MSC Week 2 Test Questions and Correct
Answers
Long bones can be subdivided into three anatomical areas: - CORRECT
ANSWER✅✅✅epiphysis - part of the bone that is in contact with articular cartilage. It is at
the very ends of the long bones
diaphysis - elongated, middle part of the bone
metaphysis - section of bone between the epiphysis and diaphysis
Types of bone: - CORRECT ANSWER✅✅✅bone is surrounded by a dense hard layer
called cortical bone. It's dense, structural, proteins and bone morphogenetic proteins (BMP's),
and a source of demineralized bone matrix (DBM). Considered "dead bone" since no living cells
compose the cortical layer
internally near the epiphysis is the more porous cancellous bone (trabecular). It's spongy (poros),
non-structural, marrow, mesenchymal stem cells (MSCs). Where osteoblasts, osteoclasts, and
osteogenesis occurs
Wolff's Law - CORRECT ANSWER✅✅✅states that bone grows and remodels in response
to the forces that are placed upon it
bone is formed where stresses require its presence, and resorbed where stresses do not require it
Bone Remodeling - CORRECT ANSWER✅✅✅bone remodels under Wolff's law
remodels by mechanotransduction - how cells sense physical forces and translate them into
biochemical and biological responses
remodeling is dependent on the force and load placed through the bone
,when loading increases, bone will respond by becoming stronger to resist the loading
when loading decreases, bone will become less dense and weaker due to the lack of stimulus
cancellous bone remodels quickly
cortical bone remodels slowly (dense)
The 4 steps on Bone Repair:
Step 1: Inflammation - Clout formation, 1-7 days post fracture - CORRECT
ANSWER✅✅✅bone injury results in signaling of platelets and fibrin from plasma to form a
clot (to stop the bleeding (fibrin) and to stabilize the fracture)
platelets activate and release multiple signaling growth factors
the released growth factors attract (chemoattraction): white blood cells & Mesenchymal stem
cells (rebuilding cells)
white blood cells clear wound of damaged, necrotic tissue (dead tissue)
the fracture hematoma is gradually replaced by granulation tissue
The 4 steps of Bone Repair:
Step 2: Soft Callus Formation, 2-3 weeks post-fracture - CORRECT ANSWER✅✅✅soft
callus: replacement of granulation tissue by fibrous tissue and cartilage, ingrowth of vessels into
the calcified callus (angiogenesis), this starts at the periphery and moves towards the center
proliferation - stem cells divide and multiply in number
, differentiation - stem cells differentiate into osteoblastic cells
The 4 steps of Bone Repair:
Step 3: Hard Callus, lasts 3-4 months - CORRECT ANSWER✅✅✅when fracture ends are
linked together by soft callus, hard callus stage starts
cartilage begins to be replaced by woven bone (rigid calcified tissue) and lasts until the
fragments are firmly united by new bone
process by which this happens is called endochondral ossification (how long bones heal)
bone callus growth begins at the periphery of the fracture site where the strain is the lowest, and
progressively moves towards the center of the fracture
The 4 steps of Bone Repair:
Step 4: Remodeling, a few months to several years - CORRECT ANSWER✅✅✅remodeling
stage begins when the fracture has solidly united with woven bone
woven bone is slowly replaced by lamellar bone (mature bone)
lasts until the bone has completely returned to its original morphology
Macrostructure of Bone: - CORRECT ANSWER✅✅✅wolff's law in operation: stress
follows predictable paths, bone responds by increasing mass and density, macrostructure adapts
to stresses
Answers
Long bones can be subdivided into three anatomical areas: - CORRECT
ANSWER✅✅✅epiphysis - part of the bone that is in contact with articular cartilage. It is at
the very ends of the long bones
diaphysis - elongated, middle part of the bone
metaphysis - section of bone between the epiphysis and diaphysis
Types of bone: - CORRECT ANSWER✅✅✅bone is surrounded by a dense hard layer
called cortical bone. It's dense, structural, proteins and bone morphogenetic proteins (BMP's),
and a source of demineralized bone matrix (DBM). Considered "dead bone" since no living cells
compose the cortical layer
internally near the epiphysis is the more porous cancellous bone (trabecular). It's spongy (poros),
non-structural, marrow, mesenchymal stem cells (MSCs). Where osteoblasts, osteoclasts, and
osteogenesis occurs
Wolff's Law - CORRECT ANSWER✅✅✅states that bone grows and remodels in response
to the forces that are placed upon it
bone is formed where stresses require its presence, and resorbed where stresses do not require it
Bone Remodeling - CORRECT ANSWER✅✅✅bone remodels under Wolff's law
remodels by mechanotransduction - how cells sense physical forces and translate them into
biochemical and biological responses
remodeling is dependent on the force and load placed through the bone
,when loading increases, bone will respond by becoming stronger to resist the loading
when loading decreases, bone will become less dense and weaker due to the lack of stimulus
cancellous bone remodels quickly
cortical bone remodels slowly (dense)
The 4 steps on Bone Repair:
Step 1: Inflammation - Clout formation, 1-7 days post fracture - CORRECT
ANSWER✅✅✅bone injury results in signaling of platelets and fibrin from plasma to form a
clot (to stop the bleeding (fibrin) and to stabilize the fracture)
platelets activate and release multiple signaling growth factors
the released growth factors attract (chemoattraction): white blood cells & Mesenchymal stem
cells (rebuilding cells)
white blood cells clear wound of damaged, necrotic tissue (dead tissue)
the fracture hematoma is gradually replaced by granulation tissue
The 4 steps of Bone Repair:
Step 2: Soft Callus Formation, 2-3 weeks post-fracture - CORRECT ANSWER✅✅✅soft
callus: replacement of granulation tissue by fibrous tissue and cartilage, ingrowth of vessels into
the calcified callus (angiogenesis), this starts at the periphery and moves towards the center
proliferation - stem cells divide and multiply in number
, differentiation - stem cells differentiate into osteoblastic cells
The 4 steps of Bone Repair:
Step 3: Hard Callus, lasts 3-4 months - CORRECT ANSWER✅✅✅when fracture ends are
linked together by soft callus, hard callus stage starts
cartilage begins to be replaced by woven bone (rigid calcified tissue) and lasts until the
fragments are firmly united by new bone
process by which this happens is called endochondral ossification (how long bones heal)
bone callus growth begins at the periphery of the fracture site where the strain is the lowest, and
progressively moves towards the center of the fracture
The 4 steps of Bone Repair:
Step 4: Remodeling, a few months to several years - CORRECT ANSWER✅✅✅remodeling
stage begins when the fracture has solidly united with woven bone
woven bone is slowly replaced by lamellar bone (mature bone)
lasts until the bone has completely returned to its original morphology
Macrostructure of Bone: - CORRECT ANSWER✅✅✅wolff's law in operation: stress
follows predictable paths, bone responds by increasing mass and density, macrostructure adapts
to stresses
