First half of chapter 7 Flashcards
Bones and their dynamics
Bones and teeth are the most durable remains of a once-living body .Living skeleton is made of dynamic tissues, full of cells, permeated with nerves and blood vessels. Continually remodels itself and interacts with other organ systems of the body. Osteology is the study of bone
Skeletal system
Skeletal system—composed of bones, cartilages, and ligaments
Cartilage
Cartilage—forerunner of most bones
Covers many joint surfaces of mature bone
Ligaments
Ligaments—hold bones together at joints
Tendons
Tendons—attach muscle to bone
Functions of the Skeleton
: Support and protection
Support—limb bones and vertebrae support body; jaw bones support teeth; some bones support viscera
Protection—of brain, spinal cord, heart, lungs, and more
Functions of the Skeleton:Movement and electrolyle balance.
Movement—limb movements, breathing, and other movements depend on bone
Electrolyte balance—calcium and phosphate levels
Functions of skeleton: Acid–base balance,Blood formation
Acid–base balance—buffers blood against large pH changes by altering phosphate and carbonate salt levels
Blood formation—red bone marrow is the chief producer of blood cells
Bones and Osseous Tissue:Bone (osseous tissue)
Bone (osseous tissue)—connective tissue with the matrix hardened by calcium phosphate and other minerals
Bones and Osseous Tissue:Mineralization or calcification
Mineralization or calcification—the hardening process of bone
Bones and Osseous Tissue:Individual bones (organs)
Individual bones (organs) consist of bone tissue, bone marrow, cartilage, adipose tissue, nervous tissue, and fibrous connective tissue
General Features of Bones: flat and long bones
Flat bones Thin, curved plates Protect soft organs Long bones Longer than wide Rigid levers acted upon by muscles; crucial for movement
General Features of Bones: short and irregular bones
Short bones
Approximately equal in length and width
Glide across one another in multiple directions
Irregular bones
Elaborate shapes that do not fit into other categories
General Features of Bones:Compact bone
Compact bone—dense outer shell of bone.
Skeleton three-fourths compact and one-fourth spongy bone by weight.
General Features of Bones:Spongy (cancellous) bone
Spongy (cancellous) bone—loosely organized bone tissue
Found in center of ends and center of shafts of long bones and in middle of nearly all others
Covered by more durable compact bone
Long bone features:
Diaphysis,Epiphyses and Medullary cavity (marrow cavity)
Diaphysis—shaft that provides leverage Medullary cavity (marrow cavity)—space in the diaphysis of a long bone that contains bone marrow Epiphyses—enlarged ends of a long bone Strengthen joint and anchor ligaments and tendons
Articular cartilage
Articular cartilage—layer of hyaline cartilage that covers joint surface; allows joint to move more freely
Nutrient foramina
Nutrient foramina—minute holes in bone surface that allows blood vessels to penetrate
Periosteum
Periosteum—external sheath covering most of bone
Outer fibrous layer of collagen
Outer fibrous layer of collagen
Some fibers continuous with tendons.Perforating fibers—penetrate into bone matrix
Inner osteogenic layer
Inner osteogenic layer of bone-forming cells
Important to bone growth and healing of fractures
Endosteum
Endosteum—thin layer of reticular connective tissue lining marrow cavity
Has cells that dissolve osseous tissue and others that deposit it
Epiphyseal plate (growth plate)—
Epiphyseal plate (growth plate)—area of hyaline cartilage that separates epiphyses and diaphyses of children’s bones
Enables growth in length
Epiphyseal line—in adults, a bony scar that marks where growth plate used to be.
Flat bone
Flat bone Sandwich-like construction Two layers of compact bone enclosing a middle layer of spongy bone Both surfaces covered with periosteum Diploe—spongy middle layer Absorbs shock Marrow spaces lined with endosteum
Bone Cells
Bone is connective tissue that consists of cells, fibers, and ground substance
Four principal types of bone cells
Osteogenic cells; osteoblasts; osteocytes; osteoclasts
Bone Cells: Osteogenic cells
Osteogenic cells—stem cells found in endosteum and inner layer of periosteum
Arise from embryonic mesenchymal cells
Multiply continuously and give rise to most other bone cell types
Bone Cells: Osteoblasts
Osteoblasts—bone-forming cells
Form single layer of cells under endosteum and periosteum
Nonmitotic
Synthesize soft organic matter of matrix which then hardens by mineral deposition
Stress stimulates osteogenic cells to multiply rapidly and increase the number of osteoblasts which reinforce bone
Secrete hormone osteocalcin
Stimulates insulin secretion of pancreas
Increases insulin sensitivity in adipocytes which limits the growth of adipose tissue
Bone Cells: Osteocytes
Osteocytes: Osteocytes—former osteoblasts that have become trapped in the matrix they deposited.Cytoplasmic processes of osteocytes reach into canaliculi and contact processes of neighboring cells
Gap junctions allow for passage of nutrients, wastes, signals
Some osteocytes reabsorb bone matrix while others deposit it
Act as strain sensors—when stressed, produce biochemical signals that regulate bone remodeling (shape and density changes that are adaptive)
Bone cells:Lacunae
Lacunae—tiny cavities where osteocytes reside
Bone cells: Canaliculi
Canaliculi—little channels that connect lacunae
Bone Cells, Osteoclasts
Osteoclasts—bone-dissolving cells found on bone surface
Osteoclasts develop from same bone marrow stem cells that give rise to blood cells (different origin from other bone cells)
Very large cells formed from fusion of several stem cells
Have multiple nuclei in each cell
Bone Cells, Ruffled border
Ruffled border (large surface area) faces bone
resorption bays
Cells often reside in resorption bays (pits in bone surface)
Dissolving bone is part of bone remodeling
The Matrix:
Matrix of osseous tissue
Matrix of osseous tissue is, by dry weight, about one-third organic and two-thirds inorganic matter
The Matrix:Organic matter
Organic matter—synthesized by osteoblasts
Collagen, carbohydrate–protein complexes, such as glycosaminoglycans, proteoglycans, and glycoproteins
The Matrix:Inorganic matter
Inorganic matter
85% hydroxyapatite (crystallized calcium phosphate salt)
10% calcium carbonate
Other minerals (fluoride, sodium, potassium, magnesium)
The Matrix:composite material
Bone is a composite material—a combination of a ceramic and a polymer
The Matrix,composite material: Hydroxyapatite
Hydroxyapatite and other minerals are the ceramic and collagen (protein) is the polymer
The Matrix,composite material: Ceramic portion
Ceramic portion allows the bone to support body weight without sagging
Rickets is a disease caused by mineral deficiency and resulting in soft, deformed bones
The Matrix,composite material: Polymer (protein)
Polymer (protein) gives some flexibility Osteogenesis imperfecta (brittle bone disease) results from a defect in collagen deposition
