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Histo CT
Connective Tissue Review
| Question | Answer |
|---|---|
| Connective tissue cells are derived from ______________ and _____________ precursors | Mesenchymal and Hemopoietic |
| ECM is composed of two types of fibers: | Collagen and Elastic fibers |
| Collagen | -Most abundant ECM fiber -Organized into dense regular and irregular fiber bundles -Have a high level of tensile strength, are tough to break and do not stretch |
| Collagen fiber composition | Collagen fibers are composed of collagen fibrils, which themselves are composed of tropocollagen molecules. -Tropocollagen molecules that make up the collagen fibril are regularly spaced to make the collagen have a striated appearance |
| Tropocollagen | Comprised of three alpha helix chains; 1 alpha 1 and 2 alpha 2 chains, arranged in a triple helix. Helical configuration for this helix is typically gly-X(typically proline)-Y(hydrophobic molecule) |
| Collagen stains..... | Blue with Azan stain |
| Collagen I is synthesized by what type of cell? | Fibroblasts (most abundant CT cell) |
| Collagen I synthesis | Intra: Hydroxylation, glycosylation, and triple helix formation of topocollagen. Extra:proteolysis of peptide ends, spontaneous assembly of tropocollagen molecules, and crosslinking tropocollagen by lysine oxidase. Collagen fibrils --> collage n fibers |
| Collagen synthesis steps that may lead to disease | Mutations in collagen genes Mutations in enzymes needed for synthesis Other factors that reduce the efficiency of processing enzymes |
| Collage types | I-Dermis, fascia, bone, ligaments, tendons II-fibrils in hyaline + elastic cartalige III-Reticular fibers-Skin, blood vessels, glands, lymph tissue IV-(no fibrils)Basal/External laminae VII-anchoring fibrils for Epi layers |
| Reticular fibers | Stain with silver stain due to high levels of glycosylation contain type III fibrils Lie beneath the basal lamina (in the lamina reticularis (contains collagen I as well)) and surround muscles and other cells to act as a support |
| Collagen IV | Major component of the basal lamina that support all epithelia and external laminae surrounding muscle fibers and schwann cells. Do not form fibrils, but form a 2D open network scaffold of proteins. |
| Lamina reticularis | Type I and III collagen (reticular fibers) Anchors the basal lamina, with minor collagen types, to underlying collagen types. |
| Elastic fibers | -Verhoeff stains elastic fibers black -Composed of an elastin core (doesn't stain) and a layer of microfibrils surrounding it -Found in blood vessels and skin |
| Elastin's elasticity | Elastin is made up of hydrophobic residues that when stretched change their conformation to avoid water and when allowed to retract, reconfigure into initiating configuration |
| Ground substance | A hydrated gel that embeds ECM fibers and contains glycosaminoglycans, proteoglycans,proteoglycan aggregates, adhesive glycoproteins. The major components are proteoglycans |
| Proteoglycans | Are composed of high negatively charged GAG's, which are chains of repeated uronic acid and amino sugar (many of which are sulfated) disaccharids. Very basophillic. Bind important cations and water to keep the GS hydrated |
| Proteoglycan monomer | A single polypeptide chain with GAG molecules covalently attached |
| Hyaluronic Acid | A very long, single GAG chain, that non-covalently binds proteoglycan monomers to make proteoglycan aggregates. These aggregates occupy most of the ECM and and maintain it's integrity. |
| Hyaluronidase | Enzyme secreted by bacteria that breaks down the ECM by cleaving hyaluronic acid. |
| Adhesive Glycoproteins | Fibronectin Integrins Laminin |
| Fibronectin | Important for wound healing. The polypeptide chain contains distinct regions of recognition for cell surface receptors, GAGS, and collagens |
| Integrins | Proteins composed of an alpha and beta dimer. A given combination of alpha and beta determines the specific binding of integrins to ECM components. Cytoplasmic side-cytoskeleton mol. and enzymes, thus integrins reg. cell behavior via these interactions |
| Leukocyte adhesion deficiency cause: | Mutations in the integrin chains causing a loss of function and the inability for WBC's to enter peripheral tissue due to lack of adhesion. |
| Laminin | Present in both the basal laminae and external laminae. Contain recognition domains, that differ from fibronectin, that are recognized by integrins, proteoglycans, and collagen |
| Properly functioning integrins and their interaction within the ECM is important to stop the ________________ of cancers cells | metastatic movements |
| Fibroblasts synthesize collage | type I |
| Fibroblasts | Regenerate and migrate to where needed (wound site). These cells contain high levels of euchromatin. They are specialized to produce ECM components specific to their region of residence. |
| Fibroblasts that are dormant and synthetically inactive, or that are circulating. | Fibrocytes |
| Recruitment of fibroblasts | 1. Migration of local FB's in response to chemokines. 2. Chemotraction and differentiation from circulating fibrocytes. 3. Trans determination of local epithelia: Epithelial-mesenchymal transition |
| Mast cells | Common along CT, GI, and respiratory tracts. Contain secretory granules encasing histamines, heparin, chemotactic factors, and enzymes. Release of the granules is triggered by MB or Sec IgE binding of ag and then mast cell |
| Plasma Cell | Derived from B-cells. Secrete AB specific for a single antigenic group. Have abundant ER and golgi for packaging and secretion of AB. Located in loose CT of the GI and respiratory tract |
| Macrophages | Derived from monocytes of the blood that enter the ECM space. |
| Phagocytosis | Initiated by the binding of AB-Ag complex on a give micro and the binding of the FC onto the macrophage FC receptor. Facilitated by the cytoplasmic extension and engulfment of microbe. |
| Fat Cell Function | Synthesize and store energy; insulators and cushions, supported by reticular fibers |
| Adipocyte mech for energy conversion | Adipocytes take up triglycerides from the blood stream to be stored. In response to stimulation (hormone e.g.), adipocytes break down triglycerides using Lipases and release FA's and glycerol into BS |
| Brown Fat function | Thermo-regulation; found in higher amounts in babies. |
| White vs. Brown fat | B-more vascularized B-more mitochondria B-multiple smaller droplets |
| Mech of thermoregulation | BAT contains high amount of mitochondria which express uncoupling protein - 1 (UCP-1). UCP-1, allows the movement of H+ into the mitochondrial matrix without ATP synthesis and instead generated heat. |
| UPC-1 malfunction in beta pancreatic cells is implicated in what disease? | Diabetes |
Created by:
jgenere
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