Lecture 6: Histology of Bone Flashcards
The ECM of bone is made up of what 2 major components?
What is the major function of each of these components?
Collagen - micro-flexibility
Bone salts (Ca2+) - extreme strength
What are the 5 possible classifications of bones
Flat bones Long bones Short bones Sesamoid bones Irregular bones
What type of bone contains more spongy bone than the others?
A. Flat bones B. Long bones C. Short bones D. Sesamoid bones E. Irregular bones
A. Flat bones
Which of the following is classified based on its location within a tendon?
A. Flat bones B. Long bones C. Short bones D. Sesamoid bones E. Irregular bones
D. Sesamoid bones
What are the 2 major types of bone?
Compact
Spongy
What are other names for spongy bone?
Cancellous or trabecular
Compact bone is _______, meaning mature bone
Lamellar
T/F: compact bone is solid and relatively dense, found on external suraces of long and flat bones. It encloses spongy bone
True
Spongy/cancellous/trabecular bone contains ________, which are open lattice networks of narrow plates
Trabeculae
Spongy/cancellous/trabecular bone is porous to house what substance?
Bone marrow
T/F: spongy bone is woven bone (nonlamellar)
False, it can be either lamellar or woven
What classification of bone refers to mature or secondary bone and has regular, parallel arrangement of collagen fibers?
Lamellar bone
T/F: most adult bone is lamellar
True
What classification of bone refers to immature or primary bone that is characterized by a loose arrangement of collagen fibers?
Woven bone (nonlamellar)
Woven bone has lower mineral content with more cells, and is usually replaced by what?
Lamellar bone
Under what conditions does woven bone form?
During fracture repair and remodeling
The _______ refers to the knobby regions at the ends of bone that have superficial compact bone with spongy bone deep to the surface
Epiphysis
The _________ region of bone is located between the diaphysis and epiphysis
Metaphysis
What type of bone is found in the metaphysis region?
Spongy
The elongated shaft of a bone is referred to a the ______
Diaphysis
What landmark of bone forms within the metaphysis after fusion of the epiphyseal plate?
Epiphyseal line
The _______ _______ is the cylindrical space in the diaphysis containing bone marrow
Medullary cavity
The ____________ is a bone covering made up of dense irregular CT covering the external surface
Periosteum
The periosteum does not cover _________ cartilages and is neurovascular.
It is anchored by __________ fibers embedded in the bone matrix.
It contains __________
Articular
Perforating
Osteoblasts
The ___________ is the CT lining of the medullary cavity of bone
Endosteum
What cell types are found in the endosteum?
Osteoprogenitor cells
Reticular cells of bone marrow
CT fibers
What type of bone growth is associated with the periosteum?
Appositional
Which layer of periosteum contains osteoprogenitor cells located next to mature bone that retain potential for bone injury and repair?
Inner layer
Which layer of periosteum is rich in vasculature, fibroblasts and collagen fibers?
Outer layer
What type of fibers are found in the outer layer of periosteum and anchor to outer circumferential lamellae?
Sharpey’s fibers
Bone is 90% ECM and 10% H2O and is made up of organic and inorganic components.
What are some of the organic components?
Type I collagen fibers
Proteoglycans
Other proteins: osteocalcin, osteopontin, osteonectin
Bone is 90% ECM and 10% H2O and is made up of organic and inorganic components.
What are some inorganic components?
Calcium hydroxyapatite
Mg, K, Na, F
Compact bone histology:
An _______ is a cylindrical structure in mature compact bone that runs parallel to the shaft of the bone
Osteon
What are the 3 types of canals associated with compact bone histology?
Central canal (haversian) - carries blood vessles and nerves
Perforating canals - perpendicular connections to central canal
Canaliculi - tiny channels between lacunae that allow interactions between osteocytes
What are the 4 types of lamellae associated with histological compact bone?
Concentric lamellae
Outer circumferential lamellae
Inner circumferential lamellae
Interstitial lamellae
Which of the following refers to rings of bone along the endosteum?
A. Concentric lamellae
B. Outer circumferential lamellae
C. Inner circumferential lamellae
D. Interstitial lamellae
C. Inner circumferential lamellae
Which of the following refers to rings of bone around the central canal?
A. Concentric lamellae
B. Outer circumferential lamellae
C. Inner circumferential lamellae
D. Interstitial lamellae
A. Concentric lamellae
Which of the following refers to rings of bone along the periosteum?
A. Concentric lamellae
B. Outer circumferential lamellae
C. Inner circumferential lamellae
D. Interstitial lamellae
B. Outer circumferential lamellae
Which of the following refers to pieces of old osteon that result from remodeling?
A. Concentric lamellae
B. Outer circumferential lamellae
C. Inner circumferential lamellae
D. Interstitial lamellae
D. Interstitial lamellae
Histology of spongy bone is most easily seen in bones of the _______
Skull
The calvaria and majority of the facial skeleton forms via ___________ ossification
Intramembranous
_______________ are stem cells that produce osteoblasts in the endosteum and periosteum
Osteoprogenitors
_____________ are mesenchymal cells that produce osteoid (nonmineralized organic matrix)
Osteoblasts
__________ are mature bone cells embedded in the bone matrix
Osteocytes
What is the role of osteocytes?
Maintain matrix, communicate with osteoblasts to increase deposition of bone matrix
___________ are large, multinucleated cells with ruffled borders that are produced by the fusion of monocytes
Osteoclasts
What is the role of osteoclasts?
