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What are connective tissues derived from?
mesenchyme
- splanchic mesoderm (walls of GI tract)
- somatic mesoderm (body walls)
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What composes the ECM?
fibers and ground substance
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What comprises connective tissues?
collagen and proteoglycans
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What comprises proteoglycans?
glycosaminoglycans and protein core
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How do GAGs make a hydrated gel?
GAGs have lots of negative charges and are attracted to Na+ which brings water with it
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What is the purpose of the hydrated gel of GAGs?
hydrated gel allows rapid diffusion of water-soluble molecules through ground substance but slows the passage of lg molecules and bacteria...creates turgor of ECM to resist stress
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What is the pathway of making collagen?
preprocollagen (rER)--->procollagen (rER)--->tropocollagen/collagen (outside the cell via protease)--->collagen fibrils--->collagen fibers
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Where are collagen fibers found?
CT and reticular laminae of basement membranes
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What makes collagen?
fibrocytes/blasts, sm muscle cells, chondrocytes/blasts, osteocytes/blasts
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Collagen type 1
most common, "classic collagen"
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Collagen type 2
in hyaline, elastic cartilage and fibrocartilage (intervertebral disks)
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Collagen type 3
assoc w/ type 1; called "reticular fibers", characteristic structural scaffolding of lymphoid tissues and bone marrow
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Collagen type 7
- reticular lamina
- anchoring fibrils
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Collagen type 4
- basal lamina
- lamin binding
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Where are reticular fibers synth?
fibrocytes/blasts in LCT and by reticular cells in lymphoid tissues and in bone marrow
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What are some physical characteristics of reticular fibers?
highly glycosylated; delicate silver-staining networks (vs thick bundles)
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What are the functions of reticular fibers?
supportive lattices in LCTs near epithelium and adipose tissue; hematopoietic and lymphoid tissues
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What makes up elastic fibers?
elastin and fibrillin (glycoprotein)
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What makes elastin?
sm muscle cells come' elastic arteries...NOT fibroblasts
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What type of tissue has elastic fibers?
tissues subject to stretching or expansion (elastic arteries, interalveolar septa, bronchi and bronchioles, elastic cartilage of ears)
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What is an example of CT damage?
tendon rupture
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What makes elastic fibers?
smooth muscle cells, fibrocytes/blasts, chondrocytes/blasts
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What are some physical characteristics of elastic fibers?
not easily seen w/ reg staining techniques; highly pliable and elastic
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What happens if ECM damaged?
fibrocytes--->fibroblasts--->repair---fibrocytes (same for chondrocytes/blasts, osteocytes/blasts)
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myofibroblast
special variant of fibroblast
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What are the differences between fibrocytes and fibroblasts?
- blasts: in LCT and CT in repair
- cytes: DCT
both synth and secrete ECM components but diff is activity level
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What is the job of a reticular cell?
produce reticular fibers in hematopoietic and lymphoid tissues; phagocytize Ag and debris; collect Ag on cell surface
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What lives with reticular cells?
lymphocytes, macrophages, FCD
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DCT
fewer cells, thick matrix
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Dense irregular CT
- dense matrix is nondirectional
- very eosinophilic
- few nuc
i.e. deeper CT of skin; organ trabeculae
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Dense regular CT
- dense matrix is directional (tendons, ligaments)
- tensile strength
i.e. tendons, ligaments
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What are some specialized CTs?
- adipose tissue
- cartilage and bone
- lymphatic tissue
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What are the functions of adipose tissue?
- store E in the form of stored lipids
- cushions and insulates body
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White adipose
unilocular adipose
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Brown adipose
- multilocular adipose
- lots of mit but oxidative phosphorylation step deactivated so heat is made instead of ATP in order to keep baby warm
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parenchymal tissue
aka functional tissue
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What is subcutaneous fat?
- beneath skin
- makes "panniculus adiposus" (superficial fascia)
- varies in thickness depending on adults
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What is intra-abdominal fat?
- in retroperitoneal areas
- variable amts surrounding blood/lymphatic vessels in omentum and mesenteries
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What does adipose tissue make?
aromatase....makes estradiol
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What lives in CT?
- mast cells
- macrophages
- plasma cells
- lymphocytes
- neutrophils
- eosinophils
- * do not originate here, migrate here after mature
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mast cell
- derived from bone marrow precursors
- has abundant basophilic granules in cytoplasm- heparin and histamine
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macrophage
- phagocytic
- several can fuse to make multinuc giant cell
- lg, irregular cell w/ lg, pale staining nuc; "junky" cytoplasm
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plasma cell
- abundant in areas susceptible to bact invasion (GI tract)
- lg, ovoid w/ eccentric nuc and lots rER
- clock face nuc w/ lots of heterochromatin on nuc env
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lymphocyte
- present in variable numbers
- sm, round cell w/ dk, round nuc, think cytoplasm
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neutrophil
- migratory, phagocytic, short-lived
- trilobed nuc
- abundant lysosomes
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eosinophils
- bilobed nuc
- bright-red cytoplasmic granules (lysosomes)
- internum and externum in specific granules
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What makes GAGs and collagen?
fibroblasts
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mucopolysaccharides
aka GAGs
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hexosamine
aka glycosamine in GAGs
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connective tissue diseases
Ehlers-Danlos syndrome, Stickler syndrome
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