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61 Cards in this Set
- Front
- Back
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What is connective tissue? |
It supports binds and connects epithelial, muscle, and nervous tissue, and it is present in all other types of tissue in one way or another. It is considered to be the intercellular glue-like tissue |
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What is the most distinguishing feature of connective tissue? |
The most important distinguishing feature is the extensive extracellular martrix (ECM) This is what gives connective tissue its special qualities |
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What are the components of ECM? |
Fibers (reticular, elastic, and collagen) and ground substance (proteoglycans, glycoproteins, and water) |
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What carries the stress load in connective tissue? |
The ECM, as opposed to other tissues where the cells carry the mechanical stress themselves. In connective tissue (CT) the cells are widely separated by the ECM, as opposed to tightly packed like other tissues |
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Where is the ground substance found in CT? |
It is found in the space between the cells |
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Is the ECM inert? |
No. It is a very dynamic structure. |
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What are the two (traditional) types of CT? |
Proper and other (AKA specialized, which includes bone, cartilage, blood, and lymph) |
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Connective Tissue Proper Divisions? |
-Loose (areolar) -Dense -Reticular -Adipose -Fibrous -Elastic -Mucous -Embryonic mesenchyme |
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Why is it sometimes hard to visualize distinct boundaries between one type of CT and another? |
CT types tend to grade/blend among each other |
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Characteristics of Loose (areolar) CT |
-Lot of space between the cells of the tissue -Collagen fibers are not very abundant, thus it lacks structural rigidity -Contains blood vessels and neurovascular bundles -Found in hypodermis of skin; under surface of epithelia of respiratory system and GI tract (lamina propria); camper's fascia |
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Characteristics of Dense CT |
-Higher concentration of collagen fibers than loose CT -Classified as either regular or irregular based on the alignment of the collagen fibers |
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Characteristics of Regular Dense CT |
-Fibers tend to run parallel and associate with each other, providing tensile strength -Found in tendons and ligaments |
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Characteristics of Irregular Dense CT |
-Random arrangement of fibers -Found in dermis of skin |
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Reticular |
-Has an abundance of reticular fibers (type III collagen) -Found in lymphatics organs and spleen |
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Adipose |
-Has preponderance of adipocytes -Found surrounding kidneys's and adrenal glands |
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Fibrous |
Has a large degree of highly packed ECM fibers -found in IV disc |
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Elastic |
Has lots of elastic fibers -found in regions where there is need to expand and contract like large arteries or trachea |
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Mucous |
Has a gel like (highly hydrated) ECM -Found in the umbilical cord, allowing fetus to turn without kinking the cord |
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embryonic mesenchyme |
immature, pluripotent connective tissue |
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What two main categories do CT cells fall into? |
Fixed cells and wandering cells, both derived from mesenchymal cells |
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Type of CT cell that arises within the CT and stays there in a relatively fixed postion |
Fixed Cells |
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What are the two types of Fixed Cells? |
Fibroblasts and Adipose cells |
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What do fibroblasts do? |
Make the majority of fibers and products in the ECM and hence have a lot of mitochondiria |
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Characteristics of fibroblasts |
-Most common cell type in CT -Specialized to produce proteins, which are used to build components of the ECM and ground substance, mostly collagen -Andy damage to fibroblasts (as in certain disease stages) will affect the integrity of CT -They are described as having spindle or fusiform shape with elongated nucleus -Active in wound healing via ECM production |
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Which type of fibroblasts tend to have a large nuclei comparatively? |
The active fibroblasts do, when compared to the quiescent fibroblasts (also referred to as fibrocytes) |
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Characteristics of Adipose Cells |
-Largest repository of energy -Appear as a thin rim of cytoplasm with a marginalized and squashed nucleus in traditional histological sections due to large amount of stored lipid, usually as one big body in the middle of the cell. This body is so big that it marginalizes the nucleus. -Appears as large clear space on cell slide, as fat is washed out when stained -Tissue is highly vascularized so body can make quick use of energy |
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Two types of Adipose cells |
White Adipose and brown adipose
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White Adipose |
-Is the basic energy store -Unilocular (one locus for the lipid droplet) -Used as energy store and for thermal insulation - ~20% bdy weight in men and ~25% in women |
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Brown Adipose |
