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A&P 7 Bone
A&P Lecture 3 Chap 7 Bone
| Term | Definition |
|---|---|
| Skeletal system: | composed of bones, cartilages, and ligaments joined to form a structural framework for the body |
| Cartilage is | the forerunner of most bones and covers many joints |
| Ligaments: | hold bones together at joints |
| Tendons: | attach muscle to bone |
| Osteology: | study of bone |
| Roles of the skeleton: Support: | limb bones and vertebrae support body; jaw bones support teeth; some bones support viscera |
| Protection: | of brain, spinal cord, heart, lungs, and more |
| Movement: | limb movements, breathing and other movements depend on bone |
| Bone (osseous tissue): | connective tissue with the matrix hardened by calcium phosphate and other minerals |
| Mineralization or calcification: | the hardening process of bone |
| Individual bones (each an organ) consist of | bone tissue bone marrow, cartilage, adipose tissue, nervous tissue and fibrous connective tissue - The word bone can refer to the organ or just the osseous tissue |
| Flat bones: | thin, curved plates; protect soft organs |
| Ex of flat bones: | parietal bones of skull, sternum, scapula, ribs, hip bones |
| Long bones: | longer than wide; rigid levers acted upon by muscles; crucial for movement - Classic dog bone looking bones, like tibia & fibula of lower leg, trio of bones that make up fingers (metacarpals, metatarsals, phalanges) |
| Ex of long bones: | humerus, radius, ulna, femur, tibia, fibula, metacarpals, metatarsals, phalanges |
| Short bones: | approximately equal in length and width; bones of wrist (lacunate and scaphoid) and ankle or the foots talus and cuboid |
| Irregular bones: | elaborate shapes/weirdly shaped things like the; vertebrae, pelvis, and some skull bones |
| Compact (dense or cortical bone): | dense outer shell of bone; enclosed the marrow (medullary) cavity |
| Spongy (cancellous) bone: | loosely organized bone tissue Found in center of ends and center of shafts of long bones and in middle of nearly all others Covered by more durable compact bone Skeleton is three-fourths compact and one-forth spongy bone by weight |
| Diaphysis: | shaft that provides leverage - compact bone |
| Epiphysis: | enlarged end of a long bone - spongy bone Strengthen join and anchor ligaments and tendons Bookend the bones shaft, diaphysis Surrounds a hollow medullary cavity that's full of yellow marrow |
| Epiphyseal line (growth plate): | remnant of childhood growth zone, epiphyseal plate In between the diaphysis and epiphysis Is hyaline cartilage On both sides of bone, has a proximal/distal side |
| The medullary cavity: | central, hollow space within the shaft of a long bone that contains bone marrow. In adults, this space is primarily filled w yellow bone marrow (fatty tissue) In children/some adults, it contains red bone marrow(responsible for producing blood cells) |
| Articular cartilage: | layer of hyaline cartilage that covers joint surface; allows join to move more freely Also known as hyaline cartilage in the joints |
| Nutrient foramina: | minute holes in body surface that allow blood vessels to penetrate |
| Periosteum: | external sheath covering most of the bone Outer fibrous layer of collagen and inner osteogenic layer of bone-forming cells Perforating fibers: thin layer of reticular connective tissue lining marrow cavity and all internal bone surfaces |
| Endosteum: | thin layer of reticular connective tissue lining marrow cavity and all internal bone structures |
| Flat bones have a sandwich like structure: | Inner and outer tables of compact bone enclosing layer of spongy bone in between (called diploe in cranium) |
| Inside the diaphysis is the? | medullary cavity that has yellow marrow, which is fatty tissue that needs blood within it |
| Stem cells: | have the ability to differentiate into different things - replacement cells Pluripotent cells - is able to make chondroblast and osteoblast |
| Four types of bone cells: | osteogenic cells, osteocytes, osteoblasts, and osteoclasts |
| Osteogenic cells: | stem cells found in endosteum and inner layer of periosteum Arise from embryonic mesenchyme; multiply continuously and give rise to osteoblast (bone building cell) |
| Osteoblast: | bone forming cells in endosteum and inner layer of periosteum |
| osteoblasts perform osteogenesis: | synthesize soft organic matter of matrix and promote its mineralization Stress stimulates osteogenic cells to multiply rapidly and increase the number of osteoblasts which reinforce bone |
| Osteogenic cells are | bone stem cells that differentiate into osteoblast, a bone builder, which build the matrix in bone tissue, once it builds a bone it becomes an osteocyte, a mature bone cell |
| Osteocytes: | former osteoblasts that have become trapped in the matrix they deposited Some osteocytes reabsorb bone matrix while others deposit it - Mature bone cells that monitor/maintain bone matrix - gives out instructions to osteoblasts/osteoclasts |
