Anatomy and Physiology: Bones
Anatomy and Physiology: Bones 80197 - BIOL 2220 - 001
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This 9 page Class Notes was uploaded by Jeni Erickson on Thursday September 29, 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 2 views.
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Date Created: 09/29/16
Bones 1. Cartilage 2. Bone: starts as cartilage and becomes bone. a. We are born without some of out bones. We are born without kneecaps. 3. SKELETAL CARTILAGES a. Cartilage tissue: if we damage it, it takes a long time to heel. b. Perichondrium: around the cartilage. Dense irregular connective tissue. c. All cartilage has a layer of dense irregular connective tissue around it. i. It doesn’t have blood vessels or nerves in it. d. Hyaline Cartilage: Bones that touch each other are covered with articular cartilages, which have hyaline cartilage. e. Elastic Cartilage f. Fibrocartilage 4. Growth of Cartilage: Most growth of cartilage stops during puberty. a. Appositional: On the outside. the secretion of new matrix against the external face of existing cartilage b. Interstitial: due to division of chondrocytes inside the lacunae inside the tissue. Within the tissue itself 5. Skeletal Divisions a. Axial skeleton: support and protection. Everything else attaches to the axial skeleton. Skull, vertebrae, and the ribs b. Appendicular: locomotion part. All of the upper and lower limbs. 6. Bone Classifications a. Long bone: they are longer than they are wide. Classified based on shape. i. All of the bones of our limbs with a couple expectations are long bones. (exceptions: patella, our ankles and wrists). ii. Structure: 1. Diaphysis: shaft in the middle of the bone. 2. Medullary cavity: hollow bone filled with bone marrow. a. Called yellow marrow because it is composed mostly of adipose tissue. (Anywhere we have spongy bone we have red marrow) b. Inosteum: Is osteogenic. Lines the inside of the medullary cavity of long bones. 3. Epiphyses: have an extra layer of hyaline cartilages. As long bones grow, they grow an epiphyseal plate. The round parts of the bonds on bond ends. 4. Membranes: called periosteum. Composed of dense irregular connective tissue and osteogenic tissue. There are two layers. Outer layer is dense irregular, inner lay is osteoogenic. a. Osteogenic- bone producing. Contains these two types of cells. i. Osteoblasts: build new bone The cell responsible for secreting the matrix of bone ii. Osteoclasts: consume and break down bone. Deals with calcium balance. Osteoclasts are the bone cells that break down bone. If they were activated more than normal, you should expect to see bone loss. b. Short Bone: i. Sesamoid bone c. Flat bones: i. Scapula, ribs, skull bones. Thin sandwich of compact bone surrounding spongy bone. d. Irregular Bones: i. Hipbones and vertebrae. 7. Bone Textures: a. Compact bone: dense, hard, tough. Yellow marrow. b. Spongy bone: trabecular plate that makes it look spongy. Red marrow. 8. Bone Functions a. Support b. Protection c. Movement: attached to muscle and the contraction of that muscle moves our bones to give us movement. (Locomotion) d. Mineral Storage: calcium and phosphate e. Hematopoiesis: production of blood cells. Blood cells are produced in the marrow of spongy bone. 9. Compact Bone Anatomy a. Osteons: functional unit of compact bone. Comprised of concentric layers of bone (lamellae) b. Lamellae: layers of bone around the central canal. c. Hollow core called the Haversian canal/central tissue. Blood vessels and nerve fibers run through the canal. d. Volkam’s Canals: carry the blood vessels from the periosteoum inward. e. Lacunae: bubble surrounding the cell f. Osteocytes: bone cells g. Canaliculi: mechanism of connection across the lamellae. Side channels running across. 10. Chemical Composition of Bone a. Organic components i. Cells ii. Osteoid: background matrix 1. Contains collagen fibers, glycoproteins, and proteoglycans. b. Inorganic Components i. Hydroxyapatites: mineral salts. Most of the mass of bones is mineral salts (65%). Most abundant mineral salt is calcium phosphate. The accumulation of this is what makes bone hard. 11. Ossification: Bone Formation (Os- latin word meaning bone) a. Hyaline cartilage in embryo is in the shape of a bone. Its fibrous membranes allow for it to grow. Bone formation starts six or seven weeks post conception. Bone either develops in fibrous membrane or in the cartilages i. Intramembranous: within the membrane. Required oxygen ii. Endochondral: within the cartilage. Doesn’t require oxygen. b. Both of the above processes are involved in the formation of bone but only one needs oxygen. 12. Intramembranous Ossification a. Fibrous connective tissue. b. It is embryonic so it came from mesoderm. c. We can the tissues that are still embryonic that come from the mesoderm mesocym. d. Mesocymal cells form osteoblasts. They do it in a cluster, not sporadically. Center of ossification is the production of the clusters of osteoblasts. Little dots around of osteoblasts are the production of background matrix. Eventually the matrix will cut some of the osteoblasts off. It accumulates calcium phosphates, which forms a hydroxyl appetite. Then the calcified matrix surrounds the osteoblasts and the osteoblast dies to create the plates. The voids between the plates get filled with bone marrow. Then the periosteum was formed. The deep plates go through bone reformation and will convert from spongy bone to compact bone (osteoclasts break it down and reform it). 13. Endochondrial ossificaiton 14. All of the bones in our body except to clavicle and skull bones are formed through ossification. 