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ANSC 2340 (44)
Lecture 15

ANSC 2340 Lecture 15: Bones and Cartilage
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Department
Animal Science
Course
ANSC 2340
Professor
Ira Mandell
Semester
Winter

Description
1. Bones and Cartilage (ANSC 2340) What is Bone (Dry Matter Basis)?  In this situation, the bone has been dried with all water removed  Made up of organic and inorganic matter  Define organic + inorganic matter? o Organic: C containing compounds o Inorganic: minerals  33% organic tissue: fibrous tissues + cells o Organic matrix of bone made up of Collagen o Protein and polysaccharide ground substance (type of CT found between cells & collagen fibers) called GAGS (glycoaminoglycans) (glycoprotein) which contains chondroitin sulfate  Chondrotin sulfate (a sulfated GAGS) provides resistance to compression in day to day activities  Think about the “pounding” your bones take on a daily basis with the activities you do o The collagen and ground substance including chondroitin sulfate make up a matrix with collagen fibers embedded in the GAGS o This matrix forms the background structure or organic framework of bone  Role of organic tissue in bone? o Resilience, toughness, and flexibility  resilience = referred to durability on a day to day basis and ability to return to its original form no matter how it is handles  67% inorganic salts (minerals) dry matter basis o 80% CaP (calcium phytate) o Rest is CaC3 and magnesium phosphate o Role of inorganic salts? à next slide o Tremendous amount of Ca in bone  10 cc bone contains 10 g Ca (1 cc = 1 ml in volume)  Most tissues: 6 mg or 0.006 g/ 10 cc  Not much Ca outside bones & teeth but Ca is also v important for nervous system, muscle contraction, cofactors in enzymes, blood clotting  Blood: 10 mg/ 100 ml  At least 99% of body’s Ca in bones & teeth  Minerals or inorganic salts have 3 functions: o Hardness o Rigidity o Give resistance to x-rays What is Bone?  What will happen if we remove the salts? We would affect bone structure o Process of decalcification  How would we do this?  Treat with acids to destroy the mineral  Effect on form?  Eliminate the rigidity of bone so it becomes flexible and we can tie it into a knot  What will happen if we remove the organic tissue? o This would affect bone structure o How would we do this?  Burn it (measuring ash) o Effect on form?  Removing the organic framework would turn it into dust Composition of Bone When Water is Still Present  Much water: 25% or more than what most people think that bone would contain  Mineral content (around 45%) o Primary constituents in what ratio?  Ca/P in a 2:1 ratio o Significance of this ratio to animal nutrition? Based on this ratio in bone, this is a recommended ratio for supplying Ca/P when we formulate diets for farm animals  OM content: 30% o Primary component is collagen embedded in GAGS  Lactating dairy cow and laying hen use tremendous amount of Ca going into milk and egg shells o every times a bird lays an egg –> 2g of Ca goes into the shell, 1 g comes from bone stores Composition of Bone  Appearance of bone o Lifeless tissue o Bone is a dynamic tissue  See bone turnover (formation + resorption)  Ability to repair itself nd  Bone is 2 hardest tissue in body  #1 is teeth Function of Bone:  Protection o Skull to protect 3 major components  NS, respiratory system, sense organs, digest system o Vertebral column for?  Spinal cord o Rib cage for?  Lungs and heart o Pelvis for?  Organs in hindquarter o Appearance of an animal (structure)  Scaffold to support cells and tissues o Act as a lever (acts to move objects) locomotion and work  limbs often considered machines  Mineral storage (reservoir for Ca + P) o Every day existence (roles of Ca, lactation)  Enzyme action as a cofactor; Nerve impulse transmission; Muscle contraction o High levels of production (dairy cows, hens)  Milk: a good source of Ca  Egg shell: made up of C3CO  Another name for CaC3 = limestone  Hen deposits 2 g/day Ca into the egg shell  1 g comes from the diet; other 1 g comes from her own bone stores  Blood formation due to location of bone meryl (blood cell synthesis) Mature Bone:  Osteoblasts (cells) that synthesize bone o First secrete a soft, flexible matrix of organic tissue made up of…  Collagen fibers embedded in ground substance  Support tissue or organic framework made up of PS (polysaccharide) and protein  Matrix of organic tissue also called osteoid o Then osteoblasts harden matrix via ossification  Add hydroxyapatite [C10(PO4 6(OH2 ] crystals  Deposition of Ca salts which gives bone its hardness o Osteoblasts involved in both synthesis of the organic framework and then the calcification of the organic matrix  Osteocyte is trapped by the calcified bone matrix  Presence of threadlike cellular processes: only way to communicate with each other and blood  Extensions pass through fine tubes called canaliculi Mature Bone:  Osteoblasts synthesize bone o The process of synthesizing bone traps the osteoblast in the ossified matrix called lacunae (small cavities which means little lakes)  Osteoblasts will be transformed into osteocytes (bone cells) which are trapped in the lacunae  Osteocyte is a mature bone cell o Osteocytes will have contact with each other and a blood supply via development