| Lacunae: | tiny cavities where osteocytes reside - Between the layers of lamellae are these tiny oblong cavities/spaces |
| Canaliculi: | little channels that connect lacunae (to distribute and communicate) |
| Osteoblast and osteocytes secrete the hormone | osteocalcin |
| osteocalcin - hormone | Part of body’s acute stress response, stimulates pancreatic secretion of insulin, increases insulin sensitivity, promotes energy available |
| Cytoplasmic processes of osteocytes reach into | canaliculi and contact processes of neighboring cells; gap junctions allow for passage of nutrients, wastes, signals |
| osteocytes Act as strain sensors: | when stressed, produced biochemical signals that regulate bone remodeling (shape and density changes that are adaptive) |
| Osteoclasts: | bone dissolving cells found on bone surface Very large cells formed from fusion of several stem cells; multiple (usually 3-4, but up to 50) nuclei in each cell |
| osteoclasts Perform osteolysis: | the breakdown of bone, as part of bone remodeling - Develop from same bone marrow stem cells that give rise to blood cells (different origin from other bone cells) |
| osteoclasts pt 2 | Infoldings increase surface area and form ruffled border facing bone Often reside in pits called resorption bays that they etch into the bone surface |
| Composition of osseous tissue matrix: | By dry weight, averages one-third organic and two-thirds inorganic matter |
| Organic matter: | synthesized by osteoblasts |
| Collagen and carbohydrate: | protein complexes, such as glycosaminoglycans, proteoglycans, and glycoproteins |
| Inorganic matter: | mineral component - 85% hydroxyapatite, a crystallized calcium phosphate salt - 10% calcium carbonate - Many inorganic ions - Combination forms a composite material that provides flexibility and strength |
| The matrix: | Collagen and minerals of bone form a composite material, provides flexibility and strength - Mineral portion allows the bone to support body weight without sagging |
| Rickets: | is a disease caused by mineral deficiency and resulting in soft, deformed bones Protein portion gives some flexibility |
| Collagen molecules contain | sacrificial bonds that break under stress and dissipate shock under load |
| Osteogenesis imperfecta (brittle bone disease) | results from a defect in collagen deposition |
| Concentric lamellae: | layers of matrix surrounding a central (haversian) canal running longitudinally - A central canal and its lamellae constitute and osteon (haversian system); central canals connected by transverse Perforating canals |
| Circumferential lamellae: | found encircling inner outer region of dense bone |
| Interstitial lamellae: | fill irregular regions between osteons |
| concentric lamellae has | - Collagen corkscrews down each lamella; helical arrangement in one lamella is opposite of adjacent lamella—enhances strength - Osteons separated by a cement line, which prevents spread of microfractures |
| Spongy bone anatomy: | Lattice of bone slivers (spicules) & plates (trabeculae) covered w endosteum Sponge-like appearance Spaces filled w red bone marrow |
| Bone marrow: | soft tissue occupying marrow cavities of long bones and small spaces of spongy bone |
| Red bone marrow (myeloid tissue): | Contains multiple tissues, including hematopoietic tissue—tissue that produces blood cells In nearly every bone in a child In adults, found in skull, vertebrae, ribs, sternum, part of pelvic girdle, and proximal heads of humerus and femur |
| Yellow bone marrow found in adults: | Fatty marrow that does not produce blood Can transform back to red marrow in the event of chronic anemia |
| Ossification or osteogenesis: | the formation of bone the formation of bone |
| Bone develops by two methods, both beginning with embryonic mesenchyme | Intramembranous ossification - either in membrane Enchondral ossification - or in cartilage |
| spongy bone Martrix is arranged in | lamellae, but few osteons and no central canals All osteocytes close to bone marrow Provides strength w minimal weight Trabeculae develop along bone’s lines of stress |
| Intramembranus ossification: | produces the flat bones of the skull, most of the clavicle, and part of the mandible |
| Summary of stages of intramembranous ossification happening in a membrane: | 1. Mesenchyme (stem) cells in membrane (have the ability to turn into many things) - mesenchyme give rise/become osteoblasts 2. Then the osteoblasts: a. makes collagen fibers (very organized) b. c. |
| intramembranous ossification steps pt2. what the osteoblasts do | b. makes osteoids (fluids) (on top of collagen fibers) c. make calcium phosphate crystals - triggers calcification & provides structure crystals can form on 3. Matrix hardens around osteoblasts - Osteoblast is now trapped in bone, now an osteocyte |
| Intramembranous ossification | also important in lifelong thickening and remodeling of long bones |
| Periosteum: | connective tissue on the outside of the bone |