-more specialized than white, involved in thermoregulation -multilocular (several similarly sized lipid droplets) -typically found in newborns and hibernating animals -geared to create non-shivering heat (thermogenesis) -Not very abundant in normal adults (found between the shoulder blades if anywhere) |
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What type of CT cells leave the blood stream after receiving a signal from the CT? |
Wandering Cells |
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Process of wandering cells leaving the capillaries to get to the CT |
-The cells attach to the enothelial layer of capillaries, a process called pavementing. -Diapedesis: The cells go through the endothelium and basement membrane into CT space around the blood vessel (*Lymphocytes are the only ones that may return to the blood vascular system from CT) -In CT they either become quiescent or differentiate and migrate toward the site producing the signal through chemotaxis |
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Upon differentiation, what type of blood cells do hematopoietic stem cells give rise to? |
-Plasma cells differentiate from B-lymphocyte cells, which are descendants of hematopoietic stem cells -Macrophages arise from monocytes -Mast Cells have no well-established precursor in the body |
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Plasma Cell function |
-Arise from B-lymphocytes after they have been stimulated by an antigen -The main job of the plasma cell is antibody secretion against the antigen -They are sparse in the body, but abundant in areas prone to bacterial invasion or areas where they can get screened out (like lymph nodes) |
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Characteristics of Plasma Cells |
-Eccentric (pushed out to the side) clock face nucleus -Area next to nucleus (juxtanuclear) doesn't stain well because of the golgi apparatus, which doesn't take up much stain -Well developed protein synthesizing/packaging machinery, consisting of rough ER and Golgi Apparatus (since they secrete antibodies) |
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Macrophages |
-They tend to eat, digest, or internalize relatively large particles like cellular debris and pathogens (bacteria and viruses)(mycobacterium tuberculosis and HIV abuse this) -Monocytes enlarge after they have been stimulated by the right signal and then they migrate to the CT to become macropahages -They present parts of the antigens they destroy to the lymphocytes in dermis, so the lymphocytes become activated against the antigen -They can form together to create giant cells which are associated with some diseases -Responsible for keeping things we breathe from contaminating the lungs or inhibiting gas exchange. Filled with smoking particles that can't be digested -Responsible for digesting preformed bone during remodeling process |
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Names of Macrophages |
Received different names based on location -Histiocytes: are macrophages in the CT -Kupffer cells: are in the liver -Microglia: are in the CNS -Langerhans cells: in the skin -Dust cells: in the lungs -Osteoclasts: in the bone |
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Characteristics of Mast Cells |
-Large cells with central nucleus unlike macrophages and plasma, which have eccentric nulclei -Packed with blue staining (basophilic) granules that contain histamine and other vasoactive mediators, which induce immediate hypersensitivity response upon degranulation of the cell. -Have surface receptors for IgE, antibodies related to allergic responses
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What is matachromasia? |
A property displayed by mast cells which means that applied dye changes color after interaction with the granules of the cell. |
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Degranulation reaction |
1. Antigen exposure primes plasma cell 2. Plasma cell makes antibody (IgE) 3. IgE binds to mast cell 4. Second exposure leads to quick release of histamine (when a multivalent antigen, one with multiple attaching point, binds to the IgE antibodies fixed on the mast cells, the cells will release the contents of all vesicles at once.) -Chemicals released into the surrounding tissues include *Histamine *Heparin (an anticoagulant) *Leukotrienes (a WBC activating chemical) *Eosinophil chemotactic factor of anaphylaxis |
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What is the problem with degranulation reaction being so powerful? |
It can actually harm the host and give rise to anaphylaxsis
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What is anaphylaxsis? |
-Term commonly used to denote the immediate, transient kind of immunological reaction. -It is characterized by contraction of smooth muscle and dilation of capillaries (become leaky) due to release of the substances in the mast cell granules (Bronchoconstriction and the release of fluid from leaky capillaries cause breathing to be difficult) |
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Characteristics of the ECM |
-The properties of the ECM determine the physical characteristics of the tissues and its constituent cells -The fibrous proteins of the ECM (e.g. collagen and elastin) provide tensile strength, the adhesive glycoproteins (e.g. fibronectin, laminin, and tenascin) and proteoglycans provide resistance to compressive forces |
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What are the two primary components to the ECM? |
Ground substance (composed of proteglycans, glycoproteins, and water) and ECM Fibers (provide the tensile strength; collagen and reticular and elastic fibers) |
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Proteoglycans |
-They have a core with large carbohydrate moieties called glycosaminoglycans (GAGs) covalently attached to it. These GAGs give the proteoglycan molecule a bristle like appearance -In cartilage, there are several individual proteoglycans (made of chondroitin sulfate and keratan sulfate, attached to a protein core) attached to a hyaluronan (another form of GAG) core to form what is called an aggrecan |
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Glycosaminoglycans |