Remodel and resorb bone through H+ and lysosomal proteins
What are the 2 types of osteogenesis?
Intramembranous ossification
Endochondral ossification
In what type of osteogenesis do bones develop from mesenchyme precursors?
Intramembranous ossification
Endochondral ossification begins with what type of model?
Hyaline cartilage
Which type of osteogenesis produces most bones of the skeleton?
Endochondral ossification
[bones of extremities, pectoral and pelvic girdles, vertebrae]
Describe osteogenesis of the clavicle
Central part of clavicle = intramembranous ossification
Ends of clavicle = endochondral ossification
Only select bones form via intramembranous ossification, what are some examples?
Flat bones of the skull
Some facial bones
Mandible
Ends of clavicle
Describe steps of intramembranous ossification
- Ossification centers form within thickened regions of mesenchyme
- Osteoid undergoes calcification
- Woven bone and surrounding periosteum form
- Lamellar bone replaces woven bone as compact and spongy bone form
Endochondral ossification involves what type of growth?
Appositional
During endochondral ossification, degeneration of the underlying cartilage leaves trabeculae of matrix. A ______ ______ develops from the perichondrium which has osteogenic potential
Bone collar
After formation of the bone collar during endochondral ossification, there is vascular and mesenchymal invasion into trabecular spaces. What does this produce?
Primary ossification center in the diaphysis
[contains osteoblasts and blood forming cells of bone marrow; osteoid is deposited and calcifies into woven bone]
During endochondral bone growth, where do secondary ossification centers develop?
In the epiphysis
During endochondral bone growth, in what location of the bone is bone replacing cartilage?
Diaphysis
During endochondral ossification, the ossification centers gradually become separated by the _______ _____, which provides for continued bone elongation
Epiphyseal plate
What are the histological zones of endochondral ossification from the end of the bone toward the middle?
Reserve zone
Proliferative zone
Hypertrophic zone
Vascular invasion zone
In which histological zone of endochondral ossification is the primitive hyaline cartilage responsible for the growth in length of the bone as erosion and bone deposition advance?
A. Reserve zone
B. Proliferative zone
C. Hypertrophic zone
D. Vascular invasion zone
A. Reserve zone
In which histological zone of endochondral ossification do the proliferating chondrocytes align as vertical and parallel columns?
A. Reserve zone
B. Proliferative zone
C. Hypertrophic zone
D. Vascular invasion zone
B. Proliferative zone
In which histological zone of endochondral ossification do blood vessels penetrate the transverse calcified septa and carry osteoprogenitor cells with them?
A. Reserve zone
B. Proliferative zone
C. Hypertrophic zone
D. Vascular invasion zone
D. Vascular invasion zone
In which histological zone of endochondral ossification is there apoptosis of chondrocytes and calcification of the territorial matrix?
A. Reserve zone
B. Proliferative zone
C. Hypertrophic zone
D. Vascular invasion zone
C. Hypertrophic zone
What type of bone growth begins when an osteon forms from a bone trabeculae, blood vessels invade, additional bone lamellae are deposited, more osteons surround canal, and so-on?
Periosteal bone growth
The balance between osteoblast and osteoclast activity is responsible for the bone remodeling process. What is the difference between trabecular bone remodeling and cortical bone remodeling?
Trabecular bone remodeling occurs on the bone surface
Cortical bone remodeling occurs within an osteon
Bone fractures are repaired by involving ______ formation and osteogenic activity.
Clotted blood (hematoma) is removed by macrophages and _______ resorb damaged matrix.
Periosteum and endosteum produce a soft ____ surrounding the fracture, which is gradually replaced by a hard callus (combo of endochondral and intramembranous activity)
Immature woven bone is ultimately replaced by ______ bone
Fibrocartilage
Osteoclasts
Callus
Lamellar
___________ is an autosomal dominant syndrome due to a mutation in FGFR3
It is the most common form of dwarfism characterized by the shortening of long bones, small midface (defects in cranial base), and altered spinal curvature
Achondrophlasia
[FGFR3 = fibroblast growth factor receptor 3]
__________ results from decreased mineralization of osteoid leading to progressive softening and bending of bone
Osteomalacia
What are some of the causes of osteomalacia?
Dietary vitamin D deficiency
Lack of sun exposure
GI disease
What are some of the signs and symptoms of osteomalacia?
Bone and joint pain Muscle weakness, spasms, cramps Fracture Difficulty walking Waddling gait
_________ results from a defect in mineralization of cartilage in the growth plates
Rickets (juvenile osteomalacia)
____________ rickets is caused by a calcium deficiency in the setting of normal vitamin D levels
Calcipenic
Typically rickets is caused by a vitamin D deficiency, or decreased absorption of _____ and ______ from bowels
Calcium; phosphorus
Signs of rickets include:
delayed closure of ________
Parietal and frontal ______
________ (soft skull bones)
Widening of wrist and bowing of distal radius and ulna; progressive lateral bowing of femur and tibia
Fontanelles
Bossing
Craniotabes
__________ is a pathological condition characterized by a decrease in bone mass and increased fragility in which bone loses the ability to produce organic matrix (mainly _______), as well as loses calcium and other bone salts
Osteoporosis; collagen
What is typically the FIRST clinical manifestation of osteoporosis?
Fracture
