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Tortora chapter 6
The Skeletal System: Bone Tissue
| Question | Answer |
|---|---|
| What are the 6 main functions of the skeletal system? | 1.Support; 2.Protection; 3.Assistance in movement; 4.Mineral homeostasis; 5.Blood cell production; 6.Triglyceride storage |
| Bone tissue makes up what percentage of the weight of the human body? | 18% |
| What are the two main minerals that bone tissue stores? | Calcium and phosphorus; contribute to the strength of the bone |
| What percentage of calcium does bone tissue store? | About 99% of the body's calcium |
| What is hemopoiesis? | Blood cell production; which occurs in red bone marrow after birth |
| Red bone marrow | Produces red blood cells, white blood cells and platelets, a process called hemopoiesis |
| Yellow bone marrow | Consists mainly of adipose cells, which store triglycerides |
| Diaphysis | Is the bones shaft or body |
| Epiphyses | Proximal and distal ends of the bone |
| Metaphyses | Regions between the diaphysis and epiphyses |
| Epiphyseal (growth) plate | Located in the metaphysis of a growing bone; a layer of hyline cartilage that allows the diaphysis of the bone to grow in length |
| Epiphyseal line | When a bone ceases growth between ages 18-21; the cartilage in the epiphseal plate is replaced by bone |
| Articular cartilage | Thin layer of hyline cartilage covering the epiphysis where the bone forms an articulation (joint)with another bone |
| What is the function of articular cartilage? | It reduces friction and absorbs shock at freely movable joints |
| Periosteum | Surrounds the external bone surface wherever it is not covered br articular cartilage |
| What is the periosteum consist of? | 1.outer fibrous layer of dense irregular connective tissue; 2.inner osteogeniclayer that consists of cells; some cells in the periosteum enable bone to grow in thickness, but not in lenght |
| What are the functions of the periosteum? | 1.protects bone; 2.assists in fracture repair; 3.helps nourish bone tissue; 4.serves as an attachment point for ligaments and tendons |
| Perforating (sharpey's) fibers | Thick bundles of collagen fibers that extend from the periosteum into the extracellular bone matrix |
| Medullary (marrow) cavity | Hollow, cylindrical space within the diaphysis that contains fatty yellow bone marrow in adults |
| Endosteum | Membrane that lines the medullary cavity of bones; consisting of osteogenic cells and scattered osteoclasts |
| Calcification (mineralization) | Deposition of mineral salts, primary hydroxyapatite, in a framework formed by collagen fibers in which the tissue hardens |
| Osteogenic cells | Stem cell derived from mesenchyme that has mitotic potential and the ablilty to differentiate into an osteoblast |
| Osteoblasts | Bone building; Cell formed form osteogenic cell that participates in bone formation by secreting some organic components and inorganic salts |
| Osteocytes | Mature bone cells; maintains the daily activities of bone tissue |
| Osteoclasts | A large multinuclear cell that resorbs (destroys) bone matrix |
| Resorption | The breakdown of bone extracellular matrix; cell release powerful lysomal enzymes and acids that digest protien and mineral components of the underlying bone matrix |
| Remodeling | replacement of old bone by new bone tissue |
| Compact bone tissue | Contains few spaces and is the stongest form of bone tissue; make up about 80% of the skeleton; found beneath the periosteum of all bones and makes up the bulk of the diaphyses of long bone |
| What is the function of compact bone | Provides protection and support and resists the stresses produced by weight and movement |
| Perforating or Volkmann's canal | A minute passageway by means of which blood vessels and nerves form the periosteum penetrate into compact bone |
| Central canals (haversian canal) | A circular channel running longitudinally in the center of an osteon of mature compact bone, containing blood vessels and lymphatic vessels and nerves |
| Concentric lamellae | Concentric rings of hard, calcified extracellular matrix found in compact bone |
| Lacuna | A small, hollow space, such as that found in bones in which the osteocytes lie; plural:lacunae |
| Canaliculus | A small channel or canal, as in bones, where they connect lacunae; plural: canaliculi |
| What forms the intricate, minature system of interconnected canals throughout bone and what does this system provide? | The canaliculi connect lacunse with one another and with the central canals throughout the bone |
| Circumferential Lamellae | Lamellae that encircle the bone just beneath the perioseum or encircled the meduallary cavity |
| Spongy Bone Tissue | Bone tissue that consists of an irregular latticewrok of thin plates of bone called trabeculae; spaces between trabeculae of some bones are filled with red bone marrow |
| Where is spongy bone found? | It is found inside short, flat, and irregular bones and in the epiphyses (ends) of long bones |
| What are the two differences between spongy bones and compact bones? | 1.Spongy bone tissue is light, which reduces overall weight of bone so that it moves more readily when pulled by skeletal muscle; 2.the trabeculae of spongy bone support and protect the red bone marrow |
| Where is red bone marrow stored? | The spongy bone tissue in the hip bones, ribs, sternum, vertebra, and the ends of long bones; thus where hemopoiesis(blood cell production) occurs in adults |