-GAGs (AKA mucopolysaccjarodes) are long repeating disaccharides that tend to bind to water due to their chemical nature (the anionic sugar moieties attract sodium, and sodium in turn atracts water), thus they are the main way in which CT retains water. They are found both in ECM and cell surfaces. -Chrondroitin sulfate and keratan sulfate are some of the most common GAGs -GAGs are very prevalent in the interior of the eye and in the articular cartilages |
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Degradation of GAGs |
GAG degradation depends on the presence of several lysosomal enzymes -the inability to break down GAGs is a characteristic of a genetic disorder called mucopolysaccharidoses (Hurler's syndrome) -Severity of the disease depends on the type of PG and tissue involved |
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How often are Proteoglycans produced? |
New proteoglycans are produces every 2-10 days by fibroblasts |
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Adhesive Glycoproteins (GPs) |
-They mediate normal cell adhesion and migration -Important during development of the embryo, since they tell migrating cells when to stop and differentiate -Fibronectin, laminin, and tenascin are all examples of GPs -Fibronectin connects the fibers of the ECM to integrin, which is a transmembrane protein |
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What potential role do GPs have in metastasis |
They have a potential role in controlling metastasis, because the main reason a cell metastasizes is because it no longer recognizes the adhesive GPs which keep the rogue cells in one location |
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What is integrin? |
A protein that anchors actin filaments (part of the cytoskeleton) in the cells. Integrin transmits tension across plasma membrane. |
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Collagen |
-Accounts for 25% of total protein mass in mammals -Synthesis of collagen is a multi-step process that incileves hydroxylation of proline and lysine residues. -More than 20 types of collagen have been described on the basis of amino acid composition and physical properties. |
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What are the most common types of collagen? |
Types I-V are most common with type I being most abundant. -Type I : bone and tendon -Type II : cartilage -Type III : reticular fibers -Type IV : basement membrane that attaches to integrins Type V: participates in Type I collagen function |
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How is Vitamin C involved with Proline hyroxylase? |
It is a cofactor -Deficiency of vitamin C leads to scurvy (teeth can fall out) -Vitamin C deficiency has an impact on collagen synthesis -biochemical defects in the production of collagen fall under a the set of syndromes Ehlers-Danlos |
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What are Ehler-Danlos Syndromes? |
Biochemical defects in the production of collagen |
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Ehler-Danlos Syndrome Type IV |
-Collagen Type III deficiency -Characterized by ruptures in arteries and the intestine, both of which are rich in reticular fibers. -These patients have excessively flexible joints and stretchy fragile skin. |
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Assembly of collagen fibers |
-Synthesis of alpha chains (preprocollagen) in the rough ER (RER) -Hydroxylation of proline and lysine -Glycoslyation of hydroxylysine -Self-assembly of three alpha chains to form chains to form a triple helical procollagen molecule -Procollagen is exocytosed by the golgi apparatus through secretory vesicles -Procollagen is cleaved by the enzyme procollagen peptidase, resulting in the formation of tropocollagen -tropocollagen fibers self-assemble forming fibrils, which then coalesce to form collagen fibers (NOTE: Final assembly takes place outside of the cell) |
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Relationship between type of connective tissue present and how collagen bonds come together? |
How bonds come together defines which type of CT is present -Dense irregular CT has collagen fibers that are arranged somewhat randomly but densely packed in the ECM -Dense regular CT is characterized by collagen fibers that are very tightly ordered |
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Reticular Fibers |
-In reality are collagen type III fibers -Argyrophilic fibers (stain with silver salts) -Found in places where cell is exposed to fluid, such as blood and lymph (e.g. endorine glands, arteries, liver, spleen, lymph nodes, and intestine) *form a defined lattice of fibers where the cells in CT reside, this way the fluid is allowed to permeate through it without hindering the flow of fluid |
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Elastic Fibers |
-They allow tissue to recoil after being stretched -Have two major protein components; amorphous elastin and fibrillin -Mutations in the fibrilin gene cause Marfan syndrome -These fibers are pliable and elastic; they can stretch to 150% of their length -Found in areas requiring tissue expansion and contraction (e.g. arterial walls, intra-alveolar septa, bronchi) |
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The two major components of elastic fibers? |
-Amorphous elastin -Fibrilin (larger, more fiber-like protein) *binds elastin and froms scaffolding necessary for elastin deposition. Elastin eventually makes up most of the bundles *FBN-1 is the gene most important for fibrilin |
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Marfan Syndrome |
People with this syndrome are usually tall with long arms and fingers. This disease can be associated with: -Hyper elastic joints -Enlarged vessel walls in the arteries near the heart (which can in severe cases allow blood inside the artery to escape through a defect or in less severe cases produce an aneurysm) -Possibility for spontaneous pneumothorax due to loss of elasticity of the lung tissue -Problems with suspensory ligaments, which can be easily detached, causing dislocation of lens. |
