skeleton and bones Flashcards
what does the skeleton consist of?
bones, joints and cartilage which acts as a supportive framework
what does appendicular skeleton consist of?
limbs and girdles
what does axial skeleton consist of?
long axis i.e. vertebral column, skull, ribcage
what are the functions of the skeleton ? (7)
- maintains posture
- acts as framework for muscle and tissue attachment
- allows movement as whole/ isolation as levers created
- bones protect organs and reduce injury e.g. ribs
- blood cell production
- storage of minerals e.g. calcium
- endocrine functions
what do bones provide?
resting ground for muscles and protection of vital organs
what are long bones? give an example
support bodyweight as they are longer> wide; help facilitate movement e.g. femur
what are short bones? give an example
cube- shaped bones that provide stability and allow flexibility e.g. wrist
what are flat bones? give an example
thin, flat and slightly curved to provide protection and large surface area for muscle attachment e.g. sternum, skull
what are irregular bones? give an example
complicated shapes to protect certain organs e.g. pelvis, hips
what are sesamoid bones? give an example
embedded in tendons to protect from stress e.g. hands, knees
how many bones in adult body?
206
what is spongy bone?
act as inner layer as arranged into trabecular so resist decompressing forces without deforming
where is spongy bone found?
epiphysis end
what does spongy bones contain?
- spaces in-between contain red bone marrow so can produce blood cells
- blood vessels within deliver nutrients to osteons and remove waste
what is compact bone?
more dense and solid on outer layer to protect and withstand muscle pull
where is compact bone and what percentage does it make up of mass?
- 80%
- found in diaphysis shaft
what is an osteoblast?
cell in body that builds new bone tissue
where are osteoblasts found and what do they secrete?
- found in growing portions of bone e.g. endosteum
- secrete collagen matrix and other proteins
what is an osteoclast ?
cell that nibbles at and breaks down bone; responsible for bone resorption
how do osteoclasts dissolve old bones?
release enzymes that trigger chemical reactions
what develops from osteoblast? where is it found?
osteocyte which is found in a small chamber called a lacuna ; lies within substance of fully formed bone
what do osteoblasts secrete? and its significance
osteoid which calcifies within a few days and entraps osteoblasts
what is osseous tissue?
strong connective tissue made from collagen and hard minerals e.g. calcium
what does bone matrix consist of?
intercellular substance consists of collagen fibres, ground substance and inorganic bone salts
what are the properties of osseous tissue?
very hard due to calcium salts, light weight and able to resist tension
what is the purpose of collagen in osseous tissue?
acts as framework for building calcium rich inorganic matrix
what is a osteon?
structural unit of compact bone that consists of concentric bone layers called lamella
what do lamellae in osteons surround?
long passageway called haversian canal
what is the structure of osteons- how are they aligned?
- run longitudinal axis of bone
- hollow inside
- made of central canal surrounded by expanding rings
- aligned same way as force applied
how are osteocytes connected?
cavities interconnected by canaliculi
what does central canal contain?
nerves, lymphatics and blood vessels
where is the epiphysis? describe
end of bone which is wide and filled with spongy bones
what is epiphysis covered in and why?
articular cartilage so bones can slide pass without friction
what is the metaphysis?
growth zone between the epiphysis and diaphysis during development of long bone
what is the diaphysis?
hollow, tubular shaft of long bone
what is the central cavity of diaphysis?
medullary cavity yellow bone marrow is stored
where does growth take place?
epiphyseal plate
what happens when the plate is ossified?
becomes an epiphyseal line
what does yellow bone marrow store?
fat
what does red bone marrow store?
blood
what is the endosteum?
membranous lining of hollow cavity of bone
what is the periosteum?
apart of the outer double layered structure that acts as a tough protective layer
what part doesn’t the periosteum cover and why ?
where epiphysis meets other bones to form joints as they are covered with articular cartilage
what does periosteum contain?
blood vessels, nerves and lymphatic vessels that nourish compact bone
what attach to bones at periosteum?
tendons and ligaments
how do long bones come about?
endochondral ossification
what is endochondral ossification?
process by which growing cartilage is systematically replaced by bone to form the growing skeleton
what is remodelling?
process of undergoing structural reorganisation, alteration or renewal of living tissue
describe bone remodelling
continuous metabolic process of bone breakdown by specialised cells called osteoclasts followed by formation of new bone tissue by osteoblasts
how much bone is replaced each year? what does it depend on?
10% depending on amount of stress
what is wolff’s law?
describes idea that bone density changes in response to force placed on bone
when does bone ossification begin ?
8th week of gestation until 25 years olds
what is the name of the process of epiphyseal plates increasing in thickness?
appositional growth
what is it called when meschehymal tissue is directly converted to bone?
intramembranous ossification
how does ossification begin?
mesenchymal cells differentiate into chondrocytes and form cartilage model for bones
what is formed around hyaline cartilage model?
bone collar
what happens to the hyaline cartilage?
it undergoes cavitation so empty space is formed
what invades after cavitation?
internal cavities by periosteal bud and spongy bone formation
what is formed as ossification continues?
medullary cavity
what appears in preparation for the last step of ossification?
secondary ossification centres in epiphyses
what happens in the last stage?
ossification of epiphyses ; hyaline cartilage remains only in epiphyseal plates
