Anatomy Chapter 6 PDF

Chapter 6: Bones and bone tissue: 1. List and describe the major functions of the skeletal system -Protection of vital organs such as the brain -Storage of minerals like Ca2^ and PO4^3 that are necessary for electrolyte and acid-base balance (homeostasis) -Blood cell...

Chapter 6: Bones and bone tissue: 1. List and describe the major functions of the skeletal system -Protection of vital organs such as the brain -Storage of minerals like Ca2^ and PO4^3 that are necessary for electrolyte and acid-base balance (homeostasis) -Blood cell formation: The red bone marrow is the site of blood cell formation. -Fat storage: Yellow bone marrow store triglycerides (fat in bone marrow). -Aids in movement since the muscles produce body movement via their attachment to bones (muscles attached across joint). -The skeleton stand as the support since it supports the body weight of the body 2. List different types of connective tissue that play an essential role in the skeletal system. -Compact bone -Spongy bone -Hyaline cartilage -Dense regular collagenous connective tissue (tendons & ligaments) -Dense irregular connective tissue (periosteum) 3. Compare and contrast the structure, function, and location of spongy vs. compact bone -Compact bone: Hard and dense bone tissue on the exterior of a bone. Composed of repeating units called osteons. It is the strong tissue that resists the stress placed on it. Spongy bone: The inner honeycomb-like bone. It is composed of small spicules of bones that are called trabeculae. Its framework allows it to resist forces from many directions and it provides the bone marrow with a place to reside. 4. Distinguish between the different classes of bones based on shape and give examples of bones within each class -Long bone: bone is longer than it is wide (ex. Humerus) -Short bone: Bone is about as long as it is wide: (ex. Trapezium carpal bone)  -Flat bone: bone is broad, flat, and thin (ex. Sternum) -Irregular bone: bone’s shape does not fit into other classes (ex. Vertebra) -Sesamoid bone: round, flat bone found within tendon (ex. Patella) 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 -Diaphysis: Shaft that forms the long axis of the bone. -Epiphysis: Expanded end of the bone; covered by articular cartilage -Medullary cavity: Contains the red or yellow bone marrow Red bone marrow: Hematopoietic tissue located within certain bones that produces all the formed elements of the blood. -Yellow bone marrow: Stores triglycerides and consists largely of blood vessels and adipocytes -Periosteum: composed of dense irregular collagenous connective tissue that is richly supplied with blood vessels and nerves. -Endosteum: Membrane that lines the inner surfaces of bone and contains different types of bone cells. -Perforating fibers: These fibers penetrate deeply into the bone matrix, securing the periosteum in place. -Nutrient forearm: Greatest source of blood that comes from one or two nutrient arteries that enter the bone via a small hole in the diaphysis. 6. Describe the structure and function of the different components of bone extracellular matrix. Identify which components are organic and which are inorganic) - ECM organic components: Osteoid – Produced by osteoblasts, provided flexibility and tensile strength (resists twisting and stretching). It has a semi solid ground substance containing proteoglycans, GAG’s, and glycoproteins. Contains collagen. -ECM inorganic components: Hydroxyapatite crystals (primarily calcium and phosphorus salts). Other salts and ions are also incorporated into the bone matrix. They play a role of hardening the matrix and provide compressional strength. 7. List the types of cells found in bone tissue and contrast the functions of the different cell types -Osteoblasts: “immature cell”) are cuboidal to columnar cells found in the inner periosteum and endosteum that build bone. Osteoblasts perform the process of bone deposition, during which they secrete the organic matrix and aid in formation of the inorganic matrix. -Osteocytes: surrounded and eventually trapped by secreted bone matrix in a small cavity known as a lacuna. Osteocytes secrete chemicals that are required for maintaining the ECM. They also appear to recruit osteoblasts to build up areas of the bone under tension. -Osteoclasts: Osteoclasts are large, multinucleated cells derived from the fusion of cells formed in the bone marrow. They reside in shallow depressions on the internal or external surfaces of bone. Osteoclasts are responsible for the process of bone resorption, during which they break down the bone ECM. - Osteogenic cells: Stem cells that differentiate into bone building cells. 9. Contrast intramembranous & endochondral ossification and describe the steps involved in bone building in each process. -Intramembranous: The process by which certain flat bones form from mesenchymal model: Steps below: 1. Osteoblasts develop in the primary ossification center from mesenchymal cells 2. Osteoblasts secrete organic matrix, which calcifies, and trapped osteoblasts become osteocytes. 