Mon and Wed - week 14 - histology of bone flashcards
What makes osteoid and what is it?
osteoblasts, it is the pre-bone
How does PTH interact with bones?
PTH stimulates osteoblasts directly, which release osteoclast stimulating factor to stimulate osteoclasts resorb calcium from bone tissue.
Where do osteocytes reside? Where do their filopodia?
in lacunae
in canaliculi
How do osteocytes communicate?
gap junctions
osteoclast
5 features
large, multinucleated bone resorption come from monocyte amitotic (cell division via clevage of the nucleus without spindle formation) lots of lysosomes
Which bone cells have a “ruffled border”
why does it exist?
osteoclasts
membrane of the ruffled border pumps H+ into sub-osteoclastic compartment to lower the pH and liberate mineral, which enter the osteoclast and are delivered to capillaries.
Also secretes enzymes to degrade organic compounds of decalcified bone, which are endocytosed and put into capillaries.
Where do osteoclasts reside?
howship’s lacunae
Inorganic part of bone matrix
calcium phosphate
hydroxyapatite crystals
organic component of bone matrix
type 1 collagen.
ground substance: Proteoglycan aggrecans: chondroitin sulfate; keratan sulfate, hyaluronate
glycoproteins are used to bind things together.
Two types of bone
synonyms: cancellous, spongy bone, trabecular: spicules (trabeculae) of bone form spongy network. INTERIOR
Compact - dense bone, EXTERIOR
What type of bone is in the metaphysis
spongy (cancellous) bone
Two layers of the periosteum
outer - fibrous: fibroblasts, collagten, elastin. protects
inner - osteogenic: osteoblasts, progenitor cells and osteoclasts if remodeling is occurring.
What anchors periosteum to bone?
Sharpey’s fibers
What kind of growth describes bone growth?
appositional growth (like rings in a tree trunk)
Endochondral vs membranous ossification:
which precursor is vascular?
membranous precursor collagen highly vascular
Cells in synovial membrane?
They secrete?
Fibroblasts = type B cells
Secrete synovial fluid (hyaluronate and glycosaminoglycans)
Macrophages = type A cells
This promotes calcium deposition
This promotes calcium resorption
Calcitonin (Inhibits osteoclast activity)
Parathyroid hormone PTH
Vit D deficiency in children
Rickets (improper absorption of calcium from the intestinal mucosa and)
spicules distort under strain
Prolonged deficiency of vitamin D in adults
Osteomalacia
rapid destruction of bone tissue by osteoclasts most common in post-menopausal women
Osteoporosis
