1/2 TOB Connective Tissue

  1. tissues
    Societies of cells with their associated extracellular matrix (ECM) which are specialized to carry out specific functions
  2. What are the 4 primary phenotypes of mature tissues?
    • 1) Epithelium
    • 2) Connective Tissue (CT)
    • Soft
    • Firm: Cartilage, Bone
    • Blood & Lymph
    • 3) Muscle
    • Striated: Skeletal, Visceral, Cardiac
    • Smooth
    • 4) Nervous Tissue
  3. Epithelium
    first tissue formed in embryo; composed of sheets of cells attached to each other by specialized adherens junctions and to an underlying ECM
  4. H&E (hematoxylin and eosin)
    • Eosin stains BASIC components
    • E=pink/red (intra/extracellular proteins, cytoplasm)
    • Structures that stain w/ acidic eosin = basic

    • Hematoxylin stains ACIDIC components
    • H=blue (Nuclei)
    • Structures that stain w/ basic hematoxylin = acidic

    melanin stains yellow & brownhydrophobic structures (adipocytes, myelin, Golgi membranes) remain clear
  5. Glycoproteins stain poorly with _______ but stain positively with ___________
    Glycoproteins stain poorly with eosin but stain positively with the PAS reaction
  6. PAS (Periodic acid-Schiff) Stain
    • used for structures that contain carbohydrates (glycogen, glycoprotein, proteoglycans)
    • periodic acid breaks C-C bonds --> creates aldehydes --> aldehydes react with the Schiff reagent to give purple-magenta color
  7. Epithelial-Mesenchymal Transformation (EMT)
    process by which epithelial cells lose cell polarity and cell-cell adhesion, and gain migratory and invasive properties to become mesenchymal cells
  8. Mesoderm
    • forms mesenchyme (embryonic connective tissue), mesothelium (forms the muscles), non-epithelial blood cells and coelomocytes
    • one of the 3 primary germ layers in the very early embryo
  9. Ectoderm
    originates from the outer layer of germ cells; differentiates to form nervous system, tooth enamel and epidermis (among other mature structures)
  10. Connective tissue
    • one of the four basic tissue types that functions to support other tissues; made up of cells & the matrix
    • it consists of several cell types and extracellular products which, together, provide essential functions of mechanical reinforcement, immune surveillance, transport/diffusion of nutrients and wastes, & energy storage (fat)
    • Embryonically, connective tissue is derived from mesoderm/mesenchyme
  11. What are the two different types of cellular components of the connective tissue?
    Indigenous cells & Immigrant cells
  12. Indigenous cells
    • connective tissue cells that originate in the connective tissue itself
    • 1) Fibroblasts
    • 2) Adipocytes
    • 3) Mesenchymal cells
    • [FAM: like family is the closest unit, arise w/in itself]
  13. Immigrant cells
    • connective tissue cells that originate from hematopoietic stem cells in bone marrow, circulate in the blood, then move into connective tissue where they differentiate and subsequently function
    • 1) Plasma Cells (derived from B-Lymphocytes)
    • 2) Eosinophils
    • 3) Neutrophils
    • 4) Macrophages (derived from monocytes)
    • 5) Lymphocytes
    • 6) Mast cells
    • [PEN & MaLM I dunno just remember it]
  14. What are the main components of the extracellular matrix?
    fibrous constituents and the ground substance
  15. What are the different types of fibrous constituents in the extracellular matrix?
    • Collagen fibers
    • Elastic fibers
    • Reticular fibers (collagen type III)
  16. Image Upload 1
    • collagen fibers; resist stretching
    • I = acidophilic; in bone, dense CT, dermis
    • II in hyaline & elastic cartilage (car-TWO-lage)
    • III = argyrophilic; recticular fiber stroma, smooth muscle
    • IV basal & external laminae
    • VII anchoring fibrils associated with basement membr.
  17. Image Upload 2
    • 1) fibroblast nucleus
    • 2) fibroblast cytoplasm
    • 3) collagen fibril bundles
    • 4) ground substance
  18. Collagen Fiber Diseases
    • 1) Ehlers-Danlos Syndrome results from defects in quality or quantity of collagens affecting skin & joints
    • 2) Scleroderma results from fibrosis (too much collagen), sclerosis (tissue hardening), immune activation, vascular damage & can be caused genetically or environmentally
    • 3) Keloids excessive scar tissue in dermis during connective tissue repair

