Connective Tissue and Stem Cells Overview
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Questions and Answers

What is the primary origin of muscle tissue in the embryo?

  • Mesenchymal stem cells (MSC) (correct)
  • Neural stem cells (NSC)
  • Hematopoietic stem cells (PHSC)
  • Adipose tissue

    • Which type of tissue retains tissue-specific stem cells in adults?

  • Skeletal muscle (correct)
  • Adipose tissue
  • Cardiac muscle
  • Epithelial tissue

    • Which of the following statements is true regarding adult adipocytes?

  • They continuously divide throughout adulthood.
  • They are derived from hematopoietic stem cells.
  • They change their volume based on lipid storage. (correct)
  • They can trans-differentiate into muscle cells.

    • What role does UCP-1 play in fat metabolism?

    <p>It determines the thermogenic potential of fat.</p> Signup and view all the answers

    What process allows a differentiated cell to revert to a stem-like state?

    <p>De-differentiation</p> Signup and view all the answers

    Which collagen type is primarily found in hyaline cartilage?

    <p>Type II collagen</p> Signup and view all the answers

    What characteristic is unique to muscle progenitors during embryonic development?

    <p>They elaborate within connective tissue compartments.</p> Signup and view all the answers

    Which stem cell type is not considered to exist in humans based on the information provided?

    <p>Embryonic stem cell</p> Signup and view all the answers

    What is the main distinction between brown fat and white fat?

    <p>Brown fat is formed from a different lineage than white fat.</p> Signup and view all the answers

    What type of collagen serves as a scaffold in the initial formation of bone?

    <p>Type X collagen</p> Signup and view all the answers

    Which type of stem cell is responsible for generating adipose tissue?

    <p>Mesenchymal stem cells (MSC)</p> Signup and view all the answers

    Which cells are derived from MSC in the context of cartilage formation?

    <p>Osteocytes and chondrocytes</p> Signup and view all the answers

    What is the main clinical application of F-18 FDG PET imaging mentioned in the context?

    <p>Metastasis detection in melanoma</p> Signup and view all the answers

    What kind of fibers must be present to produce elastic cartilage?

    <p>Elastic fibers only</p> Signup and view all the answers

    What is the characteristic of the interface between bone and cartilage?

    <p>They are connected by a fibrous periosteum or perichondrium.</p> Signup and view all the answers

    What is a primary function of proteoglycans in cartilage?

    <p>To resist compression</p> Signup and view all the answers

    What is synonymous with 'basal lamina'?

    <p>Basement membrane</p> Signup and view all the answers

    What role do proteoglycans play in the extracellular matrix?

    <p>They provide weak bonding sites for water</p> Signup and view all the answers

    What happens to proteoglycans in standard preparations?

    <p>They are not normally visible</p> Signup and view all the answers

    What is a function of perineuronal nets (PNNs) in the brain?

    <p>To guide developing axons' connections</p> Signup and view all the answers

    What effect does the disruption of PNNs by chondroitinase have?

    <p>It restores plasticity in a visual system model</p> Signup and view all the answers

    What is the primary characteristic of ground substance in the extracellular matrix?

    <p>It is not preserved in standard preparations</p> Signup and view all the answers

    Which of the following is true regarding proteoglycans?

    <p>They consist of very large molecules</p> Signup and view all the answers

    What common misconception might people have about basement membrane?

    <p>It is only found in epithelial tissues</p> Signup and view all the answers

    What is true about blood in relation to connective tissue (CT)?

    <p>Blood is a type of connective tissue with high cellularity.</p> Signup and view all the answers

    What is the function of cytokines in the immune response?

    <p>They control the cellular response.</p> Signup and view all the answers

    Which of the following cells is primarily involved in innate immunity?

    <p>Macrophage</p> Signup and view all the answers

    In insects, what is the role of hemolymph?

    <p>To circulate nutrients and waste.</p> Signup and view all the answers

    What type of immune response do T-lymphocytes specifically target?

    <p>Intracellular pathogens</p> Signup and view all the answers

    What is a characteristic of the ground substance in connective tissue?

    <p>It consists of plasma and modified interstitial fluid.</p> Signup and view all the answers

    Which type of fat is classified under adipocytes?

    <p>Brown fat is multilocular.</p> Signup and view all the answers

    What type of fiber is normally absent in connective tissue but can be present in certain conditions?

    <p>Fibrin</p> Signup and view all the answers

    What type of collagen fibers is characterized as small and includes reticular fibers?

    <p>Type III</p> Signup and view all the answers

    Which type of collagen is a major structural component that contributes to the creation of fibrillar structures?

    <p>Type I</p> Signup and view all the answers

    At what stage does the assembly of Type I collagen occur according to the information provided?

    <p>Extracellularly</p> Signup and view all the answers

    What characteristic feature can help to differentiate between areas dominated by Type I or Type III collagen?

    <p>Density of collagen fibrils</p> Signup and view all the answers

    Which type of collagen is specifically mentioned as being non-fibrillar and consists of many others?

    <p>Type IV</p> Signup and view all the answers

    In terms of morphology, what distinctive feature do collagen fibers show under high-magnification electron microscopy?

    <p>Banding characteristic specific to their structure</p> Signup and view all the answers

    Which type of collagen is known for its role in forming a meshwork structure?

    <p>Type IV</p> Signup and view all the answers

    Which types of collagen are described as the structural, 'rope-like' collagens?

