Test 3 Study Guide Chapter 6 Bone Tissue Functions of Bone ligaments 1 Support by acting as a structural framework and attachment site for tendons and 2 Protection for internal organs 3 Assists in body movement in conjunction with muscles 4 Stores and releases salts of calcium and phosphorus 5 Participates in blood cell production Hematopoiesis 6 Stores triglycerides in adipose cells of yellow bone marrows Tissues of the Skeletal System The two main tissues are 1 Bone osseous tissue which is highly vascularized connective tissue with a hard mineralized extracellular matrix It consists in two different arrangements i Compact bone Good at providing protection and support Forms the diaphysis of long bones and the external layer of all bones ii Spongy bone lightweight and provides tissue support It forms much of the epiphysis and internal cavity of long bones 2 Cartilage is a poorly vascularized connective tissue with a matrix composed of chondroitin sulfate and various fibers a Articular Cartilage is the thin layer of hyaline cartilage covering the epiphysis of long bones It is found where the bone forms and articular joint surface where one bone moves against another bone Tissue types Periosteum tough sheath of dense irregular connective tissue on the outside of the bone Contains Osteoblasts which helps the bone grow in thickness but not in length It also assists with fracture repair and serves as an attachment point for tendons and ligaments Endosteum the membrane that lines the medullary cavity the space within the diaphysis of the long bone that contains fatty yellow bone marrow in adults The endosteum is composed of osteoclasts osteoblasts and connective tissue Perichondrium a dense irregular connective tissue membrane that surrounds cartilage Chondrocytes are cells that form cartilage Cells of Osseous Tissues Osteogenic Cell develops into an osteoblast Osteoblast Forms builds bone extracellular matrix They synthesize and secrete collagen fibers and other organic components Osteocyte Maintains bone tissue They are mature osteoblasts Osteoclast Functions in reabsorption the breakdown of bone extracellular matrix Additional Tissues of Skeletal System Epithelium endothelium form the capillary walls Nerves the periosteum is especially tender Red marrow hematopoiesis Yellow Marrow fat storage Chemical Constituents of Bone 50 65 mineral salts hydroxyapatite crystals o Calcium Phosphate Ca3PO4 2 o Calcium Carbonate CaCO3 o Other trace elements magnesium fluoride sulfate o collagen fibers provide flexibility and tensile strength 25 organic proteins 25 water Types of Bones Bone Structure Epiphyses the distal and proximal ends of a long bone Diaphysis The shaft or body of the long bone Metaphyses the areas where the epiphyses and diaphysis join Epiphyseal Growth plate In adolescents until the end of active growth the epiphysis contains hyaline cartilage Which is actively dividing and causing the bone to elongate from each end Epiphyseal line Hyaline cartilage is no longer present in adults and elongation has stopped The cartilage is replaced with calcified bone Histology of Bone Tissue Osteons Haversian Systems units found within compact bone which are made up concentric lamellae Concentric Lamellae rings of calcified matrix Interstitial Lamellae between osteons are left over fragments of older osteons Outer circumferential Lamellae encircle the bone beneath the periosteum Inner Circumferential Lamellae encircle the medullary cavity Lacunae small spaces between lamellae which house osteocytes Canaliculi are small channels filled with extracellular fluid connecting the lacunae Central canal houses blood and lymphatic vessels found within the osteon Perforating Volkmann s Canals allow transit of these vessels to the outer cortex of the bone Trabeculae found in spongy bone this is the lattice of thin columns in which the lamellae are arranged due to the lack of osteons in spongy bone They support and protect red bone marrow and are oriented along lines of stress Involved with hematopoiesis blood cell production Within trabecula are lacunae which contain osteocytes that nourish the mature bone tissue from the blood circulating through the trabeculae Blood and Nerve Supply of Bone Bone is richly supplied with blood Periosteal arteries and veins supply the periosteum and compact bone Nerves accompany the blood vessels this is often the case o The periosteum is rich in sensory nerves sensitive to tearing or tension Bone Formation Ossification or osteogenesis is the process of forming new bone Bone formation occurs in four situations Formation of bone in an embryo Growth of bones until adulthood Remodeling of bone Repair of fractures Osteogenesis occurs by two different methods beginning about the 6th week of embryonic development Intra membranous ossification produces spongy bone This bone may subsequently be remodeled to form compact bone It is the simpler of the two methods It is used in forming the flat bones of the skull mandible and clavicle Bone forms from mesenchymal cells that develop within a membrane without going through a cartilage stage recall that mesenchyme is the tissue from which almost all other C T develop Many ossification centers Steps of Bone Formation Intra membranous Ossification 1 Development of ossification center osteoblasts secrete organic extracellular matrix 2 Calcification calcium and other mineral salts are deposited and extracellular matrix 3 Formation of trabeculae extracellular matrix develops into trabeculae that fuse to form 4 Development of the periosteum mesenchyme at the periphery of the bone develops calcifies hardens spongy bone into the periosteum Endochondral ossification is a process whereby cartilage is replaced by bone Forms both compact and spongy bone Endochondral ossification is the method used in the formation of most bones especially long bones It involves replacement of cartilage by bone There are one primary and two secondary centers of growth Steps of Bone Formation Endochondral Ossification 1 Development of cartilage model mesenchymal cells develop into chondroblasts which form the cartilage model 2 Growth of cartilage model growth occurs by cell division of chondrocytes 3 Development of primary ossification center in this region of the diaphysis bone tissue 4 Development of the medullary marrow cavity bone breakdown by osteoclasts forms replaced most of the cartilage the medullary cavity 5 Development of secondary ossification centers
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