Anatomy & Physiology - Bone
Anatomy & Physiology - Bone 80197 - BIOL 2220 - 001
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80197 - BIOL 2220 - 001
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This 9 page Class Notes was uploaded by Courtney Luber on Tuesday September 27, 2016. The Class Notes belongs to 80197 - BIOL 2220 - 001 at Clemson University taught by John R Cummings in Fall 2016. Since its upload, it has received 7 views. For similar materials see Human Anatomy and Physiology I in Biology at Clemson University.
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Date Created: 09/27/16
Bone Skeletal tissues o Cartilage Almost all bone starts out as this, then gets converted to bone tissue o Bone Skeletal cartilages o Cartilage tissue No blood vessels or nerves running through it Damage is hard to heal because no blood supply o Perichondrium Connective tissue layer covering the outer surface of cartilage tissue Dense irregular connective tissue Rich in blood vessels and nerves o Hyaline cartilage Most abundant in the skeletal system Ends of bones are covered in hyaline cartilage Costal cartilage, rings of trachea, cartilage that forms larynx, external nose, etc. o Elastic cartilage Make sup external ear (pinna), and epiglottis o Fibrocartilage Cartilage found at bones and joints Extra pad of cartilage at some joints Growth of cartilage o Appositional growth From the edge growth that is produced by the perichondrial cells Perichondrial cells secrete new matrix; matrix then leads to new space, invaded by chondrocytes, etc. o Interstitial growth Grows from within the cartilage itself Due to chondrocytes in the lacunae divide and secrete new matrix o Almost all cartilage stops growing at adolescence due to production of sex hormones Not nose or ears Skeletal divisions o Axial skeleton Function: protection and support Skull, vertebral column, ribs o Appendicular Function: locomotion/movement Everything that attaches to axial skeleton Bones of limbs and girdles Bone classifications o Long bone Longer than it is wide Upper limb bones & lower limb bones are almost all long bones NOT patella, carpals, & tarsals Every other bone in limbs ARE Diaphysis – central portion of long bone Hollow – medullary cavity o Lightens the bone Filled with marrow o Yellow marrow - marrow on medullary cavity of diaphysis of long bone; composed of adipose tissue o Red marrow - found mostly in spongy bone; blood vessels Dense, hard bone compact bone Membranous bone spongy bone Epiphyses – ends of long bones Proximal & distal No medullary cavity Epiphyseal line – if thin, adult bone; if thick, child Site of growth for bones Can predict height from epiphyseal line Membranes Periosteum - layer of dense irregular connective tissue that covers outside of bone o Outer portion & inner portion o Inner - osteogenic tissue “bone producing” Osteoblasts – build matrix that becomes bone; bone producing cells Osteoclasts – consume bone; break down bone Endosteum – lining that covers inside of bone o Composed of mainly hyaline cartilage o Also osteogenic tissue Bone textures o Compact bone Dense Provides strength and protection Made up of harversian system o Spongy bone Made up of little plates of bone called trabeculae A lot of blood vessels Bone classifications o Short bone As wide as they are long Carpals, tarsals Sesamoid bone – grows within a tendon o Flat bone Sternal, manubrium, skull, scapula, ribs o Irregular bone Bones that don’t fit in any other category Vertebrae, hip bones Bone functions o Support Rib cage supports chest muscles which allow us to breathe o Protection Skull protects brain; vertebra protect spinal cord o Movement Skeletal muscle attaches to bones locomotion o Mineral storage Ca & Po o Hematopoiesis Blood cell production Produced in red marrow Compact bone anatomy o Osteons – functional unit of bone Concentric ring of bone o Lamellae Matrix part of bone Hardened o Harversian canal “central” canal Hollow opening on middle of osteon Nerves and blood vessels run through this Blood vessels that go into our bones come from periosteum and penetrate in o Volkman’s canals “Perpendicular” canals Perpendicular to central canal o Lacunae Area that houses the osteocyte o Osteocytes Cell o Canaliculi Little canals Small channels that connect the osteocytes Chemical composition of bone o Organic components Cells Osteoblasts, osteocytes, osteoclasts Osteoid Matrix w/o middle Consists of collagen fibers, glycoproteins, and proteoglycans (central core of proteins & carbohydrate parts that stick off; mesh with each other; hold background matrix together) o Inorganic components Hydroxyapatites Mineral salt 65% of the mass of the bone Mostly calcium phosphate (CaPo ) 4 Ossification o Latin Os o Process of bone formation Ossification processes o Intramembranous Ossification from within a fibrous membrane Fibrous tissue bone o Endochondral Ossification from within cartilage (specifically hyaline cartilage) Far more common Forming bone in the first place is basically the same process as growth and repair of bone Intramembranous ossification o Membrane is center for ossification to begin o Mesoderm gives rise to bone (mesenchyme is tissue) o Accumulation of osteoblasts within membrane into a cluster in the middle of the membrane (center of ossification) o Osteoblasts start to produce bone matrix o Mineral salts are deposited in matrix and matrix hardens – calcification Mineral salts are calcium rich o Individual osteoblasts are surrounded by calcified matrix They get cut off from an oxygen supply they die = spongy bone & trabecular plates Holes in trabeculae start to fill with blood vessels o Spongy bone fills with red bone marrow o **Bone formation always starts with spongy bone** o Trabecular plates become compact leads to compact bone o Mesenchymal cells become periosteum Dense irregular connective tissue Endochondral ossification o Occurs within a cartilage model hyaline cartilage o Bone templates made of hyaline cartilage these become bone o All of the bones in your body except skull bones and clavicles are formed through endochondral ossification o Perichondrium (dense