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71 Cards in this Set
- Front
- Back
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What is the origin of connective tissue?
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Mainly mesoderm, but some head connective tissue originates from NCCs.
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Name some general functions of connective tissue.
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Supports, connects, protects, and binds to other tissues; matrix for intercellular communication and exchange; site of tissue reactions like immune response and inflammation; insulation and thermoregulation; vascular support for other tissues.
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What are the two major components of connective tissue?
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Cells and ECM. There's a variety of cells embedded/suspended in the ECM. There can be wide variety of cx tissue depending on function.
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What are the components of ECM?
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Water, electrolytes, minerals, wastes, nutrients, fibers, and characteristic macromolecules like glycoproteins and proteoglycans.
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Name the categories of connective tissue.
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Loose/Areolar, Dense (regular and irregular), and specialized (adipose, embryonic, elastic, reticular, cartilage/bone, blood).
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Where would you expect to find areolar connective tissue?
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Underlying and supporting epithelia in most visceral organs.
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How are dense cx tissue subdivided? Why?
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Regular and irregular, based on the organization of fibers in the matrix. Dense regular fibers are arranged in bundles; dense irregular fibers are scattered.
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Give two examples of dense regular cx tissue.
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Tendons and ligaments.
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Give two examples of dense irregular cx tissue.
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Dermis and periosteum.
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When talking about cx tissue, what does the word "fiber" mean?
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It's referring to protein molecules.
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What's the matrix in blood?
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Plasma.
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What's another word for embryonic cx tissue?
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Mesenchymal.
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What are the specific components of CT matrix?
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Fibers, ground substance, and interstitial fluid.
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What are some examples of CT matrix fibers?
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Collagen, elastin.
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What's in the CT matrix ground substance?
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Glycoproteins and proteoglycans.
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In CT, what role do glycoproteins and proteoglycans play?
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Located in the ground substance, they are viscous and bind the interstitial fluid.
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What's the general structure of a glycoprotein? Give some specific examples of them.
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Protein with branched carbohydrates. Fibronectin, laminin, and chondronectin are all glycoproteins.
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What role does fibronectin play?
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In the ground substance of CT matrix, it provides cell adhesion and a cell migration surface.
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Where would you find laminin?
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It's a major component of the basal lamina and lamina reticularis.
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Where would you find chondronectin?
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In the cartilage matrix.
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What's the general structure of a proteoglycan?
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Core protein + glycosaminoglycans (GAGs).
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What purpose do proteoglycans serve in cx tissue matrix?
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They provide structure and maintain hydration.
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What are glycosaminoglycans?
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They are polysaccharides with an amine sugar.
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Give some good examples of specific glycosaminoglycans.
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Heparan, keratin sulfate, dermatan sulfate, and chrondroitin sulfate.
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Name a really important GAG that doesn't bind to protein to form a proteoglycan. What does it do?
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Hyaluronic Acid. It is an important component of the ECM in cx tissue. It permits formation of large aggregates that bind to water (important in diffusion of molecules through cx tissue and in lubricating organs/joints).
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Name the six cell types found in cx tissue.
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Fibroblast, macrophage, plasma cells, mast cells, adipose cells, and blood cells.
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What do fibroblasts look like?
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Stellate; elongated with extensions.
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What do fibroblasts do?
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They make fibers (collagen, elastin, etc.) and matrix substances such as proteoglycans and glycoproteins. They are factories.
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What do macrophages derive from?
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WBCs. Blood monocytes.
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What do macrophages do?
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They are phagocytic hematopoietic cells. They endocytose particles that are digested within their lysosomes. They're important in first-line immune defense. They serve as APCs
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What are macrophages shaped like? What's their size.
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They're irregularly shaped. They're huge relative to other cx tissue cells.
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Give three examples of special macrophages in different parts of the body.
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Alveolar dust cells in the lung, Kupffer cells in the liver, and splenic macrophages.
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Plasma cells are found in cx tissue and in ____.
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Lymphatic organs.
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What's the characteristic shape of plasma cells?
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They have an eccentric nucleus that looks like a clock face b/c of its chromatin.
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What's the major role of plasma cells in the cx tissue?
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Synthesis of antigen-specific antibodies.
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From what do plasma cells in the cx tissue derive?
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From B-lymphocytes, after these have been exposed to specific antigen.
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What is the easiest way to identify mast cells in cx tissue?
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Their cytoplasmic granules.