| As people age, some central (haversian) canals may become blocked. What effect would this have on the surrounding osteocytes? | The central (haversian) canals are the main blood supply to the osteocytes of an osteon (haversian system), so their blockage would lead to death of the osteocytes |
| Why is bone considered a connective tissue? | Like other connective tissues, bone, or osseous tissue, contains an abundant extracellular matrix that surrounds widely separated cells |
| What factors contribute to the hardness and tensile strength of bone? | a bone's hardness depends on the crystallized inorganic mineral salts, a bone's flexibility depends on its collagen fibers; collagen fibers and other organic molecules provide tensile strength, resistance to being stretched or torn apart |
| What is the composition of the extracellular matrix of bone tissue? | The extracellular matrix is about 25% water, 25% collagen fibers, and 50% crystallized mineral salts. The most abundant mineral salt is calcium phosphate [Ca3(PO4)2]. It combines with another mineral salt, calcium hydroxide, to form crystals of hydroxyapa |
| What is the functional significance of the periosteum? | It is essential for growth in bone thickness, bone repair, and bone nutrition; It also serves as a point of attachment for ligaments and tendons |
| How do red and yellow bone marrow differ in composition and function? | 1.Red bone marrow consists of developing blood cells, adipocytes, fibroblasts, & macrophages within a network of reticular fibers; Blood cell production 2.Yellow bone marrow consists of adipose cells, which store triglycerides |
| Where do periosteal arteries enter bone tissue and what do they supply? | Periosteal arteries enter bone tissue through perforations (Volkmann's canals); they supply the periosteum and outer part of the compact bone |
| Where is the nutrient foramen located and what passes through it? | It is a hole located near the center of the diaphysis in compact bone; a large nutrient artery passes through |
| What does the nutrient artery supply? | On entering the medullary cavity, the nutrient artery divides into proximal and distal branches that supply both the inner part of compact bone tissue of the diaphysis and the spongy bone tissue and red marrow as far as the epiphyseal plates (or lines) |
| Where does the metaphyseal artery enter and what does it supply? | It enters the metaphyses of a long bone and, together with the nutrient artery, supply the red bone marrow and bone tissue of the metaphyses |
| Where does the epiphyseal artery enter and what does it supply? | It enters the epiphyses of a long bone and supply the red bone marrow and bone tissue of the epiphyses |
| Veins that carry blood away from long bones are evident in what three places? | (1) 1 or 2 nutrient veins accompany the nutrient artery and exit in the diaphysis; (2)many epiphyseal and metaphyseal veins accompany their arteries & exit in the epiphyses; (3)small periosteal veins accompany their arteries and exit in the periosteum |
| Which part of a bone contains sensory nerves associated with pain? Describe one situation in which this is important | The periosteum is rich in sensory nerves, some of which carry pain sensations; these nerves are especially sensitive to tearing or tension, which explains the severe pain resulting from a fracture or a bone tumor |
| What ossification or osteogenesis? | The process by which bone forms |
| Bone formation occurs in four principal situations what are they? | (1) the initial formation of bones in an embryo and fetus; (2) the growth of bones during infancy, childhood, and adolescence until their adult sizes are reached; (3) the remodeling of bone; (4) the repair of fractures throughout life |
| What are the two methods of bone formation? | (1) intramembranous ossification;it is the simpler of the two methods (2) endochondral ossification |
| Intramembranous ossification | The method of bone formation in which the bone is formed directly in mesenchyme arranged sheet like layers that resemble membranes; |
| What are the 4 stages of intramembranous ossification? | (1)development of the ossification center; (2)Calcification; (3)formation of trabeculae; (4)development of periosteum |
| Endochondral ossification | The replacement of cartilage by bone |
| What are the 6 stages of endochondral ossification? | (1)Development of the cartilage model; (2)growth of the model; (3)develpoment of the 1st ossification center; (4)development of the medullary cavity; (5)development of 2nd ossification centers (6)formation of articular cartilage & epiphyseal plate |
| Interstitial growth | Growth from within, as in the growth of cartilage; results in an increase in length |
| Appositional growth | Growth due to surface deposition of material, as in the growth in diameter of cartilage and bone; results in an increase in thickness |
| Where in the cartilage model do secondary ossification centers develop during endochondral ossification? | Secondary ossification centers develop in the regions of the cartilage model that will give rise to the epiphyses |
| The growth in length of long bones involves two major events, what are they? | (1) interstitial growth of cartilage on the epiphyseal side of the epiphyseal plate and (2) replacement of cartilage on the diaphyseal side of the epiphyseal plate with bone by endochondral ossification |
| The epiphyseal (growth) plate | Is a layer of hyaline cartilage in the metaphysis of a growing bone; site of lengthwise growth of long bones |
| The epiphyseal (growth) plate consists of four zones, what are they? | 1.Zone of resting cartilage; 2.Zone of proliferating cartilage; 3.Zone of hypertrophic cartilage; 4.Zone of calcified cartilage. |
