Cell Biology of Connective Tissue Flashcards
Connective tissue is composed of […] and […]
Cells
Extracellular Matrix
- What does the ECM of connective tissue consist of?
- What is its function?
- Fibrous tissue; Collagen; Glycosylated Proteins
- Provide structure and information abut mechanical environment and intracellular environment
Connective tissue is derived from embryonic […]
Mesoderm
The ratio of matrix to cells in connective tissue is […]
High
What are the fibers found in extracellular matrix of connective tissue?
Collagen
Elastic fibers
Reticular fibers
What is the function of connective tissue?
To provide mechanical and structural support by interaction of matrix with cells and organs
What tissues are considered “specialized connective tissue”?
- Tendons and ligaments
- Bone
- Cartilage
- Blood
- Hematopoetic tissue
- Adipose tissue
What is the function of osteoblasts?
- Synthesize and secrete ECM (osteoid) which contains collagen and noncollagenous proteins
- Express alkaline phosphatase and mineralize osteoid via matrix vesicles
- Regulates bone turnover
This is an image of the basic multicellular unit. Label all the indicated structures.
What does collagen contribute to the material properties of bone?
- Tensile strength
- Bone fracture resistance
- Allows cartilage to recover from compressive forces when loaded
- Allows tendons to resist tensile forces and transmits energy from muscle to bone
- What is P1NP?
- What does its serum level reflect?
- Collagen is produced in stages, and its precursor protein has a short signal sequence in the N-terminus region that is removed by proteinases. This is P1NP.
- Because it represents a piece of newly made collagen, this is a marker of synthesis of collagen and bone formation
What effect does cross-linking the hydroxyl residues on collagen have on its mechanical properties?
Increases strength of collagen network and increases toughness (resistance to fracture) of bone
What are NTX and CTX?
These are fragments of type 1 collagen and they are used clinically to measure the rates of bone resorption
What enzyme is responsible for crosslinking hydroxyl groups on collagen fibrils?
Lysyl oxidase
Describe the arrangement of collagen fibres in bone.
Parallel in the same plane but perpindicular in adjacent planes, like a sheet of plywood. This makes bones more able to accomodate different types of external forces.
What does the mineral phase of bone contribute to the mechanical properties of bone?
Compressive strength
What is alkaline phosphatase?
Alkaline phosphatase is an ubiquitous membrane-bound glycoprotein that catalyzes the hydrolysis of phosphate monoesters at basic pH values. This phosphate that is liberated can then be used to produce hydroxyapatite.
- What disease results when there is a mutation in tissue non-specific alkaline phosphatase (Liver, kidney and bone ALP)?
- What is the treatment?
- There is insufficient phosphate for mineralization of the skeleton so children born with this mutation will have an unmineralized skeleton.
- This used to be a death sentence, but a TNAP replacement enzyme exists called Strensiq that can be administered to mineralize their skeleton
Bone has high […] strength but poor […] strength
Compressive
Tensile
The collagen in bone makes it more […] and have a […] elastic modulus and the intrafibrillar cross-linking contributes to […] by […] rather than fracturing
Elastic
Lower
Toughness
Deforming
The mineral content of bone makes it […] and have a […] elastic modulus. Bone strength and toughness are […] correlated to bone mineral content. When bone becomes too highly mineralized it can become […].
Stronger
Higher (more stiff)
Positively
Brittle
How can you estimate toughness by looking at a stress strain curve?
Area under the curve
What changes occur in the mineral and collagen of bone due to aging and osteoporosis?
- Loss of mineralized bone –> decreased strength and stiffness
- Decreased collagen content and cross-linking –> decreased resistance to fracture and elastic properties
- What is osteogenesis imperfecta?
- What effect does this disease have on the mechanical properties of bone?
- Mutation in type 1 collagen that results in abnormal cross-linking and as a result abnormal template for bone mineralization
- Bone has lower stiffness due to lack of elasticity from collagen and improper mineralization –> more brittle
- Unable to resist deformation
- Deficient toughness because collagen cross-links are not mature so there is low fracture resistance and high crack propogation
Bone that is […] from the neutral axis at the center of the bone contributes most to its bending strength.
Farthest
A bone’s bending strength is proportional to the […] of its distance from the neutral axis
Fourth power (i.e. radius4)
Boys develop a larger periosteal perimeter than girls from mid-puberty. Who has stronger bones?
Boys
Girls have less periosteal bone growth and more endosteal bone growth. Does this give girls an advantage or disadvantage?
Disadvantage - cortical bone will be closer to neutral axis of long bone and less resistant to bending
[…] is the primary proteoglycan of cartilage
[…] and […] are the primary GAGs of cartilage
Aggrecan
Chondroitin sulfate and keratin sulfate
Do chondrocytes express ALP?
Some do - there are chondrocytes in transitional zones or in calcified regions of cartilage that express ALP in order to mineralize the cartilage to bone
The […] defines the biomechanical properties of cartilage
Extracellular matrix
What gives cartilage its compressive strength?
Negatively charged and hydrated molecules (water)
What allows cartilage to deform in response to load?
Solid matrix of proteoglycans and collagen
What part of collagen reduces stress at the boundary of the collagen with bone?
The presence of mineral in the zone of transitional tissue
Which is stronger - tendons or ligaments?
Tendons
Where are fibrochondrocytes found?
At insertions sites of tendons to bones
Fibrochondrocytes
- […] differentiated
- Location?
- What do they secrete?
- What important protein and unique do they express?
- Terminally
- Sparsely located in lacunae between type 2 collagen fibrils
- ECM
- ALP
What is a tenocyte?
Fibroblast like cell found in rows between collagen fibrils (type of fibrochondrocyte)
What is an enthesis?
When a tendon directly inserts into the periosteum of the metaphysis or diaphysis. Composed of dense fibrous tissue.
