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bone physiology
| Question | Answer |
|---|---|
| What are two components of bone composition? | 1)Orgainc Component 2)Inorganic Component |
| Organic Component | Osteoid=a matrix of collagen & noncollagenous proteins Type I collagen (most abundant strutural protein in osteoid and 95% of total volume) |
| Inorganic Component | 1)Intially: calcium phosphate salts2)Later: transformed to hydroxyapatite (an insoluble macrocrystalline mineral) |
| Two types of bone formation, growth & remodeling? | 1) Embryological and Fetal Developemt2) Growth and remodeling after birth |
| First four steps of Embryological and fetal development of skeletal system? | 1) Skeletal system initially consists of cartilage 2) During fetal development osteoblasts cover the cartilage 3)Flat bones: Ossification ("calcification") of fivrous membranes 4)Most other bones: Ossification of hyaline membrane (cartilage) |
| The last (5th) step of embryological and fetal development of skeletal system? | 5) Later in fetal development the cartilage inside is largely replaced with bony matrix. |
| osteoblasts | 1)bone-forming cells2) osteoblasts lay down new bone matrix osteoid, as hard calcium salts when being pushed or pulled on. |
| two exception where bone matrix does not form in fetal development of skeletal system | 1) Except for articular cartilages that cover the ends of the bones2) epiphyseal plates located near the ends of the bones. |
| Growth & remodeling of bones after birth? | 1) After birth, growth and remodeling of bones continues to take place2) Bone-marrown stem cells are stimulated by cytokines (and possibly estrogen) to become osteoblasts and osteoclasts. |
| Three stimulants of osteoblasts? | 1)Hormones2)Hypercalcemia3)Increased mechanical stress |
| Three hormones that stimulates osteoblasts? | 1) Growth hormone2) Thyroid hormone3) Sex hormones (Estrogens & Androgens) |
| Four Increased mechanical stresses that stimulates osteoblasts? | 1)Physical exercise2)Muscle tension3)Weight-bearing activity4)Gravity |
| Osteoclasts | Bone-destroying cells that remove bone matrix |
| What stimulates Osteoclasts | Hormones |
| Four hormones that stimulates osteoclasts | 1)PTH due to hypoclacemia and decreased stress (such as bed rest)2) Increase Corticosteroids (both endogenous & exogenous)3)Increased thyroid hormone4)Decrease weight-bearing exercise |
| Two other names for PTH? | parathormone and parathyroid hormone |
| Bone formation is _____ than bone degradation during childhood. | Bone formation is greater than bone degradation during childhood. |
| Bone formation ________ Bone degradation after about 20 years of age. | Bone formation equals bone degradation after about 20 years of age. |
| Bone formation is ______ than bone degradation in later life. | Bone formation is less that bone degradation in later life. |
| Bone is lost when ______ activity is greater than _____ osteoblastic activity. | Bone is lost when osteoclastic activity is greater than osteoblastic activity. |
| Bone density peaks at about age ___. | Bone density peaks at about age 35. |
| Is living bone ever metabolically at rest? | Living bone is never metabolically at rest. Its matrix and mineral stores are constantly being remodeld along the lines of mechanical stress. |
| What is the Cortical bone remodeling rate at the age of two and adult? | 1)50%/year at age 22)5%/year in adult |
| Bone as calcium strage organs:There is about ___ kg of calcium in the the body and ____% is in the bone. | There is about 2kg of calcium in the body and 98% is in the bone. |
| Is calcium hoeostasis needed to main tain serum calcium levels? | Calcium homeostasis is needed to maintain serum calcium level between narrow limits. |
| Why does the body need to maintain normal range of blood calcium? | Body needs to maintain normal range of blood calcium in order to maintain neuromuscular function and other cellular activities |
| Is bone turnover constant? | Bone turnover is constant. Over 20 to 30% of skeleton turns over each year. |
| What are two calcium sources? | 1)Intestinal transport -Dietary intake -Intestinal absorption2)If intestinal intake is inadeque, in order to maintain blood levels PTH is secreted. |
| Three things PTH regulates? | 1) Bone is resorption 2) Intestinal absorption of calcium from istestinal juices3) Tubular reabsorption of urinary calcium (In kidney PTH reclaims calcium) |
| Hypercalcemia is? | 1)increased serum calcium levels2) stimulation of "C cells" in thyroid gland |
| Where are C cells found? | The C ells are found in the connective tissue between the follicles of the thyroid gland. |
| The stimulated C cells produce what? | The stimulated C cells produce increased calcitonin (a hormone) |
| Calcitonin stimulates what? | Calcitonin stimulates the osteoblasts to lay down more bone matrix. |
| What is used in the process of crating more calcified bone? | In the process of creating more calcified bone calcium from the blood is used. |
| What are five things that happen during hyperclacemia? | 1)Increased serum Ca++2)Increased calcitonin (from thyroid glands)3)Increased osteoblastic activity4)Increased calcium deposition (bone matrix formation5) decreased serum Ca++ |
| What is Hypocalcemia? | 1)decreased serum calcium levels2) Stimulation of parathyroid gland |
| What are the four things that happen when hypercalcemic? | 1)increased serum calcium levels 2)stimulates the C cells in the thyroid gland 3) The stimulated C cells produce increase Calcitonin 4)Calcitonin stimulates osteoblasts to lay down more bone matrix |
| What happens when hypocalcemic? | 1) decrease serum calcium levels stimulates the parathyroid gland |
| PTH is called "the mnost important" of what? | PTH is called the most important regulator of calcium ion (Ca++) homeostasis" |
| What are the first two roles of PTH? | 1)PTH stimulates the osteoclasts to tear down bony matrix2)In the process the calcium removed form the bone is dumped into the blood |
| What are the last two roles of PTH? | 3) PTH also stimulates the nephrons of the kidney to absorb more calcium from the urine4) PTH also stimulates the intestines to absorb more calcium from dietary intake |
| Summary of Hypocalcemia (first two steps)? | 1)decrease Ca++2)increaes PTH (from parathyroid gland)3)increased osteoclastic activity which increases destruction of bony matrix and serum Ca++ |
| Summary of Hypocalcemia (last two steps)? | 3)Increases renal (kidney absorption of calcium which increases serum Ca++4)increases intestinal absorption of calsium which increases serum Ca++ |
Created by:
katiem55