| Endochondral ossification: | bone develops from hyaline cartilage model, produces most bones of body (bones of limbs, vertebrae, ribs, sternum, scapula, pelvic girdle, Produces more complex bones like humerus (long bones) - Starts when you're a fetus until you’ve hit puberty |
| Summary of stages of endochondral ossification happening inside the cartilage: - makes more complex shapes of bone | 1. hyaline cartilage model of bone (mesenchyme arise chondroblast --> makes cartilage & becomes chondrocytes) 2. Chondrocytes explode to make crystalized cartilage 3. Mesenchyme cells differentiate & make osteoblast - mesenchyme cells coexist |
| stages of endochondral ossification pt 2. what the osteoblasts do | a. Produces collagen b. Produces osteoids (fluids) c. Produce calcium phosphate crystals 4. Matrix hardens, osteoblast is trapped in bone = osteocyte 5. Osteoclast remodels bone - dissolves cartilage - prevents it from being inside bone |
| The growth plate is | cartilage, a continuation of cartilage growing into an area capable to grow In the growth plate they undergo the steps of endochondral ossification |
| Bone elongation: | cartilage of epiphyseal plate is depleted by late teens, early twenties Primary and secondary marrow cavities unite into one cavity Junction is filled with spongy bone Site of original epiphyseal plate is now epiphyseal line |
| Bone widening and thickening: | appositional growth & deposition of new tissue at the bone surface |
| bones continually remodeled (absorption and deposition) throughout life, | replacing 10% of skeleton per year Repairs microfactures, releases minerals into blood, reshapes bones in response to use and disuse, |
| Wolfs law of bone: | architecture of bone determined by mechanical stresses placed on it Remodeling is a collaborative and precise action of osteoblasts and osteoclasts Bony processes grow larger in response to mechanical stress |
| Bone widening and thickening Occurs by intramembranous ossification at bone surface: | Osteoblasts of inner layer of periosteum deposit osteoid tissue become trapped as tissue calcifies Layer down matrix in layers parallel to surface, forming circumferential lamellae Osteoclasts of endosteum enlarge marrow cavity |
| Mineral deposition (mineralization): | crystallization process in which calcium, phosphate, and other ions are taken from blood and deposited in bone |
| Mineral resorption: | process of dissolving bone; releases minerals into blood - It secrete proteases (Acid-tolerant protease enzyme digests collagen) to break down the organic matrix, - it removes the degraded products. |
| Mineral deposition (mineralization): 2 | - Osteoblasts produce collagen fibers that spiral length of osteon; fibers become encrusted w minerals - 1st few crystals act as seed crystals that attract more calcium & phosphate from solution |
| Mineral resorption: 2 | - Osteoclasts are large that secrete acid to resorb or dissolve the bone tissue away - osteoclasts adhere to the bone to form a sealed zone, pump protons into the zone to lower the pH, secretes hydrogen - It dissolves the mineral component. |
| Calcium: | needed for bone structure, neuron communication, muscle contraction, blood clotting, and exocytosis Minerals deposited in skeleton & withdrawn when they are needed for other purposes About 18% of skeletal calcium is exchanged with blood each year |
| Normal calcium concentration in blood plasma is: | 9.2–10.4 mg/dl |
| Hypocalcemia: | calcium deficiency; causes excessive excitability of nervous system and muscles |
| Hypercalcemia: | calcium excess; causes nerve and muscle cells to be less excitable than normal - Hypercalcemia is rare, but hypocalcemia results from a variety of causes (low vitamin D, diarrhea, thyroid tumors, underactive parathyroid glands) |
| Calcium homeostasis depends on: | a balance between dietary intake, urinary and fecal losses, and exchanges between osseous tissue |
| Calcium homeostasis is regulated by 2 hormones: | Calcitonin Parathyroid hormone |
| Calcitonin: | produced by parafollicular (clear, C) cells of thyroid gland; secreted when blood calcium levels are too high |
| Calcitonin Lowers blood calcium concentration in two ways: | Osteoclast inhibition Osteoblast stimulation |
| Osteoclast inhibition: | thereby reducing bone resorption |
| Osteoblast stimulation: | to deposit calcium into bone |
| Calcitonin is Important in children but: | weak effect in adults Osteoclasts more active in children due to faster remodeling May inhibit bone loss in pregnant and lactating women |
| Parathyroid hormone (PTH) | : is secreted by parathyroid glands on posterior surface of thyroid, in response to low calcium in blood |
| PTH raises calcium blood level by four mechanisms: | - Binds to receptors on osteoblasts - stimulate osteoclasts to resorb bone - Promotes calcium reabsorption by kidneys - Promotes final step of calcitriol synthesis in kidneys, - Inhibits collagen synthesis by osteoblasts, inhibiting bone deposition |
| For Phosphate Homeostasis in the Average adult they have: | 500 to 800 g phosphorus with 85 to 90% of it in the bones Normal plasma concentration is 3.5 to 4.0 mg/dl |
