Chapter 6 Powerpoint Slides PDF

Chapter 6: Bones  1. List and describe the major functions of the skeletal system 2. List different types of connective tissue that play an essential role in the skeletal system. 3. Compare and contrast the structure, function, and location of spongy vs. compac...

Chapter 6: Bones  1. List and describe the major functions of the skeletal system 2. List different types of connective tissue that play an essential role in the skeletal system. 3. Compare and contrast the structure, function, and location of spongy vs. compact bone 4. Distinguish between the different classes of bones based on shape and give examples of bones within each class 5. Define the following terms and briefly describe the function of these structures: diaphysis, epiphysis, medullary cavity, red bone marrow, yellow bone marrow, periosteum, endosteum, perforating (Sharpey’s) fibers, nutrient foramen 6. Describe the structure and function of the different components of bone extracellular matrix. Identify which components are organic and which are inorganic) Learning 7. List the types of cells found in bone tissue and contrast the functions of the different cell types 8. Describe and contrast the structure, function, and location of compact bone vs. spongy bone Objectives 9. Contrast intramembranous & endochondral ossification and describe the steps involved in bone building in each process. 10. Describe the structure of the epiphyseal plate and explain how bones increase in length 11. Explain why injuries affecting the epiphyseal plate can be problematic 12. Describe the process of appositional growth and how it differs from growth in length. 13. Distinguish between resorption and deposition and identify the cell types involved in each process 14. Describe the feedback look involved in blood calcium homeostasis and list the factors that influence rates of deposition or resorption 15.What is osteoporosis and why does it increase susceptibility to bone fractures? 16. Briefly describe the steps in bone repair following a fracture The Skeletal System Bones are the primary organs of the skeletal system. Two types of osseous (bone) tissue will be found in bones: 1. Compact bone 2. Spongy bone Other connective tissues are also important components of the skeletal system: 1. Hyaline cartilage 2. Fibrocartilage 3. Dense regular collagenous connective tissue (tendons & ligaments) 4. Dense irregular connective tissue (periosteum) Bones can be classified by shape.  Epiphysis Expanded end of the bone; covered by articular cartilage Gross Diaphysis anatomy of shaft that forms the long axis of the bone a long bone Epiphysis Expanded end of the bone; covered by articular cartilage Internal Structure of a Long Bone Regions of compact bone & spongy bone Epiphyseal line: remnant of the epiphyseal plate Medullary cavity containing red or yellow bone marrow Endosteum: membrane that lines the inner surfaces of bone and contains different types of bone cells Most surfaces of the long bone are covered Tough sheath with by an outer the layer of dense irregular connective tissue periosteum. Richly supplied with blood vessels and nerves Anchored to the bone by Perforating (Sharpey’s) fibers composed of collagen Inner cellular layer contains different types of bone cells Bone is highly vascularized & innervated. Blood vessels are especially numerous in areas with spongy bone Blood vessels enter from periosteum Typically only 1 nutrient artery enters and 1 nutrient vein leaves the bone through the nutrient foramen Nerves also go through the nutrient foramen and innervate the bone, periosteum, endosteum, and marrow cavity Bone Marrow  Red Bone Marrow is hematopoietic. Contains reticular connective tissue, blood cells, and adipocytes  Yellow Bone Marrow stores triglycerides and consists largely of blood vessels and adipocytes Structure of other External surface of compact bone bone classes: Interior of spongy bone Bone Cells and Bone Matrix Bone extracellular matrix (ECM) contains organic and inorganic components. ECM Organic Components : Osteoid (~33%) Produced by osteoblasts Provides flexibility and tensile strength (resists twisting and stretching) Collagen Semi solid ground substance containing proteoglycans , GAGs, and glycoproteins ECM Inorganic Components (~67%) Hydroxyapatite crystals (primarily hydroxyapatite: calcium and phosphorus salts) Ca10(PO4)6(OH)2 Other