Bone: Structure and Function Flashcards
1
Q
_______ is the major connective tissue of the body
A
bone
2
Q
the extreme hardness of bone is due to ________
A
mineralization of its extracellular matrix
3
Q
5 functions of bone
A
- provide support for the body’s organs and soft tissue
- function as attachment sites for muscles
- provide protection for organs
- enclose hematopoietic tissues
- serve as metabolic stores for selected minerals
4
Q
______: very dense bone
A
compact or cortical bone
5
Q
______: lattice-like bone, composed of spicules and trabeculae of bone within bone marrow
A
cancellous/trabecular/spongy bone
6
Q
5 features of (the majority of) bones
A
- articular surfaces covered by articular cartilage
- cortex
- a medullary cavity
- periosteum
- endosteum
7
Q
______: the outer wall of compact bone
A
cortex
8
Q
_______: the space bounded by the cortex that contains cancellous bone and bone marrow
A
medullary cavity
9
Q
_____: a layer of fibrous connective tissue tat completely lines the external surface of the cortex except for the articular surfaces
A
periosteum
10
Q
_____: a layer of fibrous connective tissue that completely lines the inner surface of the cortex as well as the surfaces of spicules/trabeculae of cancellous bone and the canals of cortical bone
A
endosteum
11
Q
3 additional features of long bones
A
- diaphysis
- metaphysis
- epiphysis
12
Q
flat bones of the skull develop by ________ ossification
A
intramembranous ossification
13
Q
most bones develop via _____ ossificatin
A
endochondral ossification
14
Q
what makes up the axial skeleton?
A
the head, ribs, vertebrae, and sternum
15
Q
what makes up the appendicular skeleton?
A
thoracic and pelvic limbs
16
Q
3 examples of flat bones
A
- skull
- scapula
- pelvis
17
Q
long bones make up the _____
A
appendicular skeleton
18
Q
the primary center of ossification occurs in the _____
A
diaphysis
19
Q
the secondary center of ossification occurs in the _____
A
epiphysis
20
Q
_____: the end of a long bone
A
epiphysis
21
Q
_____: the shaft or central part of a long bone
A
diaphysis
22
Q
_____: the wide portion of a long bone that contains the growth plate (funnel shaped)
A
metaphysis
23
Q
the ______ layer of the periosteum participates in appositional growth
A
osteogenic (cambium) layer
24
Q
4 types of cells unique to bone
A
- osteoblasts
- osteocytes
- bone lining cells
- osteoclasts
25
osteoblasts are cellularly derived from _______
mesenchymal stem cells
26
osteoblasts are present where on the bone?
on the bone surfaces
27
_____ are responsible for bone formation
osteoblasts
28
osteoblasts are responsible for _____
bone formation
29
osteoblasts produce ______ and initiate ______
- bone matrix (osteoid)
| - mineralization of the bone matrix
30
What is a counterintuitive function performed by osteoblasts?
they control the resorption of matrix by the osteoclasts
31
3 substances/materials produced by osteoblasts
- type I collagen
- proteoglycans
- bone specific proteins
32
(osteoblasts/osteoclasts): possesses a single and eccentric nucleus
osteoblasts
33
(osteoblasts/osteoclasts): ovoid to cylindrical in shape and become more flattened with age
osteoblasts
34
(osteoblasts/osteoclasts): never found singly; occur in groups along bone surfaces
osteoblasts
35
unmineralized bone matrix, known as an _______ is found between active osteoblasts and the bone surface
osteoid seam
36
What is an osteoid seam?
the line of unmineralized bone matrix found between active osteoblasts and the bone surface
37
osteocytes are most abundant where?