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What function do mast cells serve in cx tissue?
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Their granules store mediators of inflammation like histamine, heparin, proteases, Eosinophil Chemotactic Factor, and leukotrienes. They contain membrane-bound receptors for IgE (antigen-specific antibody made by plasma cells).
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What do mast cells do when specific antigen binds to their IgE receptors?
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They degranulate (release their granule product). The result is a Type I hypersensitivity reaction. These can include swelling, redness and itching. If there's an allergy, this can lead to anaphylactic shock.
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What is unilocular fat also called?
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White fat.
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What functions do adipose cells serve?
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Insulation, padding, energy storage.
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Is white fat innervated?
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No.
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Chemically, what does norepinephrine do to white fat?
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It activates lipases that break down fat to triglycerides which are circulated to meet energy needs (especially of muscle cells).
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What's the characteristic appearance of adipose cells?
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Signet ring.
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How does the appearance of brown fat cells compare to white fat cells?
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They're smaller, nuclei aren't as far to the periphery, and they contain multiple fat droplets.
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What are the two major CT fibers?
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Collagen and Elastin.
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What is the chief characteristic of collagen?
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It provides tensile strength.
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What's the chief characteristic of elastin?
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It provides elasticity.
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Where is Type I collagen?
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Dermis, bone, dentin.
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Where is Type II collagen?
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In hyaline/elastic cartilage.
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Where is Type III collagen?
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It makes up reticular fibers found in cx tissue; the fine reticulum serves as a supporting mesh in liver, spleen, and bone marrow. Also important in skin, blood vessels, and granulation tissue (wound healing).
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Where is Type IV collagen?
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Basal lamina.
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What cells synthesize collagen?
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Fibroblasts. It is then secreted and further assembled outside the cell, where the 5 step biosynthesis sequence begins.
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What are the five steps of collagen biosynthesis?
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1) PRE-PRO-collagen (sequestered in ER; rich in PRO and LYS); ("pre"=signal peptides)
2) PRO & LYS are hydroxylated by enzymes; some glycosylation, too. 3) Registration peptides included, too; thus PROCOLLAGEN is secreted. 4) Registration peptides (non-helical) cleaved extracellularly yielding TROPOCOLLAGEN. 5) Tropocollagen then aggregates as fibrils or fibers. |
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Why does Vit C deficiency lead to scurvy?
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Because without it, defective collagen is made. Hydroxylation of specific prolyl and lysyl residues in the ER fails.
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What are the 3 destinations of proteins made in the ER?
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Lysosome, PM, secretion from cell.
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List the steps in elastin synthesis.
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1) Secretion of an elastin precurson (tropoelastin).
2) Cross-linking of tropoelastin molecules occurs via Desmosine and Isodesmosine (AAs). 3) Fibrillin-1, a glycoprotein forms fine microfibrils that act as a "scaffolding" upon which elastin is deposited, to form elastic fibers. |
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Where would you find elastic fibers in the body?
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Elastic artery walls, skin, ligaments, vocal cords.
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Describe Marfan Syndrome.
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It's a genetic disease due to mutation of the fibrillin gene; results in abnormal elastic fibers. Pts are typically tall, have elongated limbs, and are suscptible to aortic aneurysms and dislocation of the eye lens.
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As far as AAs go, elastin is rich in ____ & ____, but is poor in ____ & lacks ____.
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Proline, glycine; hydroxyproline, hydroxylysine.
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What causes the random coiling in elastic fibers?
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Random arrangement of glycine molecules.
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What kind of collagen makes up reticular fibers?
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Type III collagen.
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What's characteristic of the arrangement of reticular fibers?
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Arranged in a mesh-like network.
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What function do reticular fibers serve and where can you find them?
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They support, and you find them in highly cellular organs like the liver, spleen, and lymph nodes.
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Are reticular fibers visible on H&E stain?
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No.
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What kind of staining shows reticular fibers?
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Silver staining; they are argyrophilic.
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Is Cx tissue in the gut loose or dense?
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Loose.
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What's the most abundant cell in cx tissue?
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Fibroblasts.
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How do fibroblast nuclei appear?
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Skinny, flat, and elongated.
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Where in the body is a good place to find dense cx tissue?
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The dermis. Periosteum around bone. Anchors teeth in their sockets.
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What is mesenchyme? How does it appear?
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Embryonic cx tissue. It's indistinct and diffuse. Cells scattered in a matrix. Undifferentiated.
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