Connective Tissue PDF

Connective Tissue Dr Amany  Structure 1- Cells. 2- Ground substance 3- Fibers. Matrix  The ground substance It is composed of: 1. Interstitial fluid :that escape through the capillary wall as a result of the hydrostatic pressure. Edema: an increase in t...

Connective Tissue Dr Amany  Structure 1- Cells. 2- Ground substance 3- Fibers. Matrix  The ground substance It is composed of: 1. Interstitial fluid :that escape through the capillary wall as a result of the hydrostatic pressure. Edema: an increase in the tissue fluid due to loss of the equilibrium between the tissue fluids entering and leaving the matrix of CT. 2. Proteoglycan 3. Glycoprotein 4. glycosaminoglycan  Types of CT cells 1- Resident (fixed) cells:  Origin: within the connective tissue.  Characters: stable & long-lived.  Examples: fibroblasts and fat cells. 2- Transient(wandering) cells:  Origin: in the bone marrow, circulate in the blood and when they receiving a stimulus , they leave the blood and migrate into the connective tissue to perform specific functions.  Characters: motile, short-lived and labile.  Examples: plasma cells and white blood cells. 1-Undifferentiated mesenchymal cells Origin: mother cell of CT. Function: Stem cells that divide and differentiate into many types of CT cells. Structure:  Shape: stellate with few processes.  Nucleus: pale.  Cytoplasm: pale basophilic (polysomes).  2- Fibroblasts They are the most common cells in CT. Origin: UMC. Function:Secrete the ground substance&the fibers of the matrix. Structure: LM:  Shape: spindle with processes.  Nucleus: large& pale.  Cytoplasm: deeply basophilic. EM: protein synthesizing cells  numerous rough endoplasmic reticulum & well developed Golgi but no secretory granules. After they synthesize the matrix, they become quiescent and are called fibrocytes.  3- Fibrocytes Origin: Less active fibroblast. Function: maintenance of the matrix. Structure: LM:  Shape: smaller with fewer processes.  Nucleus: small & dark.  Cytoplasm: eosinophilic. EM: fewer organelles( fewer rER and small Golgi). If the matrix is injured, they can return to their more active state (fibroblast) to repair the matrix  Fibroblast Fibrocyte 1- Origin Undifferentiated mesenchymal Fibroblast after being inactive. cells. 2- Function Secretes ground substances& Maintains matrix. fibers. 3- LM A- Shape Spindle with processes. Smaller with fewer processes. B- Nucleus Large & pale. Small & dark. C- cytoplasm Deep basophilic. Acidophilic. 4- EM Protein synthesizing cells: Less active cell: Many rER, well developed Golgi Few rER, small Golgi but no secretory granules.  4-Fat cells (adipocytes) Origin : UMC. Function: storage of fat. Structure: 1- Unilocular adipocytes:  Shape: large cells, spherical.  Cytoplasm: occupied by a single large lipid droplet that pushes the cytoplasm to a thin peripheral rim with peripheral flattened Single nucleus giving them a signet ring appearance. lipid 2-Multilocular adipocyte: droplet  Shape: polygonal and smaller.  Nucleus: central rounded.  Cytoplasm: numerous small lipid droplets and numerous mitochondria. Fat Cells (adipocyte) empty spaces with H&E (signet ring appearance)  Fat cells(Sudan III) Large cells of variable sizes Orange in color  Unilocular fat cell Multilocular fat cell 1- Shape Large rounded or polygonal. The same but smaller. 2- Cytoplasm Contains single, large lipid Contains numerous lipid droplet. droplets & numerous mitochondria. 3-Nucleus Flattened & peripheral ( signet Rounded & central. ring appearance). 4- Function Storage of energy. Production of heat.  5-Mast cells Origin: Haemopoietic stem cells. Function: Secrete histamine and heparin that initiate allergic and local inflammatory response. Structure: LM  Shape: a large cell.  Nucleus: rounded and central.  Cytoplasm: contains basophilic granules that may obscure the nucleus. Metachromasia: e.g. toluidine blue stain gives a purple color instead of blue, due to the chemical composition of the secretory granules(heparin). EM: numerous secretory granules).  7- Plasma cells Origin: B lymphocytes. Function: synthesis of antibodies against foreign bodies entering the CT. Structure: LM:  Shape: large oval.  Nucleus : spherical and eccentric with a cart wheel appearance( due to arrangement of chromatin).  Cytoplasm: basophilic with negative Golgi image ( prominent juxtanuclear Golgi apparatus appears unstained against the deeply basophilic cytoplasm). EM  Protein synthesizing cells: numerous rER, large well developed Golgi but no secretory granules.  6- Macrophages Origin: Blood monocytes. Function: phagocytosis of foreign materials including bacteria& dead cells. Structure:  Shape: large& irregular.  Nucleus: eccentric kidney shaped.  Cytoplasm: numerous lysosomes.  Mast cell Macrophage Plasma cell 1- Origin Hemopoietic stem cell. Monocyte B- lymphocyte. 2- Function Secretes histamine & Phagocytosis. Secretes antibodies. heparin 3- LM A- Shape Large. Large & irregular. Large & oval B- Nucleus Rounded & central. Kidney shaped & Spherical, cart wheel & Basophilic with large eccentric. eccentric. C- Cytoplasm granules, showing Basophilic with metachromasia. negative Golgi image. 4- EM Secretory granules. Lysosomes. Protein synthesizing cells: many rER & well developed Golgi.  