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Main page | Structure | Departments | Department of Histology and Embryology | Materials for students | Modul 1 | CONNECTIVE TISSUES. LOOSE IRREGULAR connective tissue.

CONNECTIVE TISSUES.         LOOSE   IRREGULAR  connective tissue.
All   CONNECTIVE  tissues    are:      1) Developed from MESENCHYME,
                                                    and  2) Composed of    2 c o m p o n e nts:
               1) CELLs       and      2) EXTRACELLULAR   MATRYX  (=ECM)  between cells.
  ECM  is composed of 2 components: A) FIBRES   and    b) GROUND substance.
                           3  types of fibres:    1) Collagen fs,     2) Elastic fs,      3) Reticular fs .
 GROUND substance  is composed of : a) GlycosAminoGlycans (=GAGs),  b) Proteoglycans,
 c) Glycoproteins.  GAGs are 2 types: 1) Sulfated GAGs, such as chondroitin sulfate, heparan sulfate,
dermatan sulfate;        2) NONsulfated GAGs,    such as   HYALURONIC  acid.
If amount of cells and ground substance more, than number of fibres – connective tissue is LOOSE.
If amount of  fibres  more, than number of cells and ground substance- connective tissue is DENSE.
If fibres  arranged  PARALLELLY – con. tis. is  REGULAR; if it form mashwork - IRREGULAR.
        LOOSE  IRREGULAR  connect. tis. (=LICT).  It  locates in all inner organs around nerves and
around blood vessels.                    Main   c e l l   t y p e s   of    LICT
  1) DIFFERENTIATED  (or, MATURE) FIBROBLAST. Has abundance of rER and Golgi apparatus.
   Funct.: Secretion of ALL components of ECM. It means, secretion of : a)  GAGs  and proteoglycans 
 for formation of GROUND  substance,  b)protein COLLAGEN and protein ELASTIN for formation of collagen FIBRES and elastic FIBRES. After necrosis (in skin, in myocardium) it secrets TOO MUCH  
 of collagen, resulting in formation of  COLLAGEN SCAR (connective tissue scar),  replacing of necrotic zone.         SCAR is composed of   100%   thick bundles    of collagen fibres.
2) MAST cell.  It contains basophilic metachromatic GRANULES.    Granules contain
HEPARIN and HISTAMINE.  Funct.:  mast cell PREVENTS blood coagulation   (by heparin)  and INCREASES allergic reactions  and inflammation (by histamine).
3) Tissue MACROPHAGE (=MP). It is developed from blood MONOCYTE. Monocyte is developed from  PHSC of red bone marrow.    Macrophage has cytoplasmic PROCESSES (pseudopodia), a lot of LYSOSOMES. Funct.:  PHAGOCYTOSIS   of  bacteria    and it killing by   LYTIC enzymes.
Macrophages of all inner organs form    SYSTEM of   mononuclear phagocytes,    because ALL of it
originate from MONOCYTE  and    function   of  it ALL  is - P H A G O C Y T O S I S.
MP of liver is KUPFFER cell; MP of nervous tissue is MICROGLIA; MP of bones is OSTEOCLAST;
MP of lungs is   ALVEOLAR macrophage  ( or dust cell).
4) PLASMA cell.  It originates from  B-LYMPHOCYTE.  B-lymphocyte originates from PHSC.   Funct.: secretes  5   classes of     immunoglobulins (or antibodies):  Ig A,  Ig D,  Ig E,  Ig G,   Ig M.
5) PERICYTES.    It  surround endothelial cells of capillary wall and  regulate it diameter.
6) MYOFIBROBLASTS. Locate in wounded surfaces during it healing. Funct.:contract area of wound.
7) BROWN  adipocytes  (or multilocular fat cells). It contain  many small-sized lipid droplets in cytoplasm  periphery, nucleus is in centre.   Funct. of brown adipose cs – is  HEAT  production.
8) WHITE adipocites (or unilocular fat cs). It contain  ONE big-sized lipid droplet in centre; nucleus –is in cytoplasm  periphery.   Funct.-  is  fat storage and   origin of energy.
   DENSE REGULAR  connective tiss. locates in TENDON and ligaments. Is composed of a) thick bundles of collagen fibres,  arranged PARALLELLY; b) thin layers of LICT between bundles, named
 endotendineum and peritendineum.
   DENSE  IRregular   connective tiss. Locates in reticular layer of skin dermis. Is composed of:
  a) Thick bundles of collagen fibres,  arranged into MESHWORK (not parallelly), b) a little number of fibroblasts and ground substance.
SPECIAL connective tissues:
1) Brown adipose tis.  It situates  in  newborn between scapulas.  It is composed of  BROWN ADIPOCYTES.      Funct.: it  regulates body temperature due to HEAT production.
2) White adipose tis. It  locates in adults skin hypodermis. It is composed of WHITE ADIPOCYTES.
3) MUCUOUS connective tiss (or Whartons jelly). It locates in umbilical cord. It is composed of  fibroblasts  and   too MUCH HYALURONIC acid. Funct.: prevents compression of umb. vessels.
4) RETICULAR connective tissue. It  locates in red bone marrow and forms it stroma. Is composed  
 of  anastomosing  RETICULAR cells and reticular FIBRES, forming MESHWORK.  Funct.:  reticular cells secrete factors, stimulating  hemopoiesis.   Such as:   ILs   (interleukins)  and    CSFs.   
 Составитель – доцент В.В. Бондаренко.                
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