| Phosphate is also needed in | DNA, RNA, ATP, and phospholipids Phosphate levels are not regulated as tightly as calcium levels Calcitriol raises phosphate levels by promoting its absorption by small intestine - PTH lowers blood phosphate levels by promoting its urinary excretion |
| Bone growth especially rapid in: | puberty & adolescence Surges of growth hormone, estrogen, testosterone occur & promote ossification - it stimulate multiplication of osteogenic cells, matrix deposition by osteoblasts, and chondrocyte multiplication and hypertrophy in metaphysis |
| Difference in puberty in male/female: | Girls grow faster than boys and reach full height earlier— estrogen has stronger effect than testosterone on bone growth Males grow for a longer time and also taller |
| Anabolic steroids cause growth to | stop as epiphyseal plate “closes” prematurely; results in abnormally short adult stature |
| Orthopedics: | branch of medicine for prevention and correction of disorders of bones, joints, muscles Bone fractures classified as stress fracture or pathological fracture |
| Stress fracture: | break caused by abnormal trauma to a bone (example: in a fall) |
| Pathological fracture: | break in a bone weakened by disease (such as bone cancer or osteoporosis), usually caused by a stress that would not break a healthy bone |
| Fractures also classified by structural characteristics: | Direction of fracture line, such as nondisplaced,displaced Cracked or in multiple pieces, such as comminuted, greenstick |
| Uncomplicated fracture heals in about: | 8-12 weeks; longer for more complex fractures |
| 1st stage of healing a fracture: | Hematoma formation, blood clot (fracture hematoma) converted to granulation tissue |
| 2nd stage of healing a fracture: | Soft callus formation, deposition of collagen and fibrocartilage converts granulation tissue to soft callus |
| 3rd stage of healing a fracture: | Hard callus formation, osteoblasts deposit temporary bony collar to unite broken pieces while ossification occurs |
| 4 stage of healing a fracture: | Bone remodeling, small bone fragments are removed by osteoclasts; osteoblasts deposit spongy bone and convert it to compact bone |
| Beginning around age 40: | net loss of bone mass as resorption outpaces deposition |
| Contributing factors to other bone disorders: | Sex—women more affected than men Build—small, light frames affected more than heavier people Ancestry—White women of Asian and European origin especially vulnerable Age—older individuals are more vulnerable |
| Osteopenia: | measurable decline in bone density; may advance to osteoporosis |
| Osteoporosis: | severe loss of bone density; bones easily fracture |
| Common assessment procedure of osteoporosis: | Bone densitometry, or DEXA scan , scans spine/ hips with low-dose X-rays Treatment strategies: drugs that stimulate bone deposition or slow rate of resorption Preventative methods: weight-bearing exercise throughout life, even old age |
| Axial bones: | includes 80 bones divided into the skull, vertebral column, and thoracic cage (rib cage) regions - are found along the bodies vertical axis The foundation, carry other body parts, provide skeletal support, and organ protection |
| Appendicular bones: | every other bone that helps us move around Bones in limbs, pelvis, shoulder blade, Then these are classified into long bone, short bones, flat bones, and irregular bones |
| Red bone marrow: | responsible for producing blood cells |
| yellow bone marrow: | stores energy as a fat, a fatty tissue. |
| Osteons: | basic structural unit of bone Cylindrical, weight bearing structures that run parallel to the bone’s axis Inside a bone there are cross-sections of osteons Each tube is lamellae |
| Lamellae: | a tube of osteon in the bone that is filled with collagen fibers that run in the same direction Inside each other they go in alternating direction to resist torsion stress/twisting of bone |
| Central Canal | Running inside each tube of the osteoblasts is central canals with nerves/blood vessels |
| Osseous matrix is composed of? | Calcium phosphate |
| The matrix of osseous tissue averages, by dry weight, about | 1/3 organic & 23 inorganic matter organic matter, synthesized by osteoblasts, includes: collagen, various protein–carbohydrate complexes inorganic matter is abt 85% crystallized calcium phosphate salt, 10% calcium carbonate, inorganic ions. |
| Which of the following best describes osseous tissue? | A connective tissue with a hardened matrix that makes up bone |
| Which of the following is not a component of the skeletal system? | Tendons Tendons are similar to ligaments, however, they connect muscles to bones. |
| _________ is/are found in compact bone but not spongy bone. | central canals Central canals are not necessary in spongy bone because of the close proximity of the marrow. |
| The bones of the skull form by which type of ossification? | Intramembranous |
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Katepop10