15. Blood vessel arrives and penetrates the dense irregular tissue. It delivers oxygen and forms osteoblasts in a ring around the center of the cartilage template. This is called a bone collar Compact bone tissue is adapted to support weight and withstand torsion stresses The hydroxyapatite is the rigid portion of the bone matrix. As hydroxyapatite is removed from the bone, more of the body's weight would be transferred to the collagen of the osteoid, which would bend under the weight. Interstitial growth occurs when chondrocytes divide and form new matrix, thereby expanding the cartilage tissue from within. This causes the cartilage to lengthen. Glycogen production (glycogenesis) is not a role of bone; it takes place primarily in muscle and liver cells A fracture in the shaft of a bone would be a break in the diaphysis Bones (Part 2) We have a medullary cavity that forms in a template. (Starts in the center, which is primary ossification) o Spongy bone replaced with compact bone. Blood arrives at the center portion first and as the bone grows, the blood vessels branch out to the ends. (The ends are the secondary ossification). o Spongy Bone is maintained here Two sections on the bones maintain hyaline cartilage from template. Epithelial plates also maintain hyaline cartilage. Bone Growth: o Longitudinal growth- growth in length Occurs at the epithelial plate There is one of each end of a long bone. Cartilage to bone Cells on the diaphyseal side divide and push the plate away from the center. The older cells that are deeper toward the diaphysis enlarge, die and calcify. (the result is spongy bone) Osteoclasts digest cells of spongy bone to lengthen the medullary cavity and make it compact bone on the outer edge. Marrow Cavity enlarges o Appositional growth- growth in width All bones thicken Bone Remodeling o Bone deposit Osteoblasts produce the bone. The osteocytes produce the matrix devoid of minerals. The matrix without minerals is called the osteoidcean. The accumulation of calcium and phosphate ions in area trigger production of hydroxyapatite Ions go out of solubility and go into a crystalized form. Catalyzes crystallization of calcium salts in area. That hardening becomes bone. o Bone resorption T lymphocytes activate osteoclasts to secrete enzymes that break down (digest) the matrix. Enzymes are produced by osteoclasts, enzymes are proteins, so they come from the Smooth ER. (Review how enzymes are formed from Smooth ER) Also secretes acid that converts calcium salts to soluble form Digested matrix and dissolved minerals released into interstitial fluid on non-bone side of osteoclasts. Bone is acting like a storage unit for calcium ions. Enters the bloodstream Factors that control bone growth o Diet Calcium rich diet o Vitamin D Calcium will pass right through digestive tract and not absorbed until Vitamin D is present. It allows Calcium to be absorbed in to the bloodstream. o Hormones Regulates calcium Parathyroid and thyroid secretions function in feedback loop Parathyroid=PTH o When calcium levels drop, PTH stimulates osteoclasts so bone is resorbed and calcium is released into the blood stream. When there is enough calcium, PTH is shut off. Thyroid=calcitonin (not that important) o Only turns on when there are extremely high levels of calcium in bloodstream. Encourages bone deposition. Growth Hormones Stimulates bone growth Testosterone/Estrogen Aid in bone growth, but they will also cause the disintegration of the epithecial plate. It is reduced down to a thin line. Bone growth basically stops after puberty with the exception face, nose, and ears. Stresses determine location of hormonal influence. Bone Fractures o Fracture means broken o Partial: break that doesn’t go all the way through the bone. o Complete: Break goes all the way through the bone. o Simple/Closed: Bones that are broken, but are not protruding through the skin o Open: Bones that are broken and protruding through the skin o Displaced: when the bone alignment is lost o Comminuted: splintered at the fracture o Spiral: twisted so far that it broke. o Greenstick: special type of partial fracture. One side of the bone is broken and the other side is just bent. Common in children o Impacted: one part of the bone is forcefully shoved into another bone after the break. o Pathologic: Break in the bone due to bone cancer. Overly resorbed bones. Fracture Repair o When we damage the bone we go through a series of steps: Fracture hematoma forms (blood clot) The clot turns into a callus The first stage of the callus is the fibrocatilagenous callus (referred to as the soft callus). o Fibroblasts and osteoblasts come from periosteum and endosteum and begin to rebuild the bone. The second stage of callus is the bony callus. o Spongy Bone forms and then is remodeled. o Some of it will be remodeled into compact bone depending on where the break is. The repair is wider than the actual bone was. There is a full thick bone place through the medullary cavity so the osteoclasts have to come in and hollow the medullary cavity back out and to smooth the wider spots on the outside if the bone out. Effects of Aging o Decrease in protein formation Causes a decrease in the osteiod matrix that is used to make bones. Elderly people have brittle bones due to the lack of protein. o Loss of Calcium Loss of sex hormones Causes a reduction in bone mass. Osteoporosis: A bone become so soft that there is a compression of the vertebrae and leaves a curvature in the spine. Osteopenia: not as bad, but on its way to osteoporosis. Bone Disorders o Rickets: Bone disease in children Insufficient amount of calcium in body causes bones to stay soft and spindly. Can be reversed by an increase of calcium in diet. Symptoms: bowed legs Epithecial plates enlarge. o Osteomalcia: Person all of a sudden doesn’t have enough calcium in body later in life. Bones are broken down at intense rates and become brittle. o Padget’s disease: Excess bone resorption and deposition. You get a really high proportion of spongy bone and there is a lack of mineralization. The bones become weak and they deform. o Coordinated activity of osteoblasts and osteoclasts.