Connective tissue pt2 Flashcards
What is connective tissue derived from?
Mesenchyme
What are the fixed cells present in connective tissue?
Fibroblasts, myofibroblasts, adipose cells, mast cells, macrophages
What are the transcient (free or wandering cells) present in connective tissue?
-originate in bone marrow and circulate in blood
-Plasma cells, lymphocytes, neutrophils, eosinophils, basophils, monocytes, macrophages
What are fibroblasts and what 2 categories do they divide into?
-Fixed cell - most abundant, least specialised cells in connective tissue
-Active or inactive fibroblasts
-derived from undifferentiated mesoenchymal cells
What are active fibroblasts?
-Elongated, fusiform (iiregular shape) cells
-Granular ovoid nucleus
-Specialised for tisue repair with contractile ability
-pale staining cytoplasm
What are inactive fibroblasts?
-Smaller, more ovoid, acidophilic cytoplasm, nucleus is smaller, elongated and more deeply stained
-Maintain structural integrity - synthesise and secrete ECM
What are adipocytes and what 2 types can they be?
-Fixed cells from undifferentiated fibroblast like mesochymal cells
-Store and metabolise fat
-Unilocular (white) or multilocular (brown)
What are unilocular adipocytes?
-Large spherical cells
-Single large lipid droplet, pushes cytoplasm to edge of cell
-Gives signet ring or chicken wire like appearance under microscope
What are multiocular adipocytes?
-Less abundant, smaller and more polygonal
-Several small droplets
-Nucleus isnt squeezed against plasma membrane, more mitochondria, fewer ribosomes
-found throughout body in loose ct, along blood vessels
What are Macrophages?
-Some act as fixed and some as transient cells
-Mononuclear phagocytic system
-Subdivided into phagocytes and antigen-presenting cells
-Large, irregularly shaped, ovoid indented nucleus, lysosomes appearing as small dense granules
-eccentric nucleus
What are mast cells?
-Fixed cell
-Among largest of fixed cells
-Ovoid, centrally placed spherical nucleus
-Identifying characteristic - presence of granules
-Has primary and secondary mediators that initiate inflammatory response
Primary vs Secondary mediators -Mast cells
Primary mediators - histamine, heparin etc in granules
Secondary mediators - cytokines, func initiation of inflammatory response
Mast cells - what happens during first and subsequent exposure to foreign antigen?
First exposure
-IgE antibody formation
-IgE antibodies bind to Fc receptors on plasma membrane of mast cells
Subsequent exposure
-Antigen binds to IgE on mast cell surface - crosslinking and clustering of receptors
-Release of primary mediators from granules e.g histamine
-Initiate inflammatory response
What does the crosslinking and clustering activate in the subsequent exposure of mast cells to a foreign antigen?
-Activate membrane bound receptor coupling factors which initiate the release of primary mediators from granules and synthesise and release secondary mediators from mast cells
How are granules released from mast cells?
By exocytosis
What are plasma cells?
-Transcient cell -found mostly in areas of chronic inflammation and where foreign substances have entered tissues
-Part of adaptive immune repsonse
-Derived from B lymphocytes
-Produce antibodies for specific antigens
-Large, ovoid, with eccentrically placed nucleus
-Short life span - 2-3 weeks
