BSCI201 EXAM 3 STUDY GUIDE- Dr. Opoku Spring 2014BONESBone 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 fracturesFactors that Control Bone Remodeling-2 factors:1. Hormonal control: hormones are released to correct homeostatic imbalancesa. 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 bloodi. Calcitonin binds to receptors on osteoblasts to activate the osteoblasts to secrete new bone tissue, calcified/mineralized using ionic calcium in the form of calciumphosphateb. 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 INDIRECTLYi. 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 bloodii. 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 bloodc. I,25 dihydroxyvitamin D stimulates calcium reabsorption from the small intestines2. Mechanical Stress:a. Bones remodel/grow in response to mechanical stresses placed on the bones= Wolff’s Lawb. Forms of evidence in support of Wolff’s Law:i. Bone attachment sites for active skeletal muscles appear thicker- projections suchas trochanters and spinesii. Bones of upper limb often used are thicker than the less used limb- bones in rightarm of a right-handed individual are thicker than bones in left arm and vice versaiii. Long bones are thickest in the middle region of diaphysis where bending stresses are greatest1iv. Bedridden individual not subjected to the stresses of walking or exercise lose bone densityv. 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 jointa. Synarthrotic joints (Synarthroses)= immoveable jointsb. Amphiarthrotic joints (Amphiarthroses)= slightly moveable jointsc. Diarthrotic joints (Diarthroses)= freely moveable joints2. Structural Classification- based on the material binding the bones at the site, and the absence or presence of a joint cavitya. Fibrous joints= bones are bound by dense regular CT; joint cavity absent1. Sutures: located only in the skull i. Functional class of sutures in baby skull: Amphiarthrotic joints; allows growth and expansion of brain to 3 lbsii. 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 teeth3. Syndesmoses: bones are connected by ligaments (dense regular CT/Synarthroticjoints) 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 absent1. Synchondroses: hyaline cartilage connects bone (Synarthrotic joints)i. Amphiarthrotic joints= rest of costal cartilagesii. Synarthrotic joints= epiphyseal plates and 1st intercostal cartilage2.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 joints3.Formed by long bone the epiphyseal surfaces are capped by articular cartilageGeneral 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 byarticular capsule-Articular capsule: double-layered 1. Outer fibrous capsule2. Inner synovial membrane (immediately surround joint cavity)a. Dense irregular CT/Areolar CT= highly vascularized; blood inside these layers filtered toform synovial FLUID inside joint cavity2b. 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 ligaments)3. Intracapsular ligaments- located deep to
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