    <p>Type I and Type III</p> Signup and view all the answers

    Study Notes

    Connective Tissue Definition

    • Connective Tissue (CT) is a type of tissue that connects and supports other tissues in the body.
    • It's derived from Mesenchymal Stem Cells (MSCs)

    Trans-differentiation

    • MSCs can trans-differentiate into various cell types including adipocytes, muscle, myeloid, lymphoid, fibroblasts, red blood cells (RBCs), and granulocytes.
    • This process involves a change in cell type without going back to an embryonic stem cell.

    De-differentiation

    • MSCs can de-differentiate towards an embryonic stem cell state, but this process is not known to occur in humans.

    Muscle Tissue

    • Muscle tissue originates from MSCs.
    • Muscle progenitors form during embryonic and fetal development.
    • Smooth and skeletal muscle retain tissue-specific stem cells in adults, but cardiac muscle likely does not.

    Adipose Tissue

    • Adipose tissue is a specialized type of CT.
    • Adult adipocytes (fat cells) do not divide but change their volume by storing lipids.
    • Adipose tissue can be classified as white fat, beige fat, or brown fat.

    Thermogenic Fat

    • Uncoupling protein 1 (UCP-1) in mitochondria determines whether fat is thermogenic, converting mitochondrial respiration products from ATP to heat.

    Adipose Lineage

    • White fat may be interconvertible with beige fat.
    • Brown fat is a separate lineage.

    Special CTs - Bone & Cartilage

    • Progenitor cells for bone and cartilage are derived from MSCs: osteoprogenitors and chondroprogenitors.
    • Cells: bone has osteocytes and cartilage has chondrocytes.
    • Fibers: Bone is composed of mineralized type I collagen, with type X collagen used as a scaffold initially. Cartilage is primarily type II collagen, with type I collagen in fibrocartilage and elastic fibers in elastic cartilage.
    • Ground Substance: Cartilage has many proteoglycans, which resist compression.
    • Interface: Bone and cartilage are always bounded by a collagen sheet (fibrous periosteum or perichondrium) that functions as the mechanical structure of the joint capsule.

    Blood

    • Blood is highly cellular and considered a distinct compartment in humans, separate from connective tissue.
    • Humans lack fibers in blood (except for fibrin).
    • Blood's ground substance is plasma.
    • Unlike connective tissue, blood is not derived from MSCs.

    Insect Blood

    • Insects have hemolymph that circulates in the hemocoel compartment, where blood and interstitial fluid are identical.

    Resident Cells from MSCs

    • Fibroblasts: These cells can be precursors, general fibroblasts, location-specific types, or activated types (myofibroblasts).
    • Adipocytes: Composed of white fat (unilocular), beige fat, or brown fat (multilocular).

    Cells of the Immune System

    • Immune system cells are derived from the hematopoietic stem cell (HSC).
    • Innate Immunity: Macrophages (often resident in tissue), neutrophils (1st cellular response and chemotaxis), mast cells (enhancing leukocyte response through inflammation), eosinophils (inflammatory response), and basophils.
    • Adaptive Immunity: B-lymphocytes and plasma cells (response to extracellular pathogens), T-lymphocytes (response to viruses, intracellular pathogens).

    Cytokines and Antibodies

    • Cytokines regulate cellular response, with inflammatory cytokines (Il-1, TNF-alpha, Il-6) driving migration and diapedesis of leukocytes. Anti-inflammatory cytokines (Il-4, Il-6, Il-10, Il-11, Il-13) also play a role.
    • Antibodies control inflammation, with mast cells responsive to allergens (IgE) and plasma cells producing antibodies specific to the environment (IgM, IgG, IgE, IgA, IgD).

    Collagen Fibers

    • Collagen fibers are identifiable under electron microscopy (EM).
    • Fibrillar anchoring type VII and meshwork type IV are key types of collagen fibers.
    • Collagen fibers can be categorized into three types:
      • Type I: Large, structural collagen, responsible for strength.
      • Type III: Smaller, provides flexibility and structure.
      • Type IV: Present in basement membranes, acts as a scaffold.

    Type I Collagen Assembly

    • Type I collagen assembly is completed extracellularly.
    • Type I collagen fibrils aggregate as their density increases.
    • Type III collagen does not undergo the same aggregation process as type I.

    Type I & III Collagen Microscopic Appearance

    • Type I and Type III collagen are both structural, "rope-like" collagens.
    • The relative abundance of each type can be distinguished under microscopy.

    Basal Lamina & Basement Membrane

    • "Basal lamina" (from EM) and "basement membrane" are synonymous terms referring to the thin layer that surrounds epithelial cells and muscle fibers.

    Proteoglycans

    • Proteoglycans are large molecules that hydrate the extracellular matrix by providing negatively charged regions that weakly bond with water (H2O).
    • Proteoglycans are difficult to visualize in standard preparations.

    Proteoglycans in the Brain

    • Proteoglycans in the brain form perineuronal nets (PNNs) that surround neurons.
    • PNNs are thought to influence neuronal plasticity and stability.
    • Disrupting PNNs with chondroitinase can restore plasticity.

    Component Imbalance

    • Imbalance in the components of connective tissue can lead to various disorders.

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    Connective Tissue PDF 2024

    Description

    This quiz covers key concepts related to connective tissue, including its definition, the role of mesenchymal stem cells, and the processes of trans-differentiation and de-differentiation. It also explores the origins of muscle and adipose tissues and their specific characteristics. Test your knowledge on these essential aspects of human biology.

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