Bone cells Flashcards
True or false; bone is another type of connective tissue but is harder and less flexible than cartilage
true
What are the 4 main functions of bone
Structural support
Levers for muscle
Protect organs/house bone marrow
Metabolic reserve for minerals
65% of the dry weight of bone comes from where?
inorganic matrix
What makes up the inorganic matrix of bone
(minerals)
Hydroxyapatite crystals
calcium phosphate
other minerals
35% of the dry weight of bone comes from where?
organic matrix
80-90% of the organic matrix is made of what?
Collagen (primarily type 1)
True or false; the organic part of bone has a highly organize fiber arrangement
true
What are the 3 parts of the organic matrix of bone
Collagen (primarily type 1)
GAGs
Glycoproteins
What are the 2 types of GAGs in the organic matrix of bone
Sulfated (more numerous) - chondroitin and keratin
Non-sulfated - Hyaluronic acid
What are binding proteins
proteins that bind minerals to collagen
True or false; vitamin D stimulates arrangement of minerals
true
True or false; there is a higher amount of organic matrix in adult bone compared to children
false; more in children (aka more flexible - greenstick fractures)
True or false; the arrangement of bone is more random in childhood and increases uniformity as we age
true
Are osteoprogentic cells mitotic?
Yes
What is the function of osteoprogenic cells? What are their appearance?
change into osteoblast
flat
What is the location of osteoprogenitor cells? What are they derived from?
Located in endosteum and periosteum
Derived mainly from mesenchyme, but sometimes chondrogenic
What are the appearance of osteoblast? Where are they located?
Cuboid to columnar
Endosteum and periosteum
What are osteoblast derived from? What are their functions?
Derived from osteoprogenitor
Produce osteoid, materials (matrix vessicles) - initiates calcification of newly produced boney matrix
And respond to PTH (parathyroid hormone)
Are osteoblast mitotic?
No
What response do osteoblast have to PTH (parathyroid hormone)
Secrete factor that creates more osteoclasts
Produce enzymes to condition bone for osteoclast activity
What is the appearance of osteocytes
conforms to lacuna
What is the location of osteocytes? What are they derived from?
Surrounded by bony matrix
Derived from osteoblast
What are the functions of osteocytes
Maintain and monitor bony matrix
Release factors to influence osteoblast activity, and cause creation of more osteoclasts
Are osteocytes mitotic?
NO
What is the appearance and location of bone-lining cells? What are they derived from?
Flat
Endosteum and periosteum
Usually from osteoblast, sometimes osteocytes
What is the function of bone-lining cells
to wait and become osteoblast when needed
Are bone-lining cells mitotic?
NO
What is the appearance and location of osteoclasts? What are they derived from?
Large and multinucleated
Endosteum and periosteum
Pre-osteoclast from bone marrow; related to monocytes
What is the function of osteoclasts
reabsorb bone (highly specialized)
Where does the mechanism of bone reabsorption take place?
Subosteoclastic compartment
True or false; an increase in osteoclast activity is associated with a drop in pH in the area
true, this is due to an increase in carbonic acid which is used to dissolve the inorganic matrix of bone
How is the organic matrix of bone broken down?
by lysosomal enzymes
What are the 2 main hormones effecting osteoclast activity? What do they cause?
PTH (parathyroid hormone) - has an indirect influence on osteoclast by causing release of osteoclast stimulating factor (increasing activity)
Calcitonin - decreasing activity
Are osteoblast directly or indirectly influenced by PTH? What about osteoclasts
Osteoblast = direct Osteoclast = indirect
What are the 2 types of bone?
Primary (immature bone) - woven
Secondary (mature) - lamellar
Where would you expect to find primary bone (immature woven)?
Found in fetal development and bone repair
True or false; Primary bone (immature - woven) have many osteocytes, low minerals and more random collagen 1
true
True or false; bone cells are connected by gap junctions
true (exchange material, transfer nutrients)
True or false; compact bone have lamellae with no enlarged vascular channels
true
Which circumferential lamellae is considered periosteal lamellae, is often associated with sharpey’s fibers
Outer circumferential lamellae
Inner circumferential lamellae or Endosteal lamellae are associated with what?
newer bone next to cancellous bone and marrow cavity
Haversian systems or osteons are composted of what?
Osteocytes in lacunae
lamellae (rings of bone created by osteoblasts)
Canaliculi (tiny channels with osteocyte cell processes)
Central (Haversian) Canal
Volkmann’s Canals (connected adjacent osteons)
Cancellous bone is also called what?
Trabeculae or spongy
True or false; trabeculae are always aligned
false; align with stress
Are trabeculae vascular?
yes, very
Does cancellous bone or spongy bone have osteon structure
typically no
True or false; Fibrous periosteum contains a lot of collagen type 1
true
What is the function of fibrous pericardium
carry blood vessels and nerves (parasym, symp, and sensory)
Osteogenic periosteum has how many layers of cells?
Single layer
What is the function of osteogenic periosteum
remodeling, growth and healing
________ is a single layer of cells that line internal bone surfaces
Endosteum
True or false; endosteum is found in lacuna
false; not found in lacuna or canaliculi
In intramembranous ossification what is the sequential sequence in development
Mesenchyme cells-osteoprogenitor-osteoblast-secrete matrix-osteocyte
Vascular mesenchyme between trabeculae/osteons can develop into what?
bone marrow and endosteum
True or false; most long and short bones ossify via endochondral ossification
true
True or false; chondrogenic cells can become osteoprogenitor cells in endochondral ossification
true
Osteoblasts secrete osteoid just inside the periosteum which will form what
periosteal collar = subperiosteal collar
Diaphysis = what?
Shaft
Epiphysis = what?
End
Metaphysis = what?
area of transition between epiphyseal growth plate and diaphysis
True or false; bone growth advances away from growth plate
false; it advances toward growth plate
Cartilage continues to grow within epiphysis by ______
interstitial growth
True or false; cartilage grows via interstitial growth because no perichondrium
true
Appositional growth is associated with
perichondrium
True or false; secondary centers of ossification result in bone length
false; think rings of a tree
What does an increase in bone length result from
bone metaphysis growing toward epiphysis as cartilage in epiphyseal growth plate continues to develop (grow)
What controls bone growth
HGH, thyroid hormones, sex hormones
Cancellous bone remodeling is influenced by..
bone marrow cells
What does somatotropin (HGH) stimulate in bone growth? What happens if low
Stimulates osteoblasts and fibroblast formation
lower bone density
Scurvey which is Vit C deficiency affects collagen 1 how?
Reduce bony matrix and bone development
delay healing
Rickets (vit D deficiency) in children causes what in regards to Ca absorption
decreases
What is osteomalacia
Prolonged vit D deficiency in adults (new formed bone doesn’t ossify)
What are the primary cells involved in osteoporosis
osteoblast and osteoclasts
What are 3 signs of osteoporosis
curvature of spine (kyphosis)
severe back pain
decrease height
What are 2 types of osteoporosis
postmenopausal and age related
What is postmenopausal osteoporosis caused by
decreased estrogen
Age related osteoporosis is due to what?
decreased somatotropin (HGH)
Reducing osteoclast/osteoblast lifespan
Activating osteoblast to secrete osteoid
Slow bone remodeling
are all associated with what?
smoking and alcohol abuse
