Artifact 12 10

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Artifact 12 10

  1. 1. © Many football players are able to name their long bones (like thehumerus) because of incidents that they may have experienced in a game.For those of us who have not broken or fractured enough bones to have memorized what theyare, here is a list of the four different types of bones… © 1) Types of bones- all bones contain two types of bone tissue (compact and spongy) Long bones o The name really says it all o Name is based off of the shape and length of the bones o Examples: femur and humerus Short bones o Not long bones o Are small, “box shaped” (1)
  2. 2. o Length is about = to the width o Examples: wrist and ankle bones Flat bones o Are usually quite large o “Generally broad and thin with a flattened and often curved surface” (1) o Examples: shoulder blades, ribs, and breastbone Irregular bones o “various sizes and shapes” (1) o Examples: spine and facial bones o Sesamoid- kneecap/patella 2) Structure of Long Bone o Diaphyis- shaft, cylinder shape, provides support o Epiphyses- top and bottom, bulbous shape, mainly spongy bone o Articular cartilage- covers joint surfaces o Periostereum- “dense, white fibrous membrane that covers bone except at joint surfaces” (1) o Medullary- hollow tube space, in the diaphysis, necessary for survival of the bone o Endosteum- lines the medullary cavity, epithelial membrane o (1) 3) Bone Tissue-“Consists of cells, fibers, and extracellular material, or matrix” (1)
  3. 3. o Inorganic Salts- hydroxyapatite calcium crystals give the bone structure by being hardened in a process known as calcification in order to give the bones their strength (the crystals are hardened) (1). o Measuring density- Osteoporosis is a disease that forms over time where the bones lose density. o Organic matrix- made up of “collagenous fibers… protein and polysaccharides called ground substance” (1), adds to strength and flexibility of bones. ©Haversian systems Lamelle: concentric, cylinder-shaped layers of calcified matrix Lasunae: small spaces containing tissue fluid in which bone cells lie imprisoned between the hard layers of the lamellae Canaliculi: ultrasmall canals radiating in all directions from the lacunae and connecting them to each other and into a larger canal, the Haversian canal Haversian canal: extends lengthwise through the center of each Haversian system; contains blood vessels, lymphatic vessels, and nerves from the Harversian canal; nutrients and oxygen move through canaliculi to the lacunae and their bone cells—a short distance of about 0.1 mm or lessBone Cells Osteoblasts: small cells that synthesize and secrete a specialized organic matrix, called osteoid
  4. 4. Osteoclasts: giant multinucleate cells that are responsible for the active erosion of bone minerals Osteocytes: mature, nondividing osteoblasts that have become surrounded by matrix and now lie within lacunaeFive homeostatic functions of bones: 1. Mechanical support of soft tissues 2. Levers for muscle action 3. Protection of the central nervous system 4. Release of calcium and other ions for the maintenance of a constant ionic environment in the extracellular fluid 5. Housing and support of hemopoiesis(2)Intramembranous vs. Endochondral boneIntramembranous bones are always flat bonesEndochondral bones include the long, short, and irregular bones (3) © Describe steps involved in bone fracture repair. “How fracture healing happensBone fracture healing is a complex process with four steps. All bone fractures must go throughthis process.” (4)
  5. 5. “Step 1: “Step 2: Soft Inflammation callus When a bone As blood cells fractures, white divide and blood cells move multiply near in to the area to the break, new clean up debris blood vessels created by the develop to fuel break. This creates the repair © (4)© (4) inflammation, process. The which triggers the body also growth of new begins to create blood cells — the cartilage around first stage of the bone healing.” (4) fracture to bridge the gap in the bone. Called the soft callus, this cartilage is simply fibrous tissue.” (4) “Step 3: Hard “Step 4: callus Remodeling Eventually, the In the final body replaces the stage of bone soft callus with a fracture healing, hard callus, the body connecting the replaces old bone fragments bone with new more solidly. This bone in a© (4) © (4) stronger callus, continual which creates a process called bulge at the site of remodeling.
  6. 6. the fracture, can Remodeling generally be seen makes bones in X-rays just a stronger and few weeks after more compact the bone fracture and blood occurs.” (4) circulation in the bone improves.” (4)“When a patient breaks a bone, doctors take measures to encourage strong, quick repair. Thesemeasures include: Setting and immobilizing the break. If necessary, a physician will move bone segments back into place before immobilizing the fracture using a cast or brace. Surgery. Some patients may need surgery to set and stabilize a fracture — a process that can involve metal plates, screws or nails. If fractures do not show signs of healing, additional intervention is necessary. Some doctors choose to perform additional surgeries; others turn to devices like EXOGEN. Bone growth stimulation. To help heal fractures, many doctors prescribe a device like EXOGEN — the only stimulator that uses ultrasound waves to stimulate the body’s natural healing process, helping boost bone growth. Therapy. If a patient is in a cast for a long period of time, he or she may benefit from physical therapy to regain full use of stiff or weak muscles.” (4) Compare the basic structural units of bone andcartilage. 1.Cartilage: Collagenous fibers embedded in a rubbery ground-substance calledChondrin, which is a protein-carbohydrate complex. The chondron is secreted by chondrocytes.2.Bone: mineralized connective tissue. Cells called osteocytes deposit a matrix of collagen andcalcium-phosphate which harden to form crystals of a substance called hydroxyapatite.Mammalian bone is constructed from repeated units called HaversianUnits.The process ofmaking new bone is called ossification.
