PBL 1 Flashcards
What is the periosteum?
a tough connective tissue sheath that surrounds the bone surface wherever it is not covered by articular cartilage
what is the function of the periosteum?
protects the bone, assists in fracture repair helps nourish bone tissue, serves as an attachment point for ligaments and tendons
what does the medullary cavity contain?
what is the function?
fatty yellow bone marrow and blood vessels
the minimise the weight of the bone
what is the endosteum?
a thin membrane that lines the medullary cavity. it contains a single layer of osteoprogenitor cells and a small amounts of connective tissue
how are the outer circumferential lamellae connected to the periosteum?
by perforating fibres (Sharpey’s fibres)
what are the canals called that blood vessels and nerves from the periosteum penetrate the compact bone with?
transverse perforating canals (Volkmann’s canals)
what are the 2 functions of spongy bone?
to reduce the overall weight of the bone so it can move more readily
the trabeculae support ad protect the red bone marrow
where does the large nutrient artery pass through the compact bone?
through the nutrient foramen
when and how does the nutrient artery divide?
as it enters the medullary cavity
it divides into proximal and distal branches
how are the ends of long bones supplied with blood?
metaphysical and epiphyseal arteries
describe the veins within the bone?
one or 2 nutrient veins accompany the nutrient artery and exit through the diaphysis
numerous epiphyseal and metaphysical veins exit through the epiphyses and metaphases
many small periosteal veins exit through the periosteum
describe how calcitonin can also be stimulated by gastrin?
if we eat high calcium foot then the duodenum senses this and gastrin is released which stimulates the thyroid gland to secrete calcitonin
what is bone remodelling?
the ongoing replacement of old bone tissue by new bone tissue. it involves bone resorption and bone deposition
what is bone resorption?
the removal of minerals and collagen fibres from the bone by osteoclasts
what is bone deposition?
the addition of minerals and collagen fibres to bone by osteoblasts
what are the 3 benefits of bone remodelling?
new bone grows thicker and is therefore stronger than old bone
the shape of the bone is altered for proper support based on stress patterns
new bone is more resistant to fracture than old bone
describe the process of bone resorption?
osteoclast attach to the bone surface and formed a leakproof seal at the edges of its ruffled borders, it releases lysosomal enzymes and acids which digest collagen fibres and bone minerals. osteoclasts carve out a small tunnel in the old bone. the degraded bone proteins and minerals enter the osteoclast by endocytosis, cross in a vesicle and undergo exocytosis to enter the interstitial fluid.
osteoblasts now move in to rebuild that bone
what are the 6 factors that cause variation in bone remodelling?
age (after 30 bone resorption exceeds deposition),
gender (hormones)
protein intake (high protein increases serum insulin-like growth factor 1 levels which promotes oestoblast activity)
smoking (has an adverse effect on bone mineral density)
physical activity (responses to mechanical activity improve the ability of the body to cope)
overtraining (bone remodelling cycle is unable to repair the micro damage as the rate in which it occurs)
in bone repair, why do nearby cells die?
as the haematoma stops circulation of blood
what are the key features of osteoporosis?
bone resorption outplaces bone deposition. bone mass becomes so depleted that bones fracture under mechanical stresses of everyday living.
what are some of the signs of osteoporosis?
frequent fractures shrinkage of vertebrae height loss hunched back back pain bone pain
what are the 2 reasons in which women suffer from osteoporosis more than men?
women’s bones are less massive than mens
production of oestrogen declines dramatically at menopause whilst production of testosterone in men wanes gradually
what are some risk factors for osteoporosis?
gender family history European or asian ancestry thin or small body build inactive lifestyle a diet low in calcium or vitamin D cigarette smoking alcohol certain medications
what are the 6 types of medications we can give to treat osteoporosis?
bisphosphonates selective eostrogen receptor modulators parathyroid hormones treatments calcium and vitamin D supplements hormone replacement therapy testosterone treatment