3. Osteoblasts lay down trabeculae of early spongy bone, and some of the surrounding mesenchyme differentiates into periosteum. 4. Osteoblasts un the periosteum lay down early compact bone. -Endochondral: Endochondral ossification begins during the fetal period for most bones (beginning as hyaline cartilage), although some, such as those in the wrist and ankle, ossify much later. Steps below: 1. The chondroblasts in the perichondrium differentiate into osteoblasts. 2. Osteoblasts build the bone collar on the bone’s external surface as the bone begins to ossify from the outside.  3. Simultaneously, the internal cartilage begins to calcify, and the chondrocytes die. 4. In the primary ossification center, osteoblasts replace the calcified cartilage with early spongy bone; the secondary ossification centers and medullary cavity develop. 5. As the medullary cavity enlarges, the remaining cartilage is replaced by bone; the epiphyses finish ossifying. 10. Describe the structure of the epiphyseal plate and explain how bones increase in length -Epiphyseal plate- composed of hyaline cartilage that did not ossify (growing in length!: five different zones cells: o Zone of reserve cartilage: (closest to the epiphyseal) cells that are not directly involved in bone growth but can be recruited for cell division if needed. o Zone of proliferation: actively dividing chondrocytes in lacunae. o Zone of hypertrophy and maturation: mature chondrocytes o Zone of calcification: dead chondrocytes with some calcification. o Zone of ossification: (furthest from epiphyseal) calcified chondrocytes and osteoblasts. 11. Explain why injuries affecting the epiphyseal plate can be problematic - If a bone fracture damaged epiphyseal plate, fractured bone may be shorter than usual once adult status is reached. Damage to the cartilage can accelerate closure of the plate and inhibits lengthwise growth of bone. 12. Describe the process of appositional growth and how it differs from growth in length. -Appositional growth involves osteoblasts between the periosteum and bone surface laying down new bone. The first forms circumferential lamellae and eventually deeper circumferential lamellae are removed or incorporated into osteons. Appositional growth is growing in width! 13. Distinguish between resorption and deposition and identify the cell types involved in each process -Resorption: The deconstruction of bone tissue by osteoclasts. Osteoclasts secrete hydrogen ions (H+) from their ruffled borders onto the bone ECM. The hydrogen ions make the pH more acidic, which breaks down the pH-sensitive hydroxyapatite crystals in the inorganic matrix. To degrade organic matrix, osteoclasts secrete enzymes to catalyze reactions that break down proteoglycans, glycosaminoglycans, and glycoproteins. -Deposition: The formation of new bone through osteoblast. They secrete certain proteoglycans and glycoproteins that bind to calcium ions, and it appears that they also secrete vesicles containing calcium ions, ATP, and enzymes. Begins the process of calcification. 14. Describe the feedback look involved in blood calcium homeostasis and list the factors that influence rates of deposition or resorption - If the calcium ion concentration in the blood drops too low or rises too high, major disruptions in homeostasis, therefore the response of the feedback loop involves a hormone called parathyroid hormone (PTH): → Stimulus: Blood calcium ion level decreases below normal range. → Receptor: Parathyroid gland cells detect a low blood calcium ion level. The cells of the parathyroid gland act as receptors that detect a lower-than-normal concentration of calcium ions in the blood. → Control center: Parathyroid gland cells release parathyroid hormone (PTH) into the blood. The cells of the parathyroid gland also act as control centers. When they are stimulated, they release PTH into the bloodstream. → Effector/response: Parathyroid hormone stimulates effects that increase the blood calcium ion level. → Homeostasis and negative feedback: The calcium ion concentration returns to the normal homeostatic range, and negative feedback decreases parathyroid gland cell secretion of PTH. The cells of the parathyroid gland detect when the calcium ion level has returned to the normal range. In response, they secrete smaller amounts of parathyroid hormone via a negative feedback mechanism. 15.What is osteoporosis and why does it increase susceptibility to bone fractures? - Osteoporosis is a done disease due to inadequate inorganic matrix in ECM. The bones become brittle and fracture more easily. The causes are due to dietary factors, female sex, age, lack of exercise, hormonal factors, and genetic factors. 16. Briefly describe the steps in bone repair following a fracture → Fracture break first → A hematoma fills the gap between the bone fragments → Fibroblasts and chondroblasts infiltrate the hematoma, having a soft callus form. → Osteoblasts build a bone callus → The bone callus is remodeled, and primary bone is replaced with secondary bone.