Connective Tissue

  1. Where is connective tissue typically derived?
    • Mesoderm
    • (middle embryonic germ layer)
  2. What type of connective tissue underlies epithelium?
    Loose CT
  3. Where is dense regular connective tissue typically found?

    Tendons / ligaments

  4. What type of connective tissue forms layers in organs?

    • Dense Irregular CT

    • - reticular layer of dermis
    • - submucosa of digestive organs
  5. What are the functions of adipose tissue?

    • Insulation
    • Energy storage
    • Provides physical contours that distinguish men and women
  6. What are the components of connective tissue?

    • 1) Ground Substance
    • 2) Fibers
    • 3) Cells
  7. Characteristics & Composition of Ground Substance
    amorphous / colorless / homogenous


Proteoglycans - synthesized / secreted by resident cells of CT. Protein backbone covalently bound to glycosaminoglycans. Proteoglycans are very hydrophilic (stain with eosin). Typically surrounded by a thick layer of solvation water.

    • Glycoproteins - laminin (major component of basal lamina) & fibronectin

    • Tissue fluid - similar to blood plasma (accumulation = edema)
  8. Major types of connective tissue fibers
    • Collagen fibers
    • Elastic fibers
    • Reticular fibers
  9. Most abundant types of collagen
    Types I - IV

    (90% = Type I)
  10. What forms classically described collagen fibers / collagen bundles?
    Type I Collagen
  11. Synthesis of collagen
    Image Upload 1
  12. Collagen bundles: acidophilic or basophilic? Why?
    • Acidophilic due to charged amino groups
    • (stains pink with Eosin in H&E)
  13. Type I Collagen
    Connective tissues (skin, bone, tendon, ligaments, fascia, etc...90% of body collagen) 

    Provides resistance to force, tension, stretch
  14. Type II Collagen
    • Cartilage (hyaline, elastic)
    • Notochord
    • Intervertebral Disks
  15. Type III Collagen
    Loose connective tissue (organ tissue, blood vessels, smooth muscle, etc...)

    Reticular fibers (forms loose meshwork - i.e. lamina propria, lymphatic organs, etc...)
  16. Type IV Collagen
    Basal lamina of epithelia
  17. Type VII Collagen
    Secures basal lamina to connective tissue fibers

(Anchoring fibrils of skin, eye, uterus, and esophagus)
  18. Type IX Collagen
    Found in cartilage associated with type II collagen fibrils

    (stabilize type II fibers by interaction w/ proteoglycan molecules)
  19. Type X Collagen
    Produced by chondrocytes in zone of hypertrophy of normal growth plate

    Contributes to the mineralization process by forming hex. lattices to arrange types II, IX, XI collagen within the cartilage
  20. Type XI Collagen
    • Produced by chondrocytes
    • (associated w/ type II collagen fibrils, forms core of type I collagen fibrils)

    Regulates size of type II collagen fibrils; it is essential for cohesive properties of cartilage matrix
  21. Composition of elastic fibers
    Composed of elastin and fibrillin
  22. Orecin / Resorcin-fuchsin is used to stain _______
    Elastic fibers
  23. Where are elastic fibers found?
    Walls of blood vessels (tunica media of aorta)

ligamentum flavum (stretch)
  24. Composition of reticular fibers
    Formed by type III collagen
  25. Where are reticular fibers found?
    Framework of specialized organs (lymphoid, kidney)

    Loose connective tissue

    Reticular lamina / lamina propria
  26. Silver salts are used to stain _______
    Reticular fibers (argyrophilic)
  27. Most common type of connective tissue resident cell?
  28. Migrating connective tissue cells? Found mainly in which tissue?
    • Mast cells
    • Plasma cells
    • Leukocytes
    • Macrophages

    (Mainly found in loose CT)
  29. Function of fibroblast
    Synthesize ECM (ground substance & fibers)
  30. Types of adipose tissue
    • White fat - unilocular

    • - mostly in adults

    • - energy storage, insulation, cushioning, hormone secretion

    • Brown fat - multilocular

    • - large amount in newborns (adults = adrenals, aorta, neck, mediastinum)

