Connective+Tissue+Part+2


 * 31 August 2006**
 * Connective Tissues Part 2**
 * Dr. Robert Crissman, Ph.D.**

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=**Proteoglycans**=


 * Viscosity and slipperiness
 * Protein core with sulfated GAGs attached
 * GAGs are glycosaminoglycans
 * Bottle brush appearance
 * Pulls water
 * 6 Different GAGs can be components of proteoglycans
 * Hyaluronic acid
 * Exception: isn’t sulfated
 * Aggrecan and Perlecan
 * Peripheral proteins
 * Syndecan and Fibroglycan
 * Integral proteins

=**Glycoproteins**=


 * Adhesion Molecules
 * Smaller than proteoglycans
 * Branched sugars
 * Fibronectin, laminin, tenscin, entactin, nidogen
 * Attach or bind to other molecules in extracellular space, including other glycoproteins
 * Necessary for cell motility

=**Interstitual Fluid**=


 * Responsible for transport of water and nutrients between blood vessels and parenchyma
 * Metabolic support function of connective tissue
 * Bound together by proteoglycans and hyaluronic acid
 * Water comes from the blood vessels and moves into extracellular space via hydrostatic pressure
 * Water is continuously in motion between endothelial cells and parenchyma
 * Oncotic pressure pulls water back in from interstitial fluid to blood vessel, working agains hydrostatic pressure
 * Excess fluid is always left in the extracellular space which is picked up by the lymphatic system and dumped in the thoracic duct and in back to the blood system
 * Edema
 * Pitting Edema – pushing on it leaves a dent
 * Abnormal buildup of water in extracellular space
 * Causes:
 * Blocked lymphatic vessels – surgery, elephantiasis
 * Blocked venous return – compromised veins, venous thrombosis (clot)
 * Increased vascular permeability – histamine from mast cells, anaphylactic shock
 * Hypertension – due to increased hydrostatic pressure at arterial end of capillary bed
 * Liver disease – insufficient albumin (produced by liver) to pull H2O back into vessel
 * Starvation – causes lack of plasma proteins that results in H2O remaining in extracellular space
 * Myxedema – overproduction of GAG’s during hypothyroidism
 * Mucous edema – doesn’t pit

=**Basement Membrane**=


 * Light microscopic term
 * Found in extracellular space
 * Surrounds all cells except connective tissue cells
 * Fixed and wandering cells don’t have basement membranes
 * Epithelium, muscle and nerve had basement membranes
 * Can act as a macrocellular sieve

**Electron Microscope Level**

 * Three layers:
 * Lamina Lucida
 * Lamina Densa
 * Made of collagen type IV
 * Lamina Reticularis
 * Fine reticular fibers (type III collagen) attaches to Lamina Densa
 * Basal Lamina – Lamina Lucida + Lamina Densa
 * Sometimes defined differently in cells with very reduced lamina lucida
 * e.g. muscle cells, where basal lamina = lamina densa
 * Function:
 * Physical attachment
 * Macromolecular filter
 * Structure:
 * Integrin proteins from epithelial cell plasma membrane attaches to glycoproteins lamina and fibronectin, and proteoglycan perlecan in the basal lamina