Myofibroblasts and Fibrocartilage Quiz

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Questions and Answers

What morphological characteristic do myofibroblasts possess?

Elongated spindle-shaped morphology (correct)

Circular shape with extensive Golgi apparatus

Cuboidal shape with microvilli

Irregular shape similar to macrophages

Which protein is primarily regulated by TGF-β in myofibroblasts?

Keratin

Beta-actin

Alpha-smooth muscle actin (α-SMA) (correct)

Vimentin

What role do myofibroblasts play in the body?

They are responsible for wound healing and tissue repair. (correct)

They facilitate the transport of oxygen in the bloodstream.

They are primarily responsible for the production of hormones.

They assist in neural regeneration and development.

Which of the following statements about myofibroblasts is true?

They have an extensive cytoplasm in activated fibroblasts. Signup and view all the answers

What is a key characteristic that distinguishes myofibroblasts from smooth muscle cells?

Myofibroblasts lack a surrounding basal lamina. Signup and view all the answers

What type of collagen is primarily found in fibrocartilage?

Type II collagen Signup and view all the answers

Which proteoglycan is secreted in larger amounts by fibroblasts in the extracellular matrix of fibrocartilage?

Versican Signup and view all the answers

What initiates the differentiation of chondroprogenitor cells into chondroblasts during chondrogenesis?

Transcription factor SOX-9 Signup and view all the answers

What is the main functional characteristic of fibrocartilage?

It serves as a shock-absorbing tissue. Signup and view all the answers

What happens to the proportion of type II collagen with age in fibrocartilage?

It increases. Signup and view all the answers

From where does most cartilage arise?

Mesenchyme Signup and view all the answers

Which of the following substances forms highly hydrated proteoglycan aggregates in fibrocartilage?

Hyaluronan Signup and view all the answers

Chondrogenesis is regulated by which of the following?

Extracellular ligands and nuclear receptors Signup and view all the answers

What role do growth factors play when binding to proteoglycans?

They cause either aggregation or dispersion that influences cell movement. Signup and view all the answers

What defines the tetrasaccharide linker in the formation of proteoglycans?

It consists of one xylulose and two galactose residues plus a glucuronic acid. Signup and view all the answers

Which of the following statements about proteoglycans is correct?

The number of GAGs varies significantly across different proteoglycans. Signup and view all the answers

Which cells are considered resident connective tissue cells?

Macrophages and fibroblasts. Signup and view all the answers

What is the primary function of fibroblasts in connective tissue?

They synthesize ECM fibers and ground substance carbohydrates. Signup and view all the answers

Which of the following correctly describes multiadhesive glycoproteins?

They have specific binding sites for various ECM proteins and cell-surface receptors. Signup and view all the answers

How do hyaluronan and other polysaccharides regulate plasma protein distribution?

They act as efficient insulators, limiting protein diffusion. Signup and view all the answers

What characterizes transient or wandering cells in connective tissue?

They have migrated into the tissue from the blood due to specific stimuli. Signup and view all the answers

Which statement about the core proteins of proteoglycans is accurate?

Core proteins allow for multiple GAG attachments due to serine and threonine residues. Signup and view all the answers

What is a key role of proteoglycans in connective tissues?

They link the ECM with cellular components. Signup and view all the answers

What is the primary function of chondrocytes in cartilage?

To produce and maintain the extracellular matrix. Signup and view all the answers

Which type of cartilage mainly contains type II collagen fibers?

Hyaline cartilage Signup and view all the answers

What component of hyaline cartilage provides resilience and facilitates the diffusion of small metabolites?

Ground substance Signup and view all the answers

Which type of collagen is responsible for regulating the fibril size in hyaline cartilage?

Type XI collagen Signup and view all the answers

What is the role of the perichondrium in cartilage?

To provide a source of new cartilage cells. Signup and view all the answers

Which characteristic differentiates fibrocartilage from other types of cartilage?

Dense packing of type I collagen fibers. Signup and view all the answers

How do chondrocytes in hyaline cartilage respond to changes in matrix composition?

By synthesizing appropriate types of new molecules. Signup and view all the answers

What distinguishes elastic cartilage from hyaline cartilage?

Elastic cartilage does not calcify with aging. Signup and view all the answers

Which zone of articular cartilage contains round chondrocytes that are randomly distributed within the matrix?

Intermediate (transitional) zone Signup and view all the answers

What happens to hyaline cartilage under normal circumstances throughout a person's life?

It undergoes continuous remodeling. Signup and view all the answers

Which glycosaminoglycan is primarily associated with the proteoglycan monomer aggrecan in hyaline cartilage?

