Presentation on theme: "6-2 Bone cells Osteoblasts Osteocytes Osteoclasts Stem cells or osteochondral progenitor cells Woven bone : collagen fibers randomly oriented Lamellar."— Presentation transcript:
6-2 Bone cells Osteoblasts Osteocytes Osteoclasts Stem cells or osteochondral progenitor cells Woven bone : collagen fibers randomly oriented Lamellar bone : mature bone in sheets Cancellous bone : trabeculae Compact bone : dense
Bones are composed of connective tissue, chemicals, and fats Solid outer layer - compact bone Composed of osteons An inner layer of spongy bone a honeycomb of flat, needle-like projections called trabeculae. Above: Note the relationship btwn the compact and spongy bone. Below: Close up of spongy bone.
Volkmanns canals Perpendicular to the haversian canals. Connect the blood and nerve supply in the periosteum to those in the haversian canals and the medullary cavity. Haversian canals allow the passage of blood vessels, lymphatic vessels, and nerve fibers. Surrounded by layers of bone called a lamella. osteon
Osteoblasts Bone building cells Synthesize and secrete collogen fibers and other organic components of the bone matrix Initiate calcification Found in the periosteum and the endosteum Ossification Formation of bone by osteoblasts. Cells surround themselves by matrix. osteoblasts Bone matrix
6-7 Osteocytes. Mature bone cells. Osteoblasts that have become trapped by the secretion of matrix. Responsible for maintaining the bone tissue Lacunae spaces occupied by osteocyte cell body Canaliculi canals that allow for nutrient filled liquid to fill the lacunae
Osteoclasts Cells that ecretes digestive enzymes to digest bone matrix bone resorption Concentrated in the endosteum. On the side of the cell that faces the bone surface, ruffled border. Pumps out hydrogen ions Create an acid environment that eats away at the matrix.
BoneTissue.ppt Why is there a depression underneath the osteoclast? What advantage might a ruffled border confer? What is the name of the third cell type shown here? What do you think the tan material represents?
Diaphysis - Shaft Compact bone Epiphysis - End of the bone Cancellous bone Epiphyseal plate - growth plate Hyaline cartilage; present until growth stops Epiphyseal line: bone stops growing in length Medullary cavity: contains marrow In children medullary cavity is red marrow, In adults marrow is yellow in limb bones and skull (except for epiphyses of long bones). Red marrow is found in in the cavities of the spongy bone of flat bones
Periosteum Outer is fibrous Inner is single layer of bone cells including osteoblasts, osteoclasts and osteochondral progenitor cells connected to bone matrix via Sharpeys fibers Endosteum. Similar to inner layer of periosteum. Lines all internal spaces
Consists of organic and inorganic components. Organic component are secreted by the osteoblasts: Collagen fibers Elastin Inorganic component Calcium phosphate Calcium hydroxide magnesium, fluoride, & sodium.
What if the collagen and elastin were removed from this bone. What if the Calcium phosphate, Calcium hydroxide and the other minerals were removed from this bone?
Prenatal: cartilage model Fetus: some conversion to bone Childhood: primary and secondary ossification sites formed Adolescence: cartilage growth plate elongates
Changes in shape, size, strength: Dependent on diet, exercise, age Bone cells regulated by hormones: Parathyroid hormone (PTH): removes calcium from bone Calcitonin: adds calcium to bone Repair: hematoma and callus formation
Protection: encases most internal organs Support: allows body positions Permit movement: muscle attachments for movement Mineral reservoir: calcium, phosphorus