Epithelial Polarity and Specializations
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Questions and Answers

What role do fibroblasts play in connective tissue?

  • They primarily store energy in the form of lipids.
  • They reduce inflammation in tissue.
  • They produce and maintain the extracellular matrix. (correct)
  • They facilitate cellular communication.

Which of the following types of connective tissue is derived from mesenchyme?

  • Embryonic connective tissue (correct)
  • Adipose tissue
  • Mature cartilage
  • Dense regular connective tissue

Which type of adipocyte is specialized for heat production?

  • Mature adipocytes
  • Transitional adipocytes
  • Brown adipocytes (correct)
  • White adipocytes

What are transient cells in connective tissue primarily involved in?

<p>Immune responses and repair (B)</p> Signup and view all the answers

How are connective tissues classified?

<p>Using the arrangement and type of the extracellular matrix (A)</p> Signup and view all the answers

Which of the following cells are considered permanent residents of connective tissue?

<p>Fibroblasts and macrophages (A)</p> Signup and view all the answers

What is the primary function of dense regular connective tissue?

<p>Providing tensile strength in one direction (D)</p> Signup and view all the answers

Which cell type primarily comprises adult adipose tissue?

<p>Adipocytes (A)</p> Signup and view all the answers

What transformation do fibroblasts undergo after synthesizing the matrix?

<p>Convert into fibrocytes (D)</p> Signup and view all the answers

Which type of connective tissue is characterized by its undifferentiated mesenchymal cells and gel-like ground substance?

<p>Mucoid connective tissue (C)</p> Signup and view all the answers

What is a characteristic feature of unilocular adipocytes?

<p>A single large lipid droplet (D)</p> Signup and view all the answers

Which type of transient cell is primarily responsible for initiating allergic responses?

<p>Mast cells (A)</p> Signup and view all the answers

What type of connective tissue is most widely distributed in the body?

<p>Loose areolar connective tissue (A)</p> Signup and view all the answers

What are multilocular adipocytes primarily characterized by?

<p>Numerous small lipid droplets (D)</p> Signup and view all the answers

Which of the following cells is derived from B lymphocytes and enters connective tissue?

<p>Plasma cells (B)</p> Signup and view all the answers

Which category of connective tissue includes cartilage and bone?

<p>Specialized connective tissue (A)</p> Signup and view all the answers

What is the main role of fibroblasts in connective tissue?

<p>To synthesize the extracellular matrix (B)</p> Signup and view all the answers

Which type of connective tissue is primarily found in the umbilical cord?

<p>Mucous connective tissue (C)</p> Signup and view all the answers

What distinguishes white adipocytes from brown adipocytes?

<p>Brown adipocytes are rich in mitochondria (C)</p> Signup and view all the answers

Which type of cell is considered a transient cell in connective tissue?

<p>Macrophage (D)</p> Signup and view all the answers

What characteristic is specific to elastic fibers in connective tissue?

<p>They allow for stretching and recoiling (A)</p> Signup and view all the answers

Which of the following components is NOT part of the connective tissue ground substance?

<p>Collagen fibers (D)</p> Signup and view all the answers

Which type of connective tissue fiber is primarily responsible for providing tensile strength?

<p>Collagen fibers (D)</p> Signup and view all the answers

Flashcards

Fibrocytes

Mature connective tissue cells that secrete the matrix.

Adipocytes (fat cells)

Cells filled with lipid droplets, either unilocular or multilocular, derived from mesenchymal cells.

Unilocular Adipocytes

Adipocytes with a single, large lipid droplet pushing the nucleus to the periphery.

Multilocular Adipocytes

Adipocytes with multiple small lipid droplets and abundant mitochondria.

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Transient cells

Short-lived connective tissue cells originating in bone marrow and circulating in blood.

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Loose Areolar Connective Tissue

Widely distributed connective tissue binding body parts while allowing movement. It has many blood vessels.

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Mesenchymal Connective Tissue

Embryonic connective tissue, containing undifferentiated cells and a gel-like matrix.

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Mucoid Connective Tissue

Embryonic connective tissue found in the umbilical cord, containing abundant ground substance.

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Occluding Junction

A type of cell junction that prevents the passage of substances between cells. It acts as a tight seal, forming a continuous belt-like junction around the perimeter of each cell.

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Anchoring Junctions

Cell junctions that provide strong attachment between adjacent cells. They act as a link between the cytoskeletons of neighboring cells.

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Zonula Adherens

A type of anchoring junction that encircles the apical part of two adjoining cells. It contains cadherins, which require calcium to bind.

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Macula Adherens (Desmosomes)

A type of anchoring junction consisting of two disk-shaped attachment plaques, dense vertical filamentous material, and keratin intermediate filaments. They connect adjacent cells strongly.

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Hemidesmosomes

A type of anchoring junction that connects epithelial cells to the underlying basement membrane. They contain integrins that link the cell to the extracellular matrix.

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Communicating Junction (Gap Junction)

A type of cell junction that allows communication between adjacent cells. They permit the exchange of small molecules and ions.

