PSIO 201 5th Edition Lecture 9Outline of Last Lecture Skeletal System Outline of Current Lecture I. Composition of BoneII. Bone Modeling and RemodelingIII. Goals of Modeling/RemodelingIV. Composition of Bones (2)Current Lecture- Osteoblasts : build bone- Osteoclasts: Break down bone- Osteogenic cell makes osteoblast makes osteocyte ; osteoclasts are separate organism1. Osteoblasts: still immature cell; involved in bone formation and synthesis of collagen and calcification2. Osteocytes: mature cell; maintains homeostasis and senses damage in bone; maintains bone tissue and signals for repair3. Osteoclast: breaks down bone; resorption (dissolves) matric through enzymes and acids; Helps regulate calcium in the blood. Calcium and proteins must pass through the cell; process known as trancytosis.Bone Modeling: Constructions of bone from scratch; formed by osteoblastsBone Remodeling: reconstruction; first bone is resorbed and then formed in same location by osteoblasts. This process happens throughout entire life. Goals: achieve strength for loading and lightness. During growth goal is to achieve peak strength by removing damaged bone- During remodeling; 1. Bone is able to detect location and magnitude of damage by use of osteocyteThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- 2. The Osteoclast removed the damage- 3. The Osteoblast replaces the old bone ( micro and macro fixes)Remodeling goes through 5 stages of reconstruction: 1. activation: preosteoclasts differentiate and mature into active osteoclasts2. resorption: osteoclasts digests minerals in matrix removing old bone3. Reversal: ends resorption; recruits osteoblasts4. Formation: osteoblasts synthesize new bone matrix5. Quiescence: osteoblasts rest bone lining for new bone completion Composition of Bone (2):Organic Substances:- Ground substances (GAGS) Glycoproteins (polysaccharide and protein) - Negatively charged tap water- Collagen fibers (type 1); fibrous protein arranged in helical form; very resistant; provides flexibility- Type 1 Collagen: Tropocollagen (3 twisted) in helical form; inside fibers are microfibrils<Fibril<Fibers. - Microfibril: found in ECMInorganic Substances:- Water- Hydroxyapatite mineral; formed by plates-
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