Connective Tissue & Cartilage Flashcards
What are the broad classifications of CT
- Connective tissue proper (soft tissue): components in a fluid or gelatinous ground substance
- Supportive CT (hard tissue): Components embedded in a solid ground substance
What are the classifications based on
- Relative density of components
2. Characteristics of ECM
What are the types of loose CT proper
- Areolar
- Adipose
- Reticular
- Hemopoietic
What are the types of dense CT Proper
- Irregular arranged
2. Regular arranged: Tendons, Ligamens
What are components of CT
- Fibers
- Ground substance
- Cells
What are the types of fibers
- Collagen
- Elastic
- Reticular
What are some features of collagen fibers
- Don’t stretch or contract
- Heat labile: becomes gelatinous and gluelike
- High molecular weight
- Composed of glycine, proline, and hydroxyproline
- Basic molecule (monomer): tropocollagen
- Fibers are straight/wavy
- Loosely or densely packed depending on the location and functional need
How is collagen produced?
- Intracellular
2. Extracellular
What is the precursor of collagen intracellularly
procollagen
What produces collagen
fibroblast
What are characteristics of procollagen
- helical tripeptide composted of 2 alpha-1 and one (alpha-2)
- Held together by hydrogen bonds.
Where does the synthesis of intracellular collagen fibers occur
Rough ER: Proline and lysine are hydroxylated. Ascorbic acid acts as a cofactor (coenzyme) and then moves to Golgi for glyprorotein addition
What is the synthesis of extracellular tropocollagen
- procollagen cleaved to form tropocollagen via prollagen peptidase
- cross links bet tropocollagen molecules polymerize (lysyl oxidase) to form microfibrils.
- Microfibrils form fibrils
- Fibrils form fibers (collagen) and bundles (collagen)
What are the types of collagen?
- Type 1: most common
- Type 2: cartilage
- smooth muscle, aorta, uterus, spleen, lungs
- Type 4: basal lamina
- Type 5: placental membranes
What are the features of elastic fibers
- Can stretch and return to original size.
2. Resistant to heat
What is the composition of elastic fibers
- Elastin (amorphous protein) surr by microfibrils (fibrillin)
- Elastic protein: rich in glycine and proline (valine, alanine, desmosine and isodesmosine)
What are features of reticular fibers
- Usually loc where collagen is found but not vice versa
- Abundant at boundaries bet CT and other tissues
- Forms majority of stroma in bone marrow, lymphoid tissues, liver
- Not easily diff from collagen or elastin with H&E staining
- Stains darker w/PAS than collagen
- Fibers are argyrohillic- blackens with silver stains
- Very similar to collagen
What is the composition of reticular fibers
Type III collagen fibrils (Never forms bundles!)
What is ground substance
A mixture of proteins, lipids, carbs, and water, varies in consistency from a viscous solution to a hard material
What are the components of ground substance
- Glycoproteins
2. Glycosaminoglycans (GAGS)
What are GAGs
- polysaccarides with 1+ amino sugar moieties
- long, branching polymers, form 3d networks for strength and support.
- have many hydrophilic groups
- may serve as a selective barrier to diffusion of inorganic ions and charged molecules.
- ex: hyaluronic acid, chondroitin sulfate, dermetan sulfate
What are features of ground substance
Viscosity of ground substance is related to types of GAGs present
What are the common types of GAG’s
- Hyaluronic acid: non sulfated GAG capable of binding large amounts of water. Its present in large amounts in skin and contains glucosamine
- Chondroitin sulfate: sulfated GAG, present in the hard CT (cartilage)
What are components of loose connective tissue
All three types of fibers: collagen, elastin, and reticular
What is the function of loose areolar CT
binds organs together; loosely arranged collagen predominates
What is the function of Adipose CT and which structure predominates.
Fat storage; adipocytes predominate
What is the function of reticular CT and which structure predominates
Forms stroma of lymph nodes, liver, spleen and bone marrow. Reticular fibers predominate
What are the cells of loose CT
- Fibroblast
- Mesenchymal
- Adipocytes
- Macrophages
- Mast cells
What are features of fibroblasts
- fusiform or stellate shaped
- nucleus composed of fine chromatin
- 1-2 nucleoli
- arise from other fibroblasts or mesenchymal cells
- most common cell in loose CT
What is the function of fibroblasts
Produces fibers and ground substance, very impt in repair during wound healing
What are the features of mesenchymal cells
- similar to fibroblasts, except that chromatin is more coarse
What is the function of mesenchymal cells
Undifferentiated stem cells capable of giving rise to other cells of mesenchymal origin
What are features of adipocytes
Unilocar (yellow) fat:
- form severeal small lipid droplets
- fuse into a single large droplet
- cytoplasm and nucleus displaced peripherally
- multiocular (brown) fat, the adipocytes retain multiple lipid droplets
- main component of adipose tissue
What is the function of adipocytes
store lipids
What are the features of macrophages
- irregular outline, avoid nucleus
- usually distinguished from fibroblasts by the presence of phagocytosed matter
- May fuse to form giant cells
What is the function of macrophages
- phagocytosis of cell debris, altered intercellular material, microorganisms and foreign material
- contribute to the initiation of the immunological reactions of the body by processing antigens.
What are the the features of mast cells
- granulocyte
- cytoplasm full of secretory granules (vesicles)
- usually assoc. with capillaries
- small, dark staining nucleus
What are the function of mast cells
contain heparin (anticoagulants) and histamine (dilates blood vessels)
What are hematopoetic tissue
arises from stem cell and can become myloid or lymphoid. Lymphoid diff into B or T cells. B cells prod antibody and can prod plasma cell. Myloid prod RBC, platelets, and granulocytes.
What are features of lymphocytes
smallest of cells in the CT, large dark staining nucleus, thin rim of basophilic cytoplasm.
where are lymphocytes loc
numerous in CT, supp the epithelium of the respiratory and GI tracts.
What are the function of T cells
cell mediated immunity; direct and regulate immune responses, directly attack infected or cancerous cells.
What are B cells
recognize antigen, each B cell is programmed to make one specific antibody