II- Connective tissue fibers 1- Collagen fibers 2- Elastic fibers 3- Reticular fibers  1- Collagen fibers Characters: 1- They are the most abundant CT fibers. 2- They are the strongest type ( high tensile strength i.e.the ability to resist longitudinal stress). 3- In fresh state: they have a white appearance( white fibers). Structure: 1- Cylindrical structures. 2- Run in wavy bundles. 3- The individual fibers do not branch while the bundles of fibers do. 4- They stain pink with H&E (eosinophilic).  Types of collagen About 20 different types of collagen fibers, differ by their composition, morphology, distribution in tissues and functions. Type I : in connective tissue proper, fibrocartilage and bone. Type II: in cartilage. Type III : reticular fibers. Type IV: in basement membrane.  2- Elastic fibers Characters: They contain protein called elastin that allows them to stretch and recoil. In fresh state: they appear yellow (the yellow fibers). Structure: A-They may exist in two forms: 1- Long and thin branching fibers. 2- Parallel sheets. B- They stain weakly with H&E, brick red with orcein  3- Reticular fibers They consist of type III collgen. They are short, thin and branching fibers forming a network. They are not stained by H&E, they are stained by silver stain( brown to black ). They have supportive function ( support the cells and blood vessels of the organs).  Collage fibers Reticular fibers Elastic fibers 1- Fresh state White. --------- Yellow. 2- Stain H&E : pink. Silver: brown. H&E: faint. Orcein: brick red. 3- Types 20 types, most Collagen type III. common is type I. 4- Description Cylindrical. Short branching fibers Either long & thin Run in bundles. that form a network. branching fibers or Fibers are not parallel sheets. branched but bundles do. 5- Function Tensile strength. Support. Flexibility & elastic recoil ( due to elastin protein).  Types of CT CT proper Blood Cartilage bone  Types of CT proper 1- Loose, Areolar, Ordinary CT 2- White fibrous CT - Regular - Irregular 3- Elastic CT 4- Reticular CT 5- Adipose CT - White - Brown 6- Embryonic (Mucoid CT- mesenchymal) I-Embryonic CT Mesenchymal Muciod  1- Mesenchymal CT Structure: Cells: UMSCs with their processes come in contact with each other forming a network. Fibers: reticular fibers. Ground substance: gel- like. Site: embryo.  2- Mucoid CT Structure: Cells: UMSCs (spindle) appear like fibroblasts. Fibers: collagen (Ground substance(Wharton jelly): abundant, basophilic & homogenous composed of hyaluronic acid. Site: umbilical cord  Mucoid C.T- Umbilical cord 2 umbilical arteries & 1 umbilical vein Branched undifferentiated mesenchymal cells  1- Loose areolar CT Structure : Cells: All types cells especially fibroblasts & macrophage. Fibers: All fibers (collagen, elastic& reticular). Ground substance: Abundant Function: 1- Fibers: supports and binds tissues. 2- Ground substance: nutrition. 3- Cells: defends against infection (by its white blood cells, plasma cells, mast cells and macrophages).  1- Loose areolar CT Sites: it is the most widely distributed connective tissue in the body. 1- Under the epithelium in all mucous membranes. 2- The papillary layer of dermis. 3- It surrounds glands, blood vessels and nerves.  2-Dense regular CT (White fibrous CT) Structure: Fibers: collagen bundles, wavy, parallel in one direction. Cells: rows of flattened fibroblasts( tendon cells). Ground substance: little. Function: resist pulling force in one direction. Sites: 1-Tendons. 2- Ligaments.  3- Dense Irregular CT Structure: Fibers: collagen run in all directions (irregular). Cells: few fibroblasts. Ground substance: little. Function: resist tension in different directions. Sites: 1- the reticular layer of dermis of the skin. 2- the capsules of the organs. 3- the capsules of the fibrous joints.  4- Elastic CT Structure: Elastic fibers that run in all directions or they may form fenestrated membranes. Function: flexibility and elastic recoil. Sites: 1- arteries. 2- vocal cords. 3- ligamenta flava & ligamenta nuchae.  Ligamentum nuchi (T.S.) (Van Gieson) to show elastic fibers Yellow elastic fibers Red collagen fibers  5- Reticular CT Structure: Fibers: Reticular fibers forming a network. Cells: Reticular cells (fibroblasts). Function: Form framework to support cells of an organ. Sites: 1- Liver. 2- Spleen, lymph nodes & bone marrow.  Reticular fibers - silver stain A meshwork that acts as a structural framework for organs such as lung, spleen, thymus, and lymph nodes  6- Adipose CT Structure: Cells: Adipose cells. Fibers: Reticular fibers. Ground substance: Sparse. It is highly vascular. 6- Adipose CT  Sites & Functions of unilocular adipose CT Sites: All the subcutaneous tissue of the body& around vital organs. Functions: 1-Storage of energy. 2- Shaping body. 3-Shock absorber( especially in palm& sole). 4- Support vital organs e.g. heart & kidney. 5- Thermal insulation(due to the poor heat conduction of adipose tissue).  Sites & function of multilocular adipose CT Sites: in certain areas in the abdomen and neck of the human embryo and the newborn. Function: Thermogenesis Production of heat to protect the newborn against cold. As children grow, the lipid droplets coalesce together and the brown fat changes into white fat.