    • Image Upload 3
    • keloid collagen branching
  19. the basement membrane has collagen types:
    • 3, 4 & 7
    • 3 & 4 are held TOGETHER by 7 (3+4=7)
  20. argyrophilic
    having an affinity for silver (eg. recticular fibers/cartilage III)
  21. Image Upload 4
    Image Upload 5
    • Elastic fibers
    • facilitate stretching --> mainly composed of elastin cross-linked to fibrillin
    • has unique lysine derivatives
    • elastic ligaments (ligamenta flava) can be found in vertebral column - facilitate spine flexibility
  22. In blood vessels, elastic tissue is a product of _____________ but it's formed by __________ in the connective tissue
    • smooth muscle cells make elastic tissue of the blood vessels
    • fibroblasts make elastic tissue in the CT
  23. What are the two forms of elastin?
    • 1) Fibrillar: BRANCHED fiber/fibril elastic tissue found in CT (eg. skin dermis); fibrillar elastin is complexed with fibrillin
    • 2) Lamellar: lamellae (sheets/layers) elastic tissue found in large blood vessels (eg. elastic arteries)
  24. Elastic Fiber Diseases
    • 1) Cutis laxa: mutation in elastin gene that affects blood vessels, skin, & lungs [baggy skin]
    • 2) Marfan Syndrome: mutation in fibrillin-1 gene results in multisystem disease
  25. Image Upload 6
    • Reticular fibers
    • made up of cross-linked collagen III and acts as a supporting mesh in soft tissues (liver, bone marrow, spleen, lymphatic system)
    • visible only by staining with silver salts
    • also found in basement membranes
  26. Image Upload 7
    • Collagen = thicker fibers
    • Elastic = thin fibers
  27. What can be found in the ground substance of the extracellular matrix?
    • Water
    • Proteoglycans
    • Glycosaminoglycans (GAGs)
    • Glycoproteins
    • it's the background material within which all other connective tissue elements are embedded
    • consists mainly of water that provides a route for communication + transport (by diffusion) between tissues
    • a complex of GAGs, proteoglycans, & glycoproteins stabilizes the water
  28. Proteoglycans
    • small & large linear polymers of disaccharides covalently linked to a protein core [GAGs]
    • hydrophilic, negatively charged (polyanions) due to sulfate groups on the sugar residues
    • they account for the porous nature of CT that allows diffusion of metabolites and waste products to traverse to and from blood vessels
    • Glycoproteins
    • multifunctional proteins that have oligosaccharides attached; they can bind cells to matrix molecules for adhesion & signaling (eg. fibronectin and laminin)
  29. Image Upload 8
    • Fibroblasts
    • they synthesizing collagens + other ECM molecules (eg. elastin, proteoglycans & glycoproteins)
    • major cell type of both regular & irregular dense connective tissue
    • they have an elongated appearance with flattened, surf-board-like nuclei and cytoplasm with lots of RER & golgi
  30. Where do fibroblasts originate?
    they are a type of indigenous cell of the CT that develop from undifferentiated mesenchymal cells and spend all their life in the connective tissue
  31. myofibroblasts
    type of cell intrinsic to the CT that is in between a fibroblast and a smooth muscle cell in differentiation
  32. What are these CT cells?
    Image Upload 9
    • fibroblast, collagen and mesenchymal cell
    • Image Upload 10
  33. What are these CT cells?
    Image Upload 11
    • fibroblasts, macrophages, mast cells
    • Image Upload 12
  34. Image Upload 13
    • Macrophage (immigrant cell)
    • large cells that phagocytose cellular debris, foreign bodies, air-born particles etc.
    • their distinguishing characteristics are their large size, and their nuclei, which are large and irregularly shaped
    • their cytoplasm is full of vacuoles (phagosomes) that contain phagocytosed material
  35. Mast cells
    type of immigrant cell of the CT that are known for participating in allergic reactions
  36. Image Upload 14
    • Mast Cells
    • 1) numerous intensely stained, basophilic cytoplasmic granules [due to polyanions (negative charges)]
    • 2) spherical central nucleus.
  37. Image Upload 15
    example of basophilic
  38. Medical Connection: Allergic Reactions & Mast Cells
    • Mast cell granules contain
    • 1) heparin: a polyanionic GAG & anticoagulant
    • 2) histamine: a vasodilator that makes venules & capillaries leaky, releasing soluble blood components into the CT
    • during an allergic reactions, immunoglobulin IgE binds to mast cell surface receptors when it comes in contact with a previously encountered antigen
    • this triggers the release histamine and heparin
    • the strength of this response can range from mild itching/edema to stronger (potentially-fatal anaphylactic shock)
  39. Image Upload 16
    degranulation is a cellular process that releases antimicrobial cytotoxic molecules from granules (secretory vesicles found inside some cells, here a mast cell) by the immune system
  40. Image Upload 17
    • Plasma cells
    • responsible for the synthesis of immunoglobulins
    • oval: one side has the nucleus, the other has the "apron” of basophilic cytoplasm
    • heterochromatin in nucleus has a distinctive “wagon wheel”/“clock-face” arrangement
    • have lots of RER (synthesize IgGs) in cytoplasm --> stain basophilically
    • clear area btwn basophilic cytoplasm & nucleus is the Golgi (where glycosylation and further processing of the IgGs occurs)