Chondroitin sulfate Signup and view all the answers

Which feature is not typically associated with fibrocartilage?

Surrounding perichondrium. Signup and view all the answers

Which type of cartilage includes a high content of elastic fibers in its matrix?

Elastic cartilage Signup and view all the answers

What term describes the clusters of recently divided chondrocytes in hyaline cartilage?

Isogenous groups Signup and view all the answers

What primarily composes ground substance in the extracellular matrix?

Water, glycosaminoglycans, proteoglycans, and glycoproteins Signup and view all the answers

What characteristic of glycosaminoglycans (GAGs) contributes to their function in the ground substance?

They are highly negatively charged and attract water. Signup and view all the answers

Which statement about proteoglycans is correct?

They consist of GAGs covalently attached to core proteins. Signup and view all the answers

What role does the extracellular matrix (ECM) play in connective tissue?

It influences extracellular communication and mechanical properties. Signup and view all the answers

What is the relationship between GAGs and proteoglycans?

Proteoglycans are composed of GAGs that are covalently bonded to proteins. Signup and view all the answers

How does the composition of the extracellular matrix vary?

It varies depending on the connective tissue type. Signup and view all the answers

Why are GAGs often referred to as mucopolysaccharides?

They consist of repeating disaccharide units. Signup and view all the answers

What forms the 'amorphous gel-like' characteristic of the ground substance?

The presence of negatively charged GAGs and water. Signup and view all the answers

What is a significant function of water in ground substance?

It aids in the formation of a hydrated gel structure. Signup and view all the answers

How does the extracellular matrix (ECM) influence cells in a tissue?

It creates a dynamic system that informs cells about external changes. Signup and view all the answers

Which type of tissue is responsible for protecting and supporting other tissues and organs?

Connective tissue Signup and view all the answers

What is the primary component of elastic fibers that provides their unique properties?

Elastin Signup and view all the answers

What is the primary role of reticular fibers in connective tissue?

Forming a meshlike support framework Signup and view all the answers

Which type of collagen fibers is most abundant in the human body?

Type I collagen Signup and view all the answers

Which structure is primarily responsible for the covalent bonding of elastin molecules?

Desmosine Signup and view all the answers

What component is NOT typically found in the extracellular matrix of connective tissue?

Nerve fibers Signup and view all the answers

During wound healing, which type of fibers initially forms before being replaced by stronger fibers?

Type III collagen fibers Signup and view all the answers

Which extracellular matrix component is known for having a high water content?

Ground substance Signup and view all the answers

What characterizes the banding pattern found in collagen fibrils?

Repeats every 68 nm Signup and view all the answers

Which type of connective tissue fiber is known for its flexibility and tensile strength?

Collagen fibers Signup and view all the answers

What is the diameter range of collagen fibrils found in different tissues?

15-300 nm Signup and view all the answers

What structural role do glycoproteins play in connective tissues?

Facilitating cell adhesion and communication Signup and view all the answers

Which type of cell is primarily responsible for the production of reticular fibers in most tissues?

Fibroblasts Signup and view all the answers

Which statement is true regarding the composition of elastic fibers?

They consist of a core of elastin surrounded by fibrillin microfibrils Signup and view all the answers

Study Notes

Introduction to Cell Biology

October 24, 2024 lecture by Dr. Zane Kalnina
Discusses connective tissue and its continued role in cell biology.

Connective Tissue (Continued) - Part 1

The human body has four basic tissue types:
- Epithelium - lines and covers surfaces
- Connective tissue - protects, supports, binds; fills gaps between organs and tissues
- Muscular tissue - produces movement
- Nervous tissue - receives stimuli and conducts impulses

Connective Tissue Composition

Connective tissue is made of:
- Cells
- ECM (extracellular matrix)
- Fibers
Cells types in connective tissue include:
- fibroblasts
- collagen
- plasma cells
- elastic fibers
- macrophages
- endothelial cells
- mast cells
- eosinophils
- adipose cells
- lymphocytes
Fibers in connective tissue include:
- Collagen
- Reticular
- Elastic
Ground substance is the non-cellular part of the extracellular matrix in connective tissue.

Fibers

Collagen fibers are the most abundant connective tissue fiber.
- Collagen fibers have high tensile strength and are flexible.
- They appear as bundles of fine, threadlike subunits called collagen fibrils.
- Fibrils are relatively uniform in diameter (15-300 nm).
- Fibrils have a repeating 68-nm banding pattern.

Collagen Fibrils

A sequence of closely spaced transverse bands repeat every 68 nm along the length of the fibril.
This repeating pattern occurs throughout the length of collagen fibril..

Fibrillar Collagens

Types I, II, III, V, and XI
Collagen molecules have a head and a tail section.
The collagen molecules align head-to-tail in overlapping rows.

