone; not mitotico Osteocytes: mature bone cellso 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 boneLecture 11 (October 7)Osseous Tissue- 1/3 is organic matter (collagen, proteoglycans, etc.): synthesized by osteoblastso Osteogenesis: imperfect or brittle bone disease caused by a collagen (protein) deficiency- 2/3 is inorganic matter: calcium, phosphate, etc.; together as hydroxyapatiteo 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 childrenBone 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 middleo 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 boneBone Elongation- Metaphysis: the growth zone where cartilage is being replaced by bone- Layers of the metaphysiso Zone of reserve cartilage: chondroblasts are always producing cartilageo Zone of cell proliferation: chondrocytes multiply/proliferateo Zone of cell hypertrophy: cells grow in sizeo Zone of calcification: minerals are added to the matrixo Zone of bone deposition: bone matrix is laid down- Directions of bone growth: o Length (interstitial growth) stops at some point in lifeo 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 balanceo 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 downo Osteogensis imperfect (brittle bone disease) Autosomal dominant disorder of type 1 collagen which makes bones brittleo 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 bedo 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 depositiono Inhibitors: keep other tissue from mineralization; neutralized by osteoblastso Seed crystals: first few crystals formedo 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- Osteoclastso Ruffled border increases surface areao Hydrogen pumps: on ruffled border; pump hydrogen onto boneo Chloride ions are then put onto boneo Hydrochloric acid forms (pH of 4 – very acidic) which dissolves bone