of long cytoplasmic extensions (threadlike cellular processes: their only way to communicate with each other and to blood)  These extensions will pass thru fine tubes called canaliculi  Cytoplasmic extensions will pass into regions where diffusion can take place  Importance = acquiring nutrients and getting rid of waste products Cancellous Bone  = spongy bone  Central portion of bone filled with bony spicules (spines or rods) or trabeculae (plates) o Arrangement of spicules (similar to the framework of a sponge)  Lots of spaces between them which are occupied by bone marrow and blood vessels o Functional basis of spicules:  Deal with muscles, gravity, and other bones  Handle strains + stresses exerted by muscles  As muscles contract, they pull on bones  Handle pushing + pulling by bones, muscles, gravity  Act as shock absorbers  Architecture of this bone looks like a sponge  Doesn’t look it but it is very strong  Can handle multiple strains/stresses  Found in extremities of long bones o Need resistance to compression w/o a lot of added weight o 2 major characteristics  Very light in weight  Very strong  Red marrow found in cancellous bone enclosed which does not degenerate (lessen) as the animal gets older o Age effect on red marrow  In the other bone type, (compact bone), red marrow will be present in young animals but converted to yellow marrow as animal ages  Red marrow found in ends of long bones, ribs, sternum, vertebrate  Rib + sternum marrow o Primary source to synthesize blood cells The Other Bone Class: Compact Bone  Characteristics: heavy, dense, strong  Found in shafts of long bone and the outside layer of all bones o What’s a long bone? Simply a bone that is longer than it is wide o Examples: limb bones such as Humerus, Femur, Radius  Composed of tiny, tightly compacted cylinders (laminated tubes) of bone called Haversian or osteonal systems  Each osteon contains o Central canal or Haversian canal which contains blood vessels, lymph vessels and nerves o This canal surrounded by circular plates of bone called osteonal lamellae (ossified bone matrix) which form the laminated tube or cylinder  Haversian or osteonal systems: tight compact cylinders of bone  Osteon made up of a central or Haversian canal which contains blood vessels, lymph vessels, and nerves  Osteocytes contact each other via canaliculi  Canaliculi used for nutrient + waste exchange  Canal surrounded by circular plates of bone called osteonal lamellae  Osteoblasts are forming the lamellae sequentially working from outside towards the haversian canal  Textbook describes the lamellae as paper towels wrapped around a cardboard roll  Compact bone covers the shaft of the long bones and the outside layers of all bones Components of Long Bone (KNOW)  Epiphysis  Diaphysis  Epiphyseal plate or physis  Articular cartilage  Endosteum  Periosteum Components of Long Bone  Made up of shaft and 2 extremities  Epiphysis: two of them which make up the extremities (ends of the bone) Made up primarily of spongy or cancellous bone o Contains trabeculae (plates) or spicules (rods) of mineralized tissue  Provide lightness + strength  Acts as shock absorbers and levers o Where is compact bone located here? Covers the extremities and make up the shaft  Diaphysis: also called shaft; lies between extremities o Contains marrow or medullary cavity  Covered by compact bone  Site of where bone can increase in diameter  Medullary cavity important for the layer (laying hen) for providing calcium for egg shell production  50% of the Ca requirements coming from the diet while the other 50% comes from the medullary cavity (stores Ca from the diet)  Epiphyseal plate or physis  known as a growth plate o Layer of hyaline cartilage between ends (Epiphyses) + shaft (Diaphysis) of long bone o Site of where bone will increase in length o Layer of hyaline cartilage will be replaced by bone as the animal gets older o Separates the extremities from the shaft, eventually the hyaline cartilage will be osteofied  Articular cartilage o Found where?  On the surface of compact bone where one bone will come in contact with another bone to form a joint  Aren’t “end” of bones made up of cancellous or spongy bone?  “End” of bones covered by another 2 “layers”  At the end of bones, the cancellous/spongy bone is covered by compact bone which is then covered by articular cartilage o Hyaline cartilage makes up articular cartilage  Why? Reduces friction and wear & tear in joints o As people get older, they will lose this cartilage (have bone-on-bone contact)  Endosteum o Membrane which lines all surfaces facing medullary cavity: contains osteoblasts (bone making cells) and osteoclasts (bone destroying cells) o Made up of connective tissue Periosteum  Periosteum = covers all bone except for joint surfaces o Made up of connective tissue  Made up of 2 layers o Outer made up of fibrous tissue (CT) o Inner layer with osteoblasts  Synthesize + secrete organic matrix  Mineralization of organic matrix  Inactive in adults  Acts to o Increase shafts + diameter o Heal fractures Types of Marrow  Red o Most common form in the young o Found in limited areas in older animals o Blood forming  Yellow o Hard, fatty o Stores fat o No blood forming capabilities o Most common type of bone marr
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