Flashcards in Connective Tissue - Histology Deck (39)
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Connective Tissue is derived from...
Mesoderm
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Special Connective Tissue
Adipose
Blood
Cartilage
Bone
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Components of Connective Tissue
Cells - Fixed and transient
Extracellular Matrix (material between cells) - Fibers (resist tensile forces)
Ground Substance - Amorphous (reisist compressive forces)
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Collagen
Resist Tensile Forces
Most abundant
White (tendons)
Formed by fibroblasts and non-connective tissue
28 types
DO NOT BRANCH
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Collagen Formation
1) 3 PREPROCOLLAGEN (glycine, proline, hydroxyproline, and hydroxyglysine)
ALLIGN = PROCOLLAGEN MOLECULE = rope, soluble
2) At secretion = terminal protein removed by procollagen peptidases = TROPOCOLLAGEN
3) TROPOCOLLAGEN polymerizes in extracellular matrix = FIBRILS
4) FIBRILS polymerize = COLLAGEN FIBERS
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Reticular Fibers
Type II Collagen
AGYROPHILLIC
BRANCHES (Lattice Network)
SILVER STAIN
Small (glycoprotein coat prevents enlargement)
Make up LCT and Reticular CT
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Elastic Fibers
Elastin
NO HYDROXYLYSINE = stretch
4 lysine molecule with a desmosome link (elasticity)
Surrounded by microfinrils (fibrillin)
BRANCHES
Can form internal elastic membrane (DRCT) = sheath - cont around an artery
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Elastic Fiber Formation
1) Elastin is deposited on the scaffold of microfibrils forming amorphous structures
2) initially fiber consists of fibrollin microfinrils secreted by fibroblasts and smooth muscle
3) Elastin accumulates = occupies most of electron-dense center of single elastin fiber and fibrillin microfibrils remain at the fiber surface
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Elastin resists digestion by ---------- but is hydrolyzed by----------
Proteases
Pancreatic Elastase
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Elastin (unlike collagen) can form...
...a sheet = ELASTIC MEMBRANE or ELASTIC LAMINA
Prominent in arteries
Formed by fibroblasts and smooth muscle cells
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Ground Substance
Stuff in between the cells and the fibers
Hydrated gel of complex sugars (glycosaminoglycans (GAGs), proteoglycans, and multiadhesive glycoproteins)
Resists forces of compression, lubricant, and barrier to the penetration of invaders
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Glycosaminoglycans (GAGs)
Unbranched, negatively charged long chain of disaccharides
Attracts water = hydrated gel which resists compression
Repel each other = slippery texture that resists compression
EX = HYALURONIC ACID (common)
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Proteoglycans
Made of test-tube brush proteins with GAGs attached
Negative
Attract water and repulse each other
Form hydrated gel
Act as diffusion barrier
Aggrecan = macromoleculs that allows for gel state and barrier for diffusion
Many bact secrete hyaluronidase = gel state ot sol state = rapid spread of bact
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Multiadhesive Glycoproteins
1) Attachment to cells in ECM
2) Mediate interaction between cells
3) Has transient regulatory substances (interleukins, growth factors, hormones, plasma proteins, etc.)
EX = LAMININ (basal lamina of stratified epithelium and external lamina of nerves and muscle fibers) and FIBRONECTIN (ECM)
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Movement of Fluids
Water leaves capillary and goes into ECM at arterial end of capillary = Hydrostatic P
Water is pulled back in at the venous end of the capillary = Plasma Colloid Osmotic P
Mix of nutrients, etc.
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Connective Tissue is classified by....
