Bone Basics Flashcards
What is the function of bone
Protect internal organs
Stores and releases fat
Produces blood cells
Stores and releases minerals
Facilitates movement
Supports the body
what are the two types of bone marrow and what are their functions
red - produces blood cells/platelets
yellow - colour comes from fat mostly, produces white blood cells
what kind of marrow do infants have
all red marrow
in adults what is the distribution of the different types of bone marrow in the body
all limb bones are yellow marrow, and the red bone comes from the spine/ribs/skull
what are the different cells in bone and what are their functions
Osteocytes
Maintains bone tissue
Forms from trapped osteoblasts in the matrix
Primary cell of mature bone
Osteoblasts
Forms bone matrix
In higher concentrations in areas of bone growth
Osteogenic cells
Undifferentiated cells
As osteocytes/osteoblasts cannot divide into other cells, this is the main source of mitosis in the bone
Osteoclasts
Forms from monocytes not osteogenic cells, so completely different structure
Resorbs bone
Typically found on the surface of bone
what are the different types of bone
Woven bone
Lamellar Bone
what are the properties of woven bone
Early, Healing bone
Rapidly formed with randomly aligned collagen fibres
Weak but more elastic
More even distibution of force
No lamellae
Found in embryonic/neonatal skeleton, fractures of young children
Pathologically found in pagets/Osteogenesis imperfectica etc
what are the types of lamellar bone
Cortical bone
Cancellous/spongy/trabecular bone
periosteum
what are the properties of cortical bone
Tightly packed lamellae (lots of circles with a central vessel canal containing blood vessles, nerves lymph
Osteocytes typically found trapped between the circles
These circles are called osteons
what are the properties of spongy bone
Still has osteocytes in laccunae
No osteons
Lattice like network called trabeculae
Lamellae not as concentric
Trabeculae form along lines of stress in the bone
Large surface area compared to cortical bone so much more metabolically active
Much less dense and tehrefore strong
what is periosteum
Outer fibrous layer
Inner osteogenic later
Contains osteogenic cells
Has some pain sensation
where does vitamin D comes from predominantly
UV light
Diet
what are the actions of vitamin D
Increases absorption of calcium/phosophate in gut and kidney to increase serum calcium/phosphate
how is vitamin D metabolised
hyroxylated in liver then kidney to form the active 1,25,(OH)- Vit F
what are the actions of parathyroid hormone
secreted in response to low calcium
Increases bone resorption
Stimulates hydroxylation of 25(OH)VitD in kidney
Increases phosphate excretion
Increases intestinal absorption of calcium
Overall, calcium levels increase, phosphate decrease