irregular connective) surrounds hyaline cartilage model o Need stimulus to get cartilage to change Arrival of a blood vessel = stimulus o Blood vessel arrival changes local conditions of tissue o Blood vessel penetrates perichondrium in the middle of hyaline cartilage template and stimulates process o Osteoblasts start to form at that site of blood vessel arrival o Osteoblasts form ring (bone collar) around center of hyaline cartilage template o Primary center of ossification – osteoblasts build up in that place o Middle begins to ossify before the ends o Osteoblasts cause cartilage cells to burst raises pH changes solubility of Ca o Bone collar starts to calcify (harden) o Cavities form early production of spongy bone in ring around center of template o Blood vessel finally gets to the middle of the template now called periosteal bud Artery, vein, and a bunch of nerves o Center is opened up to become medullary cavity Osteoclasts break down spongy bone and make this cavity o Secondary centers of ossification form as ossification extends toward ends o Plate forms between ends of bones and middle of bones o Plates are wide and don’t close until puberty o Secondary ossification process is same process as primary ossification But, no bone remodeling occurs No medullary cavity o Center of bone gets turned into compact bone through bone remodeling while ends stay predominantly as spongy bone except for the part just deep of the periosteum Bone growth o Length Longitudinal bone growth Typically the long bones that grow longer o Width Appositional bone growth Maintain medullary cavity and ratio of compact and spongy bone Growth in length o Occurs in cartilage in epiphyseal plates o Cells on diaphyseal side divide and push plate away o Older cells deeper toward diaphysis enlarge, die and calcify o Bone produced is modified into compact bone o Spongy bone is formed FIRST o Osteoclasts digest cells to lengthen medullary cavity Growth in width o Osteoblast beneath periosteum deposit bone one external surface o Osteoclast on endosteal surface remove bone o Marrow cavity enlarges Bone remodeling o Bone deposit o Bone reabsorption o Coordinated activity of osteoblasts and osteoclasts o Can occur at periosteum and at endosteum o Can aslo occur to help us remain mineral balance in body (specifically Ca) o If we have a surplus of Ca we’ll store it in bone o If we need Ca, we’ll take it from bone Bone deposit o Osteocytes (osteoblasts) produce matrix devoid of minerals Osteoid seam – matrix w/o minerals o Mineral accumulates – Ca & Po ions form hydroxyapatite accumulation comes from blood flow and nutrient you consume o Change in conditions o Minerals go out of solubility and crystalize calcification which lead to bone Bone reabsorption o T lymphocytes activate osteoclasts to secrete enzymes that digest matrix o Also secrete acid that converts Ca salts to soluble form o Digested matrix and dissolved minerals released into interstitial fluid on non-bone side of osteoclast o Eventually block bloodstream Factors controlling bone growth o Diet Foods high in calcium o Vitamins Need vitamin D to allow calcium absorption Vitamin D also produced by the skin o Hormones Affect bone growth Hormonal control of calcium o Parathyroid hormones and thyroid secretions function in feedback loop Function: regulates blood calcium levels Parathyroid = PTH Thyroid = calcitonin o Low calcium levels trigger release of PTH which activates release of osteoclasts, which release calcium o Stresses determine location of hormonal influence Only active at sites of stress o Calcitonin released when blood calcium levels are high Shuts off osteoclasts promotes calcium deposition into matrix Other hormones o Growth hormone Stimulates growth Increases bone production o Testosterone/estrogen Aid in bone growth Close epiphyseal plates Growth spurt as sex hormones are secreted Growth stops after puberty Faces/noses/jaws keep growing Fractures o Partial Break doesn’t go all the way through “incomplete fracture” o Complete Break goes all the way through o Simple (closed) Break doesn’t cause bone to go through skin o Compound (open) Break causes bone to go through skin Creates an opening for pathogens into both body and bone o Displaced Complete fracture where bones aren’t aligned anymore Have to “set” the fracture o Comminuted Causes bone to become splintered at break Broken into tiny pieces o Spiral Bones twist and separate apart o Greenstick Common in children because bones are flexible Partial fracture – one side of bone is broken and other side is bent o Impacted One part of the bone is driven forcefully into another part o Pathologic Due to disease Weakening of bone (i.e. bone cancer) Fracture repair o Fracture hematoma forms Special blood clot o Prevents loss of blood from broken blood vessels o Callus forms Fibrocartilagenous – “soft” callus Puts other connective tissue in at site of break Fibrocartilage Reestablishment of blood vessels Phagocytic cells clean area Osteoblasts begin reconstruction Bony o Remodeling Osteoclasts reopen medullary cavity and eat away excess outside part Spongy bone compact bone Where the break occurred is stronger after it is repaired than before Effects of Aging o Decrease in protein formation Matrix won’t be as strong Leads to brittle bones Can break without a trauma o Loss of calcium Osteoblast activity decreases as a result of the reduction of sex hormones Particularly important when loss of estrogen occurs Loss of calcium/bone osteoporotic bone Effects of bone thinning after menopause can be offset by changing what you do in 20’s Bone disorders o Rickets Not enough vitamin D Bones stay soft – diaphysis fail to ossify & epiphyseal plates enlarge Bowed legs weight of body forces bones to bend o Osteomalacia Not enough vitamin D as an adult Causes demineralization of bone which causes bones to soften and weaken o Padget’s disease Excessive bone deposition and reabsorption Bone constantly goes through remodeling Lots of deformities Clothes never look like they fit Initially stimulated by getting a viral infection in the bone
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