....amount, direction, and tyoe
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Dense Connective Tissue
1) DENSE REGULAR CONNECTIVE TISSUE
Elastin or collagen
Tendons, ligaments, cornea
Fibers on one direction
Tensile strength
One break = whole thing is weakened
2) DENSE IRREGULAR CONNECTIVE TISSUE
Elastic or collagen
Dermis, capsules of organs, and periosteum
Protective Coating
Multiple directions
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Loose Connective Tissue
Areolar
Superficial fascia, lamina propria of intestines
Less fibers = more cells and open space (amorphous material)
Exchange
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Reticular Connective Tissue
Spleen and lymph nodes
Basement membranes
Agyrophilic = silver
Cellular movement and nutritional exchange
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1st sign of decrease in collagen
Teeth falling out
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Connective Tissue Cells
1) Fixed Cells
Fibroblast
Fibrocyte
Pericyte
Adipocyte
Mast Cell
Myofibroblasts
2) Transient Cells
Plasma Cell
Neutrophil
Eosinophil
Lymphocyte
Macrophage
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Fibroblast
FIXED CELL IN CONNECTIVE TISSUE
Most numerous cell in connective tissue
Produces and maintains the ECM (with smooth muscle cells) = Fibers and Ground Substance
Metabolically active (open faced = euchromatin in nucleus)
Spindle shape
Cytoplasm not apparent
Tendinoctytes in tendon
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Myofibroblasts
FIXED CELL IN CONNECTIVE TISSUE
Modified fibroblasts that demonstrate similar characteristics to fibroblasts (by creating massive amounts of ECM) and smooth muscle cells (by contracting)
Common in healing wounds = speed healing by contracting edge of wounds
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Pericytes
FIXED CELL IN CONNECTIVE TISSUE
Immature mesenchymal cell
Wall of capillaries and venules
Cytoplasm with actin and myosin
Can differentiate into other cell types (myofibroblasts, smooth muscle cels, or endothelial cells)
FUNCTIONS:
Blood brain barrier
Blood flow regulator
Damage to = diabetic retinopathy
Too many in brain = Alzheimer's Disease
Tumors cannot recruit = weakness and disorganization of tumor vasculature
When they die, they constrict
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Adipocyte
FIXED CELL IN CONNECTIVE TISSUE
1) Unilocular/ White - single large lipid droplet
Energy storage
Prominent in SER
Lipid metabolism
Endocrine tissue
Nucelus is pushed to the side
2) Multilocular/Brown
Multiple lipid droplets
Heat Production = non-shivering thermogenesis
Abundant MITOCHONDRIA
Neonatal/ hibernating animals
Lipid only present in vivo (removed due to processing)
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Mast Cell
FIXED CELL IN CONNECTIVE TISSUE
W/in connective tissue of organs with orifices, skin, and serous membranes
Also prominent in LCT of blood vessels
Primary Mediators:
Chondrotin sulfate
HISTAMINE
Eosinophil chemotactic factor (ECF) = limit inflammatory response
Neutrophil chemotactic factor (NCF) = limit inflammatory response
Secondary Mediators
D2
leukotrienes C4 and D4
Basophilic granules can obscure nucleus BUT cytoplasm is easily identified
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Mast Cell Tumors
Most common cutaneous tumor found in dogs
Affects heart rate, BP, etc.
Develop in dermis and subcutaneous
Found commonly on trunks
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Leukocytes
TRANSIENT CELL IN CONNECTIVE TISSUE
WBC
1) Granulocyte - sp. granules; segmented/lobed nucleus
Neutrophil (PMN)
Eosinophil
Basophil
2) Agranulocyte:- NO sp. granules BUT contain primary granules; round nuclei and minimal cytoplasm
Common in CT of mucous membranes, spleen, thymus, lymph nodes, tonsils, etc.
Lymphocytes
Monocyte (can only ident. in a blood smear)
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Macrophage
TRANSIENT CELL IN CONNECTIVE TISSUE
Agranuloctyes = from Monocyte (stays in blood; out of blood = macrophage)
Kidney bean shaped nucleus = open- faced
FUNCTIONS:
Ingest and destroy
Secretion of cytokines (messages)
Antigen Presentation
Cell shape is ueven due to filopodia projections
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