salts and ions are also incorporated into the bone matrix Harden the matrix and provide compressional strength Bone Cells Bone Cell Types Osteoblasts & Osteocytes Osteoclasts Structure of Compact Bone Osteon or Haversian system Structural unit of compact bone Consists of: Concentric Lamellae Central Canal Lacunae Osteocytes Canaliculi  Concentric Lamellae  Thin layers arranged in concentric rings  Collagen fibers in a single lamella run the same direction  Collagen in different lamellae runs in opposite directions  Prevents twisting (adds strength)  Central (Haversian) Canal  Contains blood vessels and nerves 6-  Lacunae  Small cavities in bone that contain osteocytes  Canaliculi  Hair-like canals that connect lacunae to each other and the central canal  Osteocytes extend through the canaliculi to contact neighbors  Allow oxygen and nutrients to reach all osteocytes 6-  Osteons are not permanent structures but are regularly resorbed and rebuilt.  Interstitial lamellae  Lamellae outside of the osteon  Remnants of resorbed osteons  Fill gaps between forming osteons or are the remains of osteons that have been cut through by bone remodeling  Circumferential lamellae  Extend around the entire circumference of the diaphysis  Just deep to the periosteum  Resist twisting of the entire bone  Perforating canals (Volkmann’s canals)  Channels lying at right angles to the central canal  Connect blood and nerve supply of the periosteum to that of the Haversian canal Microscopic Structure of Spongy Bone Trabeculae composed of concentric lamellae with osteocytes in lacunae Usually not arranged into osteons No central or perforating canals 4-   Two types of Ossification: Bone  Endochondral  Most bones Developme  Built on a hyaline cartilage model nt:  Intramembranous  Many flatbones Osteogenesi  Built on a model of embryonic s& connective tissue (mesenchyme) Ossification  Both methods of ossification produce immature primary (woven) bone that is then remodeled and replaced with mature secondary or lamellar bone 6- Intramembran ous Ossification Endochond ral Ossificatio n Endochond ral Ossificatio n Fetal Ossificatio n Osteoporosis  Bone disease due to inadequate inorganic matrix in ECM  Bones become brittle and fracture more easily  Causes include dietary factors, female sex, age, lack of exercise, hormonal factors and genetic factors  Treatments are designed to prevent further bone loss and increase surviving bone mass Image from: https://www.endocrine.org/patient-engagement/endocrine-library/osteoporosis Growth in Length 4-   Epiphyseal plate – composed of hyaline cartilage that did not ossify; five different zones of cells:  Zone of reserve cartilage – (closest to epiphysis) cells that are not directly involved in bone growth but can be recruited for cell division if Structure of needed the  Zone of proliferation (next region) – actively dividing chondrocytes in lacunae Epiphyseal  Zone of hypertrophy and maturation (next region closer to Plate diaphysis) – mature chondrocytes  Zone of calcification (second to last region) – dead chondrocytes; some calcified  Zone of ossification (last region) – calcified chondrocytes and osteoblasts 4- Structure of the Epiphyseal Plate 4- Structure of the Epiphyseal Plate 4- Structure of the Epiphyseal Plate 4-   If bone fracture damages epiphyseal plate, fractured bone may be Fracture of shorter than usual once the adult status is reached Epiphyseal Plate  Damage to cartilage accelerates closure of the plate  inhibits lengthwise growth of bone Appositional Growth  Appositional growth involves osteoblasts between the periosteum and bone surface laying down new bone  First forms circumferential lamellae  Eventually deeper circumferential lamellae are removed or incorporated into osteons Age Determinatio n Using Ossification Bone Continuous process of bone formation and loss after growth in length has finished Remodeling Deposition & Resorption Reasons for bone formation & loss: Maintenance of calcium ion homeostasis Replacement of primary bone with secondary bone Bone repair Replacement of old brittle bone with newer bone Adaptation to tension and stress Homeostasis & Feedback Loops for Blood Calcium Levels Factors impacting resorption & deposition  Fracture (break) Bleeding Bone Repair: Hematoma (pool of blood) Steps in repairing a Soft Callus fracture Bony Callus Secondary Bone Bone Repair: Steps in repairing a fracture