| How does the epiphyseal (growth) plate account for the lengthwise growth of the diaphysis? | The lengthwise growth of the diaphysis is caused by cell divisions in the zone of proliferating cartilage and replacement of the zone of calcified cartilage with bone (new diaphysis). |
| The appearance of the epiphyseal line signifies what? | That the bone has stopped growing in length |
| What is the last bone to stop growing? | The clavicle |
| If a bone fracture damages the epiphyseal (growth) plate,a fractured bone may be shorter than normal once adult stature is reached,why? | This is because damage to cartilage accelerates closure of the epiphyseal plate, thus inhibiting lengthwise growth of the bone |
| Bones grow in thickness or diameter due to the addition of new bone tissue by periosteal osteoblasts around the outer surface of the bone, what is this called? | Appositional growth |
| Bone remodeling | Is the ongoing replacement of old bone tissue by new bone tissue |
| What does bone remodling involve? | (1)bone resorption;(2)bone deposition |
| Bone resorption | The removal of minerals and collagen fibers from bone by osteoclasts; results in the destruction of bone extracellular matrix |
| Bone disposition | The addition of minerals and collagen fibers to bone by osteoblasts; results in the formation of bone extracellular matrix |
| Remodeling may be triggered by 3 factors, what are they? | (1) exercise; (2)sedentary lifestyle; 3) changes in diet |
| Bone spurs | If too much mineral material is deposited in the bone, the surplus may form thick bumps on the bone that interfere with movement at joints |
| Excessive loss of calcium or tissue weakens the bones, and they may break, in what condition does this happen? | Osteoporisis |
| Excessive loss of calcium or tissue weakens the bones, and they may break, or they may become too flexible, in what conditions does this happen? | Rickets & osteomalacia |
| Abnormal acceleration of the remodeling process results in what condition? | Paget's disease, in which the newly formed bone, especially that of the pelvis, limbs, lower vertebrae, and skull, becomes hard and brittle and fractures easily |
| Normal bone growth in the young and bone remodleing in the adult depend on 3 factors, what are they? | (1) adequate dietary intake of minerals; (2) adequate dietary intake of vitamins; (3)sufficient levels of several hormones |
| Open (compound) fracture | The broken ends of the bone protrude through the skin |
| Closed (simple) fracture | Does not break the skin |
| Comminuted fracture | The bone is splintered, crushed, or broken into pieces, and smaller bone fragments lie between the two main fragments; This is the most difficult fracture to treat |
| Greenstick fracture | A partial fracture in which one side of the bone is broken and the other side bends; occurs only in children, whose bones are not yet fully ossified and contain more organic material than inorganic material |
| Impacted fracture | One end of the fractured bone is forcefully driven into the interior of the other |
| Pott's fracture | A fracture of the distal end of the lateral leg bone (fibula), with serious injury of the distal tibial articulation |
| Colle's fracure | A fracture of the distal end of the lateral forearm bone (radius) in which the distal fragment is displaced posteriorly |
| Stress fractures | Is a series of microscopic fissures in bone that forms without any evidence of injury to other tissues |
| The repair of bone fractures involves 4 stages, what are they? | (1)formation of fracture hematoma; (2)fibrocartilaginous callus formation; (3)bony callus formation; (4)bone remodeling |
| Why does it sometimes take months for a fracture to heal? | Calcium and phosphorus deposition is a slow process, and bone cells generally grow and reproduce slowly |
| Bone is the body's major calcium reservoir,what percentage of calcium is stored in bone tissue? | 99% |
| The role of bone in calcium homeostasis is to help “buffer” the blood Ca2+ level, how is this accomplished? | (1)releasing Ca2+ into blood plasma (using osteoclasts) when the level decreases; and (2)absorbing Ca2+ (using osteoblasts) when the level rises |
| Parathyroid hormone (PTH) | A hormone secreted by the chief (principal) cells of the parathyroid glands that increases blood calcium level and decreases blood phosphate level |
| Calcitonin (CT) | A hormone produced by the parafollicular cells of the thyroid gland that can lower the amount of blood calcium and phosphates by inhibiting bone resorption and by accelerating uptake of calcium and phosphates into bone matrix |
| What body functions depend on proper levels of Ca2+? | Heartbeat, respiration, nerve cell functioning, enzyme functioning, and blood clotting |
| Mechanical stress increases bone strength by what? | Increasing deposition of mineral salts and production of collagen fibers; example: bones in an athlete |
| Removal of mechanical stress weakens bone through what? | Demineralization and collagen fiber reduction; example: a person that is bed ridden or an astronaut |
| What are two principal effects of aging on bone tissue? | (1)loss of bone mass; (2)brittleness |
| Demineralization | Loss of calcium and phosphorus from bones |
| What causes bones to become brittle? | Decreased production of extracellular matrix proteins (mostly collagen fibers);collagen fibers, gives bone its tensile strength and loss of tensile strength causes the bones to become brittle and susceptible to fractures |
Created by:
jbbogart
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