Reticular Fibers

Provide a framework for the cells of various tissues and organs
Composed of type III collagen fibrils.
Exhibits a branching meshlike pattern, and typically do not bundle to form thick fibers.
Primarily made by fibroblasts, except for hemopoietic and lymphatic tissues (produced by reticular cells).

Elastic Fibers

Allow tissues to stretch and distend.
Thinner than collagen fibers.
Arranged in a branching pattern to form a 3D network.
Interwoven with collagen fibers.
Prevent tearing from excessive stretching.
Produced by fibroblasts and smooth muscle cells.

Elastic Fiber Structure

Composed of two parts:
- Central core of elastin
- Surrounding network of fibrillin microfibrils.
- Elastin is rich in proline, glycine, and hydrophobic amino acids.
- Elastin contains desmosine and isodesmosine, two amino acids unique to elastin.
- Elastin forms fibers of various thicknesses, such as lamellar layers .

Fibrillin Microfibrils

Glycoprotein that forms microfibrils.
Measuring 10 to 12 nm in diameter.
Used as substrates for the assembly of elastic fibers.
Forms first before elastin material deposits on the surface.
Plays a major role in organizing elastin into fibers.

Ground Substance

Amorphous, gel-like substance surrounding cells.
Does not include collagen and elastic fibers.
Composed of water, glycosaminoglycans (GAGs), proteoglycans, and glycoproteins.
Component's vary by tissue type.

Extracellular Matrix (ECM)

A complex network that surrounds and supports the cells.
Composed of fibers and ground substance.
A varying quantity of ECM molecules is secreted by each connective tissue cell.
ECM properties vary by tissue type.

Glycosaminoglycans (GAGs)

Long unbranched polysaccharides
Most abundant in ground substance
Responsible for the physical properties of ground substance
Synthesized by connective tissue cells as a modification of proteins called proteoglycans.
Highly negatively charged which attracts water and forms hydrated gels.

Hyaluronic Acid

A long, rigid molecule
Not covalently bound to protein, so it does not form proteoglycans.
A large molecule, 100 - 10,000 kDa.
Synthesized on the surface of the cell.

Proteoglycans

GAGs linked to core proteins
Major component of hyaline cartilage.
Rich in serine and threonine residues. Allowing multiple GAG attachments.

Multiadhesive Glycoproteins

Plays a role in stabilizing the ECM and linking it to cell surfaces.
Possesses binding sites for a variety of ECM proteins: collagens, proteoglycans, and GAGs.

Connective Tissue Cell Populations

Resident cells: fibroblasts, myofibroblasts, macrophages, adipocytes, mast cells, adult stem cells
Transient/wandering cells: lymphocytes, plasma cells, neutrophils, eosinophils, basophils, monocytes
Fibroblasts: principle cell of connective tissue.
- Synthesizes ECM fibers and ground substance.
- Captures and stores nutrients needed by the body.

Myofibroblasts

Elongated, spindle-shaped cells, resembling smooth muscle.
Lack a surrounding basal lamina.
Expression of α-smooth muscle actin is influenced by TGF-β.

Chondrogenesis

Process of cartilage development.
Begins with the aggregation of chondroprogenitor cells into a mass of rounded, closely apposed cells called a chondrogenic nodule.
Involves chondroprogenitor cell differentiation triggered by SOX-9 expression and deposition of cartilage matrix material.

Cartilage Growth

Appositional: new cartilage is formed at the surface of existing cartilage.
Interstitial: chondrocytes in their lacunae divide and form new matrix within the existing cartilage.

Calcification

The process of cartilage matrix undergoing calcification in situations like contact with the bone tissue in growth and adult bones and as a part of aging process involving the embedding of calcium phosphate crystals into the cartilage matrix.

Hyaline Cartilage

Contains numerous chondrocytes in lacunae surrounded by matrix material.
High concentration of proteoglycans, and type II collagen.
Found in the articular surfaces of joints.

Elastic Cartilage

Dense network of branching elastic fibers in addition to hyaline cartilage components.
Does not calcify with age.
Found in the external ear and epiglottis, maintaining flexibility and support.

Fibrocartilage

Combination of dense regular connective tissue and hyaline cartilage in various ratios, containing considerably less matrix material.
Contains abundant type I collagen fibers.
Found in intervertebral discs, symphysis pubis, and certain tendon attachments.

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Description

Test your knowledge on myofibroblasts and fibrocartilage with this engaging quiz. You will explore their characteristics, roles, and the specific proteins involved in their function. Perfect for students of biology or medicine looking to deepen their understanding of connective tissue.