in mature bone
38
______: differentiated osteoblasts buried in the bone matrix which subsequently becomes calcified
osteocytes
39
______ occupy the lacunae in mature bone and ______ occupy the canaliculi
- osteocyte nuclei
| - osteocyte cell processes
40
osteocytes sense and translate _____ into _____ to orchestrate bone gain or bone loss as needed
- mechanical strains
| - biochemical signals
41
_______: flattened cells covering resting bone surfaces
bone lining cells
42
bone lining cells communicate with osteocytes via ______ within _____
- cell processes
| - canaliculi
43
bone lining cells are involved in the regulation of what?
the flow of calcium ions from bone to the extracellular fluid
44
certain hormonal and mechanical stimuli induce bone lining cells to convert into __________
osteoblasts
45
_______ are involved in the regulation of the flow of calcium ions from bone to the extracellular fluid
bone lining cells
46
conversion of bone lining cells into osteoblasts can be triggered by the hormone _____
parathyroid hormone (PTH)
47
(osteoblasts/osteoclasts): large and multinucleated cells
osteoclasts
48
______ are responsible for bone resorption
osteoclasts
49
osteoclasts are responsible for _________
bone resorption
50
osteoclasts are cellularly derived from ___________
hematopoietic stem cells
51
__________: the resorption surface/concavity of osteoclasts
- resorption bay
| - Howship's lacuna
52
osteoclasts increase activity under the influence of _________
parathyroid hormone
53
osteoclasts decrease activity under the influence of _____ and _______
- estrogen
| - calcitonin
54
osteocyte activation is controlled by __________ and ________
- osteoblasts
| - bone marrow stromal cells
55
bone resorption is regulated mainly via the _________ pathway
RANK-RANKL-OPG signaling pathway
56
the RANK-RANKL-OPG signaling pathway is primarily responsible for regulating what process?
bone resorption
57
(osteoblasts/osteoclasts) possess numerous vacuoles in the cytoplasm
osteoclasts
58
___________: extensive membrane infoldings at the bone/osteoclast interface
ruffled borders
59
2 steps to bone resorption
- decalcification of the bone matrix
| - digestion of the organic components of the bone matrix (collagen, proteoglycans, etc.)
60
_____________ is the solubilization of calcium salts by acidification of the local microenvironment within the subosteoclastic compartment
decalcification of bone matrix
61
digestion of the organic components of bone matrix requires the release of ____________ (______) in the subosteoclastic compartment by exocytosis
lysosomal acid hydrolases (cathepsins)
62
three main components of bone matrix
- amorphous ground substance
- collagen fibers (type I)
- minerals
63
the 2 primary minerals in bone matrix are _______ and ______ which are arranged into ________ that are deposited in the gap regions of collagen fibers
- calcium
- phosphorus
- hydroxyapatite crystals
64
the endosteum is composed of _________ and a ________ lining (osteoprogenitor cells)
- loose connective tissue
| - squamous cell lining
65
3 principal lamellar patterns in cortical bone
- haversian systems/osteons
- interstitial lamellae
- outer and inner circumferential lamellae
66
_________: consist of concentric rings of matrix surrounding a circular vascular canal
haversian systems/osteons
67
__________: angular lamellae situated between haversian systems
interstitial lamellae
68
_______: cortical lamellae that extend completely around the entire cortex just beneath the periosteum and endosteum
outer and inner circumferential lamellae
69
_______: thin lines of uncalcified matrix that delineate the margins of haversian and interstitial systems are
cement (reversal) lines
70
_______: the central openings of haversian systems which contain 1-2 small vessels supported by delicate connective tissue
haversian canals
71
most often the vessels found within haversian canals are ______ or ______
- capillaries
| - postcapillary venules
72
2 principal vascular channels that communicate with haversian canals and their vessels
- Volkmann's canals/communicating canals
| - perforating canals
73
___________/______: tubes passing transversely or obliquely through the lamellae that connect adjacent haversian canals
Volkmann's canals/communicating canals
74
_________: tubes that allow blood vessels from the periosteum and the endosteum to connect with haversian canals
perforating canals
75
the orientation of cancellous bone usually reflects _______________
adaptation (modeling) to mechanical stresses applied to the bone
76
trabecular bone is also arranged in lamellae which are oriented ______to the surface
parallel
77
sclerostin is secreted by ______
osteocytes
78
_______: a protein secreted by osteocytes which binds to the lipoprotein receptor-related protein 5 (LRP5) receptor on osteoblasts, thereby inhibiting bone formation
sclerostin
79
What is the function of sclerostin?
