Unit 6: Key Terms A and P
Skeletal System
bones, joints, and associated supporting tissues
Long bone
bone is longer than it is wide. ex: Humerous
Short bone
bone is about as long as it is wide. ex: trapezium (carpal bone)
Flat bone
bone is broad, flat, and thin. ex: sternum
Irregular bone
bone's shape does not fit into other classes. ex: vertebra
Sesamoid bone
round, flat, bone found within tendon. ex: patella
Epiphysis
expanded end of bone
Diaphysis
bone shaft
Spongy bone
makes up epiphyses, honeycomb-like framework of bony struts
Compact bone
wall of the diaphysis, hard, dense outer region: allows the bone to resist liner compression and twisting forces
Articular cartilage
covers epiphysis
Periosteum
membrane surrounds bone, dense connective tissue
Perforation fibers (Sharpey's fibers)
made of collagen, anchors periosteum
Medullary cavity
hollow chamber in diaphysis, contains marrow
Endosteum
lines spaces, cavity
Bone marrow
red or yellow marrow, lines medullary cavity, spongy bone spaces
Histology of bone: compact bone
continuously subjected to a great deal of stress, must be able to withstand those forces or suffer damage.
Osteon
compact bone cross-section resembles forest of tightly packed trees, each tree is a unit called osteon
Lamellae
rings of each tree, made up of thin layers of bone
Central canal (Haversion canal)
endosteum-lined hole in the center of each osteon, blood vessels, and nerves supply bone
Interstitial lamellae
fill spaces between circular osteons, represent remnants of old osteons
Circumferential lamellae
outer and inner layers of lamellae
Perforating canals (Volkmann's canals)
travel at right angles (perpendicular) to central canal of neighboring osteons: connect them to one another
Structure of spongy bone
usually not weight-bearing like compact bone, much less densely packed, network of struts reinforces compact bone, resists forces from variety of directions, provides protective structure for bone marrow tissue
Trabeculae
struts or ribs of bone covered with endosteum, usually not arranged into osteons, composed of concentric lamellae with osteocytes in lacunae, no central or perforating canals supplying blood, obtain blood from vessels in bone marrow
Bone/Osseous tissue
primary tissue found in bone, composed mostly of ECM with a small population of cells scattered throughout
Extracellular matrix of bone
unique, has inorganic and organic
Inorganic matrix
minerals make up 65% of bone's total weight
Organic matrix
makes up the remaining 35%, consists of collagen fibers and usual ECM components
Bone
dynamic tissue, continually changing as older bone is broken down for raw materials to build new bone
Bone cells
responsible for bone's dynamic nature, 3 types: osteoblasts, osteocytes, osteoclasts
Osteogenic cells
flattened cells, differentiate into osteoblasts when stimulated by specific chemical signals
Osteoblasts
metabolically active bone cells in the periosteum and endosteum, bone-building cells, perform bone deposition
Bone deposition
osteoblasts secrete organic matrix materials, assist in formation of inorganic matrix
Osteocytes
eventually surround themselves with matrix in small cavities (lacunae), no longer metabolically active, neighboring lacunae are connected by a network of small passageways (canals) in matrix called canaliculi
Lacunae
small cavities
Canaliculi
network of small passageways (canals) in matrix
Osteoclasts
bone resorption, cell secretes hydrogen ions and enzymes, break down bone matrix, large multinucleated cells, resemble jellyfish, derived from fusion of cells from bone marrow
Osteopetrosis
"marble bone disease", defective osteoclasts, don't properly degrade bone, the creation of new bone doesn't keep up with the loss of old bone
Ossification of osteogenesis
process of bone formation, begins through childhood with most bone completing process by age 7
Intramembranous ossification
are built on model (starting material) made of membrane of embryonic connective tissue, direct ossification
Endochondral ossification
built on model of hyaline cartilage, indirect ossification
Intramembranous ossification cont.
forms many flat bones(skull and clavicles) during fetal development, formed within mesenchymal membrane composed of embryonic connective tissue
Mesenchymal membrane
bone formed within this during intramembranous ossification
Mesenchymal cells
stem cell in the mesenchymal membrane
Primary ossification center
the middle layer of spongy bone ossifies before outer compact bone layers,begins in this
Fantanels
example of early incomplete ossification, soft spots in a skull of newborn babies
Endochondral ossification cont.
bone development of all bones below head except clavicles, begins in fetal stage of development
Hyline cartilage model
surrounded by connective tissue membrane
Perichondrium
connective tissue membrane
Longitudinal growth
long bones lengthen by this, involves division of chondrocytes in epiphyseal plate
Epiphyseal plate
line of hyaline cartilage found in developing bones of children
Appositional growth
bone growth in width