Bone tissue, Case study 4 Flashcards
necrosis
- cell or tissue death
- if blood flow is cut off to femoral head, the bone tissue & marrow will die
- if blood supply stops for a long period of time, bone tissue and joint structure will degenerate
what is a DEXA scan?
what does it measure?
(or DXA) Dual Energy X-ray Absorptiometry
measures mineral component of bone (inorganic) and determines fracture risk
- does not measure info re: levels of organic components (protein) in bone
how does a DEXA scan work?
sends x rays through body w 2 energy peaks
- one peak is absorbed by soft tissue
- one peak is absorbed by bone and so we can see both
osteoporosis
- a loss of bone density
happens when osteoclast activity is greater than osteoblast activity
some factors affecting osteoporosis
- menopause: loss of estrogen results in lack of osteoblast cells to come build bone
- calcium and phosphorus levels in the blood: if too low, increases osteoclast activity
why is weight bearing physical activity used to treat/prevent osteoporosis?
any force on bone stimulates osteoblast cell activity
resistance exercise is best
what drugs are typically used to treat osteoporosis?
bisphosphonate drugs
- slow resorption (process of breaking down bone tissue)
- triggers osteoclast cells to undergo apoptosis
functions of the skeletal system
support - bone is rigid, cartilage is flexi&strong
movement - muscles attached to bones via tendons
storage - Ca & P in bone. Fat in yellow marrow
protection - cranium, ribs, vertebrae
blood cell production - red bone marrow
red bone marrow
produces blood cells and platelets
- replaced by yellow bone marrow as we age
yellow bone marrow
a means of fat storage
types of cartilage
hyaline cartilage
elastic cartilage
fibrocartilage
hyaline cartilage
- fairly strong
- present in moveable joints (ie usually synovial)
- found in nose, trachea (rings)
elastic cartilage
- has elastic fibres in it, along w collagen
- found in external ear
fibrocartilage
- strongest
- found in weight bearing joints (ex. disks b/w vertebrae, meniscus of knee)
- no perichondrium therefore very hard to fix, repair
some things about cartilage
- avascular: must get blood supply from outside
- composed of cartilage cells and matrix
- matrix composed of 70-85% water, proteins, ground substance
main cell type in cartilage is ? tell me more
chondrocyte
located in a cavity called a lacuna
- an immature chondrocyte is called a chondroblast
chondroblast
- produce matrix: collagen, proteoglycans
- produce matrix around them and then get trapped inside the matrix and thus become chondrocytes
perichondrium
- double layer of dense irregular CT that covers most cartilage
- composed of fibroblasts & gets pushed out as chondroblast layer beneath grows
- – the blood vessels and nerve supply for cartilage is here so nutrients and such must diffuse from here
articular cartilage
a type of hyaline cartilage
- no perichondrium therefore, it must get blood supply from nearby bone tissue
what are the name for which cartilage grows?
interstitial growth
appositional growth
interstitial growth
growth from within
- 2 chondrocytes split and secrete matrix between them, this pushed other cells outwards
- occurs during childhood and into adolescence
appositional growth
growth outside of cartilage w chondroblasts
bone composition? what’s it like?
- made of extracellular matrix and bone cells
- bone cells are trapped in matrix, constant breakdown and replacing of old bone matrix
bone matrix
55% inorganic; crystallized mineral salts, white portion of bone, what mineralizes our bones
hydroxyapatite=calcium phosphate crystals
– gives compressive, weight bearing strength
45% organic: collagen / proteoglycans, water
– gives flexible strength