BSCI201 EXAM 3 STUDY GUIDE Dr Opoku Spring 2014 BONES Bone Remodeling Adult bones constantly undergo bone formation on the periosteal surface and bone reabsorption on the endosteal surface Bone remodeling In healthy adults the bone density remains constant because rate of bone formation rate of bone reabsorption If the rate of reabsorption outpaces rate of formation osteoporosis Children rate of bone formation outpaces bone resorption Functions of bone remodeling To maintain calcium levels in blood homeostasis o Total ionic calcium in the body 1 2 kg 1 kg is stored in bone tissue as hydroxyapatites or calcium phosphates o Normocalcemia is required to support all physiological reactions in the body i e activates enzymes a clotting factor involved in blood clot formation and is required for muscle contraction o Normocalcemia 9 11 mg 100 cc of blood To allow for bone repair after fractures Factors that Control Bone Remodeling 2 factors 1 Hormonal control hormones are released to correct homeostatic imbalances a Under hypercalcemic above 11 mg 100 cc conditions calcitonin is released by parafollicular cells inside thyroid gland C cells to stimulate osteoblasts to produce bone tissue and stimulate mineralization uses calcium from blood i Calcitonin binds to receptors on osteoblasts to activate the osteoblasts to secrete new bone tissue calcified mineralized using ionic calcium in the form of calcium phosphate b Under hypocalcemic below 9 mg 100 cc conditions parathyroid hormone PTH is released to stimulate osteoblasts to cause bone reabsorption to release calcium from bones into blood PTH affects osteoclast activity and calcium absorption from small instestines INDIRECTLY i PTH binds to PTH receptors on osteoblasts osteoclasts do not have these receptors PTH stimulates osteoblasts to produce osteoclast activating factors OAFs this activates osteoclasts to cause bone resorption calcium phosphate into the blood ii PTH stimulates excretion of phosphate increase phosphate in urine to leave behind calcium increase calcium in blood toward normal range iii PTH activates hormone I 25 dihydroxyvitamin D the only hormone that can stimulate calcium absorption from the small intestine into the blood I 25 dihydroxyvitamin D stimulates calcium reabsorption from the small intestines c a Bones remodel grow in response to mechanical stresses placed on the bones Wolff s b Forms of evidence in support of Wolff s Law i Bone attachment sites for active skeletal muscles appear thicker projections such as trochanters and spines ii Bones of upper limb often used are thicker than the less used limb bones in right arm of a right handed individual are thicker than bones in left arm and vice versa iii Long bones are thickest in the middle region of diaphysis where bending stresses are greatest 2 Mechanical Stress Law 1 iv Bedridden individual not subjected to the stresses of walking or exercise lose bone density v Astronauts who spend appreciably amount of time is space lost bone density no gravity no walking JOINTS ARTICULATIONS functional class of skeletal system 2 Classifications of joints 1 Functional Classification based on amount of movement allowed at the joint a Synarthrotic joints Synarthroses immoveable joints b Amphiarthrotic joints Amphiarthroses slightly moveable joints c Diarthrotic joints Diarthroses freely moveable joints 2 Structural Classification based on the material binding the bones at the site and the absence or presence of a joint cavity a Fibrous joints bones are bound by dense regular CT joint cavity absent 1 Sutures located only in the skull i ii Functional class of sutures in baby skull Amphiarthrotic joints allows growth and expansion of brain to 3 lbs Functional class of sutures in adult skull Synarthrotic joints once correct anatomical size of brain is attained the sutures ossify to become synarthrotic provides protection 2 Gomphoses located only between teeth and bony alveolar sockets peg in sockets i Functional class of gomphoses synarthrotic joints when it becomes amphiarthrotic loss of teeth 3 Syndesmoses bones are connected by ligaments dense regular CT Synarthrotic joints or bones are connected by interosseous membranes Amphiathrotic joints to allow movement of one bone around another bone b Cartilaginous joints cartilage connects the bones joint cavity is absent 1 Synchondroses hyaline cartilage connects bone Synarthrotic joints i ii Amphiarthrotic joints rest of costal cartilages Synarthrotic joints epiphyseal plates and 1st intercostal cartilage 2 Symphyses fibrocartilage connects bones amphiarthrotic joints i e intervertebral discs and pubic symphysis c Synovial joints ligaments cord of dense regular CT bind the bones joint cavity present ALL synovial joints are diarthrotic joints 1 The type of movement allowed at a synovial joint is dictated by the articular surface shape of the bones forming the synovial joints structure defines function 2 Plane joints pivot joints saddle joints hinge joints condyloid joints ball and socket joints 3 Formed by long bone the epiphyseal surfaces are capped by articular cartilage General Characteristics of Synovial Joints Articular cartilage caps the ends of the bones Joint cavity space that contains synovial fluid which acts like a lubricant to reduce friction enclosed by articular capsule Articular capsule double layered 1 Outer fibrous capsule 2 Inner synovial membrane immediately surround joint cavity a Dense irregular CT Areolar CT highly vascularized blood inside these layers filtered to form synovial FLUID inside joint cavity 2 b Acts as lubricant and provides nutrients to articular cartilage hyaline avascular lack of nutrients to the articular cartilage will result in erosion of the articular cartilage and the ends of bones rub against each other when the synovial joint moves VERY painful c Osteoarthritis rheumatoid arthritis autoimmune disease results in inflammation of synovial membrane restricting movements of synovial joint Ligaments that reinforce synovial joints 3 types of ligaments based on their location in relation to the articular capsule 1 Capsular or intrinsic ligaments located inside fibrous capsule i e medial collateral ligaments 2 Extracapsular ligaments located external to the articular capsule i e tibial collateral 3 ligaments Intracapsular ligaments located deep to the articular capsule i e anterior cruciate ligament ACL a blow to front of extended knee tears ACL Very active joints used often have added
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