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Connective Tissue

The most abundant and widely distributed tissue in the body. It arises from mesenchyme and consists of cells embedded in an extensive extracellular matrix.

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Extracellular Matrix

The non-cellular component of connective tissue, composed of fibers and ground substance. It provides support, structure, and allows for cell communication.

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Ground Substance

The fluid-filled, non-cellular component of connective tissue that acts as a medium for diffusion, support, and lubrication. It's composed of interstitial fluid, adhesive glycoproteins, and proteoglycans.

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Proteoglycan Aggregate

Large, complex structures formed by multiple proteoglycans linked to hyaluronic acid. They trap water, giving ground substance its gel-like consistency.

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What is the function of collagen fibers in connective tissue?

Collagen fibers provide significant tensile strength, making connective tissue durable and resistant to pulling forces. They are the most abundant type of fiber in connective tissue.

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How do elastic fibers contribute to connective tissue?

Elastic fibers allow connective tissue to stretch and recoil, providing flexibility and resilience. They are found in areas that require stretching and rebounding.

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What is the role of reticular fibers?

Reticular fibers form delicate networks that support the cells of organs and surround small blood vessels, creating a framework for these structures.

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Where are collagen fibers synthesized?

Collagen fibers are synthesized inside fibroblasts, specialized cells that produce the components of connective tissue matrix.

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Fibroblast

Spindle-shaped cells with abundant rough endoplasmic reticulum and a well-developed Golgi complex, responsible for producing and maintaining the connective tissue matrix.

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Hyaluronidase

An enzyme that breaks down hyaluronic acid in the ground substance, facilitating bacterial invasion.

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Study Notes

Epithelial Polarity

  • Epithelial cells have apical, basal, and lateral surfaces
  • These surfaces have specialized structural modifications for specific functions
  • Apical specializations include microvilli and stereocilia
  • Microvilli are non-motile projections increasing surface area for fluid absorption
  • Stereocilia are long, branching microvilli, common in the male genital ducts
  • Cilia and flagella are motile projections
  • Cilia are hair-like and longer than microvilli
  • Flagella are similar to cilia but much longer, and typically one per cell
  • Cilia and flagella have a basal body, a shaft, and rootlets, made of microtubules

Basal Specializations

  • Basal infoldings increase the surface area for ion transport (e.g., in kidney tubules)
  • Basement membrane is a structural modification in the basal domain
  • Cell-to-matrix junctions include hemidesmosomes connecting cells to the basement membrane

Cell Adhesion Molecules (CAMs)

  • Transmembrane glycoproteins with extracellular domains that bind other CAMs or matrix proteins
  • Cytoplasmic domains attach to cytoskeleton
  • Cell adhesion is a dynamic process, essential for migration and metastasis

Connecting Cell Junctions

  • Occluding junctions (tight junctions): prevent passage of substances between cells
  • Anchoring junctions: provide strong attachment and link cytoskeletons of adjacent cells
  • Communicating junctions (gap junctions): allow the exchange of ions/molecules between cells

Connective Tissue

  • Connective tissue is the most abundant and widely-distributed tissue in the body
  • Composed of cells and extracellular matrix
  • Extracellular matrix is a non-living material filling spaces between cells
  • Extracellular matrix consists of interstitial fluid and proteins (like fibronectin, laminin), proteoglycans
  • Proteoglycans form a gel-like substance trapping water and acting as a medium for nutrient diffusion
  • Connective tissue fibers include collagen, elastic, and reticular fibers

Connective Tissue Fibers

  • Collagen fibers: strong, high tensile strength, appear white in fresh state, run in bundles
  • Elastic fibers: flexible, allow stretching and recoiling, appear yellow
  • Reticular fibers: form a network, support cells, found in organs like bone marrow, spleen

Connective Tissue Cells

  • Fixed cells (resident): fibroblasts, chondrocytes, osteocytes, adipocytes
  • Transient cells (wandering): macrophages, mast cells, plasma cells, leukocytes
  • Fibroblasts: synthesize ground substance and fibers, can become quiescent fibrocytes
  • Adipocytes: store energy in triglycerides, unilocular (fat) or multilocular (brown fat)
  • Mast cells: release granules containing histamine, other mediators in allergic reactions

Connective Tissue Types

  • Embryonic connective tissue (mesenchymal and mucous)
  • Connective tissue proper (loose and dense irregular/regular, elastic, reticular)
  • Specialized connective tissue (cartilage, bone, blood)

Integumentary System

  • Skin is a major organ, composing about 16% of body weight
  • Skin has two layers: epidermis (ectodermal) and dermis (mesodermal)
  • Epidermis is a stratified squamous epithelium; keratinocytes are predominant, also melanocytes, Langerhans cells, Merkel cells
  • Keratinocytes are continually shed and replaced from the basal layer

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Epithelial Polarity and Cell Surface Specializations PDF

Description

Explore the intricacies of epithelial polarity, including the apical, basal, and lateral surfaces of epithelial cells. Learn about the specialized structures like microvilli, stereocilia, and their roles in various functions. This quiz will also delve into basal specializations and cell adhesion molecules.

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