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MSK-L2 Cartilage and Bone Structure

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zijimubo1's version from 2017-01-09 01:01

Cartilage Overview

Question Answer
Is cartilage vascular or avascular? Explain the significance in nutrients.Avascular; thus low oxygen environment and diffusion of nutrients controlled by matrix.
Name the THREE types of cartilage.Hyaline cartilage - homogenous matrix

Elastic cartilage - contains elastic fibers

Fibrocartilage - fibrous connective tissue; predominantly type I collagen
Name the FOUR types of cells in cartilage. Indicate their location.Chondrogenic cells - located in perichodrium; differentiate into chondroblasts

Chondroblasts - located on the outside edge of the matrix

Chondrocytes - embedded w/in the matrix in LACUNAE

Chondroclasts - called osteoclast; responsible for cartilage degradation
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Hyaline Cartilage

Question Answer
What is the role of hyaline cartilage in fetal skeleton?It is the fetal precursor to long bones.
What is the role of hyaline cartilage in adults?Hyaline cartilage remains at joint surfaces(articular cartilage) and some parts of respiratory system facilitating movement of surfaces.
What cell types are ACTIVE in cartilage matrix synthesis and why?Chondroblast and chondrocytes because they have prominent RER and large Golgi.
Where are chondrocytes located within cartilage?In the lacunae.
What are the major components of ECM in hyaline cartilage?Type II Collagen and proteoglycan aggrecan (amorphous ground substance)
What is the major proteoglycan in the ECM of hyaline cartilage?Aggrecan (amorphous ground substance)
What is perichondrium and what is it composed of?Dense connective tissue surrounding cartilage - Type I collagen, fibroblasts, blood vessels
Describe the structural layers of perichondrium.Outer fibrous layer and an inner cellular(chondrogenic cells, chondroblast) layer.
What cartilage surfaces are absent of perichondrium?Cartilage at joint surfaces
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Growth of Hyaline Cartilage

Question Answer
Most growth of hyaline cartilage occurs when?Embyonic stage
How does deposition of hyaline cartilage initiate?Mesenchymal stem cells that aggregrate, differentiate into chondroblasts, and secrete cartilage matrix.
What controls the initial deposition of hyaline cartilage?Bone morphogenic proteins(BMPs, regulatory growth factors and cytokines)
What does adjacent mesenchymal tissue to stem cells become?Perichondrium
What is appositional(along edges) growth of cartilage?New cartilage added to the surface of pre-existing cartilage
What is interstitial(within) growth of cartilage???
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Elastic Cartilage and Fibrocartilage

Question Answer
Function is to increase elasticity, and provide flexible supportelastic cartilage
Present in special locations such as auditory canal, epiglottis, and larynxelastic cartilage
Similar organization as hyaline cartilage, including perichondrium, but contains elastic fibers along Type II Collagen in the ECMelastic cartilage
Does not calcifyelastic cartilage
Function is to create resistance to compression and shear; high tensile strengthfibrocartilage
Its chondrocytes are located within dense regular connective tissue(Type 1 collagen)fibrocartilage
Present in specialized locations such as intervertibral discs and joint meniscifibrocartilage
Lacks perichondriumfibrocartilage
Ruptured or slipped discs refers to a tear infibrocartilage
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Bone Overview

Question Answer
What does the term mechanoresponsive mean?Movement imposes forces on bone, and bone responds by remodeling themselves maximum ability to withstand force while minizmizing amount of bone mass necessary.
What is the organic component of bone?Osteoid, 80-90% type I collagen
What is the inorganic component of bone?Calcium phospate (Hydroxyapatite), 50% dry weight of bone
What provides bone with high tensile strength and elasticity?Collagen component
What provides bone with stiffness(resists stress)?hydroxyapatite
What are the FOUR types of cells in bone?Osteogenitor cells
Osteoblasts
Osteocytes
Osteoclasts
Explain the statement "Bone as organ".Bones of the skeletal system come in a variety of shapes.
Explain the statement "Tissues of bones".Blood vessels, nerves, fat, hematopoietic, cartilage, and bone.
Explain "Bone tissue".Bone tissue is the STRUCTURAL tissue of bone organ.
Where is woven or primary bone found?Site of Newly synthesized (immature) bone
Where is secondary bone found(2)?Sites of remodeled (mature) bone:
1) Compact-along edges
2) Spongy-marrow cavity
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Long Bones

Question Answer
Where is the epiphyseal plate found?Between the epiphysis and diaphysis in long bones that are still increasing in length.
What is the periosteum and where is it found?Connective tissue capsule surrounding compact bones.
***Except at joint surfaces.
What is the composition of periosteum?Outer fibrous layer containing FIBROBLAST; and
Inner layer containing osteopogenitor cells.
What is the function of perisosteum(2)?1) Type I collagen fibers penetrate into bone matrix and attach the periosteum to bone.

