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Ch. 6
| Question | Answer |
|---|---|
| Skeletal cartilage | -made of highly resilient, molded cartilage tissue that consists mainly of water -has no blood vessels or nerves |
| Perichondrium | -layer of dense connective tissue surrounding cartilage like a girdle -helps cartilage resist outward expansion -has blood vessels for nutrient delivery to cartilage |
| Cartilage is made up of | -chondrocytes, cells encased in small cavities (lacunae) within jelly-like extracellular matrix |
| Three types of cartilage | -hyaline -elastic -fibrocartilage |
| Hyaline cartilage | -provides support, flexibility, and resilience -most abundant type; contains collagen fibers only -articular (joints), costal (ribs), respiratory (larynx), nasal cartilage (nose tip) |
| Elastic cartilage | -similar to hyaline cartilage, but has elastic fibers -external ear and epiglottis |
| Fibrocartilage | -thick collagen fibers: has great tensile strength -menisci (pad like cartilage of knee); vertebral discs |
| What are the two ways cartilage grows? | -appositional growth -interstitial growth |
| Appositional growth | -cartilage forming cells in perichondrium secrete matrix against external face of existing cartilage -new matrix laid down on surface of cartilage |
| Interstitial growth | -chondrocytes within lacunae divide and secrete new matrix, expanding cartilage from within -new matrix made within cartilage |
| Calcification of cartilage | -occurs during normal bone growth in youth, but can occur in old age -hardened cartilage isn't same as bone |
| What are the 7 functions of bone? | -support -protection -movement -mineral and growth factor storage -blood cell formation -triglyceride (fat) storage -hormone production |
| What are the 4 shapes that bones are classified into? | -long bones -short bones -flat bones -irregular bones |
| Bones are organs because? | -they contain different types of tissues |
| What tissues do bones contain? | -bone (osseous) tissue mainly -nervous tissue -cartilage -fibrous connective tissue -muscle cells -epithelial cells in its blood vessels |
| What are the 3 levels of structure? | -gross -microscopic -chemical |
| What is compact bone (Lamellar bone)? | -dense outer layer on every bone that appears smooth and solid |
| What is spongy bone? | -made up of a honeycomb of small, needle-like or flat pieces of bone called trabeculae -open spaces between trabeculae are filled with red or yellow marrow |
| Structure of short, irregular, and flat bones | -consist of thin plates of spongy bone (diploe) covered by compact bone -compact bone sandwiched between connective tissue membranes -periosteum covers outside of compact bone, and endosteum covers inside portion of compact bone -bone marrow is scattered throughout spongy bone; no defined marrow cavity -hyaline cartilage covers area of bone that is part of movable joint |
| Structure of typical long bone | -all long bones have a shaft (diaphysis), bone ends (epiphyses), and membranes (periosteum and endosteum) -consists of compact bone surrounding central cavity filled with yellow marrow in adults -between diaphysis and epiphysis is epiphyseal line |
| Epiphyses (ends of long bones) | -consist of compact bone externally and spongy bone internally -articular cartilage covers articular (joint) surfaces |
| Hematopoietic tissue in bones? | -red marrow is found within trabecular cavities of spongy bone and diploe of flat bones, such as sternum |
| Red marrow | -in newborns, medullary cavities and all spongy bone contain red marrow -in adults, red marrow is located in heads of femur and humerus, but most active areas of hematopoiesis are flat bone diploe and some irregular bones (such as hip bone) |
| Yellow marrow | -can convert to red, if person becomes anemic |
| Bone markings | -sites of muscle, ligament, and tendon attachment on external surfaces -areas involved in joint formation or conduits for blood vessels and nerves |
| What are the three types of bone markings? | -projections -depressions -opening |
| Projections | -outward bulge of bone -may be due to increased stress from muscle pull -or is a modification for joints |
| Depressions | -bowl or groove-like cut-out that can serve as passageways for vessels and nerves -or plays a role in joints |
| Openings | -hole or canal in bone that serves as passageways for blood vessels and nerves |
| What are the 5 major cell types of bone tissue? | -osteogenic cells -osteoblasts -osteocytes -bone-lining cells -osteoclasts |
| Osteogenic cells (osteoprogenitor) | -mitotically active stem cells in periosteum and endosteum -when stimulated, they turn into osteoblasts or bone-lining cells -some remain as osteogenic stem cells |
| Osteoblasts | -bone-forming cells that secrete unmineralized bone matrix called osteoid -osteoid is made up of collagen and calcium-binding proteins -collagen makes up 90% of bone protein -osteoblasts are actively mitotic |
| Osteocytes | -mature bone cells in lacunae that no longer divide -maintain bone matrix and act as stress or strain sensors -communicate info. to osteoblasts or osteoclasts so bone remodeling can occur |
| Bone-lining cells | -flat cells on bone surfaces believed to also help maintain matrix (along with osteocytes) -on external bone surface, lining cells are called periosteal cells -on internal surfaces called endosteal cells |
| Osteoclasts | -bone resorption (breakdown of bone) -giant, multinucleate cells -when active, cells are located in depressions called resorption bays -cells have ruffled borders that increase surface area for enzyme degradation of bone, also seals off area from surrounding matrix |
| Microscopic anatomy of Compact bone (Lamellar bone) consists of? | -Osteon (Haversian system), Canals and canaliculi, and Interstitial and circumferential lamellae. |
