Ch 5 Flashcards
2 divisions of skeleton
Axial and appendicular
2 types of bone tissue
Compact and spongy
Components of the skeleton
Cartilage, bone, tendons, ligaments
Functions of the skeletal system
Protection, support, movement, storage, and blood cell production
Cartilage consists of:
Cells: Chondrocytes Extracellular matrix: Collagen/elastic fibers Ground substance of chondrites sulfates
Cartilage
No arteries, veins, or lymphocytes
Types are hyaline, elastic, and fibrocartilage
Hyaline cartilage
Most common but weakest
Chondrocytes, chondrotin sulfate, some collagen
Found in embryonic skeleton, articulate surface surfaces, respiratory passageways, nasal septum, between ribs and sternum
Elastic cartilage
Made of chondrocytes, chondrotin sulfate, densely packed elastic fibers
Found in auricle, tip and lateral walls of nose, epiglottis
Fibrocartilage
Made of chondrocytes, chondrotin sulfate, densely packed collagen fibers
Found in intervertebral disc, public symphysis, articulate cartilage in knee
Perichondrium
Fibrous connective tissue
Surrounds cartilage
Provides support and protection, and new chondrocytes
Found in hyaline cartilage and elastic cartilage
Layers of perichondrium
Outer:binds cartilage to adjacent tissue and provides support and protection
Inner: for growth and maintenance
Appositional Growth
starts in perichondrium, stem cells at periphery form in inner layer, then they move toward matrix to become chondrogenic cells, chondrogenic cells aggregate and become chondroblasts which secrete matrix, they then become enclosed in matrix and become chondrocytes
Interstitial Growth
chondrocytes are enclosed in matrix and divide, as they move apart, matrix forms in b/w them, growth of cartilage from w/in
Osseous Tissue
Supportive CT
contains specialized cells
solid extracellular matrix
Extracellular matrix
osteoid, ground substance and water
Osteoid
organic portion, protein fibers
Ground substance
Ca salts
Bone cells
osteoprogenitor, osteoblasts, osteocytes, osteoclasts
Osteoprogentior
mesenchymal cells
predecessor to osteoblasts
play role in initial bone growth and fracture repair
Osteoblasts
derived from osteogenic cells secrete osteoid common in growing bone predecessor to osteocytes increased osteoblast activity=stronger bone
Osteocytes
mature cells
exist within matrix
maintain Ca and PO4 homeostasis
found in spaces called lacunae
Osteoclasts
involved in osteolysis (breakdown of bone)
increase osteoclast activity=weaker bone
very large
formed from the fusion of many white blood stem cells and consume bone cells
Bone matrix
inorganic materials, osteiod
resulting composite is both strong and flexible
Types of bone tissue
compact and spongy
Compact bone
arranged in osteons
has osteocytes- communicate through canaliculi that radiate outward an connect one cell to the next
Osteons
a unit of compact bone
contains blood vessels and nerves
concentric lamellae of matrix surrounding a central canal
Lamellae
concentric, interstitial, and circumfrential
Concentric lamellae
layers of bone surrounding the central canal
make up osteons
Interstitial lamellae
found b/w osteons
represents older osteons partially removed during tissue remodeling
Circumferential lamellae
surround the compact bone
directly produced from periosteum
Spongy bone
contains:
trabeculae, osteocytes, canaliculi, and matrix
no osteons or central canal
Trabeculae
latticework of thin plates of bone oriented along lines of stress
spaces are filled with red marrow where blood cells develop
found in ends of long bones and inside flat bones
Periosteum
encloses bone
absent at the site of attachment of muscles, tendons, and ligaments
outer fibrous and inner layers
Endosteum
1 cell layer
covers surfaces of spongy bone and medullary cavity
cell types: osteogenic, osteoblasts, and osteoclasts
Anatomy of a long bone
Diaphysis, Epiphysis, Metaphysis, articular cartilage, and medullary cavity
Diaphysis
shaft
Epiphysis
one end of a long bone
Metaphysis
growth plate region
Articular cartilage
over joint surfaces, acts as friction and shock absorber
Medullary cavity
marrow cavity
Yellow marrow
areolar and adipose ct
in medullary cavity of long bones
energy storage
absent in infants
Red marrow
areolar and myeloid tissue
produces all types of blood cells
found in medullary cavities of infants and spongy bone in adults
Periosteal arteries
supple periosteum
Nutrient arteries
enter through nutrient foramen
supplies compact bone of diaphysis and yellow marrow
Metaphyseal and epiphyseal arteries
supply red marrow and bone tissue of epiphyses and metaphysis
Ossification (Bone growth)
replacing CT with bone (all our bones are due to this)
Intramembranous (simple)
mesenchymal cells to spongy bone
Endochondral (simple)
hyaline cartilage to spongy bone
Intramembranous Ossification
begins at week 8, finished by week 15
forms: cranial flat , facial, dentary, clavicle, and sesmoid bones
Intramembranous ossification process
mesenchymal cells arrange around BV’s
bone morphogenic proteins released
mesench. cells different. into osteoblasts which secrete osteoid and then they become isolated and turn into osteocytes
produce spicules of bone that interconnect
mesech. cells at surface form inner layer of periosteum
calcified matrix is degraded by osteoclasts to form spongy bone
end up with spongy bone covered in thin layer of compact
Endochondral Ossification
Bone replaces a cartilage model
begins at week 7 and continues to adulthoood
forms: long bones, most short bones, noncranial irregular and flat bones, and middle ear ossicles
Endochondral Ossification process
Hyaline cartilage forms model of future bone
cartilage enlarges, chondrocytes near center die
BVs grow around and penetrate cartilage
cells differentiate into osteoblasts
compact bone forms around diaphysis
spongy bone forms in center of model
remodeling of shaft and formation of medullary cavity
length increases and BVs penetrate the end of model
some cartilage remains (articular cart. and epiphyseal plate)
Bone Growth: Elongation
occurs at epiphyseal plate
growth in length continues until 2 ossification centers meet
relative thickness of epiphyseal plate does not change until growth almost complete
Bone Growth: Appositional
compact bone deposited beneath periosteum
bone thickens
bone remodeling occurs throughout life
Bone remodeling
ongoing, since osteoclasts carve out small tunnels and osteoblasts rebuild osteons
continual redistribution of bone matrix along lines of mechanical stress
Fractures: break in a bone
simple: does not penetrate skin and compound: penetrates through skin
Bone repair
fractures treated by reduction and immobilization
repair: fracture hematoma, fibrocartilage callus, bony callus, and remodel tissue
Fracture hematoma formation
a fracture hematoma forms within hours of the injury
mass of blood
swelling and inflammation occur in response to dead bone cells
phagocytes and osteocytes eliminate dead cells/broken matrix
Fibrocartilage callus formation
consists of a mass bridging the broken end of the bone
fibroblasts in periosteum produce collagen
periosteum cells differentiate into chondrocytes
results in fibrocartilage (3 weeks)
Bony callus formation
occurs as the fibrocartilage callus is converted to spongy bone trabeculae
lasts 3-4 months
Factors affecting growth, repair, and development
nutrition, sunlight, hormones, and physical stress
osteoporosis
Osteoporosis
abnormal reduction of bone mass because of loss of estrogen, deficiency of minerals in youth, and imbalance in activity b/w osteoblasts and osteoclasts
Fibrodysplasia Ossificans Progressiva
fibrous tissue becomes ossified
genetic disorder
injury results in inappropriate bone formation
no treatment