2) Osteoprogenitor cells differentiate into osteoblasts during bone growth.
What is endosteum and where is it found?Lining all internal bone surfaces including Haversion canals, bone trabeculae, and compact bone surrounding marrow cavity.
What is yellow marrow and where does it come from?Yellow marrow is adipocyte rich and comes from aging.
What is a lamellae?Thin layer of bone matrix
What gives bone its lamellar appearance?The orthogonal deposition of Type I collagen by osteoblast.
What is the main organizational unit of bone?Osteon or Haversian system with central canals running in parallel.
How are Haversian Canals interconnected?Through Volkmann's Canals.
What part of the bone shaft lack a Haversian system?Outer and concentric lamellae.
How does the structure of immature different compared to mature bone?Immature bone is "woven" with collagen fibrils that are deposited in an interlaced arrangement. showing less specialized organization.
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= Osteoblasts
Question Answer
What is the function of osteoblasts?Synthesize bone
What type of cell shapes are osteoblasts?Single layer of high cuboidal to columnar cells forming against growing bone
What is a canaliculi?Connection/channels between bone cells established by cell extensions into the matrix.
How do osteoblast form new bone?Secrete osteoid (ECM of bone) and collagen Type I
Compare the staining between ECM of bone and ECM of cartilage?Bone stains pink because it has more protein than PG compared to cartilage that stains blue.
What is osteocalcin? How does it act as a hormone?The most abundant non-collagenous glycoprotein that binds calcium. Stimulates beta cell proliferation and insulin production.
How is osteocalcin used clinically?It serves as a serum marker for increased bone turnover.
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Osteocyte

Question Answer
Osteocytes differentiate from what type of cells?osteoblasts
Spaces that osteocytes occupy within bone are called?lacunae
T/F Osteocytes divide.False, osteocytes lose their secretory phenotype (RER, Golgi less prominent)
How do osteocytes communicate with other osteocytes or osteoblasts allowing nutrient exchange?Via gap junctions
What is osteolysis?Local bone absorption by osteocytes that can help modulate blood calcium levels.
What happens to an osteocyte that is released from the matrix during remodeling?It becomes an osteoblasts again.
What happens when an osteocyte dies within the matrix?It triggers bone resorption by osteoclasts.
Define bone resorption.Breakdown of bone and release of calcium into blood.
T/F Shear forces exerted on osteocyte processes by flow of fluid through canaliculi cause osteocyte-generated signals that regulate osteblast-mediated bone formation.True
T/F Strain forces exerted on osteocyte processes by flow of fluid through canaliculi cause osteocyte-generated signals that regulate osteblast-mediated bone resorption.False, osteoclast-mediated bone resorption
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Osteoclasts

Question Answer
Osteoclasts differentiation from what type of cells?Monocytes (regulated by osteoblasts)
How does an osteoclast become multinucleated?Fusion of many individual cells.
How does an osteoclast attach to bone?By an attachment region characterized by a ruffled cell border that are stabilized by cortical microfilaments.
Name two substances released by secretory vesicles of osteoclasts.1) Carbonate/citrate that dissolves calcium phosphate via acidification.

2) Lysosomal hydrolases that degrage organic matrix.
What effect does Parathyroid hormone have on osteoclasts?Increased osteoclasts activity by promoting osteoblasts secretion of osteoclast-differentiation factor.
What effect does Calcitonin have on osteoclasts?Reduce osteoclast activity by inhibiting ruffled cell border.
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Bone Histogenesis

Question Answer
What is the main secretion by osteoblasts?Osteoid
Intramembranous ossification is present in what type of bones?Flat bones of skull and face
How does intramembranous ossification begin?Differentiation of mesenchymal cells into osteoblasts.
What forms the trabeculae pattern of bone in intramembranous ossification?Connective tissue/Blood vessels
What is the first step in endochondral ossification begins and when does it begin? What is the precursor?Perichondrial cells form the bone collar. 3 months in fetus. Fetal hyaline cartilage.
In intramembranous bone formation, how does the center get calcifed?Lack of oxygen causes programmed cell death of chondrocytes, releasing vesicles that cause matrix calcification.
What is the periosteal bud?Due to the lack of oxygen; blood vessels, osteoprogenitor cells, mesenchyme, that invade.
At what age does intramembranous growth begin at the epiphysis region?1-2 years
Which zone of the epiphyseal plate continues to undergo interstitial growth?Zone of proliferation, cartilage distal to diaphysis
Which zone of the epiphyseal plate undergoes hypertrophy?Zone of hypertrophy, that calcifies and then is replace by bone (zone of ossification).
What does the term epiphyseal closure indicate?Elimination of plate and end of growth
What maintains the shape of the bone as it grows in length?Combined activity of osteoclasts and osteoblasts
How is cartilage and epiphyseal plate growth regulated?Growth hormone that regulates chondrocyte proliferation required for epiphyseal plate growth.
How is epiphyseal plate closure regulated?Through estrogen and testosterone(indirectly) at puberty,
How is the Haversian system formed?Through inward deposit of osteoid followed by calcification.
In a radiograph, what does lighter areas indicate?More mineralization
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