| What are the 2 types of lamellae? | -interstitial lamellae -circumferential lamellae |
| Interstitial lamellae | -lamellae that are not part of osteon -some fill gaps between forming osteons -others are remnants of osteons cut by bone remodeling |
| Circumferential lamellae | -just deep to periosteum, but superficial to endosteum, these layers of lamellae extend around entire surface of diaphysis (shaft) -help keep long bone from twisting |
| Microscopic anatomy of Spongy bone? | -appears poorly organized but is actually organized along lines of stress to help bone resist stress -trabeculae like cables on a suspension bridge, confer strength to bone -no osteons are present, but trabeculae do contain irregularly arranged lamellae and osteocytes interconnected by canaliculi -capillaries in endosteum supply nutrients |
| Chemical composition of bone | -bone is made up of both organic and inorganic components |
| Organic components of bones | -osteogenic cells, osteoblasts, osteocytes, bone-lining cells, osteoclasts and osteoid -osteoid makes up one-third of organic bone matrix, is secreted by osteoblasts -resilience of bone is due to sacrificial bond in or between collagen molecules that stretch and break to dissipate energy to prevent fractures -in no additional trauma, bonds re-form |
| Inorganic components of bones | -hydroxyapatites (mineral salts) -makeup 65% of bone by mass -consists mainly of tiny calcium phosphate crystals in and around collagen fibers -responsible for hardness and resistance to compression |
| Ossification (osteogenesis) | -is the process of bone tissue formation |
| Formation of the bony skeleton | -endochondral ossification -intramembranous ossification |
| Endochondral ossification forms all bones inferior to skull (except clavicles), bone forms by replacing hyaline cartilage, bones are called cartilage (endochondral) bones | -bone collar forms around diaphysis of the hyaline cartilage -cartilage calcifies in the center of the diaphysis and then develops cavities -the periosteal bud invades the internal cavities and spongy bone forms -the diaphysis elongates and a medullary cavity forms. Secondary ossification centers appear in the epiphyses -the epiphyses ossify. When ossification is complete, hyaline cartilage remains only in the epiphyseal plates and articular cartilages. |
| Intramembranous ossification begins within fibrous connective tissue membranes formed by mesenchymal cells; forms frontal, parietal, occipital, temporal, and clavicle bones | -ossification centers are formed when mesenchymal cells cluster and become osteoblasts -osteoid is secreted, then calcified -woven bone is formed when osteoid is laid down around blood vessels, resulting in trabeculae and outer layer of woven bone forms periosteum -lamellar bone replaces woven bone, and re marrow appears |
| Growth is length of long bones | -interstitial growth requires epiphyseal cartilage in the epiphyseal plate |
| Epiphyseal plate has 5 zones | -resting (quiescent) zone -proliferation (growth) zone -hypertrophic zone -calcification zone -ossification zone |
| Resting (quiescent) zone | -area of cartilage on epiphyseal side of epiphyseal plate that is relatively in active |
| Proliferation (growth) zone | -area of cartilage on diaphysis side of epiphyseal plate that's rapidly dividing -new cells formed |
| Hypertrophic zone | -area with older chondrocytes closer to diaphysis -cartilage lacunae enlarge and erode, forming interconnecting spaces |
| Calcification zone | -surrounding cartilage matrix calcifies; chondrocytes die and deteriorate |
| Ossification zone | -chondrocyte deterioration leaves long spicules of calcified cartilage at epiphysis-diaphysis junction -spicules are then eroded by osteoclasts and are covered with new bone by osteoblasts -replaced with spongy bone -medullary cavity as spicules are eroded -epiphyseal plate thins, then is replaced by bone -epiphyseal plate closure occurs when epiphysis and diaphysis fuse -bone length ceases |
| Growth in width, bones widen as they lengthen through appositional growth (can happen throughout life) | -bones thicken in response to increased stress from muscle activity or added weight -osteoblasts beneath periosteum secrete bone matrix on external bone -osteoblasts remove bone on endosteal surface -usually more building up than breaking down which leads to thicker, stronger bone that isn't too heavy |
| Hormonal regulation in bone growth | -growth hormone -thyroid hormone -testosterone and estrogen -excesses or deficits of any hormones causes abnormal skeletal growth |
| Bone remodeling, about 5-7% of bone mass is recycled each week | -spongy bone is replaced ~ every 3-4 years -compact bone ~ 10 years |
| Bone remodeling consists of both bone deposit and bone resorption | -occurs at surfaces of both periosteum and endosteum -remodeling units: packets of adjacent osteoblasts and osteoclasts coordinate remodeling process |
| Bone remodeling involves | -bone resorption -bone deposition -control of remodeling |
| Bone resorption | -is a function of the osteoclasts |
| Bone deposit | -new bone matrix is deposited by osteoblasts |
| Control of remodeling occurs continuously but is regulated by genetic factors and two control loops | -hormonal controls -response to mechanical stress |
| Hormonal controls | -parathyroid hormone (PTH): made by parathyroid glands in response to low blood calcium levels -calcitonin: made by parafollicular cells of thyroid gland in response to high levels of blood calcium levels -serotonin: neurotransmitter regulates mood and sleep; also interferes with osteoblast activity |
| Response to mechanical stress | -bones reflect stress they encounter -Wolf's law -mechanical stress causes remodeling by producing electrical signals when bone is deformed |
| Wolf's law states that | -bones grow or remodel in response to demands placed on them |
Created by:
Astivers8190