    • - lipid mobilizaiton, heat generation (sympathetic stimulation)
  31. Adipose cells & Fibroblasts are derived from...
    Undifferentiated Mesenchymal Cells
  32. Ghrelin
    Polypeptide from gastric epithelium

    • Acts as an appetite stimulant via hypothalamus 

    • (short term regulation)
  33. Peptide YY
    Gastrointestinal peptide 

    • Signals satiety via hypothalamus
(short term regulation)
  34. Insulin
    • Stimulates lipid synthesis and blocks lipolysis
    • (long term regulation)
  35. Leptin
    Produced by fat cells

    • Acts on hypothalamus to suppress appetite

    • (long term regulation)

    Obese people are believed to be leptin resistant
  36. Neurogenic Lipid Mobilization Pathway
    • Norepinephrine (nerve endings) stimulates cAMP system
    • -> activates hormone-sensitive lipase
    • -> hydrolyzes stored triglycerides to free fatty acids and glycerol

    -> diffuse into capillaries where fatty acids bind to albumin (hydrophobic moiety)

    -> transported for use as energy
  37. Lipid Storage Pathway
    Triglycerides transported from intestine and liver by lipoproteins (chylo & vLDL) into blood

    -> in adipose tissue capillaries lipoproteins are broken down by lipoprotein lipase

    -> free fatty acids and glycerol are released and diffuse from capillary into adipocytes

    -> re-esterified into glycerol phosphate -> forming triglycerides (stored until needed)
  38. Mast Cells
    Large, ovoid cells w/ numerous cytoplasmic granules.

    • Originate in bone marrow
    • Differentiate in connective tissue

    • Granules contain vasoactive and immunoreactive substances.
    • - Histamine and slow reacting substance of anaphylaxis (SRS-A)
    • - Eosinophil and neutrophil chemotactic factors (ECF and NCF)
    • - Heparin (anticoagulant)
  39. Plasma Cells
    • Antibody producing cells derived from B-lymphocytes.
    • (Common in loose connective tissue of the gut and glands)

    • Basophilic cytoplasm due to RER
    • Eccentric nucleus with “clockface” chromatin
    • Prominent Golgi apparatus seen as clear, unstained region near nucleus.
  40. Mast Cell - Plasma Cell Interaction
    Mast cells have receptors for IgE

    Plasma cells make IgE in response to an antigen (i.e. bee venom)

    • Upon second exposure, antigen will bind to IgE molecules on the mast cell

    • -> This triggers mast cell degranulation
  41. Macrophages
    Derived from blood-borne monocytes.

    In tissue, best seen if they are actively phagocytic (large vacuolated cytoplasm)

    • Part of the Mononuclear Phagocytotic System.
    • (Pathologists refer to them as histiocytes)
  42. Giant Cells
    • Macrophages fuse to for very large, multinucleated cells
    • in response to a foreign body (suture material / hair) that has gotten into an incision
  43. Lymphocytes
    Connective tissue immune surveillance system

    • B-lymphocytes give rise to plasma cells that synthesize immunoglobulin.
    • T-lymphocytes are involved in cell-mediated mmunity.
    • Natural Killer (NK) Cells destroy virus infected cells and some tumor cells
  44. Neutrophils
    Granulocytes with segmented nuclei

    First cells to arrive at a site of acute inflammation (process called diapedesis)

    • Active phagocytes (sometimes called microphages)
    • Can phagocytose some bacteria. Other foreign substances must be opsinized.

    (Pus is an accumulation of dead neutrophils)
  45. Eosinophils
    Bilobed nucleus & large red granules

    • Associated with 3 conditions:
    • - Allergic reactions
    • - Parasitic infections
    • - Chronic inflammatory processes

    • Often found in the lamina propria of the gut
    • (increase in number with chronic inflammation)
  46. Loose CT vs. Dense CT
    Loose CT - lots of cells, fewer fibers

    • Dense CT - fewer cells, more fibers
    • - Dense irregular (dermis – reticular layer)
    • - Dense regular (tendons, ligaments)
Card Set
Connective Tissue
Exam 1