skeletal system Flashcards
what does the skeletal system consist of?
bones and joints(articulations)
what are its functions?
protects/supports organs
mineral storage calcium and phosphate
blood cell synthesis in red bone marrow
framework for muscle attachment
what tissues does it consist of?
compact/cortical (strong/dense organized into osteons)
cancellous/spongy (network of trabeculae)
cartilage
what are the three types of cartilage?
elastic-forms external ear and epiglottis
fibrous- forms mensici and intervertebral discs
hyaline- forms nasal cartilages, respiratory cartilages, costal cartilages, covers ends of long bones
what are bone cells?
osteocytes
how is compact bone organized?
organized into units called osteons with central canals
containing blood vessels and nerves
osteocytes sit in lucanae within matrix
what is the matrix of bone organized into?
concentric rings (lamellae)
what are the lacunae connected by?
small canals called canaliculi
what is spongy bone?
osteocytes and trabeculae web-like network
light but strong
how many bones in adults vs children?
206 in adults and 300+ in infants before fusion
what are bones considered in the skeletal system?
organs
what are the four classifications of bones?
long bones- femur, humerous, tibia, fibula, ulna, phalanges
short bones- round/square tarsals carpels
flat bones- scapula, sternum, ribs, cranial bones
irregular bones- vertebrae, maxilla, mandible, ossicles
what are bones that form between tendons?
sesamoid bones eg the patella
what are bones between the cranial bones?
sutural/wormian bones
what does spongy bone contain and covered in?
covered in endoosteum and contains red bone marrow
what does red bone marrow do?
site of blood cell synthesis
what is the process describing bone growth?
osteogenisis or ossification
when does bone growth begin?
begins during embryonic development approx 8 weeks gestation
what regulates bone growth?
regulated by the growth horomone GH secreted by the pituitary gland
what are the bones first modelled in before growth?
fibrous membrane or hyaline cartilage
how does growth occur?
mineral matrix is deposited in tissue “calcification”
when does calcification cease?
early adulthood male-22 female-18 when the epiphyseal plates ossify
what are epiphyseal plates?
are regions at the ends of long bones where growth occurs when these plates ossify an epiphyseal line remains (no more growth possible)
what are osteoprogenitors/mesenchymal cells?
stem cells- differentiate into osteoblasts
located in endosteum and periosteum
what are osteoblasts?
bone building cells
secrete osteoid (collagen and proteogylcans)
what are osteoclasts?
bone-consuming cells (large multinucliate cells derived from stem cells in bone marrow)
secrete acids and enzymes that dissolve and re-shape bones
what are osteocytes?
mature bone cells (derived from osteoblasts)
maintain bone matrix
what are the two types of ossification?
intramembranous and endochondral
what is intramembranous ossification?
growth of flat bones of skull and clavicles
bones are initially modeled in fibrous membrane (similar to dermis in structure)
what are the steps in intramembranous ossification ?
- osteoprogenitor cells cluster in fibrous membrane
- then differentiate into osteoblasts
- which secrete osteiod (collagen network) around a network of blood vessels
- osteoids then go through calcification and CaPO4 is deposited and spicules connect to form trabeculae (spongy bone)
when trabeculae thicken at surface what does it form?
compact bone
what do trapped osteoblasts mature to become what?
osteocytes
what is endochondral ossification?
most bones( long,short,irregular)
bones initially modeled in hyaline c.t
growth occurs in several ossification centres
chondrocytes die as ossification proceds and c.t in replaced by bone
growth in length occurs at epiphyseal plates in long bones
steps in endochondral ossification?
- hyaline c.t model surrounded by perichondrium
- chondrocytes of c.t die/enlarge
3.osteoprogenitor cells in perichondrium convert to osteoblasts and from periosteum - osteoblasts and blood vessels invade c.t forming a primary ossification centre in diaphysis
- osteoblasts secrete osteoid; medullary cavity formed by osteoclasts
- blood vessels/ osteoblasts migrate into epiphyses forming secondary ossification centre
- osteoblasts secrete osteoid at epiphysis (epiphyseal c.t seperates epiphysis from diaphysis
- new c.t produced at epiphyseal c.t as bone continues to lengthen
- appositional growth (increase in bone diameter) occurs when osteoprogenitor cells in periosteum differeintiate into osteoblasts and secrete osteoid
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