inhibition of bone formation by binding to the lipoprotein receptor-related protein 5 (LRP5) receptor on osteoblasts (released by osteocytes)
80
at the margins of the ruffled border, the plasma membrane is closely applied to the bone surface, forming the ___________ with an intracellular actin ring that creates an extracellular ______________ in which bone resorption occurs
- sealing zone
| - subosteoclastic compartment
81
In order to decalcify bone and solubilize calcium salts, an acidic environment is required. How is this accomplished?
The actions of carbonic anhydrase in the cytoplasm of the ruffled border produces bicarbonate and hydrogen ions. The hydrogen ions are then transported into the subosteoclastic compartment by an ATP-dependent proton pump, lowering the pH.
Additionally, chloride ions pass into the subosteoclastic compartment through a cholfide channel, which results in formation of HCl and a highly acidic microenvironment (pH 4.5)
82
the extracellular matrix of bone is approximately one-third ______ and two-thirds _________ inorganic salts
- organic matrix
| - inorganic salts
83
the amorphous ground substance of bone includes proteoglycan aggregates composed of ________, ________, and ________
- chondroitin sulfate
- keratin sulfate
- hyaluronic acid
84
bone specific proteins of the matrix include ________ and _______, which are synthesized by osteoblasts
- osteocalcin
| - osteopontin
85
_______: a bone specific protein bound to hydroxyapatite
osteocalcin
86
________: a bone specific cell binding protein like fibronectin that binds to hydroxyapatite
osteopontin
87
hydroxyapatite crystals reside principally within _________________
the gap regions of collagen fibers
88
(demineralized/organically digested) bones are very resilient and pliable and exhibit considerable tensile strength
demineralized
89
(demineralized/organically digested) bones retain their hardness but become extremely brittle
organically digested
90
2 mechanisms that appear to influence hydroxyapatite deposition:
- extracellular osteoid and calcifying cartilage contain matrix vesicles are believed to be calcification initiators (since hydroxyapatite crystals appear to form within or near matrix vesicles)
- collagen fibers and their specific molecular spacing act as nucleation sites for the deposition of hydroxyapatite within the gap regions
91
_________ are believed to be calcification initiators since hydroxyapatite crystals appear to form within or near them
matrix vesicles
92
_________ and their specific ___________ act as nucleation sites for the deposition of hydroxyapatite within gap regions
- collagen fibers
| - molecular spacing
93
__________: involves the calcification of osteoid within a few days after its formation and accounts for about 70-75% of the total mineralization
primary mineralization
94
_________: requires weeks to complete and accounts for 25-30% of the total mineral content
secondary mineralization
95
(primary/secondary) mineralization is 70-75% of the total
primary mineralization
96
(primary/secondary) mineralization is 25-30% of the total
secondary mineralization
97
RANKL has a strong _____ effect on bone resorption
stimulatory
98
RANKL is secreted by _________
osteoblasts
99
when _____ binds to _______, osteoclast precursor cells differentiate into multinucleated osteoclasts, and mature osteoclasts along bone surfaces are activated
- RANKL
| - RANK
100
osteoblasts also secrete _____ (___) which is a decoy receptor with high affinity for RANKL and, as such, acts as an inhibitor of bone resorption
osteoprotegerin (OPG)
101
osteoblasts can secrete signals to either stimulate (_______) or inhibit (_______) bone resorption and the balance between these two is a key factor in the regulation of bone resorption and remodeling
- RANKL
| - OPG