  7. 7.  Identify the three specialized types of cartilage, giveexamples of each, andsummarize the structuralandfunctional differences among them. Cartilage is a specialized form of connective tissue containing chondrocytes whichsecrete, and are surrounded by, an extensive intercellular matrix. Chondrocytes occur singly or inisogenous groups, composed of 2-8 cells derived by mitosis from a single chondrocyte. Thecells are in the lacunae (cavities) within the matrix. Matrix stains more intensely immediatelyadjacent to the lacunae and the dark staining zone is called the capsule. The strength anddurability of cartilage are properties of the matrix, which is an interlaced network of collagenousand/or elastic fibers in a ground substance, a gel of complex proteoglycans. The collagen ismostly Type II. How does this differ from dense C.T.?There are three types of cartilage characterized by the composition of the intercellular matrix.(1) hyaline, (2) elastic and (3) fibrocartilage. Hyaline cartilage is found lining articular surfaces, and in the nasal septum, tracheal rings, costal cartilages, and the epiphyseal cartilage of growing bone. Study the trachea on slide #72 (trachea). Even numbered boxes usually contain slides stained for elastic tissues, odd numbered boxes have slides stained with hematoxylin and eosin. The former will have a brown coloration, the latter, the pink and blue you are familiar with. In this slide considerable fading has occurred, and the normal basophilia of freshly stained cartilage is almost absent. The trachea is a large open tube, with cartilage constituting the principal component of its wall. Using the scanning lens, locate the cartilage rings. At higher power, identify single chondrocytes and locate isogenous groups. There are clear areas between many of the chondrocytes and the walls of their lacunae because of shrinkage of the cells brought about by fixation, and because some chondrocytes had lipid droplets which dissolved during histological preparation.Identify the perichondrium. Note the gradation of cell shape changes from fibroblast-like in theouter layer to the round cell shape within the cartilage. The perichondrium is acidophilic due tothe preponderance of collagen fibers. At the interface between perichondrium and cartilage,transitional cells can be seen which are still elongated but are beginning to be surrounded bymatrix.
  8. 8. The cartilage matrix contains collagen fibers, but these are very difficult or impossible to see.Some areas may show some dark-staining material which could be indicative of elastic fibers,but these are best seen in a later slide. Note that the cartilage matrix should be slightlybasophilic, especially around the chondrocytes, due to anionic properties of proteoglycans. Elastic cartilage is found in the ear and epiglottis, where it provides a rigid but elastic, framework. Its principal components are elastic fibers but type II collagen is also present. Some elastic fibers may be present in the tracheal cartilage. Examine a section through infant ear, slide #11 (even boxes only), which has been stained for elastin with resorcinfuchsin. The purple staining interlaced fibers run in all directions, and appear as dots when cut transversely. The nuclei and cytoplasm of the cells are not stained well. The cartilage in this section is immature and therefore richer in cells than adult cartilage. Compare this arrangement of cells and fibers of elastic cartilage with that of hyaline cartilage of the trachea. Fibrocartilage is found in intervertebral discs, the pubic symphysis, in menisci of joints, and often occurs where tendon and ligament are joined to bones. It resembles a dense C.T. which contains islands of chondrocytes embedded in cartilage matrix. Its appearance varies with its location. The major and characteristic intercellular component of this tissue consists of thick, interlaced collagenous fibers. The ground substance is much less abundant than in hyaline cartilage due to the preponderance of fibers. ©Bone Growth-During development, there are two patterns of bone formation:intramembranous and endochondral ossification. Intramembranous bones originate betweensheet-like layers of connective tissues, and endochondral bones begin as masses of hyaline
  9. 9. cartilage that bone tissue later replaces.Cartilage Growth- cartilage is formed from condensed mesenchyme tissue, whichdifferentiates into chondrocytes and begins secreting the molecules that form the extracellularmatrix· Ball-&-socket joint: allows freedom to rotate in a back-and-forth movement· Condyloid joint:this allows the bones to move in any direction, but they cannotrotate· Plane joint:this allows them to move in all directions and rotate.· Hinge joint: allows back and forth movement. (no twisting or side to side. For exampleyour elbow)· Pivot joint: this allows one bone to spin around another· Saddle joint: both of the bones that meet have odd shapes, but they are totallycomplementary to one another.

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