    Image Upload 18
  41. Where do plasma cells come from?
    B-lymphocytes that have left the circulation and move to the connective tissue; in the CT they differentiate and initiate the synthesis of immunoglobulins
  42. Polymorphonuclear leukocytes
    • blood borne [immigrant] cells that when stimulated migrate from blood stream to the CT via postcapillary venules
    • two types = neutrophils and eosinophils
    • both have multi-lobed nuclei and granules specific to each filled with substances that make them function
  43. Neutrophils (MICROphages)
    • most abundant type of circulating white blood cell
    • 1st to respond to bacterial infections by internalizing, digesting, & killing bacteria
    • phagosomes form when bacteria is ingested, which fuse with granules that release antibacterial substances

    [eg. ROS (reactive oxygen species' like superoxide anions or H2O2), lysozyme, or lactoferrin]

    neutrophil granules = light pinkish and delicate reddish-purple (azurophilic)
  44. Eosinophils
    • respond to parasitic infection (eg. worms/protozoa) where they have cytotoxic effect on the parasite (release of peroxidase/other toxic substances).
    • are involved in allergic reactions (modulate inflammation, phagocytosing antigen-antibody complexes)
    • eosinophil granules = bright red (eosinophilic)
  45. Image Upload 19
    • Mesenchyme: undifferentiated loose (embryonic)connective tissue that is derived mostly from mesoderm
    • essentially refers to morphology of embryonic cells
    • characterized by prominent ground substance matrix containing a loose aggregate of reticular fibrils and unspecialized cells
  46. Image Upload 20
    • Loose Connective Tissue
    • a loose arrangement of fibers and cells surrounded by an abundance of ground substance
    • holds organs in place and attaches epithelial tissues to itself and other underlying tissues
    • surrounds blood vessels and nerves.
  47. Compared to dense connective tissue, loose connective tissues contain _____ extracellular fibrils, but are ______ in cells (including ___________)
    • loose connective tissues contain FEWER extracellular fibrils
    • loose connective tissues are RICHER in cells (including fibroblasts)
  48. Image Upload 21
    • Dense Regular Connective Tissue
    • consists largely of tightly packed collagen fibers arranged in a parallel fashion; best examples =
    • 1) tendons (muscle to bone)
    • 2) ligaments (bone to bone)
    • their strength comes from the regular, longitudinal arrangement of collagen fibril bundles
  49. Image Upload 22
    • Dense Irregular Connective Tissue
    • composed of densely packed collagen fibers NOT arranged in parallel bundles; collagen fibers instead are arranged irregularly through the tissue
    • they still impart strength to the tissues in which they are found (eg. skin dermis)
  50. What types of connective tissues are these?
    Image Upload 23
    • comparison
    • left: dense regular
    • right: DENSE irregular
  51. Adipose Tissue
    • indigenous cell of CT that comes in two major varieties:
    • white adipose tissue - lipid storage
    • brown adipose tissue - heat production
  52. Image Upload 24
    • White Adipose Tissue
    • made up of large, fat adipocytes that have storage vacuole
    • there's also a small amount of loose connective tissue w/ blood vessels between these cells (gives a “chicken-wire’ appearance)
  53. Image Upload 25
    • Brown Adipose Tissue
    • brown b/c it has cells with numerous mitochondria (containing colored cytochromes) and LOTS of blood vessels btwn cells
    • the cells are polygonal and generally smaller than white adipose tissue cells
    • cytoplasm contains a large number of lipid droplets
    • cells express high levels of UCP1 (uncoupling protein) that prevents high energy phosphate bond formation in ATP and the energy is released as heat
    • important in nonshivering thermogenesis
  54. Beige Adipose Tissue
    exists beneath the skin near clavicles & along spine; similar to brown fat, but has different stem cell origin and normally expresses low levels of UCP1; precise significance unknown, possible relationship to obesity
  55. Special Connective Tissue
    • highly differentiated and localized forms of connective tissue that share many common features (structural components, cell lineages) with connective tissue proper
    • special forms include bone, cartilage, lymphoid tissue (spleen and lymph nodes), & blood
Card Set
1/2 TOB Connective Tissue
MBS TOB Exam 2